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Context: In the present work, the influence of aromatic ring substitution on a series of small-donor organic molecules (A, B, C, D, and E) with isoxazole cores was investigated for photovoltaic applications in organic solar cells. Frontier molecular orbital analysis, chemical reactivity descriptors, dipole moment, and population analysis showed that all the organic materials have intramolecular charge transfer abilities capable of donating electrons to the acceptor material (PCBM). The required photovoltaic parameters such as Voc, FF, Jsc, LHE, and other associated optoelectronic parameters are reported. The results demonstrate that aromatic ring substitution influences charge transfer and power conversion efficiencies of solar cells. That is, an increase in the aromatic character of a material increases its charge transfer, and as a result, its photovoltaic properties are increased. Additionally, all the investigated derivatives are good charge transporters with suitable electron reorganization energies, which are beneficial for minimizing energy loss. Hence, these organic derivatives with isoxazole backbones are promising materials and may provide fresh insights into the design of new materials for organic solar cell applications. Method: All calculations were performed using DFT and the ORCA 4.1.0 program package as the main tool for geometry optimization and frequency calculations. The Avogadro 1.2.1 visualization tool was used to prepare all input files executed by ORCA 4.1.0. The BP86, B3LYP, and wB97M series of functionals coupled with the def2/TZVP basis set were employed for geometry optimization. All energy-related calculations were carried out using the M06-2x functional. Multiwfn version 3.7 was used for aromaticity and population analysis. Excited state and UV-visible spectra were simulated using the TD-DFT method at the CAM-B3LYP-D3, wB97X-D3, and PBE0-D3 coupled with the ma-def2-TZVP basis set. Moreover, solvent effects were incorporated using the SMD scheme as incorporated in the ORCA software. Lastly, the RIJCOSX approximations were used to speed up calculations while maintaining accuracy. [ABSTRACT FROM AUTHOR]

Context: The advancement in the development of second-generation drugs in the field of antihistamines represents a significant milestone in the management of allergic diseases, targeting the effects of histamine. The efficacy of bilastine in treating allergic disorders has sparked interest in investigating its polymorphism, a crucial property that impacts quality, safety, and effectiveness as per regulatory guidelines. This study examines the polymorphism of bilastine, focusing on two crystalline forms labeled as Form I and Form II. Utilizing advanced analytical techniques, the research explores the structural characteristics and molecular interactions within these forms. Geometric parameters, such as bond lengths, bond angles, and torsion angles, are examined to comprehend molecular conformations and crystal packing arrangements. Hydrogen bonding, covalent bonds, and van der Waals forces contribute to the unique supramolecular arrangements in these forms. This study provides a significant contribution to understanding bilastine's polymorphism, offering critical insights to researchers and regulatory bodies to ensure the quality, efficacy, and safety of antihistamine products. Methods: The molecular conformation of two bilastine forms was obtained through DFT with the exchange–correlation functional M06-2X and the 6–311 + + G(d,p) basis set, and the results were compared with the experimental X-ray. The atomic coordinates were obtained directly from the crystalline structures, and charge transfer was also investigated using frontier molecular orbitals (HOMO and LUMO), and MEP map in order to evaluate the energies associated with charge transfers and regions of high electron affinity. The geometric and topological parameters and intermolecular interactions in the crystals were analyzed using Hirshfeld Surface. [ABSTRACT FROM AUTHOR]

Context: In this study, we have developed four new chromophores (TM1–TM4) and performed quantum chemical calculations to explore their nonlinear optical properties. Our focus was on understanding the impact of electron-donating substituents on 1,3,4-oxadiazole derivative chromophores. The natural bond orbital analysis confirmed the interactions between donors and acceptors as well as provided insights into intramolecular charge transfer. We also estimated dipole moment, linear polarizability molecular electrostatic potential, UV–visible spectra, and first hyperpolarizability. Our results revealed that TM1 with a strong and stable electron-donating group exhibited high first hyperpolarizability (β) 293,679.0178 × 10−34 esu. Additionally, TM1 exhibited a dipolar moment (μ) of 5.66 Debye and polarizability (α) of 110.62 × 10−24 esu when measured in dimethyl sulfoxide (DMSO) solvent. Furthermore, in a benzene solvent, TM1 showed a low energy band gap of 5.33 eV by using the ωB97XD functional with a 6–311 + + G(d, p) basis set. Moreover, our study of intramolecular charge transfers highlighted N, N dimethyl triphenylamine and carbazole as major electron-donating groups among the four 1,3,4-oxadiazole derivative chromophores. This research illustrates the potential applications of these organic molecules in photonics due to their versatile nature. Methods: The molecules were individually optimized using different functionals, including APFD, B3LYP, CAM B3LYP, and ωB97XD combined with the 6–311 + + G (d, p) basis set in Gaussian 16 software. These methods encompass long-range functionals such as APFD and B3LYP, along with long-range corrected functionals like CAM B3LYP and ωB97XD. The employed functionals of APFD, B3LYP, CAM B3LYP, and ωB97XD with the 6–311 + + G (d,p) basis set were used to extract various properties such as geometrical structures, dipole moment, molecular electrostatic potential, and first hyperpolarizability through precise density functional theory (DFT). Additionally, TD-DFT was utilized for obtaining UV–visible spectra. All studies have been conducted in both gas and solvent phases. [ABSTRACT FROM AUTHOR]

Context: Due to their unique photophysical properties, organic charge transfer crystals are becoming promising materials for next-generation optoelectronic devices. This research paper explores the impact of s-block metals on a charge transfer crystal of indol-2-one for enhanced nonlinear optical (NLO) responses with efficient energetic offsets. The study reveals that alkali metals can enhance NLO performance due to their free electrons. Method: The Perdew-Burke-Ernzerhof functional of DFT with dispersion correction (D3) was used, and the λmax values ranged between 596 and 669 nm, with the highest value for dichloromethane (DCM). Leveraging the unique properties of metals allowed for the development of nonlinear optical materials with improved performance and versatility. Softness (σ) values provide insight into electron density changes, with higher values indicating a greater tendency for changes and lower values indicating the opposite. The NLO results for the chromophores MMI1–MMI6 show varying linear polarizability (< α0 >) along with their first (β0) and second (γ0) hyperpolarizabilities. Chromophore MMI4 stands out with the highest NLO performance, having two potassium (K) atoms. Its < α0 > , β0, and γ0 values of 4.19, 7.09, and 17.43 (× 10−24 e.s.u), respectively, indicate a significant enhancement in NLO response compared to the other chromophores. The transitions involving (O20)LP → (C3-N5)π* and (O19)LP → (N12-C13)π* exhibit the highest level of stabilization, followed by (O23)π → (C10-C11)π*, while (C6-N12)π → (C6-C7)π* shows the lowest level of stabilization for chromophore MMI4. The present research work is facile in its nature, and it can be helpful for synthetic scientist to design the new materials for uniting crystal properties with metal doping for efficient NLO devices. [ABSTRACT FROM AUTHOR]

Context: Push–pull compounds are model systems and have numerous applications. By changing their substituents, properties are modified and new molecules for different applications can be designed. The work investigates the gas-phase electronic absorption spectra of 15 derivatives of push–pull para–nitroaniline (pNA). This molecule has applications in pharmaceuticals, azo dyes, corrosion inhibitors, and optoelectronics. Both electron-donor and electron-withdrawing groups were investigated. Employing machine learning–derived Hammett's constants σm, σm0, σR, and σI, correlations between substituents and electronic properties were obtained. Overall, the σm0 constants presented the best correlation with HOMO and LUMO energies, whereas the σR constants best agreed with the transition energy of the first band and HOMO–LUMO energy gap. Electron-donors, which have lower σR values, redshift the absorption spectrum and reduce the HOMO–LUMO energy gap. Conversely, electron-withdrawing groups (higher σR's) blueshift the spectrum and increase the energy gap. The second band maximum energies, studied here for the first time, showed no correlation with σ but tended to increase with σ. A comprehensive charge transfer (CT) analysis of the main transition of all systems was also carried out. We found that donors (lower σ's) slightly enhance the CT character of the unsubstituted pNA, whereas acceptors (higher σ's) decrease it, leading to increased local excitations within the aromatic ring. The overall CT variation is not large, except for pNA–SO2H, which considerably decreases the total CT value. We found that the strong electron donors pNA–OH, pNA–OCH3, and pNA–NH2, which have the smallest HOMO–LUMO energy gaps and lowest σ's, have potential for optoelectronic applications. The results show that none of the studied molecules is fluorescent in the gas phase. However, pNA–NH2 and pNA–COOH in cyclohexane and water reveal fluorescence upon solvation. Methods: We investigated theoretically employing the second-order algebraic diagrammatic construction (ADC(2)) ab initio wave function and time-dependent density functional theory (TDDFT) the gas-phase electronic absorption spectra of 15 derivatives of p–nitroaniline (pNA). The investigated substituents include both electron-donor (C6H5, CCH, CH3, NH2, OCH3, and OH,) and electron-withdrawing (Br, CCl3, CF3, Cl, CN, COOH, F, NO2, and SO2H) substituents. [ABSTRACT FROM AUTHOR]

