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Methyl N22‐methylpyropheophorbides‐a with chloride or hexafluorophosphate were prepared by chemically modifying chlorophyll‐a. The resulting product composed of cationic N‐methylated chlorin and chloride anion exhibited visible absorption and fluorescence emission maxima in chloroform at longer wavelengths than those with hexafluorophosphate. Both the absorption and emission spectra of the former were hypsochromically shifted by change of the solvent from chloroform to methanol to give almost the same corresponding spectra of the latter independent of solvents. The apparent counter‐anion dependency in chloroform and the specific solvent dependency in the N‐methyl‐chlorin with chloride are ascribable to the weak solvation of a hard chloride anion over soft hexafluorophosphate in chloroform and strong electrostatic interaction of the cationic chlorin with a chloride anion over hexafluorophosphate in chloroform as well as well solvation of both the anions in methanol. In addition, less emission of N‐methyl‐chlorin with chloride in chloroform would be due to partial fluorescence quenching based on the heavy atom effect of the adjacent chloride anion. [ABSTRACT FROM AUTHOR]

We develop a nonsolvatochromic comparison method for the determination of the α1 scale of solvent hydrogen‐bond acidity by means of 19F NMR spectrometry. We compare the 19F chemical shifts of 4‐fluoro‐2‐methylpyridine (as a sensitive hydrogen‐bond acceptor probe) and of 4‐fluoronitrobenzene (as a chemically similar but less basic reference probe). This so‐called 19F solvatomagnetic comparison method yields the hydrogen‐bonding contribution to δ (19F)(4‐fluoro‐2‐methylpyridine) that is well correlated to α1 values obtained from the solvatochromism of Reichardt's betaine dye. Therefore, this solvatomagnetic comparison method is applied to determine the α1 values of 13 choline chloride–based deep eutectic solvents. [ABSTRACT FROM AUTHOR]

Four dyes with substitutions of carbazole and phenothiazine in position C4 of naphthalimide were designed in conjugation as a donor–acceptor architecture (D–A). The absorption and emission characteristics of the prepared dyes were investigated in H2O, dimethylformamide (DMF), and their mixture (DMF:H2O = 1:1). The prepared dyes exhibited a pink and yellow color, with strong emission at λem = 526–590 nm due to charge transfer, with a positive solvatochromic effect. The feasibility of electron transfer in the dye-sensitized solar cell (DSSC) structure and energy levels were evaluated using electrochemical and density functional theory (DFT), which confirmed the use of dyes in the DSSC structure. The DSSCs were prepared using an individual strategy, and their optical properties were investigated under light of AM 1.5. The DSSCs based on dyes 1–4 achieved efficiency of 4.37%, 4.59%, 4.11%, and 4.27%, respectively. Therefore, the power efficiency increased by about 39% in the presence of the phenothiazine group. [ABSTRACT FROM AUTHOR]

The computational, solvatochromism, and preferential solvation studies have been carried out on newly synthesized bio‐active azo dye molecules, namely 5‐[(E)‐(1,5‐dimethyl‐3‐oxo‐2‐phenyl‐2,3‐dihydro‐1H‐pyrazol‐4‐yl)diazenyl]‐6‐hydroxy‐4‐methyl‐2‐oxo‐1,2‐dihydropyridine‐3‐carbonitrile (A1) and 5‐[(E)‐(1,5‐dimethyl‐3‐oxo‐2‐phenyl‐2,3‐dihydro‐1H‐pyrazol‐4‐yl)diazenyl]‐6‐hydroxy‐1,4‐dimethyl‐2‐oxo‐1,2‐dihydropyridine‐3‐carbonitrile (A2). The electronic properties, chemical reactivity, and optical characteristics of the dye molecules have been computed using density functional theory (DFT). These findings suggest that the dye molecules are chemically active and show their suitability in NLO applications. The computations related to light‐harvesting properties have been carried out on the dye molecules. The ADME properties of the dye molecules have been evaluated using SwissADME and PreADMET online tools. The solvatochromic behavior of dye molecules has been investigated using Lippert's and Reichardt's solvent polarity parameters. The dye molecules' dielectric interactions and hydrogen bonding characteristics are analyzed using the Catalan multiple regression approach. The findings of the solvatochromic studies suggest the potentiality of the molecules in polarity sensing applications. Additionally, the solvatochromic data has been exploited to determine the excited state dipole moments using various solvatochromic approaches. The HOMO‐LUMO energy values, absorption wavelengths, light‐harvesting properties, and excited state dipole moments of the synthesized dye molecules indicate their suitability in dye‐sensitized solar cell applications. The preferential solvation studies of dye molecules have been conducted in a DCM–DMSO solvent mixture. [ABSTRACT FROM AUTHOR]

