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[Display omitted] • ZDA-Cu2+complex exhibits high selectivity for glyphosate and glufosinate ammonium. • The probe ZDA and the ZDA-Cu2+system have been applied in intracellular fluorescence imaging. • The probe ZDA has good biocompatibility and low toxicity. Organophosphorus pesticides play an important role as broad-spectrum inactivating herbicides in agriculture. Developing a method for rapid and efficient organophosphorus pesticides detection is still urgent due to the increasing concern on food safety. An organo-probe (ZDA), synthesized by purine hydrazone derivative and 2,2′-dipyridylamine derivative, was applied in sensitive recognition of Cu2+ with detection limit of 300 nM. Mechanism study via density functional theory (DFT) and job's plot experiment revealed that ZDA and Cu2+ ions form a 1:2 complex quenching the fluorescence emission. Moreover, this fluorescent complex ZDA -Cu2+ was applicable for detecting glyphosate and glufosinate ammonium following fluorescence enhancement mechanism, with detection limits of 11.26 nM and 11.5 nM, respectively. Meanwhile, ZDA-Cu2+ was effective and sensitive when it is used for pesticide detection, reaching the maximum value and stabilizing in 1 min. Finally, the ZDA -Cu2+ probe could also be tolerated in cell assay environment, implying potential bio-application. [ABSTRACT FROM AUTHOR]

[Display omitted] • Effect of spirocyclization of xanthene dyes on linear and nonlinear optical properties. • Open-close form of rhodamine B and π-extended xanthene dyes. • Rhodamine B corresponds to D-π-A system, while thiophene-substituted xanthenes to D-A-D system. • Open form is energetically more stable in the S 0 state than the closed form. • The α 0 , β 0 , γ, µβ 0 , and β1064 of the open form are higher than those of close form. Spirocyclization, a unique feature of xanthene dyes, makes it a promising candidate for developing fluorescent ratiometric probes for sensing, imaging, tracking, and labeling. How will this feature of xanthene dyes influence the linear and nonlinear optical properties? To examine the effect of spirocyclization of xanthene dyes, we have selected both the open-close form of rhodamine B and π-extended xanthene dyes substituted with thienyl and thieno[3,2-b]thienyl group at position 3 and 6. Here, rhodamine B will serve as the (Donor)D-π-A(Acceptor) system and thiophene-substituted xanthene dyes will serve as the D-A-D system. The geometry optimization of the close-open form of xanthene dyes at B3LYP/6–311++G(d,p) and CAM-B3LYP/6–311++G(d,p) revealed that the open form is energetically more stable in the S 0 state than the closed form. The vertical excitation energy (ΔE), from Time-Dependent-Density Functional Theory (TD-DFT) calculation at B3LYP/6–311++G(d,p), CAM-B3LYP/6–311++G(d,p), ωB97XD/6–311++G(d,p) revealed that (ΔE) open < (ΔE) close. Further, the open form of xanthene dyes displays red-shifted absorption compared to the closed form. The λ Vt of xanthene dyes (open-close forms) is mainly assigned to HOMO → LUMO transition (S 0 → S 1) with % orbital contribution for open form ∼ 90 % and close form ∼ 60 %. The oscillator strength of xanthene dyes is obtained in the range of 0.01 – 1.74. The λ Vt of xanthene dyes is in agreement with experimental absorption. The static polarizability (α 0), first-order hyperpolarizability (β 0), second-order hyperpolarizability (γ), molecular hyperpolarizability (µβ 0), and frequency-dependent hyperpolarizability (β1064), of the open form of xanthene dyes, were found to be higher than the close form. Thus, the open form of xanthene dyes will show superior linear and nonlinear optical properties than the closed form. The thienyl[3, 2-b] thieno substituted xanthene dye with red-shifted absorption shows higher α 0 , β 0 , γ, µβ 0 , β1064, and γ values, show better linear and NLO properties than thienyl and diethylamine substituted xanthene dyes. [ABSTRACT FROM AUTHOR]

[Display omitted] • Probe NSHF was constructed for copper ion detection based on the ESIPT mechanism. • NSHF shows good selectivity and low detection limit for copper ions. • A visual detection platform was constructed by coupling with a smartphone. • NSHF can be used for the visual detection of copper ions. Copper is an essential trace element in the human body, and its level is directly related to many diseases. While the source of copper in human body is mainly intake from food, then the detection of copper ions (Cu2+) in food becomes crucial. Here, we synthesized a novel probe (E)-3-hydroxy-2-styryl-4 H -benzo[h]chromen-4-one (NSHF) and explored the binding ability of NSHF for Cu2+ using nuclear magnetic resonance hydrogen spectroscopy (1H NMR), high-resolution mass spectrometry (HRMS), Job's plot method and density functional theory (DFT). NSHF shows the advantages of fast response time, good selectivity and high sensitivity for Cu2+. The fluorescence intensity ratio (F/F 0) of NSHF shows a good linear relationship with the concentration of Cu2+ and the detection limit is 0.061 μM. NSHF was successfully applied to the detection of Cu2+ in real samples. In addition, a simple and convenient Cu2+ detection platform was constructed by combining NSHF with a smartphone and a UV lamp, which can realize the rapid detection of Cu2+. This work provides an effective tool for the real-time detection of Cu2+. [ABSTRACT FROM AUTHOR]

[Display omitted] • The adsorption behavior of folic acid on Cu3 clusters for different configurations. • SERS in the ABP-Cu3 clusters enhances the vibrational modes of ABP. • Appearance of new modes in the spectrum of complexes due to SERS. The optical characteristics of folic acid (ABP) and metal clusters of copper (Cu 3) at various locations were investigated by means of density functional theory (DFT) computations. Mulliken charge analysis and molecular electrostatic potential (MEP) surface show how charge moves from Cu 3 to ABP through the various groups. The peak in the UV–Vis spectra of ABP-Cu 3 is caused by bonding and anti-bonding orbitals. In both vacuum and aqueous conditions, the polarizability values of ABP-Cu 3 cluster are significantly higher than those of pure ABP, indicating a possible enhancement of the nonlinear optical (NLO) effect. Our research investigates the possibility of using ABP adsorbed metal clusters for NLO materials. Surface enhanced Raman scattering (SERS) in the ABP adsorbed metal clusters enhances the vibrational modes of ABP. Adsorption energies are found to be in the range −17.08 to −58.52 kcal/mol in vacuum and −53.34 to −93.44 kcal/mol in aqueous medium for the different configurations for ABP-Cu 3. It indicates that metal clusters adsorbed by ABP are stable in the aqueous media. Experimental IR and UV–Vis of ABP is in agreement with theoretically predicted ones. [ABSTRACT FROM AUTHOR]

[Display omitted] • • EA, VDE and frequencies of RhO n −(n = 1–––2) were determined by experiment and calculations. • • Based on the DFT calculations, the theoretical ADEs, VDEs and simulated PES of anionic RhO n − (n = 1–––4) clusters were obtained. • • The associated molecular orbitals (MOs), natural population analysis (NPA) and bond order analysis have been utilized. The photoelectron spectroscopies of RhO n – (n = 1–2) were obtained via using the photoelectron velocity-map imaging (PE-VMI) approach. The experimental values of the adiabatic detachment energy (ADE) and vertical detachment energy (VDE) for RhO– were reported to be 1.58 ± 0.02 eV. The experimental AED and VDE values of RhO 2 – were reported to be 2.70 ± 0.02 eV and 2.79 ± 0.02 eV, respectively. The vibrational frequencies of RhO– and RhO 2 – measured from photoelectron spectra (PES) were 817(76) cm−1 and 932(55) cm−1, respectively. Based on the density functional theory (DFT), the RhO n –1/0 (n = 1–4) clusters were investigated. The optimized configurations of corresponding ground states and low-lying clusters were discovered. Meanwhile, the simulated photoelectron spectroscopy (PES) of RhO n – (n = 1–4) and the theoretical ADE and VDE values of RhO n – (n = 1–4) clusters were unveiled to assist future experimental studies of Rhodium oxide clusters. Moreover, the associated molecular orbitals (MOs), natural population analysis (NPA) and bond order analysis have been utilized to investigate the chemical bonding in these groups. [ABSTRACT FROM AUTHOR]

[Display omitted] • Full DFT optimization and IR-VCD spectral of α-helical 25-mer peptides. • Effects of geometry, solvation and functional tested on computed spectra. • Improved isotopic substitution spectral patterns require longer length models. • Length limits suggested for transfer of parameters with different interpretive goals. Vibrational circular dichroism (VCD) spectra have been computed with qualitatively correct sign patterns for α-helical peptides using various methods, ranging from empirical models to ab initio quantum mechanical computations. However, some details, such as deuteration effects and isotope substitution shifts and sign patterns for the resultant amide I' band shape, have remained a predictive challenge. Fully optimized computations for a 25-residue Ala-rich peptide, including implicit solvent corrections and explicit side chains that experimentally stabilize these model helical peptides in water, have been carried out using density functional theory (DFT). These fully minimized structures show minor changes in the (ϕ,ψ) torsions at the termini and yield an extra negative band to the low energy side of the characteristic amide I' couplet VCD, in agreement with experiments. Additionally, these calculations give the right sign and relative intensity patterns, as compared to experimental results, for several 13C=O substituted variants. The differences from previously reported computations that used ideal helical structures and vacuum conditions imply that inclusion of distorted termini and solvent effects can have an impact on the final detailed spectral patterns. Inclusion of side chains in these calculations had very little effect on the computed amide I' IR and VCD. Tests of constrained geometries, varying dielectric, and different functionals indicate that each can affect the band shapes, particularly for the 12C=O components, but these aspects do not fully explain the difference from previous spectral simulations. Inclusion of long-range amide coupling, as obtained from DFT computation of the full structure, or transfer of parameters from a somewhat longer peptide model, rather than shorter model, seems to be more important for the final detailed band shape under isotopic substitution. However, these corrections can also induce other changes, suggesting that previously reported, limited calculations may have been qualitatively useful due to a balance of errors. This may also explain the success of simple empirical IR models. [ABSTRACT FROM AUTHOR]

[Display omitted] • Three designed novel Ag n @C 18 (n = 4–6) complexes with enhanced NLO response. • Remarkable charge transfer (CT) from silver cluster to the C 18 ring. • Ag 6 @C 18 exhibits the highest first static hyperpolarizability. • The UV–Vis absorption spectra were simulated for C 18 and Ag n @C 18 (n = 4–6). Seeking highly efficient and stable non-linear optical (NLO) materials is crucial yet challenging, given their promising applications in laser diodes and photovoltaics. In this study, we employ the excess electron and charge transfer strategies to theoretically design three novel complexes, namely Ag n @C 18 (n = 4–6), by adsorbing silver clusters onto the cyclo[18]carbon ring (C 18). Our aim is to investigate the NLO characteristics of these complexes using density functional theory (DFT) and time-dependent DFT (TD-DFT) calculations. The results reveal that the adsorption of Ag clusters onto C 18 leads to a decrease in excitation energy and an increase in dipole moment and oscillator strengths, thereby significantly enhancing the hyperpolarizability of the complexes. Strikingly, among all these complexes, Ag 6 @C 18 exhibits the highest first hyperpolarizability value of approximately 109496.2620 au calculated at the B3LYP/cc-PVDZ-pp level of theory, which is about 1.3 × 106 times higher than that of pure C 18. This finding validates the effectiveness of the proposed strategies in enhancing the NLO response of the species. Moreover, the calculated UV–Vis absorption spectrum demonstrates that the Ag n @C 18 complexes with excess electrons exhibit absorption at longer wavelengths (ranging from 385 to 731 nm) compared to C 18. In addition, the stability, chemical bonding, and charge transfer characteristics of the Ag n @C 18 (n = 4–6) complexes were also discussed. These findings highlight the potential of these complexes for the development of highly efficient NLO devices. [ABSTRACT FROM AUTHOR]