Context: It has been reported that photoexcitation of azastilbene compounds like E-1,2-bispyrazinyl-ethylene (bpe) can undergo E → Z photoisomerization of its quaternary salts via the excited triplet state. However, experimentally it is possible to get low fluorescence and photoisomerisation quantum yields in a state with higher internal conversion than intersystem crossing. We modelled bpe and its methylated derivative (bpeMe), as well as its quaternary halogen salts (bpeMeX with X = F−, Cl−, Br− and I−) to study levels of fluorescence, phosphorescence and excited state potential energy surfaces (PES). Results support experimental observations of molecules where the anion of a salt is an efficient electron donor, that molecules with weak electron-donating anions like Cl− to give increased fluorescence and photoisomerization, as compared to molecules with stronger electron-donating anions like I−, which are dominated by competing electron transfer. The fluorescence of bpeMeF and bpeMeCl was found to be stronger than bpeMeBr and bpeMeI. A deep well in the triplet excited state of bpeMeI is considered responsible for the decreased photoisomerization, compared to what was experimentally observed for bpeMeCl. Uniquely, the bpeMeI molecule is characterised by near-zero splitting of the s1 and t1 excited states that can enhance charge transfer. The quaternary salt of bpeMe with stronger electron-donating Br− anion was observed to undergo fluorescence and phosphorescence at much lower energy compared to those with weak electron-donating F− and Cl− anions. This research shows how to control the excited state fluorescence, phosphorescence and isomerization of quaternary halogen salts of methyl derivatives of 1,2-bispyrazinyl-ethylene, which aids experimental design where excited state isomerization is considered. Methods: Geometry optimization, molecular electrostatic potential (MESP), and time dependent density functional theory (TDDFT) calculations were conducted utilizing Gaussian 16 with the B3LYP functional and the 6–31 + G(d,p) basis set. The minimum energy path (MEP) for the E to Z isomerization of the molecules was established employing the Nudged-Elastic-Band (NEB) method, implemented in Orca 4.2. Precise energies of the E → Z isomerization reaction path were determined employing CASSCF and a more accurate multireference method, NEVPT2. [ABSTRACT FROM AUTHOR]

Context: A comparative study of the change in different properties of electronic and structural of the free 1H-indole-2,3-dione molecule and its complexes has been obtained. HOMA analysis was performed to investigate the effects of lithium sodium and potassium cations on the aromaticity of lithium sodium and potassium complexes of 1H-indole-2,3-dione. Methods: Several 1H-indole-2,3-dione complexes with lithium, sodium, and potassium cations were optimized at the B3LYP/6-311G(d,p) level. The cation and π interaction has been investigated from different aspects, including interaction energy calculations, charge transfer values, and changes in the aromaticity of the ring upon complexation. The charge transfer and natural population analysis for the complexes were performed with the natural bond orbital (NBO) analysis. The properties of bond critical points in complexes were studied by applying the quantum theory of atoms in molecules (QTAIM). Finally, the aromaticity change of phenyl induced upon complex formation was evaluated by applying the harmonic oscillator model of aromaticity (HOMA). [Li-INa]+ and [[Li-INb]+ were optimized with the wB97XD function using a version of Grimme’s D2 dispersion model, and the absorption energy was compared with the calculation made with the B3LYP functional. [ABSTRACT FROM AUTHOR]

Context: The purpose of the S01–S05 series of end-capped modified donor chromophores is to amplify the energy conversion efficiency of organic solar cells. Using quantum chemical modeling, the photophysical and photoelectric characteristics of the S01–S05 geometries are examined. Method: The influence of side chain replacement on multiple parameters, including the density of states (DOS), molecular orbital analysis (FMOS), exciton-binding energy (Eb), molecular electrostatic potential analysis, dipole moment (μ), and photovoltaic characteristics including open circuit voltage (VOC), and PCE at minimal energy state geometries, has been investigated employing density functional theory along with TD-DFT analysis. The molar absorption coefficient (λmax) of all the proposed compounds (S01–S05) was efficiently enhanced by the terminal acceptor alteration technique, as demonstrated by their scaling up with the reference molecule (SR). Among all molecules, S04 has shown better absorption properties with a red shift in absorption having λmax at 845 nm in CHCl3 solvent and narrow energy gap (EG) 1.83 eV with least excitation energy (Ex) of 1.4657 eV. All created donors exhibited improved FF and VOC than the SR, which significantly raised PCE and revealed their great efficiency as OSC. Consequently, the results recommended these star-shaped molecules as easily attainable candidates for constructing extremely efficient OSCs. [ABSTRACT FROM AUTHOR]

Context: Organic semiconductors (OSCs) have attracted a great deal of interest in recent days. There are various types of OSCs, among which small molecules have various inherent benefits. Further research is needed to advance this new kind of material because the field is still developing, and the current focus is on creating small molecules that exist naturally for OSCs. OSCs with nonlinear optical (NLO) characteristics offer a significant advantage over others. Thus, this study theoretically investigates naturally occurring anthraquinones such as chrysophanol and rhein as potential OSCs, as well as their NLO properties. The calculated properties include the ionization potential (IP), electron affinity (EA), and bandgap (Eg). The FMO energy levels together with the Eg, IP (8.17–8.53 eV), and EA (1.87–2.44 eV) suggest the semiconductor nature of the studied compounds. The calculated values of reorganization energy (λ) and transfer integrals (V) suggest the p-type character of both molecules. Rhein has the lowest λh (0.19 eV) and Eg (3.28 eV) and the highest Vh, predominantly because of its better p-type character. The polarizability increases due to the presence of an electron-withdrawing substituent, leading to better NLO performance for Rhein, which is supported by its lower LUMO and Eg values. Methods: The studied molecules were optimized with the DFT/B3LYP-GD3/6-31+G(d,p) method using Gaussian 16 software. The crystal structure was simulated with Materials Studio 7.0, and the V values were calculated with the ADF package. The CDD and DOS plots were obtained with the Multiwfn 3.8 program. [ABSTRACT FROM AUTHOR]

Context: Various innovative molecules have been designed and explored for use in organic photovoltaics. In this study, we devised novel molecules (KZ1–KZ7) specifically for organic solar cells (OSCs). The newly formulated acceptor compounds possess a lower bandgap (Eg = 1.85–2.02), along with bathochromic shift (λmax = 713–788 nm) compared to the reference (Eg = 2.04 eV and λmax = 774 nm). Moreover, the FMO results identified the distinct charge transfer from HOMO to LUMO, which was strongly corroborated by the TDM maps. Similarly, the new designed molecules show less excitation energy (Ex = 1.31–1.54(gas)) than reference (Ex = 1.72). Likewise, all designed molecules (KZ1–KZ7) have demonstrated an analogous open circuit voltage (Voc) with the donor polymer PTB7-Th. All seven designed molecules (KZ1–KZ7) exhibited more fill factor ranging from 97.08 to 97.29 than reference 95.25 and PCE of between 8 and 20% at short circuit current densities of 9, 12, and 15 mA cm−2. Overall, the findings support that designed molecules can be potential molecules for future practical applications. Methods: Geometric calculations were conducted with Gaussian 09W software, and the findings were visualized using Gauss View software. DFT and TD-DFT were employed to evaluate various parameters for R and designed molecules (KZ1–KZ7). Firstly, four functionals including B3LYP, CAM-B3LYP, MPW1PW91, and ωB97XD with 6-31G(d,p) DFT level were applied to R to decide the best level for results. After appropriate analysis, the MPW1PW91/6-31G(d,p) was selected for further examination by comparing the experimental and DFT-based absorption graphs of R. External and internal reorganization energy are the two main factors contributing to reorganization energy. External energy refers to changes in external environment, while internal energy deals with information related to internal geometrical symmetry or the internal environment. The effect of outside factors or external reorganizational energy is omitted because it creates too little change. [ABSTRACT FROM AUTHOR]