Organic emitters that exhibit room‐temperature phosphorescence (RTP) in neat films have application potential for optoelectronic devices, bio‐imaging, and sensing. Due to molecular vibrations or rotations, the majority of triplet excitons recombine rapidly via non‐radiative processes in purely organic emitters, making it challenging to observe RTP in amorphous films. Here, a chemical strategy to enhance RTP in amorphous neat films is reported, by utilizing through‐space charge‐transfer (TSCT) effect induced by intramolecular steric hindrance. The donor and acceptor groups interact via spatial orbital overlaps, while molecular motions are suppressed simultaneously. As a result, triplets generated under photo‐excitation are stabilized in amorphous films, contributing to phosphorescence even at room temperature. The solvatochromic effect on the steady‐state and transient photoluminescence reveals the charge‐transfer feature of involved excited states, while the TSCT effect is further experimentally resolved by femtosecond transient absorption spectroscopy. The designed luminescent materials with pronounced TSCT effect show RTP in amorphous films, with lifetimes up to ≈40 ms, comparable to that in a rigid polymer host. Photoluminescence afterglow longer than 3 s is observed in neat films at room temperature. Therefore, it is demonstrated that utilizing intramolecular steric hindrance to stabilize long‐lived triplets leads to phosphorescence in amorphous films at room temperature. [ABSTRACT FROM AUTHOR]

This review article discusses the emerging amino‐terephthalonitrile (Am‐TN) and amino terephthalate‐based single benzene fluorophores (SBFs) for their highly emissive nature and potential for numerous technical applications. Am‐TN‐SBFs are a new class of SBFs having amine as the electron donating (EDG) and dinitrile as the electron withdrawing group (EWG). The beauty of these Am‐TN‐SBFs lies in excellent intramolecular charge transfer between the EDG and EWG. The placement of two nitrile groups in para‐position on the benzene ring allows better charge transfer from the donating amines to the linear nitrile group leading to the strongly emissive nature. We also outline here the latest developments in the well‐known family of amino terephthalate SBFs reported in the last 2 to 3 years. Amino terephthalate SBFs have esters as the EWG and amine as the EDG. These have intramolecular H‐bonding between the EDG and EWG which is responsible for their emissive behavior. [ABSTRACT FROM AUTHOR]

Herein, a deep blue emitter (PI‐TPB‐CN) with a synergistic effect of hybridized local and charge transfer excited state (HLCT) and aggregation‐induced emission (AIE) properties is successfully designed and synthesized to improve the performance of deep blue organic light‐emitting diodes (OLEDs). It is constructed using a 1,2,4,5‐tetraphenylbenzene (TPB) as an π‐conjugated AIE core being asymmetrically functionalized with a phenanthro[9,10‐d]imidazole (PI) as a weak donor (D) and a benzonitrile (CN) as an acceptor (A), thereby formulating D‐π‐A type fluorophore. Its HLCT and AIE properties verified by theoretical calculations, solvatochromic effects, and transient photoluminescence decay experiments, bring about a strong blue emission (452 nm) with a high photoluminescence quantum yield of 74 % in the thin film. PI‐TPB‐CN is successfully employed as a blue emitter in OLEDs. Non‐doped OLED with the structure of ITO/HAT‐CN (6 nm)/NPB (30 nm)/TCTA (10 nm)/PI‐TPB‐CN (30 nm)/TPBi (40 nm)/LiF (1 nm)/Al (100 nm) demonstrates excellent electroluminescence (EL) performance with blue emission (451 nm) and maximum external quantum efficiency (EQEmax) of 7.38 %. The device with a thinner layer of PI‐TPB‐CN (20 nm) and TPBi (30 nm) exhibits a deeper blue emission (444 nm) with CIE coordinates of (0.156, 0.096), a low turn‐on voltage of 3.0 V, and EQEmax of 6.45 %. [ABSTRACT FROM AUTHOR]