[Display omitted] • The ESIPT triggers the generation of zwitterion. • The resonance of neutral and charge-separated structures was investigated. • The effect of resonance structure on fluorescence attribution is revealed. Molecules with zwitterionic characteristics exhibit significant potential for utilization in nonlinear optics, optoelectronics, and organic lasers owing to their large dipole moments. Recently, the synthesized compound 2,4-bis (4,5-diphenyl-1H-imidazol-2-yl) phenol (2,4-bImP) by Sakai et al. has been noticed for its unique photochromic properties in solvents [J. Phys. Chem. A, 125 (2021), 4784–4792]. The observed fluorescence in chloroform was attributed to the keto tautomer. Based on the excited state intramolecular proton transfer, the photochromism of 2,4-bImP in chloroform was interpreted as zwitterion production. However, the zwitterion with a specific electronic structure can be in resonance with the conventional neutral structure. The impact of the resonance contribution from the zwitterion and the conventional neutral structure on fluorescence attribution was not taken into account in the previous studies. In this investigation, the ESIPT mechanism of the 2,4-bImP in chloroform has been explored using both the density functional theory and the time-dependent density functional theory. The optimized geometric configuration parameters illustrate the molecular resonant properties. The calculated fluorescence spectra on the basis of the optimization results further corroborate that the fluorescence peaks after proton transfer originates from the resonance of the zwitterionic and the neutral configuration. The zwitterionic nature of the molecule was demonstrated by electrostatic potential and atomic dipole modified Hesfeld atomic charge (ADCH) analysis. Furthermore, the characterization of potential energy curves and IR spectrum further verified the resonance of both the zwitterionic and neutral structures. The results reveal that the 2,4-bImP molecule generates the neutral o-quinoid structure and the zwitterionic structure resonance phenomenon following ESIPT. The aforementioned resonance structure offers novel insights into the ascription of fluorescence. These discoveries establish the theoretical foundation for the exploration and development of zwitterions. [ABSTRACT FROM AUTHOR]

[Display omitted] • Interactions of phenylalanine (Phe) and Au clusters (NCs) have been studied using theory for the first time. • The NCs with magic number of electrons were the most favorable ones. • Metal-ligand intracomplex interactions were partially covalent and partially electrostatic. • The presence of gold significantly enhanced the Raman spectra signal of Phe. Nanomaterials are widely used nowadays in industry and medicine. The specific properties of gold nanoclusters (Au NCs) are chemical stability, low cytotoxicity, low photobleaching, high sensitivity to the molecular environment. This set of properties allows to use Au NCs as nanosensors in bioimaging and diagnostics. We have investigated gold cluster complexes with proteinogenic amino acid phenylalanine (Phe). Detection of phenylalanine is essential for diagnostics of phenylketonuria, vitiligo, sclerosis, cancer, tuberculosis, etc. We have studied the complexes of Phe with Au n q clusters with atomic number equal 1–6, 8, 20 and a charge equal 0–2. We have established that the clusters Au 4 0, Au 2 1+ and Au 3 2+ form the most stable complexes with Phe among NCs with charge 0, +1 and + 2, respectively. Intracomplex interactions have been studied using Atoms-In-Molecules (AIM) theory and Natural Bond Orbital (NBO) analysis. It has been shown that metal–ligand intracomplex interactions are partially covalent and partially electrostatic. Also, we have simulated the UV–vis absorption and Raman spectra of the Phe-Au NCs. We have established that the clusters possess prospective features if being used for colorimetric and Raman detection of Phe. Au 20 cluster is remarkable for its six-times enhancement of the Raman signal. Moreover, our study provides insights into metal–ligand interactions for clusters synthesized inside a polypeptide globula. Hence, to the best of our knowledge this is a first attempt to perform a detailed analysis of Phe interactions with gold using quantum chemical calculations. [ABSTRACT FROM AUTHOR]

[Display omitted] • Increasing the nitrogen content of the cyclometallated ligands lower the energy of the highest occupied molecular orbital, which was achieved by introducing 2,4′-bpy moieties. • Decreasing the electron donating ability of the ancillary ligand raise the energy of the lowest unoccupied molecular orbital, which was achieved by introducing diamine ligands. • Combining both approaches produced unexpected deep-blue emission at wavelengths shorter than 400 nm, which, to the best of the author's knowledge, has never been reported. Deep-blue emitters based on combining two approaches are reported here. In the first approach, the nitrogen content of the cyclometallated ligand is increased using 2,4′-bpy ligands, leading to a low highest occupied molecular orbital energy. In the second approach, 2,2′-bpy is replaced with a lower electron donating ligand, leading to a high lowest unoccupied molecular orbital (LUMO) energy. Thus, three new ionic transition metal complexes of [Ir(2,4′-bpy) 2 (NN)]PF 6 [where NN is 2,2′-bpy (1), o -phenylenediamine (2), and 4-methoxy- o -phenylenediamine (3)] were synthesized, and their electronic and photophysical features were studied. In solution, [Ir(2,4′-bpy) 2 bpy]PF 6 emits blue light centered at 396 nm, which is blue-shifted compared to [Ir(ppy) 2 bpy]PF 6. The low electron donation of the diamine ancillary ligands introduces the contribution of the cyclometallated ligand to the LUMO, changing the nature of the emission and leading to different photophysical features. Density functional theory calculations indicate the long bond distances of Ir–Ns at the diamine ligands, suggesting weak metal–ligand interactions and low quantum yields. 1 1 DFT Density functional theory, ECP Effective core potential, FMO Frontier molecular orbitals, HOMO Highest occupied molecular orbital, LEEC Light-emitting electrochemical cells, LUMO Lowest unoccupied molecular orbital, NMR Nuclear magnetic resonance, OLED Organic light-emitting diodes, SCF Self-consistent-field, ILCT Interligand charge transfer, LLCT Ligand to ligand charge transfer, PLQY Photoluminescence quantum yield. [ABSTRACT FROM AUTHOR]

[Display omitted] • UV high-reference differential absorption spectrometry alleviated linear deviation. • The upper limit for As(III) direct detection could be as high as 20.00 g/L. • TD-DFT results showed that redshift was related to electron transition variation. • P within 98 %-104 % and RSD of < 1.50 % indicated good accuracy and precision. • The proposed method was faster, cheaper and more eco-friendly than common methods. The current methods for determining high-concentration As(III) in the high-acid matrix from the copper smelting industry are complex, time-consuming, and costly. This limits effective modulation of sulfurizing agent dosage for As(III) removal via sulfurization, aggravating hazardous waste generation. Herein, a simple, rapid, and nondestructive UV high-reference differential absorption spectroscopy was developed to directly determine high-concentration As(III) in simulated high-acid wastewater. Time-dependent density functional theory calculations indicated that the spectral curve redshift with As(III) concentration increasing was related to the decrease of electron transition energies and energy gaps. When using high-reference solutions, the least redshift in the maximum absorption wavelength and the highest upper limit of linear fitting concentration could be obtained. Therefore, the piecewise quantitative linear model of differential absorbance and concentration was established under high-reference. The quantitative range of the model within 0.06–20.00 g/L As(III) with a mean relative error of < 5.0 % and standard recovery rates within 98.0 %-104.0 % indicated high accuracy. Additionally, the relative standard deviations of < 1.5 % (n = 5) revealed good precision. All results indicated the high feasibility of the developed method in alleviating linear deviation caused by redshift and absorption saturation. Furthermore, it has potential significance in saving sulfurizing agent dosage and reducing hazardous waste generation from the source, thereby facilitating a cleaner process for removing As(III) via sulfurization. [ABSTRACT FROM AUTHOR]

[Display omitted] • Eight new organic dyes were designed. • The photovoltaic parameters of designed dyes were evaluated. • The theoretical PCEs of M4 , M7 , and M6 are as high as 19.93%, 15.80% and 15.38%. • M4 , M7 , and M6 are potential candidates as efficient sensitizers. In this work, a series of ZL003 -based free-metal sensitizers with the donor-acceptor-π- conjugated spacer-acceptor (D-A-π-A) structure were designed by modifying auxiliary electron acceptors for the potential application in dye-sensitized solar cells. The energy levels of frontier molecular orbitals, absorption spectra, electronic transition, and photovoltaic parameters for all studied dyes were systematically evaluated using density functional theory (DFT)/time-dependent DFT calculations. Results illustrated that thienopyrazine (TPZ), selenadiazolopyridine (SDP), and thiadiazolopyridine (TDP) are excellent electron acceptors, and dye sensitizers functionalized by these acceptors have smaller HOMO-LUMO gaps, obviously red-shifted absorption bands and stronger light harvesting. The present study revealed that the photoelectric conversion efficiency (PCE) of ZL003 is around 13.42 % with a J SC of 20.21 mA·cm−2, V OC of 966 mV and FF of 0.688 under the AM 1.5G sun exposure, in good agreement with its experimental value (PCE = 13.6 ± 0.2 %, J SC = 20.73 ± 0.20 mA·cm−2, V OC = 956 ± 5 mV, and FF = 0.685 ± 0.005.). With the same procedure, the PCE values for M4 , M6 , and M7 were estimated to be as high as 19.93 %, 15.38 %, and 15.80 % respectively. Hence, these three dyes are expected to be highly efficient organic sensitizers applied in practical DSSCs. [ABSTRACT FROM AUTHOR]