Context: In this paper, first-principle calculations reveal that the shear strength of the graphene-cementitious interface (G/C-S–H) (12 MPa) is lower than that of the epoxy, hydroxyl and carboxyl graphene-cementitious interfaces (G-O/C-S–H, G-OH/C-S–H and G-COOH/C-S–H) (21 MPa, 29 MPa and 14 MPa). This indicates that the introduction of functional groups helps to improve the mechanical properties of the graphene-cementitious contact interface. Electrical analysis of the interface reveals that functional groups adsorbed on graphene change the electron distribution on the graphene surface. The formation of a contact interface between graphene and cementitious not only promotes the interaction between the two, but also serves as a bridge connecting the graphene and the cementitious, exacerbating the charge transfer between the two and promoting the generation of solid chemical bonds. Method: All calculations were performed by the CASTEP module in Materials Studio software, using the GGA-PBE functional for structural optimization. The convergence criteria for the geometry optimization are set to a self-consistent field iteration convergence criterion of 2.0 × 10−6 eV and a structural optimization convergence criterion of 0.02 eV/Å. [ABSTRACT FROM AUTHOR]

Context: This article is based on the study of pyrrolic derivatives and their oligomers. Knowing that, pyrrolic derivatives are widely studied on an industrial scale. The aim of this work is to find pyrrolic derivatives having the same physicochemical characteristics such as the pyrrolic edifice. Six derivatives were studied by substituting the hydrogens in the β position of the pyrroles with the following radicals: –CHO, –Cl, –CN, –NO, and –OH. The study was carried out theoretically using ab initio and density functional of theory (DFT) methods. In the first step, molecules of four units were taken into consideration in order to make the comparison between them. This comparison showed that the majority of molecules exhibited high intramolecular charge transfer (ICT) compared to the molecule composed of four pyrrolic units (OP4), and also exhibited strong nucleophilic and electrophilic characteristics. Natural bond orbital (NBO) analysis has shown continuous ICT mechanisms for certain molecules. The studied derivatives showed good solvation in several solvents compared to OP4. The molecules substituted by the radicals –CHO, –CN, –OH, and –NO generated several peaks in the excited states, which is the opposite case for the other molecules with a single peak. The effects of chain elongation revealed exponential equations generated by the two parameters energy gaps (ΔEH–L) and maximum wavelengths (λmax) as a function of the number of units (n). These equations were used to predict the maximum and minimum values of the above parameters for more elongated oligomers. Method: The software used to make the calculations is Gaussian 16. All geometries were calculated by B3LYP functional and 6–31++G(d,p) basis set. The electronic parameters ΔEH–L were calculated by the following functionals: B3LYP, CAM–B3LYP, LC–wPBE, LC–BLYP, wB97X, M062X, M06HF, and M11 in addition to the second-order Møller-Plesset method (MP2) while always keeping the basis set mentioned before. An effect of basis set variation was studied by the optimal functional in combination with the following basis sets: 6–31G(d,p), 6–31++G(d,p), cc–pVDZ, AUG–cc–pVDZ, 6–311G(d,p), 6–311++G(d,p), cc–pVTZ, and AUG–cc–pVTZ. The NBO study was carried out with the M06HF/6-31++G(d,p) functional using the NBO method. The solvation parameters were calculated by M06HF/6–31++G(d,p) in the presence of the implicit solvation model Solvation Model based on Density (SMD). The excited states were calculated by M06HF/6–31++G(d,p) by the implicit solvation model Conductor Polarizable Continuum Model (CPCM). [ABSTRACT FROM AUTHOR]

Context: Quantum mechanical calculations involving electron correlation, frequency dispersion, and solvent effects were carried out to examine the second-order nonlinear optical response of various acceptor, X (-CF3, -CN, -NO2) substituted in N,N-dimethylaniline (DMA) and julolidine(JLD). Here, both DMA and JLD acts as donor and the three substituted groups, X (-CF3, -CN and -NO2) at the para position of both the ring systems as acceptor. The NLO response (βHRS) of -CF3 and -CN substituted DMA and JLD is relatively lower compared to DMA-NO2 and JLD-NO2. The charge distribution is found higher in case of -NO2 substituted DMA and JLD (±443 and ±449) compared to their -CF3 or –CN substitution. Electronic characteristics such as UV-Vis absorption spectra, crucial excited state parameters and charge transfer contribution to βHRS have been used to explain the NLO parameter of DMA-X and JLD-X. Variation of the incident optical frequency of light shows fluctuation of βHRS value and highest values of βHRS are obtain at the λmax frequency of each compound. Solvent polarity variation study on βHRS shows that βHRS varies linearly with the Kirkwood-Onsagar dielectric factor (D). Methods: All computational studies have been carried out using density functional theory (DFT) based method. Since CAM-B3LYP based hybrid functional improves the asymptotic behavior of the exchange interaction by dividing into short-range and long-range components, first hyperpolarizability values in the present study were computed using DFT/ CAM-B3LYP/ 6-31G+(d,p) level of theory. [ABSTRACT FROM AUTHOR]

Introduction: First-principles calculations were used to study the adsorption behavior of environmentally significant gases CO, CO2, NO, NO2, SO, and SO2 on pure buckled aluminene (b-Al) for gas sensing applications. Therefore, structural, electronic, and adsorption properties including adsorption energy values and recovery time have been calculated and discussed. Methods: All the structures were optimized using Amsterdam Density Functional (ADF) code BAND. In addition, triple zeta polarization basis with slater-type orbitals were utilized. Results: For every gas analyzed, we observed favorable adsorption energy values and charge transfer occurring between the gas molecule and b-Al. In the valance band, there was a strong hybridization between the p orbitals of gas and b-Al, this led to enhanced conductivity in the density of states (DOS). The recovery time suggested that the adsorption of NO, NO2, SO, and SO2 gases on b-Al is good for the application of reversible gas sensors. The recovery time indicated that the b-Al material is very sensitive to NO, NO2, SO, and SO2 gas molecules. Conclusion: The conclusion in light of all these results is that b-Al based materials can appear as a probable candidate for high gas sensing performance. [ABSTRACT FROM AUTHOR]

Context: Heavy metal ion removal from wastewater has become a global concern due to its extensive negative effects on human health and the environment. The density functional theory is employed to investigate the possibility of removing Pb2+, Hg2+, and Cd2+ ions from wastewater using nano-graphene. Researchers have shown that NG can efficiently remove heavy metals from media. Additionally, it was shown that the adsorption of Pb2+, Hg2+, and Cd2+ ions might reduce the large pristine NG (HOMO–LUMO) gap. Methods: HSE06 may accurately represent NG electrical characteristics. The DFT-D3 method was also used to account for Van der Waals interactions in the present study. The results demonstrated that charge transfer and binding energy remained greater in cation-NG systems with greater electron transfer rates. Pb2+, Hg2+, and Cd2+ adsorption results indicated that Egap was significantly reduced by 68%, 15%, and 21%, respectively. The Pb2+@NG complex exhibited the strongest oscillator strength. This may be explained by the enormous occupation number difference between the 2px orbital of the C atoms and the 6 s orbital of the Pb2+ cations. The greater Ebin value of Pb2+@NG is consistent with the increased predicted redshifts (199 nm). DFT (hybrid functional HSE06) studies that rely on time showed that the relevant complexes have "ligand-to-metal charge transfer" excitations. In general, it was found that Pb2+@NG had the greatest k value, binding energy, redshifts, and charge transfer rate among the complexes. The theoretical insights of this study may influence experimental efforts to identify NG-based compounds that are effective and efficient at removing pollutants from wastewater. [ABSTRACT FROM AUTHOR]

Context: Heavy metals are highly noxious, and their presence can cause diverse effects on living organisms and the environment. Crown ether porphyrins and phthalocyanines are known to effectively extract these pollutants and are also used in photovoltaic devices. This study aims to evaluate various factors that govern intramolecular charge transfer (ICT) and photo-injection processes, including maximum absorption wavelength (λmax), density of states (DOS), charge transfer dipole (μCT), light harvesting efficiency (LHE), open-circuit voltage (Voc), and free energy change of electron injection (ΔGinj) in order to investigate the performance of different compounds designed from metalloporphyrins for bulk-heterojunction organic solar cell (BHJ-OSC) applications. The porphyrin complex showed the best optoelectronic properties, with remarkable LHE values and CT amounts compared to phthalocyanine derivatives. The central metal played a significant role in optimizing the optical properties of the materials for use in solar cells. HgPr4O and CdPr4O were found to have optimal Voc values, resulting in effective injection, high electron, and hole mobilities, making them ideal materials for highly efficient BHJ-OSC devices. Methods: Density functional theory (DFT) approach was employed with the B3LYP functional and the def2TZVP basis set as implemented in the Gaussian 16 revision C.01 program to investigate the designed complexes and to compute geometrical parameters, frontier molecular orbitals (FMOs), and natural bond orbital (NBO). Furthermore, the time-dependent density functional theory (TD-DFT) method was used to analyze the optical properties and photovoltaic characteristics of selected metalloporphyrins by examining the UV-Vis spectra. In summary, the study presents a thorough description of the structural and electronic properties of the investigated complexes and provides insights into their potential use in photovoltaic applications. [ABSTRACT FROM AUTHOR]