A straightforward and practical nucleophile‐induced synthetic route for the synthesis of thermally stable, fluorescently active, functionalized stilbenes has been developed. The described synthetic method involves nucleophile‐induced, base‐promoted ring transformation reactions following a more traditional approach. All reactions occur at room temperature, yielding high amounts of the desired product with minimal byproducts. Due to the inclusion of a donor‐π‐acceptor system, all the produced stilbenes exhibited impressive emission characteristics. The resulting band gaps ranged from 3.37 to 3.93 eV, indicating a notable redshift. Solvatochromic investigations underscored these positive impacts. Furthermore, the TG‐DTA analysis indicated a single‐step evaporation process, and the compounds exhibited stability up to 375 °C. [ABSTRACT FROM AUTHOR]

The 1H and 13C NMR spectra of the N‐(3,5‐dichloro‐4‐hydroxyphenyl)‐ 2,4,6‐triphenylpyridinium perchlorate and of its deprotonated betaine 4‐(2,4,6‐triphenylpyridinio)‐2,6‐dichlorophenolate (Wolfbeis's ET(33) dye) were recorded in various solvents and analyzed in search of solvent‐dependent shifts that characterize their solvatomagnetism, which was compared with the well‐known UV–vis spectral behavior of this important solvatochromic dye. Although the NMR spectra of ET(33) and its phenolic precursor in different solvents correlated only poorly with their UV–vis spectral responses, they provided valuable information on specific structural features and solute–solvent interactions that are not available from their UV–vis spectra. [ABSTRACT FROM AUTHOR]

AbstractThe stilbene functionalized star and bent shaped π-conjugate organic donor-donor (D-π-D) molecules with decorated triphenylamine central core were synthesized via Michaelis-Arbuzov and Wittig-Horner Reaction with excellent regio-specific. The photo-physical investigations clearly indicate the synthesized molecules have excellent optical properties with UV-visible regions and hypochromic shifts. The intra-molecular charge transfer (ICT) absorption of bent and star-shaped molecules was found in the region of 369–390 and 382–390 nm. The star and bent-shaped molecules exhibited emission maximums between 444–490 and 437–476 nm. While increasing the solvent polarity, the emission maximum of TDMSPA and DMSNDMPA molecules were observed in red-shift. The excited state dipole moment changed when compared to ground state due to the triphenylamine core confirmed by the Lippert-Mataga plot. The density functional theory is good evidence; the TDMSPA molecule has a twisted configuration and supports optical and electrochemical studies. Time-correlated single photon counting (TCSPC) technique showed that the excited state fluorescence lifetime of the stilbene molecules was found to be 2.25 and 2.18 ns for star and bent shaped molecules, respectively. The synthesized molecules exhibit significantly low band-gap energies between HOMO and LUMO, and the values are observed in the range between 2.86 and 2.91 eV. The triphenylamine core-based π-conjugate organic chromophore is widely used as a bio-imaging agent in Rhizoctonia oryzae (Plant fungal pathogen) as the model and the TDMSPA was an excellent bio-imaging agent and biocompatibility with fungal and bacterial cells. [ABSTRACT FROM AUTHOR]

AbstractThe compound 6-fluoro-4-hydroxyquinolin-2(1H)-one (1) was synthesized and reacted with diazotized 2, 4-dimethylaniline in a basic medium, yielding the hydrazone derivative (2) as a deep yellow crystalline compound. The structure of the purified product was confirmed through FT-IR, 1D and 2D NMR, and mass spectroscopic analyses. The results showed that the product exclusively adopts a hydrazone structure, existing as an equilibrium mixture of E and Z geometrical isomers in solution. DFT quantum calculations at the B3LYP/6-311++G (d, p) level indicated that the hydrazone form of compound (2) is more stable than the proposed azo structure, with the Z-hydrazone isomer having the lowest total energy. Additionally, UV-Vis spectroscopy studies of the E and Z isomers of hydrazone compound (2) in solvents of varying polarities showed that the E isomer is the predominant species in non-polar solvents. [ABSTRACT FROM AUTHOR]