[Display omitted] • Intensity of the band at 411 cm−1 is a measure of the PLLA areas crystallinity degree. • Intensities ratio of the bands at 2947 and 2914 cm−1 is a comonomer content measure. • CL content growth causes decrease in the crystallinity of PLLA blocks in copolymers. • DFT modeling: the most probable conformation of a PLLA molecule is helix 10 3. In this work, we study two series of the copolymers of L-lactide (LLA) and ε-caprolactone (CL) with the CL molar content of 5, 15, and 30 %. The first series was the commercial semicrystalline granules (Corbion, Netherlands), which we analyzed without any additional modification. The second series was amorphous films, prepared from the granules by hot pressing with the subsequent fast quenching in order to avoid the crystallization. We used Raman spectroscopy in conjunction with the quantum chemical modeling to evaluate the structure of the copolymers. As additional methods, we applied X-ray diffraction (XRD) analysis and differential scanning calorimetry (DSC). The main result of our study is the elaboration of the Raman methods of quantitative analysis of the relative contents of the comonomers and the crystallinity degree of the poly(L-lactide-co-ε-caprolactone). These methods are based on measurements of the ratios of the peak intensities of the poly(L-lactide) (PLLA) bands at 411 and 874 cm−1, the PLLA band at 2947 cm−1 and the poly(ε-caprolactone) band at 2914 cm−1. Raman study shows that growth of the CL content causes the monotonous decrease in the crystallinity degree of PLLA blocks. Density functional theory analysis of LLA decamer in the conformation of helix 10 3 allows us to assign the PLLA Raman bands. The Raman data on the composition and crystallinity degree of the copolymers correlate very well with the results of XRD and DSC studies, as well as with the information on the composition of the copolymers provided by manufacturer. [ABSTRACT FROM AUTHOR]

[Display omitted] • BT-based organic BT-A1-BT-A8 molecules are successfully considered as organic solar cells and non-linear optical study. • To discern the kind and character of intermolecular interactions among all molecules, NCI and RDG analyses were performed. • PCE of all molecules was nearly the same compared to the BT. • BT-A7 and BT-A8 molecules are smaller E g , compared to BT and other compounds. • The compounds BT-A2, BT-A6 and BT-A7 were good NLO performance. Eight molecular structures (BT-A1 to BT-A8) with high-performance non-fullerene acceptor (NFA) were selected for organic solar cells (OSCs) and non-linear optical (NLO) applications. Their electronic, photovoltaic (PV) and optoelectronic properties were tuned by adding powerful electron-withdrawing groups to the acceptor (A) of the D-π-A-π-D structure. Using time-dependent density functional theory (TD-DFT) techniques, based on the laws of quantum chemical calculations, the absorption spectra, stability of the highest and lowest-energy molecular orbitals (HOMO/LUMOs), electron density, intramolecular charge transfer (ICT), transition density matrix (TDM), were examined. The binding energy (E b) and density of states (DOS) were probed to realize the optoelectronic analysis of the structures BT-A1 to BT-A8. Noncovalent interactions (NCIs) based on a reduced density gradient (RDG) were used to describe the nature and strength of D-A interactions in the molecules BT-A1 to BT-A8. The new refined molecules BT-A1 to BT-A8 exhibited strong absorbance bands between 408–721 nm and high electron transfer contribution (ETC) ranges between 87–96 %, along with the smallest excitation energies (E x) between 1.71–3.55 eV in the solvent dichloromethane. Dipolar moment strengths ranging from 0.38 to 4.72 Debye in both the excited and ground states have determined with good solubility properties of BT-A1 to BT-A8 in polar solvent. Highly effective charge mobilities and prevention of charge recombination have been demonstrated by the electron (0.18–0.41 eV) and hole RE values (0.13–0.89 eV) for the new compounds. Power conversion efficiencies (PCE) of BT-A1 to BT-A8 were nearly the same because of better outcomes compared to the molecules in the BT. Compared to poly[4.8-bis(5-(2-ethylhexyl)thiophen-2-yl)benzo[1,2-b: 4,5-b']dithiophene-2,6- diyl-alt-(4–2-ethylhexyl)-3-fluorothieno[3,4-b]thiophene-)-2-carboxylate-2–6-diyl)] (PTB7-Th), the open circuit voltages (V oc) of compounds BT-A1 to BT-A8 were ranged from 1.52 to 2.13 eV. The polarizability (α) and hyperpolarizability (β) of the molecules BT-A1 to BT-A8 were used to determine the non-linear optical (NLO) properties. The results showed that BT-A2, BT-A6 and BT-A7 have good NLO activity. This computational analysis demonstrates the superiority of the molecules with NFA. Hence the compounds are advised for the use in production of high-performance OSCs and NLO activity. [ABSTRACT FROM AUTHOR]

[Display omitted] • CREST-xTB is proposed as a promising approach for sampling nifurtimox structures. • IR spectra of the nifurtimox sampled structures were calculated by DFT. • Nifurtimox IR fingerprint region was accurately assigned. • Nifurtimox presents higher molar absorptivity in aprotic than protic solvents. Considering the health relevance of Chagas' disease, recent research efforts have focused on developing more efficient drug delivery systems containing nifurtimox (NFX). This paper comprehensively investigates NFX through conformational analysis and spectroscopic characterization. Using a conformer-rotamer ensemble sampling tool (CREST-xtb), five distinct conformers of NFX were sampled within a 3.0 kcal mol−1 relative energy window. Subsequently, such structures were used as inputs for geometry optimization by density functional theory (DFT) at B3LYP-def2-TZVP level of theory. Notably, harmonic vibrational frequencies were calculated to establish an in-depth comparison with experimental results and existing literature for the NFX or similar molecules and functional groups, thereby achieving a widely reasoned assignment of the mid-infrared band absorptions for the first time. Moreover, UV–VIS spectra of NFX were obtained in several solvents, enabling the determination of the molar absorptivity coefficient for the two electronic transitions observed for NFX. Among the aprotic solvents, a bathochromic effect was observed in the function of the dielectric constants. Furthermore, a hypochromic effect was observed when the drug was dissolved in protic solvents. These findings offer crucial support for new drug delivery systems containing NFX while demonstrating the potential of spectrophotometric studies in establishing quality control assays for NFX drug products. [ABSTRACT FROM AUTHOR]

[Display omitted] • The chemosensor TZTS thiazole and thiosemicarbazide fluorophore for effectively sensing As3+ ions with high selectivity and sensitivity. • The TZTS-probe Schiff base was characterized via FT-IR, 1H and 13C NMR, & HRMS analysis. • The limit of detection (LOD) for As3+ ions was calculated to be 16.5 and 7.19 × 10−9 M. • Fluorescence imaging experiments of As3+ ions in the breast cancer cell line (MCF-7) demonstrated their practical applications in biological systems. A Schiff-base Ethyl (E)-2-(3-((2-carbamothioylhydrazono)methyl)-4-hydroxyphenyl)-4-methylthiazole-5-carboxylate (TZTS) dual functional colorimetric and photoluminescent chemosensor which includes thiazole and thiosemicarbazide has been synthesized to detect arsenic (As3+) ions selectively in DMSO: H 2 O (7:3, v/v) solvent system. The molecular structure of the probe was characterized via FT-IR, 1H, and 13C NMR & HRMS analysis. Interestingly, the probe exhibits a remarkable and specific colorimetric and photoluminescence response to As3+ ions when exposed to various metal cations. The absorption spectral changes of TZTS were observed upon the addition of As3+ ions, with a naked eye detectable color change from colorless to yellow color. Additionally, the chemosensor (TZTS) exhibited a new absorption band at 412 nm and emission enhancements in photoluminescence at 528 nm after adding As3+ ions. The limit of detection (LOD) for As3+ ions was calculated to be 16.5 and 7.19 × 10−9 M by the UV–visible and photoluminescent titration methods, respectively. The underlying mechanism and experimental observations have been comprehensively elucidated through techniques such as Job's plot, Benesi-Hildebrand studies, and density functional theory (DFT) calculations. For practical application, the efficient determination of As3+ ions were accomplished using a spike and recovery approach applied to real water samples. In addition, the developed probe was successfully employed in test strip applications, allowing for the naked-eye detection of arsenic ions. Moreover, fluorescence imaging experiments of As3+ ions in the breast cancer cell line (MCF-7) demonstrated their practical applications in biological systems. Consequently, these findings highlight the significant potential of the TZTS sensor for detecting As3+ ions in environmental analysis systems. [ABSTRACT FROM AUTHOR]

Schiff base alkyne 4 and it linked 1,2,3-triazole silane 5 has been synthesized, UV–visible sensing study of synthesized compound 4 and 5 have been performed, both are efficient to detect Zn(II) ion but the compound 5 has lower value of molar concentration to Zn(II) with limit of detection (LOD) value (1.4 x 10-6M), also the mode of binding interaction between compound 5 and Zn(II) was verified by computational Density functional theory (DFT) study was evaluated. Also the synthesized compound 5 has antioxidant properties by potential to scavenge 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical. UV–visible Sensing. [Display omitted] • Schiff base functionalized 1,2,3-triazole silane (5) has been synthesized. • Chemosensor 5 is essentially to detect Zn(II) ion analyte. • The proper binding site of Zn(II) to probe 5 is computationally evaluated through DFT study. • Antioxidant activity exhibited by the probe 5 is nearly as potential as Ascorbic acid. Schiff base linked1,2,3-triazole silane 5 has been synthesized through the Schiff base terminated alkyne with azido via click chemistry,the compound 4 structure elucidated through X-ray crystallography, and the compound 5 is well characterized through different techniques such asFT-IR, 1H and 13C NMR and Mass spectrometry. UV–visible sensing studies of synthesized compounds 4 and 5 have been performed, and both are efficient in detectingZn(II) ion, but compound 5 has imparted a higher mode of attraction to Zn(II) with limit of detection (LOD) value (1.4 x 10-6M) wherethe compound 4 is calculated to be (1.25 x 10-5M). By Job's method, the stoichiometric ratio of compound 5 and Zn(II) iscalculated to bea 1:1 ratio. The complex of compound 5 with Zn(II) was prepared. A radical and oxidative species are responsible for the deteriorating of stabilized molecules. The synthesized compound 5 hasantioxidant propertiesthat can potentially scavenge 2,2-diphenyl-1-picrylhydrazyl (DPPH) radicals. Further to verify the mode of binding interaction between compound 5 andZn(II), computational Density functional theory (DFT) study was evaluated. [ABSTRACT FROM AUTHOR]

[Display omitted] • A novel symmetrically double-armed salamo type fluorescent sensor BMS was synthesized. • The high sensitivity and selectivity of BMS in the recognition of MnO 4 - were investigated. • The limit of detection (LOD), limit of quantification (LOQ), and the binding constant (K a) were calculated. • The recognition mechanism of MnO 4 - by BMS has been postulated. • The energy gaps before and after recognition were analyzed by DFT calculation. The symmetrically double-armed salamo type fluorescent sensor BMS , incorporating benzimidazole units, was designed and synthesized. Showcasing remarkable specificity and responsiveness to MnO 4 - within a DMSO:H 2 O (V/V = 9:1, pH = 7.2) Tris-HCl buffer medium, it enabled dual-channel detection of MnO 4 - through fluorescent and colorimetric changes. Critical experimental parameters, including detection and quantification thresholds (LOD and LOQ) along with binding affinity constants (K a), were calculated using the Origin software. A rational interaction mechanism between BMS and MnO 4 - was deduced, based on fluorescence titration, Electrospray Ionization Mass Spectrometry (ESI-MS), Ultraviolet–Visible Spectroscopy (UV–Vis), Infrared Spectroscopy (IR), Stern-Volmer plots, and Density Functional Theory (DFT) computations. Additionally, the sensor BMS was applied to monitor MnO 4 - in real water samples. Advancing its practical utility, BMS was fabricated into test strips for the selective detecting of MnO 4 -. [ABSTRACT FROM AUTHOR]