Introduction: Enalapril maleate is an antihypertensive ethyl ester pro-drug with two crystalline forms. A network of hydrogen bonds in both polymorphs plays an important role on solid-state stability, charge transfer process and degradation reactions (when exposed to high humidity, temperature and/or pH changes). Computational Procedures: Supramolecular arrangement was proposed by Hirshfeld surface using the CrystalExplorer17 software and quantum theory of atoms in molecules. The electronic structure properties were calculated using the functional hybrid M06-2X with 6–311++G** base function employing diffuse and polarization functions to improve the description of hydrogen atoms on intermolecular interactions. Also, the H+ charge transfer between enalapril and maleate molecules was performed using Car-Parrinello molecular dynamics with the Verlet algorithm. In both simulations, the temperature of the ionic system was maintained around 300 K using the Nosé-Hoover thermostat and the electronic system evolved without the use of the thermostat. Results: This work evaluates the effect of maleate on the structural stability of enalapril maleate solid state. The electronic structural analysis points out a partially covalent character for N1-H∙∙∙O7 interaction; and the molecular dynamic showed a decentralized hydrogen on maleate driving a decomposition by charge transfer process while a centered hydrogen driving the stabilization. The charge transfer process and the mobility of the proton (H+) between enalapril and maleate molecules was demonstrated using supramolecular modeling analyses and molecular dynamics calculations. [ABSTRACT FROM AUTHOR]

Context: In recent years, fluorescent probe technology has received more and more attention. However, the photophysical and photochemical properties of probe molecules still need to be further explored. This paper presents the excited state intramolecular proton transfer (ESIPT) processes and photophysical properties of the probe molecule 4-bromo-2-((E)-((Z)-((5-bromo-1H-indol-2-yl) methylene) hydrazono) methyl) phenol (BHPL) and its four derivatives (BHPL2, BHPL3, BHPL4, and BHPL5). Infrared spectra and geometric structure analyses revealed that introducing the –NH2 group on the benzene ring with the hydroxyl group will enhance the intramolecular hydrogen bond, which benefits the ESIPT process. Combining their absorption and fluorescence spectra, it can be concluded that BHPL2 and BHPL4 are both excellent probe candidates due to their large Stokes shift. The hole and electron and root mean square displacement analyses manifest that the fluorescence quenching of BHPL4 may be due to the intramolecular charge transfer process. Potential energy curves of BHPL and its four derivatives noted that ESIPT process of the BHPL2 is the most favorable to occur. The frontier molecular orbital and NBO analyses indicated that besides introducing electron-donating groups to reduce the energy gap and enhance fluorescence emission, introducing double electron-withdrawing groups can also achieve this effect, explaining why the energy barrier of ESIPT process for BHPL2 is lower than BHPL5. This work would provide the theoretical basis for designing novel fluorescence probes with more prominent properties. Methods: The ground (S0) and excited (S1) state structures of all compounds were optimized by density functional theory (DFT) and time-dependent (TDDFT) method, with B3LYP/6-311+G(d,p) level, respectively. The infrared spectra and potential energy curves were simulated at the same theoretical level. The reduced density gradient scatter plots and interaction region indicator isosurfaces were drawn using Multiwfn and VMD programs. The absorption and fluorescence spectra were simulated by the TDDFT/B3PW91/6-311+G(d,p) method. All the calculations in this work are carried out in Gaussian 16 program package. [ABSTRACT FROM AUTHOR]

Context: By utilizing first-principles calculations, we studied the electronic properties of graphdiyne nanosheet (GDY) and its Si-doped counterpart, Si-GDY. Both GDY and Si-GDY sheet surfaces were examined for the drug cisplatin (CP) adsorption using adsorption energy, charge transfer, and changes in electrical conductivity as indicators. Pure GDY has little affinity for CP, according to this study. Only 7.83% of the GDY surface's bandwidth energy changed after CP adsorption. CP on Si-GDY has a gaseous energy value of −18.75 kcal/mol and an aqueous energy value of − 49.39 kcal/mol. Methods: The prescribed medications' water-phase solubility is determined by their solvation energy value. These charges are transferred between CP and the Si-GDY sheet, which is extremely positively charged, and this gives CP the necessary binding energy. After CP adsorption, electrical conductivity of Si-GDY increased by approximately 19.01%. [ABSTRACT FROM AUTHOR]

Background: In the present work, DFT and time-dependent DFT calculations were performed to investigate the role of anchoring groups on the photophysical properties and reveal structure-property correlations of triphenylamine (TPA) derivatives. The selected anchoring groups are tetrazole, acrylamide, hydantoin, and rhodanine. Results: Our results show that the different anchoring groups employed alter the planarity, intramolecular charge transfer properties, and HOMO-LUMO gap and hence influence the optoelectronic properties of the dyes. Although all molecules fulfill the basic requirements with suitable energy levels, band gap, absorption, and charge transfer properties, the dye with rhodanine acceptor (TPA4) was the most promising candidate due to its lowest HOMO-LUMO gap, red-shifted highest λmax absorption value, better ICT pattern, low total reorganization energy, and good electron injection properties. Overall, it is anticipated that the results of this investigation will point to new avenues for the experimental fabrication of remarkably effective metal-free organic dyes for solar cell applications. [ABSTRACT FROM AUTHOR]

Context: Just how much effort and detail should we invest in analyzing interactions of the order of 5 kcal mol−1? This comment attempts to provide a conciliatory overview of what is often a contentious field and to pose some questions that I hope will eventually lead at least to some consensus. Methods: This is an opinion article without calculations or data. [ABSTRACT FROM AUTHOR]

Context: The massive emission of carbon dioxide in the world causes global warming and a series of increasingly serious ecological problems. It is urgent to find efficient adsorbent for large-scale CO2 capture. Graphene as a solid adsorbent has exhibited great potential and development prospects in gas adsorption. Doping atoms at defect sites in composite graphene is considered as one of the promising approaches to enhance the gas adsorption ability. Nevertheless, composite graphene doping with different atoms has not been explored to a large extent so far. Methods: In this work, vacancy graphenes with single C-vacancy (VI-G) and with double C-vacancies (VII-G) are doped with nitrogen atoms and metal atoms M (M = Co, Mo, Mn, Fe) to form composite configurations. The Perdew-Burke-Ernzerho (PBE) functional is used under the generalized gradient approximation (GGA) basis set. A comprehensive study of the adsorption effect and charge transfer characteristics of CO2 molecule on different composite graphene configurations is carried out through DFT calculation. By analyzing the adsorption energy, adsorption distance, energy band structure, and atomic Mulliken population, it is found that the composite graphene doped with metal atoms such as Co-3N-VI, Mo-3N-VI, Mn-3N-VI, Fe-3N-VI, and Mo-4N-VII significantly enhanced the CO2 adsorption. Further analysis of charge density and density of states (DOS) demonstrates that CO2 adsorption on M-3N-VI and M-4N-VII reached the same conclusion. Thus, it is concluded that appropriate metal atoms can enhance the adsorption characteristics. [ABSTRACT FROM AUTHOR]

Context: The UV(ultraviolet) absorption spectrum of PETN under different electric field loading directions(X, Y, and Z) with the value of strength range from 0.001 a.u. to 0.006 a.u. was calculated with the TDDFT(Time-dependent density functional) in this work. With the increase of electric field strength, the absorbance of PETN in the ultraviolet band decreases. To explain the action mechanism of the electric field on PETN UV(ultraviolet) absorption spectrum, we analyzed and counted the contribution rate, oscillator strength, and vertical excitation energy of the main excitation process whose contribution rate to the UV absorption spectrum is greater than 10%. The contribution of PETN to the UV spectrum in all directions without an electric field was also listed to investigate the anisotropy of PETN in the excitation process under an electric field. The hole-electron analysis showed that the electric field will enhance the charge transfer characteristics in the excitation process of PETN. To investigate the anisotropy of the response under different electric field application directions, the contribution of the UV absorption spectrum in different directions was studied. Methods: Optimization and TDDFT calculation were performed at the level of M06-2X/def2-TZVP and PBE0/def2-TZVP respectively, with Gaussian09 program. The hole-electron analysis and UV absorption spectrum plotting were performed with Multiwfn3.8. [ABSTRACT FROM AUTHOR]