Host‐guest conjugate is a promising strategy for providing outstanding molecules. Herein, we designed host‐guest conjugate HG1, which comprises a hydrophilic host unit, tetraaza[2.2.1.2.2.1]paracyclophane CPX2 with a microhydrophobic cavity, and a guest unit, 2,3‐naphthalimide fused with two benzothiophenes G1 exhibiting fluorosolvatochromism, linked with an oxyethylene chain. HG1 initially showed a fluorescence band at 585 nm in MeOH/H2O (1/499 v/v); however, this band decreased with time, and instead, a new band at 430 nm appeared. The CIE chromaticity diagram showed that the fluorescent color changed from yellow‐orange to blue via white. NMR analysis of HG1 in methanol‐d4 exhibited different signals of the G1 unit between the blue and yellow fluorescent structures. The blue fluorescent structures showed asymmetrical signals assigned as the G1 unit, affected by the cavity environment of the CPX2 unit. Consequently, HG1 can form two conformations: In‐form and Out‐form. In In‐form, the G1 unit is inside the hydrophobic cavity of the CPX2 unit and shows blue fluorescence. In Out‐form, the G1 unit is outside the CPX2 unit and shows yellow fluorescence in an aqueous solvent. Therefore, HG1 performs as a ratiometric fluorophore depending on the in/out isomerism of the host‐guest conjugate. [ABSTRACT FROM AUTHOR]

Luminescent materials that respond to changes in microscopic chemical conditions are essential for visualizing and evaluating molecular environments. Boron complexes are often employed as robust scaffolds for constructing such responsive systems because of their inherent stimuli‐responsive properties. However, in the case of nonresponsive luminophores, the absence of these intrinsic features limits their range of applications. In this study, environment‐responsive luminescent homopolymers based on the boron β‐dialdiminate complex are developed, which is intrinsically less responsive, by introducing optimized side chains. As a key finding, the triethylene glycol‐decorated polymer exhibits more intense luminescence in chloroform but weaker luminescence in N,N‐dimethylformamide. Structural analyses using NMR and size‐exclusion chromatography suggest that this polymer forms larger aggregates in polar solvents because of the solvophobicity of its main chain, while the polar side chains assist in maintaining adequate dispersibility of these aggregates. Photophysical measurements indicate that interchromophore interactions within the aggregates should be responsible for the reduced luminescence in polar solvents. These findings suggest that side‐chain engineering should be an effective strategy for creating stimuli‐responsive polymers from otherwise nonresponsive luminophores. [ABSTRACT FROM AUTHOR]

A convergent synthesis of 2H‐benzo[b][1,4]thiazin‐2‐one was achieved via iodine‐catalyzed three‐component reaction. This strategy involves the formation of two new C−S bonds and a C−N bond from the readily available precursors ‐ aryl methyl ketones, p‐anisidine, and elemental sulfur to generate the desired heterocycle in moderate to good yields. As the synthesized benzothiazine‐2‐ones are fluorescent under UV light, photophysical properties like solid‐state emission, solvatochromism, Aggregation Induced Emission (AIE), and the relative quantum yields of the compounds were measured which proves them to be a potential candidate for the development of optoelectronic devices. [ABSTRACT FROM AUTHOR]

Electron donor–acceptor (D–A) molecules are emerging tools for designing sensitive luminogens, attracting significant research attention. However, due to poor quantum yields under certain conditions, current D–A fluorophores often suffer from fluorescence quenching in practical applications. Developing new D–A dyes and functional composites is crucial for expanding their applications. Here, a novel donor–acceptor type flavonoid dye molecule, namely “AFL”, exhibiting both polarity‐dependent fluorescence emission wavelength shift and viscosity‐dependent intensity change, for polarity measurement and temperature sensing is designed and synthesized. Because the intramolecular charge transfer (ICT) can be enhanced by a decrease of excited state energy caused in high‐polarity organic solvents, AFL undergoes fluorescence emission wavelength shift that shows fluorescence color response to solvents of different polarities and hence differentiates between them. Moreover, the actual temperature can be monitored by the as‐designed AFL@tetradecanoic acid (AFL@TA) sensor. By combining with TA, viscosity sensitively changes upon the temperature change of insoluble composites, thus realizing the fluorescence intensity response to temperature. Remarkable recyclable performance and satisfactory mechanical properties are integrated. This study provides a promising approach to developing a new D–A fluorescent probe and furnishes perspectives on the potential of such D–A type flavonoid material in stimuli‐responsive systems with a focus on visualization sensing technology. [ABSTRACT FROM AUTHOR]