[Display omitted] • Theoretical study on one-photon and two-photon absorption spectra of V-shaped and Y-shaped branching oligofluorenes. • Detail analysis on photoinduced electron excitation characteristics of the four branching oligofluorenes. • TPA cross-section can be significantly enhanced by increasing the branch length or changing the structure. • V-shaped oligofluorenes display a stronger cooperative effect among the different branches. Oligofluorenes have been identified as very promising two-photon absorption (TPA) materials and present great application potential for the fabrication of nonlinear optical devices, but the TPA mechanism and corresponding electron excitation properties have not been studied. Here, the photoinduced charge transfer characteristics of V-shaped and Y-shaped branching oligofluorenes that consist of two and three fluorene units in each branch during one-photon absorption (OPA) and TPA processes are analyzed theoretically using the density functional theory and visualization sum-over-states model. The calculated results show that the OPA intensity and TPA cross-section are significantly enhanced by increasing the branch length or changing the structure from V-shaped to Y-shaped. The long-distance charge transfer only occurs on the second transition of TPA at high excited states. Compared to Y-shaped molecules, V-shaped structures exhibit a stronger cooperative effect among the different branches. [ABSTRACT FROM AUTHOR]

[Display omitted] • Energy of FL emission of kaempferol powder and solutions was measured and calculated. • ESIPT process in KMP molecule was considered taking into account two keto forms. • FL of KMP powder is due to keto O5 form emission. • FL in solutions with low concentration is due to emission of keto O3 form. • Formation of ions in KMP crystal as a result of the ESPT process is considered. Kaempferol (KMP) is one of the most common flavonoids, currently being extensively studied for its numerous beneficial health effects. Here we study the fluorescence (FL) emission of KMP powder and of its solutions prepared using different types of solvents (polar and non-polar). In the spectra of KMP powder and KMP solutions with high concentration, the same FL peak with maximum at 1.9 eV is observed. Another FL peak, at higher energy of 2.45 eV, emerges in solutions, its relative intensity increases with decreasing solution concentration. The FL emission of solutions with lowest concentration displays only that peak. To calculate characteristic energies of absorption and emission of KMP molecule in vacuum and in solutions we use time-dependent density functional theory. Comparing the results of computations with measured FL spectra, we associate the FL band at 1.9 eV with the emission due to excited state intramolecular transfer of the proton of –OH5 hydroxyl group. The FL emission at 2.45 eV is related to the –OH3 proton transfer. We measure the FL spectra of KMP powder using two different excitation energies, 3.06 eV and 2.33 eV, and find that its FL spectrum depends on the excitation energy. To understand that dependence, we compare the FL spectra of KMP and Q monohydrate powders. We consider the excited state intermolecular transfer of the proton from –OH3′ hydroxyl group to a neighboring molecule in Q crystal and calculate the energy corresponding to the emission of the resulted anion of Q molecule. The spectral feature at 1.69 eV observed only in the FL spectrum of Q hydrate is attributed to the Q anion FL emission. [ABSTRACT FROM AUTHOR]

[Display omitted] • After introducing the amino, methoxy and naphthalene groups, the designed molecules have better photoelectric properties. • The property and position of substituents and conjugation can effect the photophysical properties and ESIPT process of HID. • The substitution and conjugation effects can affect the charge transfer capacity. 4-Aminophthalimide is a highly fluorescent signaling unit with excellent photophysical properties and wide application foregrounds. Based on this, a range of theoretical investigations are conducted on the fluorescent probe (E)-5-((2-hydroxybenzylidene) amino) isoindoline-1, 3-dione (HID) with the core of 4-aminophthalimide using density functional theory (DFT) and time-containing density functional theory (TD-DFT) methods in this paper. The optimized configurations, vertical excitation and emission energies, electronic characteristics and excited-state intramolecular proton transfer (ESIPT) behaviors of the probe HID are discussed in detail. Furthermore, to enhance the luminescent properties of HID, five novel compounds have been designed based on the structure of HID by introducing amino, methoxy and naphthalene groups (–NH 2 , –OMe and C 10 H 8). Our work thoroughly explores how the property and position of substituents and conjugation affect photophysical characteristics and ESIPT processes. We find that the ESIPT dynamics can be modulated by the substitution and conjugation effects. Specifically, the introduction of amino and methoxy groups at the ortho -position and the introduction of the naphthalene group promote the ESIPT behavior of HID1, whereas the introduction of amino and methoxy groups at the meta -position exhibits the contrary impact. Therefore, we boldly infer that the introduction of electron-donating groups in the ortho -position and the introduction of the conjugated group make the ESIPT process more effortless to occur, whereas the introduction of substituents with opposing natures in the meta -position makes the ESIPT process more difficult to occur. In addition, the ionization potentials (IP), electron affinities (EA) and reorganization energies (λ h and λ e) of molecules are calculated to assess their potential as luminescent materials. Our work not only reveals the luminescence and ESIPT mechanism of the probe HID1, but also proposes to modulate the ESIPT process through the substitution and conjugation effects. In particular, the designed molecules have better photoelectric properties as a result of their red-shifted absorption and fluorescence spectra, smaller energy gaps, larger transferred charges and greater charge transferred distances, which offers some valuable ideas for the experimental development of more efficient organic luminescent materials with ESIPT properties. [ABSTRACT FROM AUTHOR]

HL, 1:2 condensation product of 2,6-diformyl-4-ethylphenol and o -anisidine, is the first example or a very rare example of fluorescent ZnII sensors, where all of ESIPT, TICT and AIEE occur and the existence of the three aspects is well established by experimental and theoretical studies. Unusual features in the structures of zinc(II) and cadmium(II) complexes derived from HL have been found. [Display omitted] • HL is the 1:2 condensation product of 2,6-diformyl-4-ethylphenol and o -anisidine. • HL is a fluorescent turn on ZnII sensor which exhibits AIEE, ESIPT and TICT. • Crystal structures of HL and it's both ZnII and CdII complexes are determined. • HL is applied in inkless writing with the "write − erase − write" facility. • DFT calculations in both ground and excited states have been done. The basic systems in this study are HL (1 ; 1:2 condensation product of 2,6-diformyl-4-ethylphenol and o -anisidine) and its ZnII and CdII complexes of composition [ZnII(LH)Cl 2 ]·CH 3 OH (2) and [CdII(LH)Cl 2 ] (3), all of which are synthesized and characterized by CHN elemental analyses, single crystal X-ray crystallography, powder X-ray diffraction (PXRD) and fourier transform infrared (FT-IR) spectrum. It has been established from the following experimental and theoretical studies that 1 is a fluorescent turn on sensor of ZnII ion and it exhibits all of excited state intramolecular proton transfer (ESIPT), photoinduced electron transfer (PET), twisted intramolecular charge transfer (TICT) and aggregation induced enhanced emission (AIEE): (i) Detailed absorption and emission (steady state / time resolved) studies in various single solvents, in solvent mixtures, with pH variation, with various single metal ions, with mixtures of metal ions, on varying temperature and on varying viscosity; (ii) dynamic light scattering (DLS) and scanning electron microscopy (SEM) in solvent mixtures; (iii) density functional theory (DFT) and time dependent density functional theory (TD-DFT) calculations in ground and excites states of 1 – 3. It is shown that 1 can be efficaciously applied in inkless writing with the "write − erase − write" facility. The mechanisms/reasons of the observed properties have been addressed. The difference in fluorescence of ZnII and CdII complexes, unusual case of crystal structures of probe and complexes with ZnII and CdII, unusual features in the structures of 2 and 3 as well as a structure–property correlation have been discussed. [ABSTRACT FROM AUTHOR]

Effect of the excitation wavelength on the fluorescence emission spectrum of (II) in acetonitrile. [Display omitted] • Fluorosolvatochromism is studied for a couple of D-π-A+ nicotinamidine derivatives. • Dual emission is reported and is introduced as white light emitters. • Specific and non-specific interactions were investigated using Catalán's and Laurence's linear solvation energy relationships. • Non-specific interactions were found to dominate the photophysical properties with a considerable contribution of the specific interactions. Photophysical behavior of two D − π − A+ cationic compounds with the same furyl bridge and nicotinamidine group as an electron acceptor moiety and two electron donating groups, namely methoxy (I) and N , N -dimethylamino (II) groups was examined using steady-state and time-resolved techniques in variety of solvents. Time-dependent density functional theory (TDDFT) calculations were performed in some representative solvents and compared with the experimental results. Steady state and time-resolved studies in different solvents reveal that fluorescence emission of (I) is ascribed to an emission from an excited state (ICT) with higher dipole moment than the ground state while the emission of (II) is a dual emission from a state with high charge transfer nature (ICT) in addition to the locally excited state (LE). The fluorescence emission spectra of (II) were found to depend on the excitation wavelength and an increase in the excitation wavelength led to the formation of a longer wavelength emission band with lower quantum yield. It has also been found that the fluorescence excitation spectra were dependent on the emission wavelength. The effect of solvent on the nature of dual emission was examined. Correlation of the photophysical properties of the excited states of (I) and (II) with the solvent polarity, ε, reveals the charge transfer nature of (I) and the long wavelength emission band of (II), while their correlation with the solvent polarity parameter (E T N) shows two different trends when the solvents are divided to aprotic and protic solvents. For precise investigation of the impact of each solvent parameter on each photophysical property, Catalán's and Laurence's four parametric linear solvation energy relationships were studied. We have found that the non-specific interactions of the solvent are primarily responsible for controlling the photophysical properties, as demonstrated by Catalán's and Laurence's treatments. DFT and TDDFT calculations were used to anticipate the dipole moments in the ground and excited states and geometry of both states. [ABSTRACT FROM AUTHOR]

[Display omitted] • A new chalcone chemosensor like 6-cinnamoylthiochroman-4-one, and its amino derivatives have been synthesized. • The sensors can selectively recognize and sense the metal cations even at very low concentrations. • The measured fluorescence intensity [1/(F − F0)] at 625 nm fluctuates as a function of 1/[Cr3+] in a linear relationship. • The binding constant and detection limit of chemosensor to Cr3+ was found to be 1.684 × 105 M−1 and 0.2245 × 10−9 M respectively. • The ground-state geometry of the compound and its derivatives were optimized with B3LYP function and 6-31G(d,p)basis set. A new chalcone based chemosensor like 6-cinnamoylthiochroman-4-one (AZAN), has been designed and synthesized from 6-chlorothiochroman-4-one and cinnamaldehyde via keto ethylenic linkage. Its amino derivatives were synthesized by using urea (AZANU) , thiourea (AZANTU) and 2,6-diamino pyridine (AZANPy) respectively and its metal ion sensing properties were investigated. The sensors can selectively recognize and sense the metal cations by showing different fluorescent characteristics at different concentrations. The fluorescence intensity shows remarkable enhancement by Cr3+ over other common metal ions (Cd2+, Hg2+ and Pb2+). The proposed mechanism can be confirmed by UV–Vis and emission titration. The newly synthesized receptor can sense the metal ions even in nano molar level. The binding or association constant and detection limit of chemosensor to Cr3+ are 1.684 × 105 M−1 and 0.2245 × 10−9 M respectively. A computation using the density functional theory was done to gain detailed insights into the electronic structures of the ligand and its derivatives. B3LYP function and 6-31G(d,p) basis set were used to optimize the ground-state geometry of the chemical and its derivatives. [ABSTRACT FROM AUTHOR]