Context: The improvement of new organic flavone-based donor-spacer-acceptor (D-π-A) type dye molecules of the 3-(4-hydroxypiperidin-2-yloxy)-7-hydroxy-2-(3,4-dihydroxyphenyl)-4H-chromen-4-one (D1), 7-hydroxy-2-(3,4-dihydroxyphenyl)-3-(piperidin-4-yloxy)-4H-chromen-4-one (D2), and 3-((2-aminopyridin-4-yloxy)methoxy)-7-hydroxy-2-(3,4-dihydroxyphenyl)-4H-chromen-4-one (D3) were successfully designed and synthesized for dye-sensitized solar cells (DSSCs). Methods: Here, we discuss the synthesis of flavone compounds as well as their photophysical and electrochemical characterization. Using the Gaussian 09w software, the electronic structures and apsorption spectra have been calculated at the B3LYP, B3PW91, CAM-B3LYP, MPW1PW91, PBEPBE, and ωB97XD theory with the 6-311G(d,p) basis sets. Results: The computed values of the D2 molecule ground state optimized HOMOs-LUMOs energy is well positioned for advantageous charge transfer (CT) into the semiconducting material (TiO2) as well as the electron injection process. With a high power conversion efficiency (PCE) of 3.46% (VOC = 0.718 V, JSC = 7.07 mA cm−2, and FF = 0.68), the D2 compound also demonstrated good photovoltaic (PV) properties. Conclusion: These findings unequivocally demonstrate that altering the D-π-A metal-free organic material electron-withdrawing capacity is a useful strategy for enhancing the optical and electrical characteristics of the organic PV system. [ABSTRACT FROM AUTHOR]

Context: Density functional theory (DFT) method was employed to investigate the electronic structure properties, excited state dynamics, charge transfer, and photovoltaic potential of benzo [1,2,5] thiadiazole fused to 3,7-dimethyl-3a,6,7,7b-tetrahydro-5H-thieno[2′,3′:4,5]thieno[3,2-b]pyrrole to form 3,9,12,13-tetramethyl-12,13-dihydro-[1,2,5]thiadiazolo[3,4-e]thieno[2″,3″:4,5]pyrrolo[3.2-g]thieno[2′,3′:4,5]thieno[3,2-b]indole as the acceptor (A), bridge with thiophene as π-spacer to the donor moieties (D) which are 2,3-dihydrobenzo [b]thiophene-6-carboxylic acid (M4) and functionalized R, M1, M2, M3, and M5 to give a D-π-A-π-D. Here is the reverse combination for our molecules: the A-π-D-π-A type of chromophore configuration. It is also observed that tuning the dono-bridge configuration significantly increases the ease of charge transfer as the energy gap decreases in the order of 1.29 eV in M4 < 1.59 eV in M3 < 1.67 eV < 1.99 in M2 and 2.06 eV. The reorganization energy (RE) of M3 (0.0031) and M5 (0.0031) indicates an increase in the order of M3 > M5 > R > M2 > M4 > M1. The HOMO-LUMO indicates that the reactivity decreased, while the stability increased for the reference R at 0.990 eV, compared to the designed molecules M1–M5, with M1 being the least stable at 0.970 eV, while M4 exhibited the highest stability at 1.550 eV. The stability of the designed molecule decreased in the order of M4:1.550 > M3:1.257 > M5:1.197 > M2:1.010 > M1:0.970. Therefore, all results point to the electron-deficient core as an effective end-capped electron acceptor in M1–M5 compounds. As the ideal pair for successfully optimizing optoelectronic properties by reducing the HOMO-LUMO energy levels, reorganization energy, and binding energy and enhancing the absorption maximum and open-circuit voltage values in these designed molecules. Methods: DFT and TDDFT calculations were performed with Gaussian 16 program. The modelled compounds were optimized fully using the CAM-B3LYP, WB97XD, B3LYP, and MPW1PW91 functionals with the 6-31 G (d,p) basis set. The graphs for the density of states were plotted using the PyMOlyze software. Other molecular properties like the transition density matrix (TDM) and electron density difference maps (EDD) were rendered via the Multiwfn software. [ABSTRACT FROM AUTHOR]

Background: The organic dyes with non-fullerene acceptors (NFAs) have aided in the creation of competitive organic solar cells (OSCs) with long-term sustainability. A series of NFA dyes (IDIC-R1–IDIC-R9) have been designed by varying the end-capped fluorinated moieties (PD1–PD6) at indaceno (IDIC) core. Methods: All the calculations were performed by density functional theory (DFT) and time-dependent DFT (TD-DFT)–based approaches. All the geometries were optimized at B3LYP/6-31G + (d,p) of DFT level at their ground state energies. Out of several density functionals, the CAM-B3LYP with 6-31G + (d,p) basis sets was selected after a benchmark study to carry out further calculations. All the dyes had their bandgaps in 0.11–3.12 eV while their starting reference dye had a bandgap value of 2.01 eV. Results: Their ionization potential (IP) implied that these dyes have strong tendency to lose electrons. The λmax of the dyes was slightly redshifted from the IDIC (476 nm) and IDIC-R (479 nm) when changing solvent polarity from methanol to DCM and then chloroforms. The natural bond orbital (NBO) analysis showed the (S63)LP → (C61-C62)π* with highest stabilization energy. Their electron injection analysis showed that these dyes can be a good anode material against the aluminum and gold electrodes. The intramolecular charge transfer (ICT) process and stability of the dyes were investigated using frontier molecular orbital (FMO) and natural bond orbital (NBO) analysis. Conclusion: Among all dyes, IDIC-R8 has the highest linear polarizability and second-order hyperpolarizability (βtotal). All the dyes demonstrated promising non-linear optical (NLO) properties due to their low charge transfer barriers. Scientists would be able to exploit these properties to identify the best NLO materials for existing applications. [ABSTRACT FROM AUTHOR]

In this paper, the effect of substitutional doping of boron (B), carbon (C), nitrogen (N), oxygen (O), and phosphorus (P) at the S-site on the electronic structure of the monolayer TiS2 system is investigated using a first-principles calculation method. The effect of nonmetal doping on the band gap of TiS2 and its mechanism were studied by analyzing the stability, electronic structure, and charge transfer of the system. By calculating the electron cloud overlap population and formation energy, we confirmed that the system is stable, and the Ti–X bond length of the doped system undergoes different degrees of distortion. The properties of the B, C, and N doped system show different properties with different doping concentrations; the band gap of the O-atom system gradually expands with the rise of the doping rate. The hybridization positions of the impurity and the intrinsic atoms are found by comparing the DOS; combined with the charge density difference, we confirmed the interaction of impurity atoms with the system and revealed the bonding process of different systems. [ABSTRACT FROM AUTHOR]

In this work, we were devoted to explore the effect of solvent polarities on the excited-state intramolecular proton transfer (ESIPT) process of 1-acetamido-4-hydroxyanthraquinone (AcHAQ) in three different polarity solvents (acetonitrile, chloroform, and cyclohexane) based on the density functional theory (DFT) and time-dependent DFT (TD-DFT) methods, and thereby regulating the distribution ratio between the dual excited-state isomers (enol and keto). The calculated geometrical parameters and infrared (IR) vibrational spectra have confirmed the excited-state intramolecular hydrogen bond (IHB) strengthening mechanism. Natural bond orbital (NBO) population analysis indicates that the intramolecular charge transfer (ICT) around IHBs has enhanced IHB, thereby triggering the ESIPT reaction. In addition, results obtained from the scanned potential energy curve (PEC) manifest that ESIPT process prefers to occur along the O3-H2...O1 IHB and energy barriers corresponding to the proton transfer in ACN are the lowest among all the studied solvents. [ABSTRACT FROM AUTHOR]

As a neurotoxic and corrosive gas pollutant, H2S is unhealthy for all creatures and limits the development of the industry. By first-principles calculation, the adsorption behaviors of H2S gas on the original graphdiyne (GDY), non-metallic atoms decorated GDY, and metal atoms decorated GDY were initially studied. The adsorption configuration, adsorption energy, and charge transfer between H2S and GDY were calculated in detail. The electron density and the partial density of states (PDOS) were also examined. The results show that there is only weak physical adsorption between the original GDY, non-metallic atoms decorated GDY, and H2S gas molecules, so GDY and non-metallic atoms decorated GDY cannot be directly used to adsorb H2S gas. The adsorption of H2S gas on GDY decorated with metal atoms (Cu, Ti, and V) was significantly enhanced, and the adsorption in this condition belongs to chemical adsorption. They can be used as H2S gas adsorbing materials. In addition, the dissociation of H2S on transition metal atoms decorated GDY was further investigated. The results show that H2S in one of the five configurations dissociates on V-decorated GDY directly. Cu- and Ti-decorated GDY can be used as substrates for the dissociation of H2S. The energy barriers in this process are 1.605 eV and 0.360 eV, respectively. It is hoped that the research results in this work can provide insights into the development of H2S gas adsorbing and dissociating materials based on transition metal atoms decorated GDY. [ABSTRACT FROM AUTHOR]