A number of quinoidal molecules with symmetric end‐capping groups, particularly dicyanomethylene units, have been synthesized for organic optoelectronic materials. In comparison, dissymmetric quinoidal molecules, characterized by end‐capping with different groups, are less explored. In this paper, we present the unexpected formation of new formal quinoidal molecules, which are end‐capped with both dicyanomethylene and triphenylphosphonium moieties. The structures of these dissymmetric quinoidal molecules were firmly verified by single crystal structural analyses. On the basis of the control experiments and DFT calculations, we proposed the reaction mechanism for the formation of these dissymmetric quinoidal molecules. The respective zwitterionic forms should make contributions to the ground state structures of these quinoidal molecules based on the analysis of their bond lengths and aromaticity and Mayer Bond Orbital (MBO) calculation. This agrees well with the fact that negative solvatochromism was observed for these quinoidal molecules. Although these new quinoidal molecules are non‐emissive both in solutions and crystalline states, they become emissive with quantum yields up to 51.4 % after elevating the solvent viscosity or dispersing them in a PMMA matrix. Interestingly, their emissions can also be switched on upon binding with certain proteins, in particular with human serum albumin. [ABSTRACT FROM AUTHOR]

Two charge transfer compounds based on pyridazinium ylids were studied by electronic absorption spectroscopy in binary and ternary solutions, with the purpose of evaluating their descriptors of the first singlet excited state and to estimate the strength of the intermolecular interactions in protic solvents. The molecular descriptors of the excited state were comparatively estimated using the variational method and the Abe model of diluted binary solutions. Analysis of electronic properties using density functional theory was performed for several key solvents, in order to understand the solvatochromic behavior. The DFT calculations revealed that, in the polar and strongly interacting solvents, the carbanion and the terminal group become a stronger electron acceptor. The bathochromic shift of the ICT band was confirmed using DFT calculus. The ability of the two ylids to recognize and discriminate the solvents was analyzed with principal component analysis and with cluster analysis. Although the study was performed in 24 solvents, the results showed that the ylids were most sensitive to alcohols, so they can be a useful tool to identify and classify different types of low-alcoholic solvents. [ABSTRACT FROM AUTHOR]

Herein, we report the synthesis of new near‐infrared (NIR) fluorescent dyes based on the pyridinium−cyclic enolate betaine (PCB) skeleton. The formation of the electron‐donor−π−electron‐acceptor (D−π−A) type dye with the electron‐donating N,N‐diphenyl amino group and the electron‐accepting PCB skeleton through a series of π−spacers allowed us to achieve NIR fluorescence. Particularly, a dye with a thienylisothianaphthene spacer showed NIR fluorescence with a significant intensity (λPL=822 nm, ΦPL=0.19 in DMSO). Detailed experimental and theoretical analyses suggested that the structural relaxation to a planar quinoidal form in the S1 state would be critical for intense NIR fluorescence. [ABSTRACT FROM AUTHOR]

The development of highly sensitive and visual analytical methods for monitoring pH change has always attracted great attention due to significant roles in various fields including food, environmental and biological systems. In this paper, a dual-response sensor for pH detection, [1,2']biindenylidene-3,1',3'-trione L, was synthesized from substrate indane-1,3-dione, and its structure was confirmed by 1H NMR, 13C NMR, ESI–MS and single crystals. Interestingly, sensor L exhibits solvatochromic properties and visualized color changes at different poplar solutions, and it can show significant changes in fluorescence intensity, UV–Vis absorbance and color at moderate acidic (pH = 3.52–5.03) and strong basic conditions (pH = 13.09–13.27) based on intramolecular proton transfer (IPT) mechanism. These results indicate that L can act as a double functional probe for the analysis and visual detection of pH change under moderate acidic and strong basic conditions in a quite narrow pH range. In addition, L can also selectively identify solvent CH2Cl2 by inducing larger blue-shift in wavelength and increase in fluorescence intensity, which means that it may be used as an indicator for monitoring trace amount of CH2Cl2. The potent applicantions for sensor L were also investigated and that it could conveniently be made into a series of strips for pH detection was indicated. [ABSTRACT FROM AUTHOR]