[Display omitted] • Investigation of sensing nature of functionalized coronene quantum dot. • Frontier molecular orbitals and molecular electrostatic potential surface validates their chemical stability. • Higher adsorption energy was observed for gas molecules on quantum dot. • Light harvesting efficiency of functionalized quantum dots was elevated. • The designed quantum dots have potential applications in gas sensing and photosenstivity. The present study accounts for the structural and electronic properties of a zero-dimensional coronene quantum dot (QD) and its substituted structures with seven different functional groups. The substitution of functional groups lead to the alteration of the centrosymmetric geometry of the coronene flake and thus, incredible properties were observed for the functionalized QDs. The increment in the band gap after the substitution of the functional groups was responsible for the increase in the chemical stability. The cohesive energy however decreased for the functional QDs. Fourier transform Infrared spectra were traced for all the QDs to confirm the availability of the functional groups and their participation in the chemical reactivity. After the substitution of functional groups, the extremely enhanced light harvesting efficiency of functionalized QDs was obtained. Furthermore, the sensing capability of the functionalized QDs for CO, CO 2 , and NH 3 was also calculated and it was found that C-cyano, C-nitro, C-nitroso, C-pyrrolidine, and C-thionyl QDs have better sensing capabilities for CO 2 molecules. C-pyrrolidine had the highest value of light harvesting efficiency of about 96%. This reflects the potential photosensitive candidature of C-pyrrolidine. Therefore, the present study sets a perfect benchmark for designing and fabricating efficient photosensitive materials and gas-sensing devices using the introduced QDs in the near future. [ABSTRACT FROM AUTHOR]

Zn-H 2 CIA-1 and Cd-H 2 CIA-2 showed different fluorescence intensities, fluorescent probe sensitivities, and combined experiments and DFT calculations proved that photo-induced electron transfer was the main fluorescence quenching mechanism. [Display omitted] • The fluorescent Zn/Cd isomeric coordination polymers were synthesized. • The polymers exhibit considerably highly selective for NB in aqueous. • Photo-induced electron transfer was the main cause of fluorescence quenching. • The appropriate pore size makes Zn-H 2 CIA-1 highly selective for NB. • Intermolecular π-π stacking interactions result in the transfer of electrons. Nitroaromatic compounds in aqueous undermine environmental sustainability and affect human health. The development of a fluorescent sensor capable of efficiently and selectively detecting trace amounts of nitroaromatic compounds presents a considerable challenge. This study introduced Zn/Cd isomeric coordination polymers (Zn-H 2 CIA-1/Cd-H 2 CIA-2), which are synthesized using 5-((4-carboxybenzyl)oxy)isophthalic acid (5-H 3 CIA) and 1,10-phenanthroline (Phen). The polymers have zero-dimensional discrete crystal structure with a six-coordinated scissor-like shape. The two coordination polymers can be used as fluorescent sensors for detecting nitrobenzene (NB) and demonstrated favorable sensitivity, with detection limits of 1.95 × 10−8 and 4.66 × 10−7 mol/L, respectively. Zn-H 2 CIA-1 exhibited stronger fluorescence and a more sensitive response to NB compared with Cd-H 2 CIA-2. To elucidate their fluorescence-quenching mechanisms, we analyzed Zn-H 2 CIA-1 by performing DFT and TD-DFT calculations. The pore structure, density of states, excitation energy, hole–electron distribution, and orbital composition were analyzed. The suitable size of pores in Zn-H 2 CIA-1 is the main reason for its high NB selectivity. Moreover, intermolecular π-π stacking interactions result in an orbital overlap between Zn-H 2 CIA-1 and NB, enabling the transfer of electrons from Zn-H 2 CIA-1 to NB. This electron transfer is identified as the fundamental cause of fluorescence quenching in Zn-H 2 CIA-1. [ABSTRACT FROM AUTHOR]

[Display omitted] • Both shikonin and acetylshikonin exhibit dual proton transfer characteristics. • Solvent polarity affecting ESDPT properties is investigated in detail. • Both shikonin and acetylshikonin are more likely to undergo stepwise double proton transfer. • Acetylshikonin possesses one additional reaction path compared to shikonin. The excited state double proton transfer (ESDPT) mechanism of shikonin (Shk) and its derivative acetylshikosin (AcShk) were studied by density functional theory (DFT) and time-dependent density functional theory (TD-DFT) methods. The potential energy curves scanned along the coordinates of proton transfer indicate a preference for the ESDPT reaction to occur step by step. The AcShk molecule possesses an additional reaction pathway in comparison to the Shk molecule. Furthermore, efforts have been made to compute the absorption and fluorescence peak, which exhibits favorable conformity with the experimental findings of the system investigated. The fluorescence spectra in cyclohexane and acetonitrile solvents indicate that the solvent polarity affects the location of the ESDPT fluorescence peak in both Shk and AcShk systems. The fluorescence spectra concentrated in the green light region (504 nm ∼ 550 nm) are obtained, which has the potential to promote human health through disinfection and boosting the immune system. [ABSTRACT FROM AUTHOR]

[Display omitted] • Long-range and short-range charge transfer ratios are regulated and excited state properties are successfully modulated. • Deeper insights into long-range and short-range charge transfer features in balancing small ΔE ST and large f are illustrated. • Previous experimental measurements are reasonably explained and new efficient TADF molecules are theoretically proposed. Balancing the rapid radiative decay process and the fast reverse intersystem crossing (RISC) process of thermally activated delayed fluorescence (TADF) molecule remains a great challenge and efficient molecular design strategies are highly desired. Herein, from a theoretical perspective, excited state properties of three reported TADF molecules (1TICz, 1BOICz and 2BOICz) are investigated based on density functional theory (DFT) and time-dependent density functional theory (TD-DFT) calculations coupled with the thermal vibration correlation function (TVCF) method. Results indicate that, by introducing the multi-resonance (MR) acceptor, 1BOICz possesses hybrid long-range and short-range charge transfer features, balanced small energy gap (ΔE ST) and large oscillator strength (f) is obtained. Furthermore, by incorporating double equivalent MR acceptors in 2BOICz, largely enhanced f with slightly changed ΔE ST is achieved, inner mechanism for remarkable photophysical property is illustrated. Keep this strategy, seven new TADF molecules (2pDBA-bICz-1, 2pDBA-bICz-2, 2OSBA-bICz, 2DQAO-bICz, 2QAO-bICz, 2SQAO-bICz and 2OQAO-bICz) are theoretically designed, detailed physical parameters are analyzed and excited state energy consumption process is studied. Strong electrophilicity on acceptor is determined and the strength of nucleophilic sites on the bridge-phenyl of 2DQAO-bICz, 2QAO-bICz, 2SQAO-bICz and 2OQAO-bICz is increased, this promotes the short-range charge transfer property. In addition, the excitation processes for all studied molecules are dominated by long-range charge transfer from donor to acceptors, and supplemented by the short-range charge transfer on the bridge-phenyl with MR effect. Compromise energy gap and oscillator strength as well as large spin orbit coupling (SOC) constant are obtained for designed molecules. Thus, by regulating the long-range and short-range charge transfer ratios, excited state properties are successfully modulated and new efficient TADF molecules are proposed. Our research aims to provide deeper insight into long-range and short-range charge transfer features in balancing small ΔE ST and large f , which could facilitate the development of novel efficient TADF molecules. [ABSTRACT FROM AUTHOR]

[Display omitted] • An experimental/theoretical analysis was performed on the tripeptide Gly-Tyr-Gly. • Room-temperature Raman spectra of the tripeptide recorded in H 2 O and D 2 O were described. • Among the seven markers from the Tyr residue, attention was focused on the 850–830 cm−1 doublet. • The performances and deficiencies of three functionalsB3LYP, M062X and ωB97XD,were described. • The widely discussed reversal of the Tyr doublet relative intensity is of conformational nature, depending on the side chain χ 1 torsion angle. Tyrosine (Tyr) residue in a peptide chain is characterized by the presence of seven Raman markers, referred to as Y i (i = 1, ..., 7), distributed over the middle wavenumber spectral region. Particularly, the changes observed in the relative intensity of Y 5 and Y 6 markers, appearing as a side by side doublet at ca. 850–830 cm−1, has received a great attention. Primarily assigned to a Fermi-resonance effect between phenol ring planar and nonplanar modes, former density functional theory calculations led us to affiliate the Y 5 –Y 6 doublet to two distinct fundamental modes. Furthermore, despite the previous assumptions, it was evidenced that the reversal of the doublet intensity ratio cannot be solely explained by hydrogen bonding on the phenol hydroxyl group involved in Tyr. Herein, upon analyzing the observed and theoretical data collected from the cationic species of the tripeptide Gly-Tyr-Gly, the crucial effect of the aromatic side chain orientation, especially that of the χ 1 torsion angle defined around the C α C β bond, on the Tyr doublet intensity ratio has been evidenced. [ABSTRACT FROM AUTHOR]

[Display omitted] • NGQDs were synthesized using bamboo fiber powder and urea as green precursors. • The reliability of the fabricated NGQDs was demonstrated to sense Fe3+ and GSH. • DFT calculations were used to understand the mechanism involved. • The NGQD/Fe3+ system fabricated has the potential to detect GSH in real samples. Developing a sensing platform that can quickly and accurately measure glutathione (GSH) is crucial for the early detection of various human diseases. GQDs have shown great potential in many technological and biological applications. This study focused on synthesizing nitrogen-doped GQDs (NGQDs) with stable blue fluorescence using a simple and easy hydrothermal method in one step. The bamboo fiber was used as the green source for this synthesis. The NGQDs had a tiny particle size of 4.7 nm and emitted light at 405 nm when excited. They displayed a remarkable quantum yield of 40.36 % and were effectively used as fluorescent probe to specifically detect Fe3+. The energy transfer mechanism led to the NGQDs' fluorescence being deactivated by Fe3+ ions (turn- "off"). However, with the addition of GSH to the system, the fluorescence intensity of NGQDs was reactivated (turn- "on"). Thus, a fluorescence turn "off–on" system was developed for the sensitive detection of Fe3+ and GSH. Using density functional theory (DFT), it was theoretically calculated that the surface of the fabricated NGQDs possess lone pairs of electrons on oxygens and doped nitrogen causing a photo-induced electron transfer (PET) process to occur. This PET process was suppressed previously owing to complex formation between oxygen atoms of modeled structure and ferric ions. The sensing platform displayed a sensitive response to Fe3+ in the 1–1000 μM range with LOD of 34 nM and GSH in the range of 1–50 μM, with a detection limit of 45 nM. Furthermore, the NGQDs exhibited high selectivity towards Fe3+ and GSH over other electrolytes and biomolecules. Additionally, the probe exhibited non-cytotoxicity and was practically applicable for the detection of GSH in HeLa cells. [ABSTRACT FROM AUTHOR]