A new photosensitizer 1-WS55 (dyad) based on two dyes with excellent properties, azulenocyanine (1) and WS55, is proposed at the density functional theory level (M06/def2-SVP). 1 is a dye having a broad NIR absorption (~ 1000 nm), and WS55 is a metal-free organic dye that presents a huge photoelectric conversion efficiency (PCE) of 9.5%. The dyad presents a panchromatic absorption along the UV–Vis-NIR region. It exhibits two intense Q bands (880, 926 nm) in the NIR region, one strong band (672 nm) in the visible region, and several bands in 300–600 nm. Charge transfer bands in the dyad from 1 to WS55 were found in the visible region, which favors the adsorption on an anatase TiO2 surface. The interaction energies dyad (dye)-TiO2 were calculated as a periodic system and corrected by the basis set superposition error. These show better adsorption for the dyad than fragments 1 and WS55. The electron injection calculated from the dye (dyad) to TiO2 suggests an efficient solar energy conversion because of ΔGinj > 0.2 eV. Additionally, calculations performed for the reorganization energy of electrons and holes indicate that the dyad presents the highest charge mobility. In summary, the dyad proposed 1-WS55 constitutes an excellent candidate to be used as a potential photosensitizer for the DSSCs. [ABSTRACT FROM AUTHOR]

The development of detecting hypochlorous acid (HClO) in living endoplasmic reticulum has attracted much attention in the fields of biology, medicine, and pharmacy. In the present work, the one-photon absorption (OPA), one-photon emission (OPE), and two-photon absorption (TPA) properties of a series newly synthesized chemosensors with naphthalimide as the fluorophore were systematically investigated using time-dependent density functional theory in combination with response theory. Special emphasis is placed on evolution of the probes' optical properties in the presence of HClO. These compounds show drastic changes in their photoabsorption and photoemission properties when they react with HClO, indicating them to be excellent candidates as fluorescent chemosensors. To further understand the mechanisms of the two probes, we have employed the hole and electron analysis to investigate the charge transfer process for the photoemission of the molecules. The receptor effect is found to play a dominant role in the sensing performance of these probes. Specifically, two-photon absorption properties of the molecules are calculated. We have found that all probes show significant two-photon responses in the near-infrared light region. And the maximum two-photon absorption cross section of probe 2 is greatly enhanced with the presence of HClO, indicating that probe 2 can act as a potential two-photon excited fluorescent HClO probe. The theoretical investigations would be helpful to build the structure–property relationships for the naphthalimide-contained probes, providing information on the design of efficient two-photon fluorescent sensors that can be used for biological imaging of HClO in endoplasmic reticulum. [ABSTRACT FROM AUTHOR]

Mangiferin is a glycosylated xanthone widely distributed in nature, which exhibits wide pharmacological activities, highlighting its anti-cancer properties. Mangiferin interferes with inflammation, lipid, and calcium signaling, which selectively inhibits multiple NFkB target genes as interleukin-6, tumor necrosis factor, plasminogen, and matrix metalloproteinase, among others. In this work, the interactions of this polyphenol with MMP-9 and NF-κβ are characterized by using computational chemistry methods. The results show MMP-9 inhibition by mangiferina is characterized for the interact with the catalytic Zn atom through a penta-coordinate structure. It is also demonstrated through a strong charge transfer established between mangiferin and Zn in the QM/MM study. Concerning the mangiferin/NF-κβ system, the 92.3% of interactions between p50 sub-unity and DNA are maintained with a binding energy of − 8.04 kcal/mol. These findings indicate that mangiferin blocks the p50-p65/DNA interaction resulting in the loss of the functions of this hetero-dimeric member and suggesting inhibition of the cancer progression. Experimental results concerning the anti-cancer properties of mangiferin show that this natural compound can inhibit selectively MMP-9 and NF-ƙβ. Although the anti-tumor properties of mangiferin are well defined, its molecular mechanisms of actions are not described. In this work, a computational study is carried out to characterize the interactions of mangiferin with these molecular targets. The results obtained corroborate the anti-proliferative and anti-apoptotic activity of mangiferin and provide a depiction of its mechanisms of action. [ABSTRACT FROM AUTHOR]

Noncovalent interactions are ubiquitous and have been well recognized in chemistry, biology and material science. Yet, there are still recurring controversies over their natures, due to the wide range of noncovalent interaction terms. In this Essay, we employed the Valence Bond (VB) methods to address two types of interactions which recently have drawn intensive attention, i.e., the halogen bonding and the CH‧‧‧HC dihydrogen bonding. The VB methods have the advantage of interpreting molecular structures and properties in the term of electron-localized Lewis (resonance) states (structures), which thereby shed specific light on the alteration of the bonding patterns. Due to the electron localization nature of Lewis states, it is possible to define individually and measure both polarization and charge transfer effects which have different physical origins. We demonstrated that both the ab initio VB method and the block-localized wavefunction (BLW) method can provide consistent pictures for halogen bonding systems, where strong Lewis bases NH3, H2O and NMe3 partake as the halogen bond acceptors, and the halogen bond donors include dihalogen molecules and XNO2 (X = Cl, Br, I). Based on the structural, spectral, and energetic changes, we confirm the remarkable roles of charge transfer in these halogen bonding complexes. Although the weak C-H∙∙∙H-C interactions in alkane dimers and graphene sheets are thought to involve dispersion only, we show that this term embeds delicate yet important charge transfer, bond reorganization and polarization interactions. [ABSTRACT FROM AUTHOR]

Graphene and its derivatives have been widely used in the area of high-sensitivity sensing materials for small-molecule gases. Based on first-principle calculations, the present study systematically investigated the adsorption of 1,1-dimethylhydrazine on intrinsic graphene, graphene with vacancy defects, and nitrogen-doped graphene. The adsorption effects, when 1,1-dimethylhydrazine takes on different orientations, were determined separately, and the specific adsorption energy and charge transfer were calculated accordingly. The results reveal that the 1,1-dimethylhydrazine adsorption on intrinsic graphene, graphene with vacancy defects, and nitrogen-doped graphene falls into physical adsorption. Besides, both vacancy defect and nitrogen doping help enhance the adsorption but the effect of vacancy defect is superior to that of nitrogen doping. [ABSTRACT FROM AUTHOR]

With the aim of utilizing structural modeling techniques to design efficient organic solar cells, a quantum chemical density functional theory (DFT) and its time-dependent DFT (TD-DFT) study have been carried out for the examination of the photovoltaic properties of four BT-ClC-based novel non-fullerene acceptor (NFA) molecules. The designed entities (BT1–BT4) have an A-π-D-π-A configuration with seven fused ring-based BDT central core and newly substituted peripheral acceptor moieties. The optical parameters (absorption maxima, light-harvesting efficiency, first excitation energies, and dipole moments), electronic properties (frontier molecular orbitals, density of states, and molecular electrostatic potential), and charge transfer characteristics (open-circuit voltage, transition density matrix, and fill factor) of the investigated molecules were evaluated using the selected B3LYP/6-31G (d,p) level of theory. The systematic computational analysis reveals that under the influence of terminal acceptor groups, there is an augmentation in the absorption range, and reduction in the band gap values. The electron withdrawing effect of acceptor moieties is evident from the electronic density distribution on the HOMO–LUMO orbitals, along with the density of state (DOS) graphs. Transition density matrix (TDM) analyses reveal consistent charge transfer in the newly devised entities. Reorganization energies computed for electron and hole are significantly lower than the reference, making the transfer of charge carriers efficient. Open-circuit voltage (Voc) of reported acceptor entities, theoretically computed with PTB7-Th donor, revealed maximum output. Furthermore, the estimated fill factor (FF) of the investigated molecules predicted an increase in power conversion efficiencies. Consequently, all the computed parameters favor the applicability of our designed molecules in the field of organic photovoltaics by virtue of their excellent charge mobilities, increased absorption maximum values, and reduced band gaps. [ABSTRACT FROM AUTHOR]

In this article, the intermolecular interactions of cyclo[18]carbon with XCN (X = H, F, Cl, Br, I) were investigated in detail by quantum chemistry calculations and wavefunction analyses. The electrostatic potential and van der Waals potential of cyclo[18]carbon were examined, then the structures of the complexes, the interaction energies of the intermolecular interactions were studied. Quantum theory of atoms in molecules analysis was performed to help understand the specific interactions. The XCN molecules can insert into the cyclo[18]carbon ring, and ClCN, BrCN, and ICN could also bind with cyclo[18]carbon from outside. Charge transfer in the inner complex is more prominent than that of the outer complex. Plots of electron density difference revealed that electron density shift was significantly different when the X atom changed. The main driving force for molecular binding is dispersion attraction, which is disclosed by interaction region indicator analysis and energy decomposition calculations. [ABSTRACT FROM AUTHOR]