[Display omitted] • Photophysical and photochemical properties of DOX were studied. • Transient species formed after photoexcitation of DOX were identified. • Density functional theory computation of spin–orbit couplings and transient spectra. • Mechanism of photoinduced electron transfer was proposed. Doxazosin is a quinazoline derivative widely used in medicine as a drug. In this study, a combined experimental and computational approach based on the time-dependent density functional theory was used to elucidate the primary events following the photoexcitation of DOX upon interaction with light. The photophysical properties and photochemical reactivity of DOX were investigated by steady-state and time-resolved absorption and fluorescence spectroscopy. DOX in H 2 O in S 0 is present in two prototropic forms, with the protonated form dominating (∼91 %, p K a = 6.75). The computations indicated that the most basic quinazoline nitrogen is at the position 1. Upon excitation, DOX deprotonates in the singlet excited state (p K a * = 1.31), and the decay times from the singlet excited state of 5 ns and 13 ns are attributed to the non-protonated and protonated forms of DOX, respectively. The quantum yield of fluorescence in H 2 O is 0.51 and 0.64 in basic media. The quantum yield of intersystem crossing along with triplet–triplet molar absorption coefficient at 520 nm and the lifetime of the triplet excited state were obtained by LFP, Φ ISC = 0.17, ε 520 = 11600 ± 100 M−1 cm−1 and τ = 11 μs, respectively. Furthermore, LFP enabled detection of DOX radical formed by the photoinduced intramolecular electron transfer from the benzodioxane-carbamoyl to the protonated aminoquinazoline. Computations were used to back up the assignments of the detected transients and to construct an energy diagram with all plausible photophysical and photochemical pathways. These results elucidated the mechanisms of DOX photochemistry leading to DOX photodegradation which is relevant to environmental studies. They also provided insights into the potential use of such a quinazoline derivative in other applications such as push–pull chromophores or fluorescent probes. [ABSTRACT FROM AUTHOR]

[Display omitted] • Trifluoromethylphenyl and phenoxazinyl or phenothiazinyl compounds are presented. • The position of their 1CT emission band is polarity-dependent. • Phenoxazinyl disubstituted trifluoromethylphenyl shows efficient TADF properties. • Its' small singlet-triplet energy splitting is facilitated by spin-orbit coupling. • Phenothiazine derivative has efficient RTP that shows oxygen sensitivity. Two compounds consisting of electron-accepting trifluoromethylphenyl moiety and electron-donating phenoxazine and phenothiazine moieties were designed and synthesized via Buchwald-Hartwig coupling reaction. Thermal, photophysical, and electrochemical properties of the compounds are discussed. Only compound with phenothiazine form molecular glass, with glass transition temperatures of 90 °C. The geometry and electronic characteristics of the compounds were substantiated within density functional theory (DFT). 10,10′-(2-(Trifluoromethyl)-1,4-phenylene)bis(10 H -phenoxazine) shows efficient thermally activated delayed fluorescence with high spin-orbit coupling values. 10,10′-(2-(Trifluoromethyl)-1,4-phenylene)bis(10 H -phenothiazine) as efficient room-temperature phosphor shows high oxygen sensitivity. [ABSTRACT FROM AUTHOR]

[Display omitted] • A benzimidazole-based probe BIPMA was synthesized for detecting Cu2+ ions. • BIPMA exhibits a fluorescence "turn-on" mechanism upon binding with Cu2+ ions. • BIPMA can estimate Cu2+ concentrations in the nanomolar range. • The response time of BIPMA toward Cu2+ ions is ultrafast. • BIPMA estimates Cu2+ ion concentration in real water samples and image living cells. A benzimidazole-based probe, BIPMA (2-(1 H -benzo[ d ]imidazol-2-yl)- N -(pyridin-2-ylmethyl)aniline), was designed and synthesized to detect Cu2+ ions. BIPMA exhibited a fluorescent "turn-on" mechanism when bound to Cu2+ ions in an acetonitrile/water mixture (5:5, v/v, HEPES 10 mM, pH 7.4) owing to the synergistic effect of the chelation-enhanced fluorescence and internal charge-transfer mechanisms. Moreover, the BIPMA probe effectively detected nanomolar-range concentrations (0–400 nM) of Cu2+ ions in an aqueous system with a detection limit of 4.80 nM; this value is significantly lower than that set by the U.S. Environmental Protection Agency (≈20 μM). Additionally, BIPMA showed an ultrafast response to Cu2+ ions, with a maximum intensity achieved 25 s after adding Cu2+. Furthermore, BIPMA detected Cu2+ ions in solutions with a pH range of 5–11, without being influenced by pH, underscoring its applicability under various physiological conditions. Density functional theory studies revealed that internal charge transfer was responsible for emission. Finally, BIPMA effectively detected Cu2+ ions in real water samples and living cells. [ABSTRACT FROM AUTHOR]

The CH 3 CN–CH 3 OD complex broken out by the IL is the cause of the breaking azeotropy of the methanol–acetonitrile mixtures. [Display omitted] • The structural properties of IL-azeotrope (acetonitrile–methanol) mixtures are studied. • Mixing process is nonideality with interaction occurring between three components. • The species transformation with the adding IL was identified. • The nature of the phase equilibrium changes in the azeotrope was revealed. Understanding the structural properties of ionic liquids (ILs) in azeotrope mixtures is crucial for designing and synthesizing IL entrainers tailored for extractive distillation. While extensive research has been conducted to comprehend the molecular properties of IL systems, much of this work has been limited to IL-cosolvent binary mixtures and fails to fully capture the essence of breaking azeotropy. In this study, we utilized Fourier-transform infrared spectroscopy (FTIR) and density functional theory (DFT) calculations to study the microstructure of the IL-azeotropic system. Leveraging the high resolution of excess spectroscopy and employing the methanol hydroxyl group as an effective probe, our research focused on the IL–acetonitrile–methanol mixtures. This approach enabled us to pinpoint species transformations during the mixing process, revealing the nature of phase equilibrium changes within the azeotrope. Consequently, our findings offer valuable insights into the microstructures of multicomponent solutions. [ABSTRACT FROM AUTHOR]

An isatin-Schiff base ligand (ISS) bearing a pyridine-2-carboxamidine moiety was synthesized through a facile and convenient method for the highly selective colorimetric detection of Hg + 2 and F − ions. The sensing ability of the synthesized ISS sensor toward Hg + 2 and F − was established using colorimetric and UV–visible techniques. The developed sensor showed excellent selectivity in the presence of other competing ions for Hg + 2 and F − , with a color change from yellow to red. The limits of the detection for sensing Hg + 2 and F − were calculated to be 2.9 × 1 0 − 6 M and 1.4 × 1 0 − 5 M, respectively. Job's plot based on spectroscopic data revealed a 1:1 binding stoichiometry between ISS and Hg + 2 or F − ion. Furthermore, the binding mechanism, optimized structures and electronic properties of ISS , ISS -F − adduct and ISS -Hg + 2 complex were investigated using density functional theory (DFT) calculations. DFT results indicated a decrease of the HOMO–LUMO energy gap for ISS upon interaction with the F − and Hg + 2 species which were in good agreement with the experimental outcomes. [Display omitted] • Isatin Schiff base heterocycle containing pyridine-2-carboxamidine moiety was synthesized via convenient and simple method. • Introduction of pyridine-2-carboxamidine structure into the isatin Schiff base enhances the coordination ability of the sensor with the mercury ion. • Detection of important fluoride and mercury ions was established using colorimetric and UV–visible techniques. • The limit of detection value was within the permissible limit (0.006 mg/L) for mercury ion concentrations in drinking water. • The experimental results were supported by density functional theory studies. [ABSTRACT FROM AUTHOR]

[Display omitted] • The CH 3 CN–IL/ethyl acetate interaction complexes were identified. • The interaction of IL–CH 3 CN was stronger than that of ethyl acetate–acetonitrile. • Species transformation with the addition of IL was identified. • The molecular intrinsic nature of the azeotropy breaking was clear. Ionic liquids (ILs) are good candidates for azeotropy separation. Knowledge of the microstructure properties of azeotrope − IL mixtures is important because they could reveal the molecular intrinsic cause of the elimination of azeotropy and represent the basis for the practical process. In this work, the microstructures of ethyl acetate-acetonitrile azeotrope mixtures and a representative IL, 1‑butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([BMIM][Tf 2 N], which could eliminate the azeotropy of the ethyl acetate-acetonitrile system, were studied by Fourier transform infrared spectroscopy with the assistance of quantum chemical calculations and excess spectra. The C≡N stretching vibrational region of acetonitrile was closely examined. The interaction complexes of ethyl acetate-acetonitrile and ion cluster/ion pair/ion − acetonitrile were identified. Weak strength hydrogen-bonds with electrostatically dominant and closed-shell interaction properties were found in these complexes. The interactions between [BMIM][Tf 2 N] and acetonitrile were stronger than those between ethyl acetate and acetonitrile, which caused the addition of IL to easily destroy the ethyl acetate-acetonitrile interaction complex. The interactions between [BMIM][Tf 2 N] and acetonitrile were stronger than those between [BMIM][Tf 2 N] and ethyl acetate, which would influence the relative volatility of ethyl acetate and acetonitrile in the azeotrope system. When x(IL) was larger than 0.027, all the interaction complexes between acetonitrile and ethyl acetate were completely broken apart, and the azeotrope was eliminated. [ABSTRACT FROM AUTHOR]

[Display omitted] • A colorimetric and fluorescent probe NI-CIN was designed for hydrazine detection. • NI-CIN displayed an effective detection of hydrazine in real water and soil samples. • Visual detection of hydrazine under aqueous and vapor phases are realized. • NI-CIN is successfully used to image hydrazine in living cells and zebrafish. Detection of hydrazine is particularly important given its toxicity and extensive application in various industries. In the present paper, a colorimetric fluorescent probe NI-CIN based on 1,8-naphthalimide derivative was rationally designed and simply synthesized for specific detection of hydrazine based on the intramolecular charge transfer (ICT) mechanism. Upon the addition of hydrazine, a significant fluorescence enhancement at 556 nm could be observed within 4 min with a distinct color change from colorless to bright yellow, readily observed by naked eye. Except for HRMS and 1H NMR, density functional theory (DFT) calculations were also performed to support the sensing mechanism. In addition, eco-friendly paper test strips were easily prepared by NI-CIN for selective and real-time detection of hydrazine under aqueous and vapor phases. Furthermore, NI-CIN shows many potential applications for detecting hydrazine in real water and soil samples along with bio-imaging in HepG-2 cells and zebrafish. [ABSTRACT FROM AUTHOR]