The effects of B, N, and BN doping of arsenene and different strains on the stability, electronic structure, and optical properties of BN-doped arsenene were investigated using a first-principles approach. It was found that B, N, and BN doping caused the bandgap of arsenene to shift from indirect-direct, and strong charge transfer occurred between arsenene and B, N, and BN, and the transfer between N atoms and arsenene was more intense. The binding energy of the BN-doped arsenene system is always negative at different strains and in a stable state, but the stability of the structure is gradually decreasing. The bandgap of the BN-doped arsenene system shows a trend of decreasing, then increasing, and then decreasing under different tensile and compressive deformations. The only difference is that the tensile deformation continues to increase the bandgap at 2%, while the compressive deformation decreases the bandgap. The p-state electrons of the As atom near the Fermi energy level make the main contribution to the BN-doped arsenene system, and the p-state electrons of the B atom have some contribution. Red shifting occurs at the absorption and reflection peaks for doped systems with tensile deformation of 1% to 5%, and the absorption and reflection peaks for doped systems with compressive deformation of − 1% to − 5%. [ABSTRACT FROM AUTHOR]

It is important for life safety and scientific research to design new sensing materials for detecting CO, CH4, and CO2 from the environment. We theoretically designed a new Cr-doped graphene-like hexagonal borophene (CrB6) as potential sensor material for these gases. Carrying out first-principle density-functional calculations, we calculated the adsorption energy, band structure, adsorption distance, charge transfer, charge density difference, density of states, and partial density of states of CO, CH4, and CO2 gas molecules absorbed on CrB6 monolayer. The calculated results show that the adsorption behavior of CO is different from those of CH4 and CO2. CO adsorbed on CrB6 monolayer prefers chemisorption with the adsorption energy of − 2.59 eV while CH4 and CO2 adsorbed on CrB6 monolayer prefer physisorption with the adsorption energy of − 0.72 and − 0.69 eV. As a result, the different adsorption behaviors have significant influence on the band structures and density of states of CrB6 monolayer. We hope that our results can help experimentalists synthesize better sensor materials based on hexagonal borophene. [ABSTRACT FROM AUTHOR]

Graphyne (GYN) has received immense attention in gas adsorption applications due to its large surface area. The adsorption of toxic ammonia and nitrogen halides gaseous molecules on graphyne has been theoretically studied at ωB97XD/6–31 + G(d, p) level of DFT. The counterpoise corrected interaction energies of NH3, NF3, NCl3, and NBr3 molecules with GYN are − 4.73, − 2.27, − 5.22, and − 7.19 kcal mol−1, respectively. Symmetry-adapted perturbation theory (SAPT0) and noncovalent interaction index (NCI) reveal that the noncovalent interaction between analytes and GYN is dominated by dispersion forces. The significant change in electronic behavior, i.e., energies of HOMO and LUMO orbitals and NBO charge transfer correspond to the pronounced sensitivity of GYN towards considered analytes, especially NBr3. Finally, TD-DFT calculation reveals a decrease in electronic transition energies and shifting of adsorption to a longer wavelength. The recovery time for NX3@GYN is observed in nanoseconds, which is many orders of magnitude smaller than the reported systems. The recovery time is further decreased with increasing temperature, indicating that the GYN benefits from a short recovery time as a chemical sensor. [ABSTRACT FROM AUTHOR]

Selectivity of dopamine (DA), uric acid (UA), and ascorbic acid (AA) is an open challenge of electrochemical sensors in the field of biosensing. In this study, two selective mechanisms for detecting DA, UA, and AA biomolecules on the pristine boron nitride nanosheets (BNNS) and functionalized BNNS with tryptophan (Trp), i.e., Trp@BNNS have been illustrated through density functional density (DFT) calculation and charge population analysis. Our findings reveal that the adsorbed biomolecules on Trp@BNNS indicate the less sensitivity factor of biomolecule separation than the functionalized biomolecules with Trp (Trp@biomolecule) adsorbed on pristine BNNS. From the calculations, strong adsorption of Trp@biomolecule on the pristine substrate corresponds to enhancing of electron charge transfer and electrical dipole moment. Our analysis is in good agreement with the previous theoretical and experimental results and suggests new pathway for electrode modification for electrochemical biosensing. [ABSTRACT FROM AUTHOR]

We performed a structural investigation on the adsorption and activation of CO2 molecules on different sized Pt clusters to study the effect of Pt cluster size on CO2 adsorption. Several Ptx clusters (x = 1–5 and 13) were analyzed to represent metal dispersion on surfaces and nanoscale metal clusters. For (110) γ-alumina surfaces, the Pt2 cluster site was the most stable. In addition, the Pt3 cluster site was the most stable for CO2 adsorption on Pt/Al2O3. Charge transfer from Pt clusters to CO2 was critical for CO2 activation. [ABSTRACT FROM AUTHOR]

Vibronic coupling and hydration were taken into account when describing the absorption of coumarin C343 (both neutral and anionic forms) in an aqueous media. It was shown that the B3LYP functional with the 6–31 + + G(d,p) basis set and the IEFPCM solvent continuum model give theoretical vibronic absorption spectra, which are coincide with the experimental ones. Of the structural differences between C3430 and C343–, there is a different twisting of the carboxyl group additionally changing due to excitation. Upon excitation, a significant shift in the electron density occurs from the C10 atom to the C4 atom only. Thus, a charge transfer on the scale of the entire molecule does not occur. Different hydration complexes with strongly bound water molecules have been analyzed. [ABSTRACT FROM AUTHOR]

According to P.K. Chattaraj. J Phys Chem A 2001, 105, 511-513 "the maximum Fukui function site is the best for the frontier-controlled soft-soft reactions whereas for the charge-controlled hard-hard interactions the preferred site is associated with the maximum net charge and not necessarily the minimum Fukui function". Taking into account these outcomes in this research is explored this reactivity scheme using in first case the reaction between fulminic acid with ethylene (reference reaction), after is varying the dipolarophile in the reaction between fulminic acid with acetylene, and finally is varying the dipole in the reaction between formonitrile imine with ethylene. These results allow study parameter such as charge transfer, polarizability, covalent character on bonding, among other; also shown the preference by the sf- / sf+ interactions in the transition state on the sf- / sf- interactions. On the other hand, these results also were justified using net electrophilicity which is defined as the electrophilic power of a system relative to its own nucleophilic power. [ABSTRACT FROM AUTHOR]

The main goal of this work was the theoretical interpretation of the absorption spectra of neutral red in an aqueous solution (both neutral NR0 and protonated NR+ forms). To achieve this problem, TD-DFT/DFT calculations with different hybrid functionals, the IEFPCM solvent model, and the 6–31 + + G(d,p) basis set were used. MN12SX functional provided the best agreement with the experiment for both dye forms. While the absorption band of the cationic form of the dye in the visible region of the spectrum is due to one transition S0 → S1 (HOMO–LUMO), for its neutral form, there are two transitions S0 → S1 (HOMO → LUMO) and S0 → S2 (HOMO-1 → LUMO), with the latter having a higher intensity. The protonation of the dye chromophore introduces significant changes in HOMO shape. At the same time, LUMOs are almost the same for the protonated and neutral forms of the NR. During the transition from NR0 to the S1 state, its dipole moment increases more significantly than during the transition to the S2 state. Calculations confirmed the assumption of Singh et al. about the existence of two closely spaced excited states of NR0, the first of which has a larger dipole moment. However, the hypothesis of these authors about the corresponding intramolecular charge transfer, as well as the huge value of the dipole moment of this excited state (~ 20 D) declared by them, was not confirmed by present calculations. It was shown that the photoinduced charge redistribution in both the neutral and cationic forms of the dye is local, and the corresponding dipole moment is ~ 10 D. This agrees with other early theoretical work by Aaron et al. The influence on the NR+ absorption spectrum of hydrating water molecules was also analyzed. It was found that the interplay of electrostatic and site-specific contributions leads to the fact that NR solvatochromism does not have a pronounced dependence on the polarity of the solvent. [ABSTRACT FROM AUTHOR]