Nonradiative deactivation properties of naturally occurring curcuminoids bringing up the possibilities of their applications as UVA filtering agents. [Display omitted] • Efficient nonradiative decay by isomerism, rotamerism and ESIPT after photoexcitation. • Four geometrical isomerisms forming eight possible configurations in a molecule. • 16 Rotamers in equilibrium both in S 0 and S 1 states for every configuration. • Low barrier intramolecular proton transfer both in S 0 and S 1 states. • Prospects of curcuminoids as UVA filters. In this work, the deactivation pathways of curcuminoids after photoexcitation was studied by employing density functional theory to explore their UVA radiation screening capacity. A comprehensive computational characterization of the excited-state processes of curcumin, demethoxycurcumin, and bis -demethoxycurcumin was done. The molecules exist in diketo and enol forms which are in equilibrium and interconvertible through keto-enol tautomerism. The enolic forms of each of the studied molecules have eight geometric cis – trans isomers as a result of torsion rotation about three different carbon–carbon double bonds across the aliphatic chain. For each geometric isomer, sixteen possible rotamers are found to exist due to rotation about five different carbon–carbon single bond rotations, also across the skeleton of the aliphatic chain. Upon photoexcitation, the studied molecules follow three main pathways of radiationless decay: (a) rotamerism and interconversion between rotamers of comparable energies which are in equilibrium, (b) interconversion between the cis – trans geometrical isomers where an efficient vibrational relaxation path is formed at ∼90° during torsion rotation about carbon–carbon double bond, and (c) excited state intramolecular proton transfer in a single O–H stretching vibration through a cyclic intramolecular hydrogen bonded ring formed at the centre of the molecule giving back the original structure. The absorption and emission spectra of the molecules were also simulated where the theoretically obtained absorption and emission maxima are close to the reported experimental values. [ABSTRACT FROM AUTHOR]

[Display omitted] • A colorimetric Schiff base turn-off fluorescent sensor of F− ion was synthesized. • The sensor shows a detection limit of 2.35 × 10−8 M for F− ion. • The binding constant of L with F− ion was obtained to be 0.1 × 106 M−1. • A 1:1 binding stoichiometry of L with F− ion was obtained. The work described is focused on a newly developed colorimetric Schiff base fluorescent sensor that exhibits a "turn-off" response when detecting fluoride ions (F−) in an aqueous environment. The confirmation of the recognition event is accomplished through fluorescence titration, absorbance titration, and Density Functional Theory (DFT) calculation study. From the results, it is determined that the detection limit of F− is 2.35 × 10−8 M which is much lower than the World Health Organization (WHO) permissible limit for drinking water while the binding constant was obtained to be 0.1 × 106 M−1 indicating a moderate affinity for the fluoride ions. Furthermore, the binding stoichiometry between the Probe L and F− was found to be 1:1 which is evidenced by the Job's plot and DFT calculation study. Overall, the novel sensor's impressive sensitivity and selectivity make it a promising candidate for the detection of fluoride ions in aqueous media, particularly for monitoring drinking water quality to ensure compliance with WHO guidelines. [ABSTRACT FROM AUTHOR]

[Display omitted] • Yttrium nitride YN in different forms was investigated by using DFT/B3LYP level of theory. • A variety of properties of the YN (n,0) single-walled square nanotubes was studied, where the trend toward the square monolayer in the limit of large nanotube is attained. • Scanning mode procedure confirms that larger YN (n,0) single-walled hexagonal nanotubes are slightly distorted compared to their corresponding central point. Through this contribution, we aim to highlight the structural stability of low dimensional YN structures ranging from the 3D bulk to the 2D square and hexagonal monolayers and their corresponding 1D zigzag single walled nanotubes. For all arrangements, geometry optimization is achieved at the DFT/B3LYP level of theory using a Gaussian basis set. Then, the coupled perturbed Kohn-Sham and Hartree-Fock (CPKS/HF) computational approach is used to simulate Raman and IR spectrum. Rolling, cohesive and relaxation energies, electronic and vibrational contributions to the polarizability and equilibrium lattice parameters are also reported. Insights into their structural stability are provided by combining optimized parameters and vibrational phonon spectra. For the optimized 3D bulks, 2D monolayers and 1D square nanotubes, no imaginary frequency has been recorded in their vibrational spectra which reveals a dynamic stability. Likewise, imaginary frequencies appeared only for relatively large YN (n,0) single walled hexagonal nanotubes (n > 6) indicating that the optimized structures are not a real global minimum and implying a dynamic instability. A scaning mode procedure along the largest imaginary vibrational mode has been adopted to obtain the equilibrium geometry of (22,0) YN hexagonal nanotube. Therefore, it must be emphasized that the obtained potential energy surface presents two minima between a saddle point. These minima corresponds to a stable structures slightly distorted compared to the initial one. The absence of imaginary phonon frequencies in the Raman and IR spectra of the optimized (22,0) YN hexagonal nanotube confirms its structural stability. [ABSTRACT FROM AUTHOR]

[Display omitted] • Detailed theoretical study of structural, spectroscopic and electron scattering cross section study of glycolaldehyde. • Quantum chemical calculations for ground and excited states are performed using DFT and TD-DFT methods. • In the absence of sufficient experimental data on excited states of glycolaldehyde, we compare VES calculations with the available experimental data for an analogous molecule acetaldehyde. • Maiden theoretical attempt to provide Low-energy (0.1 to 20 eV) scattering cross-sectional data using R-matrix method. • We have detected one π* shape resonance in all the three models viz. SE, SEP and CC model. Detailed theoretical investigations on structural, spectroscopic and electron scattering cross sections of glycolaldehyde, the first ever detected sugar in space are reported in this work. Spectroscopic calculations are performed on the ground and excited states of glycolaldehyde using density functional theory (DFT) and time-dependent density functional theory (TDDFT), respectively. The optimized geometrical parameters and vibrational spectrum are in good agreement with the earlier reported work. Vertical excited state (VES) energies at the TDDFT/B3LYP/aug-cc-PVQZ level of theory along with detailed assignments are reported up to 30 transitions. The TDDFT predicted Rydberg series energies are compared with the Rydberg series of glycolaldehyde converging to its first IP, computed using the standard Rydberg formula and are found to be in good agreement. In the absence of sufficient experimental data on excited states of glycolaldehyde, the theoretical results are validated by comparison of VES calculations performed at the same level of theory with the available experimental data for an analogous molecule viz. acetaldehyde. Triplet excited-state energies for glycolaldehyde are reported here for the first time. Electron impact cross section calculations in the energy range 0.1 to 20 eV are carried out using ab-initio R-matrix method. We have detected one π* shape resonance in all the three models viz. SE, SEP and CC, which may also lead to a possible fragmentation channel wherein a hydrogen atom is removed from the molecule forming a glycolaldehyde dehydrogenated anionic radical (C 2 H 3 O 2 −). The π* shape resonance is correlated with the corresponding molecular orbital electronic structure calculations. Additionally, differential, electronic excitation, ionization and total cross sections are reported here for the first time. [ABSTRACT FROM AUTHOR]

[Display omitted] • Characterization of glycyl-l-phenylalanine by theoretical and experimental methods. • Torsion angle of |θ| = 110.8°. • Normal modes of vibration through density functional theory (DFT). • The phase transition is observed at 1.0 GPa. The structural and vibrational properties of the glycyl-L-phenylalanine dipeptide were investigated using vibrational spectroscopy (Raman and infrared) and first-principle calculations. Raman spectroscopy measurements were performed between 100 and 3200 cm−1 and infrared spectroscopy from 100 and 3200 cm−1 under ambient conditions. The conformational analysis of the zwitterionic form of the dipeptide was performed using the B3LYP functional, the 6–311++ base set and the Polarizable Continuum Model of solvation, determining the lowest energy conformation and assigning the vibrational modes. The effect of pressure on the glycyl-1-phenylalanine crystal was investigated using the Raman spectroscopy between 0.0 and -7.1 GPa in the spectral region of 100 – 3200 cm−1. As a result, conformational changes around 1.0 GPa were observed in the lattice modes and in some internal modes, showing a reorganization of the molecule in the crystal. In the decompression process, it was observed that the conformational change is reversible and the original Raman spectrum is recoverd. [ABSTRACT FROM AUTHOR]

[Display omitted] • Theoretical analysis of 6 and 7 donor-substituted coumarins. • NBO, FMO, and MEP were analyzed. • DFT-based descriptors and NLO properties. The linear and non-linear optical properties of 6-donor and 7-donor substituted coumarins were compared using density functional theory (DFT) and time-dependent -DFT (TD-DFT). Charge transfer characteristics were investigated through natural bond order analysis, frontier molecular orbital, and molecular electrostatic potential plots. TD-DFT results suggested that the 6-donor substituted coumarins (PS1 , PS3, and PS5) showed red-shifted absorption than the 7-donor substituted coumarins (PS2 , PS4, and PS6). The chemical potential (μ) and electrophilicity index (ω) showed direct relation with the band gap and an inverse relation with chemical hardness (η) and hyperhardness (Γ). The global reactivity descriptors μ and ω showed direct and η and Γ showed an inverse correlation with first-order hyperpolarizability (β 0) and second-order hyperpolarizability (γ). The β 0 and γ for 7-donor substituted coumarin are higher than for 6-donor substituted coumarin. [ABSTRACT FROM AUTHOR]

[Display omitted] • A fluorescent probe ( CyNa-N 3 ) based on naphthalimide and cyanine dyes was synthesized. • CyNa-N 3 can detect HClO and H 2 S with different fluorescence signals. • The sensing mechanism of CyNa-N 3 to HClO and H 2 S was confirmed by ESI–MS and 1H NMR. • CyNa-N 3 was adapted to visualize HClO and H 2 S in cell imaging. Hypochlorous acid (HClO) and hydrogen sulfide (H 2 S) play very important roles in both physiological and pathological processes, however, the methods for simultaneously detecting HClO and H 2 S were rarely reported. Here, a dual–responsive fluorescent probe ( CyNa-N 3 ) based on cyanine and naphthalimide dyes was synthesized and investigated. The fluorescence probe showed better sensitivity, high selectivity response to HClO and H 2 S by red emission and green emission bands, and the limits of detection were 0.17 µM and 0.15 µM respectively. MS (Mass Spectrum) and 1H NMR (Nuclear Magnetic Resonance) confirmed the sensing mechanism of CyNa-N 3 detected HClO and H 2 S, the calculation of density functional theory (DFT) further explained the internal mechanism of spectral change of CyNa-N 3 . Moreover, CyNa-N 3 was successfully applied to image HClO and H 2 S in living cells, which is beneficial for more efficient application in biological imaging. [ABSTRACT FROM AUTHOR]