Organic solar cells (OSCs) with bulk heterojunction (BHJ) structures consisting of electron-donor and electron-acceptor materials have achieved impressive progress over the past decade, demonstrating their great potential in practical applications. In this study, we have designed five fullerene-free acceptor-based molecules containing indaceno-dithiophene as a central core moiety. We studied the optoelectronic features of these newly architecture molecules by using DFT and TD-DFT approaches. For the investigation of the optoelectronic characteristics of the reference and newly designed molecules, we performed different parameters including FMO's, absorption maxima, excitation energy, transition density matrix (TDM) along with binding energy, dipole moment, the partial density of states, charge mobility, and charge transfer analysis. Among all engineered molecules, SK1 has proven to be the most efficient solar cell due to its promising optoelectronic and photovoltaic properties. SK1 reveals smaller band-gap (Egap = 1.959 eV) and lesser λh (0.0070 eV) and λe (0.0051 eV). SK1 illustrated comparable binding energy value (0.33 eV) and lowest excitation energy (1.62 eV) which will lead to improved power conversion efficiency values. The SK1 molecule demonstrated the highest λmax value (764 nm) in the solvent phase which could lead to redshift absorption for achieving the high efficiency of OSCs. This molecular modeling approves that the best working efficiency of organic solar devices can be achieved by terminal group modifications due to their promising photovoltaic and optoelectronic properties. It is evident from the current analysis that all the theoretically fabricated molecules (SK1–SK5) are fabulous and highly suggested to experimental workers for their synthesis and advancement of these highly competent solar devices in the future. [ABSTRACT FROM AUTHOR]

The present investigation highlights the two-dimensional design of several interesting superalkali-doped borophene derivatives for efficient nonlinear optics (NLO). The combination effects and resulting NLO responses of borophene (B36) and superalkali units (Li3O) were evaluated by orienting superalkali clusters at various sites, such as the hub, rim, and bridge, around an B36 molecule. The charge analysis was characterized by frontier and natural bond orbital analyses, a narrowed HOMO–LUMO bandgap and greater intramolecular charge transfers. Molecular electrostatic potential surfaces demonstrated enhanced optoelectronic features of these complexes that are viable due to Li3O adsorption. Singly doped and doubly doped complexes were considered, and their NLO properties were calculated. Bandgap energy was reduced approximately threefold when doped with two Li3O. As a considerably high figure of merit, first hyperpolarizability (βo) values of up to five digits (including 10,611 au for complex A) prove that these systems can be utilized as promising candidates in various NLO applications. [ABSTRACT FROM AUTHOR]

The transport properties of sodium superoxide (NaO2) are governed by the transfer of charge between O2− complexes. Although it goes through a plethora of structural phase transitions, its electronic and magnetic ground state remains shrouded in mystery. In this work, we perform first-principles density functional theory (DFT) calculations to understand the relationship between electronic structure and the reason for the non-observation of an antiferromagnetic (AFM) ground state in NaO2 vis-a-vis in KO2. In the cubic phase, uniform < Na–O-Na bond angles result in high symmetry and hence degeneracy in the O-2p orbitals. The freely rotating O2− molecules result in orbital degeneracy and hence paramagnetism at room temperature. Although the degeneracy between the bonding and anti-bonding orbitals of O2 dimers is lifted in the pyrite phase, the degeneracy between σ (σ*) and π (π*) states is still maintained and hence orbital degeneracy is partially lifted as the dimers are restricted to four directions now. The O-π* states are localized in such a manner that results in a substantial magnetic moment in the π*-orbital. The < O–Na–O bond angle (= 180°) in the c-axis facilitates a superexchange mechanism and thereby the system should be AFM in the pyrite phase. In the marcasite phase, the O-atoms are aligned parallel in alternative planes. The preservation of degeneracy among the two π* orbitals leading to only long-range orbital ordering negates any chance of quasi-one-dimensional AFM spin chains in NaO2. The difference in magnetic ground states of NaO2 and KO2 arises due to the difference in the electrostatic repulsion between electrons of Na+ and K+ ions with the O2− dimers. [ABSTRACT FROM AUTHOR]

The electronic sensitivity and adsorption behavior for mercaptan natural gas of a Ca12O12 nanocluster were studied via ab initio computations. To be more specific, to fully grasp the influence of mercaptan molecules on the chemical and electronic features of Ca12O12 nanocluster, some parameters, namely, charge transfer of natural bond orbital, molecular electrostatic potential, binding energies, and frontier molecular orbitals, are computed. The interaction between CH4S molecule and calcium atoms of Ca12O12 nanocluster through the sulfur head is strong. This strong interaction leads to a considerable transfer of charge from CH4S to the nanocluster. After mercaptan adsorption, the existing energy gap between two levels, the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) of the nanostructure, dropped by 2.21 eV, illustrating that the dissociation process has extensively increased the electrical conductance of nanostructure. This electrical signal can help to detect CH4S molecules. Moreover, it could be concluded that Ca12O12 nanocluster has a short recovery time. In addition, solvent considerably influences the geometry factors and electronic features of CH4S/Ca12O12 complexes, and the interactions between species are significantly weaker in the aqueous medium compared with those in the vacuum. [ABSTRACT FROM AUTHOR]

There have been numerous attempts for the theoretical design of a better donor- π -acceptor structural framework with improved absorption and emission properties. However, for effective dye designing, it is necessary to understand the electronic and photophysical properties of the dye systems. In this work, we report a detailed density functional theory (DFT) and time-dependent density functional theory (TD-DFT) investigations of the excited state characteristics and the influence of various groups (–HCO, =CH2, (–CH3)2, (HCO)2, and (–OCH3)2) attached to the donor group (–NH2) in a p-nitroaniline D- π -A system which are symbolized respectively as p-nitroaniline (A), N,N-dimethylnitroaniline (A2), N,N-dicarbonylnitroaniline (A3), N-methylenenitroaniline (A4), and N,N-dimethoxynitroaniline (A5). The first principles DFT and TD-DFT calculations from the ground state (S0) to the first five excited states: (S0→S1), (S0→S2), (S0→S3), (S0→S4), and (S0→S5) were utilized to explore the reactivity of D- π -A system using the conceptual DFT approach, characterization of electron excitation using the hole-electron analysis, visual study of the various real space functions in the hole-electron framework, density of states (DOS), measurement of charge transfer (CT) length of electron excitation ( Δ r ), measurement of the overlapping degrees of hole and electron of electron excitation (Λ ), interfragment charge transfer (IFCT) during electron excitation, and the second-order perturbation energy analysis from the natural bond orbitals (NBO) computation. Results of the excitation studies show that all the studied compounds exhibited an n→ π * localized type for first excitations (S0→S1) on –NO2 group in A, A2, A4, and A5 and –NCl2 in A3. π → π * charge transfer excitations were confirmed for S0→S2/S4/S5 in A and A2, S0→S3/S4/S5 in A3 and A5, and S0→S4/S5 in A4. The NBO second-order perturbation energy analysis suggest that the most significant hyperconjugative interactions were π (C 1 - C 2) → LP ∗ (1) C 6 (54.43kcal/mol), π C 1 - C 2 → LP (1) C 3 (40.82kcal/mol), π N 14 - O 16 → LP (3) O 15 (11.67kcal/mol), π (C 1 - C 6) → π ∗ (N 12 - O 13) (29.52kcal/mol), π (N 12 - O 13) → LP (3) O 14 (11.55kcal/mol), π (C 3 - C 4) → π ∗ (C 5 - C 6) (23.40kcal/mol), and π (C 5 - C 6) → π ∗ (N 12 - O 14) (24.88kcal/mol) π (C 3 - C 4) → π ∗ (C 5 - C 6) (24.64kcal/mol), which respectively corresponds to the A, A2, A3, A4, and A5 D- π -A systems under investigation, and these strong interactions stabilize the systems. [ABSTRACT FROM AUTHOR]

The present work explores the structural parameters and vibrational frequencies as well as molecular interactions of benzodiazepine derivatives, such as clothiapine (CT), clozapine (CZ), and loxapine (LX). Employing fitting experimental data to theoretical results is used to assess the structural parameters of heading composites. The main assignment is passed out according to the overall distribution of energy of the vibrational modes. From the hyper-conjugative interaction, the permanency of the structure had been predicted through natural bond orbital analysis; it is also used to identify the bonding and antibonding regions of the molecules. Moreover, electrostatic potential (ESP), density of states (DOS), and charge transfer occurring of the molecule among HOMO as well as LUMO energy were calculated and presented; utilizing electron localized field (ELF), localized orbital locator (LOL), and reduced density gradient (RDG), the chemical interactive regions are found. Additionally, mean polarizability (αtot), the first-order hyperpolarizability (βtot), and softness and hardness of the entitled compounds were also performed. The interaction between protein–ligand was also predicted by docking studies. [ABSTRACT FROM AUTHOR]