[Display omitted] • Structural conformers of HPEH were successfully theoretically identified. • Sensitivity and selectivity detection of Hg2+ by HPEH were successfully optimized using the RSM approach. • TD-DFT method successfully determined the model of interaction between HPEH and Hg2+. • Chemical phenomena occurred was successfully employed using NCI-RDG and MD simulation. A new thiosemicarbazone derivative, N -(2-hydroxyphenyl)-2-[1-(pyridin-4-yl)ethylidene]hydrazinecarbothioamide (HPEH), has been synthesized, characterized, and further developed as a highly selective and sensitive colorimetric chemosensor for Hg2+ recognition in environmental water samples. Structural conformers of HPEH were successfully identified using a combination of the potential energy surface (PES) and time-dependent density functional theory (TD-DFT) methods. The synthesized HPEH was successfully characterized further and analyzed based on its harmonic vibrational frequencies, NMR spectra, and electronic transitions using the DFT approach. Sigma profiles were generated using the COSMO-RS approach to identify a compatible medium for HPEH to act as a chemosensor. The conditions for the highly sensitive and selective detection of Hg2+ by HPEH were successfully optimized using the statistical response surface methodology approach. The optimum sensing of HPEH occurred in an 8:2 v/v DMSO/pH 7.8 solution at a 20:60 μM HPEH/Hg2+ concentration and after a reaction time of 18 min, with statistically significant independent variables (p < 0.05) for all parameters. Under optimal conditions, the lowest Hg2+ concentration detected by HPEH was 3.56 µM, indicating that HPEH can serve as an alternative and comparable probe for the detection of Hg2+ in aqueous systems. Using the optimized results, the interaction between HPEH and Hg2+ in the chemosensor system was successfully modeled, and the model was subsequently used with the TD-DFT, non-covalent interaction-reduced density gradient (NCI-RDG), and molecular dynamics approaches to gain mechanistic insights into the interaction. The results showed that the newly synthesized HPEH, in addition to being cost-effective, could serve as a suitable alternative and comparable chemosensor for Hg2+ recognition in water samples, with the advantages of being efficient, portable, and eco-friendly, and offering rapid analysis without the need of specialized training. [ABSTRACT FROM AUTHOR]

[Display omitted] • The four compounds can effectively protect against UVB radiation. • Their absorption spectra are mainly affected by their stilbene segments. • O 1 H 1 sites of EHDB and HPTP are the most active in trapping free radicals. • SPLET mechanism is the most preferred reaction pathway for the four compounds. • DPPH scavenging activities significantly improve after sunlight except for EAPD. With the continued depletion of the ozone layer, the sun protection consciousness of humans has gradually enhanced. Long-term ultraviolet (UV) rays exposure will lead to skin tanning, even skin cancer in severe cases, and generate free radicals to cause skin aging. To better protect human skin against UV rays, this work explores the absorption capacities and antioxidant activities of four stilbene derivatives (EHDB, EDMB, EAPD, and HPTP) through the computational chemistry method and DPPH radical scavenging experiment. The research results indicate that their absorption spectra cover the entire UV region, and can effectively protect against UVB radiation. Moreover, three prevailing antioxidant mechanisms: hydrogen atom transfer, sequential proton loss electron transfer, and single electron transfer followed by proton transfer mechanisms, were used to evaluate their antioxidant activities in the ground state. It can be concluded that the O 1 H 1 sites of EHDB and HPTP are the most active, and the SPLET mechanism is the most preferred for the four compounds in ethanol solvent. Furthermore, the DPPH radical scavenging experiment compensates for the theoretical calculation deficiency in the excited state, revealing that the EHDB and HPTP are the most suitable for sunscreen due to their excellent performance on antioxidant capacities, whether before or after sunlight. This work will facilitate EHDB and HPTP to be applied in sunscreen and provide a novel idea in sunscreen research. [ABSTRACT FROM AUTHOR]

The introduction of triphenylamine and π-bridge minimally affect the complete reaction process. For the light emitters, the injection abilities of hole and electron can be largely improved by introduction of triphenylamine and π-bridge, meanwile, the absorption and emission spectra appeared at longer wavelengths. [Display omitted] • The oxygenation reaction occurs through the triplet state PES, firstly. • After intersysterm crossing, dioxetanone formed along singlet diradical state PES. • Efficient chemiexcitation is associated with decomposition of neutral dioxetanone. • Triphenylamine and π-Bridge produce a bathochromic emission spectrum. • The hole and electron injection abilities can be largely improved. As light emitter of most marine organisms bioluminescence, coelenteramide (CLM) received much attention due to some exciting application in the field of bioinspired organic light-emitting devices (OLED). Nevertheless, native CLM only emit bright blue light. In order to obtain light of different colors, two CLM analogues, TPA-CLM and TPA-TP-CLM were designed by introduction of triphenylamine group and (thiophene) π-bridge. On the other hand, because the light emitter, CLM was produced by the chemical reaction which originates from the oxidation of bioluminescent substrate, coelenterazine (CLZ), it must be evaluated if and how substituent group tune the chemiluminescent (CL) reaction mechanism, firstly. In this article, the complete chemiluminescent reaction mechanism of TPA-CLZ and TPA-TP-CLZ and the photophysical properties of light emitters, TPA-CLM and TPA-TP-CLM were investigated by (time-dependent) density functional theory, (TD) DFT calculations. The calculations indicate that the introduction of triphenylamine and π-bridge minimally affect the complete reaction process. For the light emitters, TPA-CLM and TPA-TP-CLM, the calculation results indicate that the injection abilities of hole and electron can be largely improved by introduction of triphenylamine and π-bridge. The absorption and emission spectra appeared at longer wavelengths than native CLM. These results illustrate that TPA-CLM and TPA-TP-CLM are good candidates for bioinspired OLED application. [ABSTRACT FROM AUTHOR]

[Display omitted] • The ESIPT reactions for HBT-H-H in solution and aggregation state are identified. • Photocyclization by crossing the conical intersection causes fluorescence quenching of the Enol* form. • Torsion by crossing the conical intersection weakens the fluorescence intensity for the Keto* form in solution state. • Upon aggregation, torsion is suppressed so that Keto* state emission channel beats the nonradiative decay pathway. The aggregation-induced emission (AIE) effect has been demonstrated to have great potential application in different areas, from organic electronics to biomedical research and physical process monitoring. In general, molecules with AIE characteristic exhibit fluorescence enhancement in the aggregated state by restricting intramolecular motion consumption. The combination of AIE and excited-state intramolecular proton transfer (ESIPT) is meaningful for promoting luminescence. Recently, HBT-H-H molecule, as a derivative of 2-(2-Hydroxyphenyl)benzothiazole (HBT), has drawn extensive attention from researchers. The molecule possesses the intramolecular hydrogen bonding structure which has the potential for ESIPT. Moreover, the fluorescence quantum yield of HBT-H-H in the aggregation state is 35 times higher than that in Toluene. However, the interplay between excited state dynamics and the AIE effect for this molecule is not clear. Especially, how does AIE effect beat non-radiative transition channel by affecting motions of molecular structure. Herein, we investigated the excited state dynamics of HBT-H-H molecule by the spin-flip time-dependent density functional theory and QM/MM method. We found that the molecule relaxes to the conical intersection region through the twisting motion of the benzothiazole group in Toluene solvent. While the AIE effect effectively inhibits this process by preventing the torsion of benzothiazole group, which induces the emission enhancement. The interplay between the excited-state dynamics and AIE effect for the HBT-H-H molecule delineated in this work not only benefits the deep understanding of molecular behavior to the aggregate level, but also provides a guide for the synthesis of AIE materials with favorable performance. [ABSTRACT FROM AUTHOR]

[Display omitted] • A novel nicotinic hydrazone-based turn-on fluorescence probe 3 has been synthesized for the detection of carbonate ions in an aqueous medium. • The probe showed excellent selectivity, sensitivity, and good reversibility toward CO 3 2– ions. • The deprotonation mechanism of sensing was elucidated by 1H NMR, ESI-MS spectra, and DFT calculations. • An INHIBIT-type molecular logic gate was successfully constructed using probe 3- CO 3 2– and CH 3 COOH. • Probe 3 effectively senses CO 3 2– ions in the real water samples and live cells. A novel turn-on fluorescent probe 3 was synthesized by condensing salicylaldehyde and nicotinic hydrazide for the selective detection of CO 3 2– in aqueous medium. Probe 3 exhibited a turn-on fluorescence response toward CO 3 2– with excellent selectivity, sensitivity (DL = 2.76 μM), and good reversibility. The binding constant (K) of probe 3 with CO 3 2– was calculated to be 5 × 103 M−1 (log K 3.69). The 1:1 stoichiometry of the complex between probe 3 and CO 3 2– ions was confirmed by Job's plot and ESI-MS spectra. Deprotonation and hydrogen-bonding interactions are involved in the recognition of CO 3 2– ion, which was also suggested by 1H NMR, ESI-MS spectra, and Density Functional Theory (DFT) calculations. Moreover, an INHIBIT type molecular logic gate was constructed by using 3:CO 3 2– and CH 3 COOH as inputs and current signal as output. Owing to the practical applications, probe 3 demonstrated its efficiency in quantifying CO 3 2– ion in real water samples through standard addition method, thus showcasing its potential in real environment. Further, the MTT assay indicated very low cytotoxicity (IC 50 = 1 mM) of probe 3 and also the cell imaging experiments demonstrated the effective sensing of CO 3 2– ions with probe 3 in the biological systems. [ABSTRACT FROM AUTHOR]

In this work, the structure–property relationship of push–pull chalcone derivative (3DPNP) has been studied through spectroscopic experiments and density functional theory calculations. The figure on the right side shows the non-linear absorption and non-linear refraction curves of 3DPNP. [Display omitted] • The structure–property relationship of a chalcone-based push–pull molecule (3DPNP) was explored using combined experimental and theoretical studies. • The vibrational and electronic contribution to NLO activity of 3DPNP was estimated. • Frequency-dependent NLO calculations shows abrupt changes when the incident frequency is doubled which confirms SHG efficiency of 3DPNP. • Z-scan studied indicated that the molecule 3DPNP is suitable for optical limiting application in CW laser regime. • The optical limiting threshold of 3DPNP is found to be 3.26 kJ/cm2. In this work, the optical limiting response of a highly π-conjugated push–pull chalcone derivative (2 E)-3-(2,3-dimethoxyphenyl)-1-(3-nitrophenyl)prop-2-en-1-one (abbreviated as 3DPNP) has been investigated. The structure–property relationship of 3DPNP was explored through spectroscopic investigation and quantum chemical computations. The existence of weak-non-covalent interactions and charge transfer species that responsible for the chemical stability of 3DPNP were studied by AIM and NBO analyses. The quantitative and qualitative analysis of vibrational and electronic contribution to non-linear optical (NLO) response of 3DPNP were discussed in detail. The normal vibrational modes associated with a change in the dipole moment, polarizability, first- and second-order hyperpolarizabilities of 3DPNP were identified using DFT calculations followed by potential energy distribution (PED) analysis using Gaussian 09 W software and Gar2ped program, respectively. The changes in the NLO parameters with respect to the varying frequencies and electric dipole fields were studied. The abrupt changes in the NLO properties were noticed when the frequency doubled, confirming the second harmonic generation (SHG) efficiency of 3DPNP. From the non-linear absorption and refraction studies through the z-scan experiment, the optical limiting threshold value of 3DPNP is determined to be 3.26 kJ/cm2, which shows the suitability of the material for optical limiting applications in the continuous wave (CW) laser regime. [ABSTRACT FROM AUTHOR]