Silver nanoparticles associated with polyvinylpyrrolidone were synthesized using an electrochemical method. When the polyvinylpyrrolidone-adsorbed silver nanoparticles were immersed in solvents with hydroxyl groups, the polyvinylpyrrolidone interacted with the solvent by hydrogen bonding. Hence, the dielectric environment around silver nanoparticles changed, leading to dynamic coloration switching with high sensitivity, reversibility, and bistability owing to the localized surface plasmon resonance bands. This achievement can be expected to contribute to the solvatochromic devices for a kind of sensors or switches. [ABSTRACT FROM AUTHOR]

Exciplexes are excited-state complexes formed as a result of partial charge transfer from the donor to the acceptor species when one moiety of the donor–acceptor pair is electronically excited. The arene–amine exciplex formed between oligo-(p-phenylene) (OPP) and triethylamine (TEA) is of interest in the catalytic photoreduction of CO2 because it can compete with complete electron transfer to the OPP catalyst. Therefore, formation of the exciplex can hinder the generation of a radical anion OPP·− necessary for subsequent CO2 reduction. We report an implementation of a workflow automating quantum-chemistry calculations that generate and characterize an ensemble of structures to represent this exciplex state. We use FireWorks, Pymatgen, and Custodian Python packages for high-throughput ensemble generation. The workflow includes time-dependent density functional theory optimization, verification of excited-state minima, and exciplex characterization with natural transition orbitals, exciton analysis, excited-state Mulliken charges, and energy decomposition analysis. Fluorescence spectra computed for these ensembles using Boltzmann-weighted contributions of each structure agree better with experiment than our previous calculations based on a single representative exciplex structure [Kron et al., J. Phys. Chem. A 126, 2319–2329 (2022)]. The ensemble description of the exciplex state also reproduces an experimentally observed red shift of the emission spectrum of [OPP-4–TEA]* relative to [OPP-3–TEA]*. The workflow developed here streamlines otherwise labor-intensive calculations that would require significant user involvement and intervention. [ABSTRACT FROM AUTHOR]

Despite the broadly acknowledged importance of solvation effects on measured UV/Vis spectra in the context of solvatochromism or chemical reactions in solution, it is still an open challenge to calculate UV/Vis spectra with predictive accuracy. This is particularly true when it comes to the impact of nuclear quantum effects on these experimental observables. In the present work, we calculate the UV/Vis absorption spectrum of indole in aqueous solution with a combination of a correlated wavefunction method for computing electronic excitation energies and enhanced path integral simulations for rigorous sampling of nuclear configurations including the quantum effects in solution. After validating our approach based on gas‐phase benchmarking, we demonstrate that the lineshape of the spectrum measured in aqueous solution is quantitatively recovered, without the application of any shifting, scaling, or broadening, only after including nuclear quantum effects in addition to thermal fluctuations and solvation at ambient conditions. Our findings demonstrate that nuclear quantum effects are “visible” in UV/Vis spectra of chromophores measured in solution even at room temperature and, therefore, that they must be considered computationally to achieve predictive accuracy. [ABSTRACT FROM AUTHOR]

Two azo dyes 2-hydroxy-5-(4-nitrophenylazo)benzaldehyde and 2-hydroxy-5-(4-chlorophenylazo)benzaldehyde dissolved in carbon tetrachloride, hexane, acetone and acetonitrile were irradiated with 365 nm UV light, and processes, occurring in them, were studied by NMR and UV–vis spectroscopy. It was established that reversible trans/cis photoisomerization of the molecules occurs in the non-polar solvents and is not observed in the polar solvents. 2D NOESY NMR spectroscopy was used to identify isomers of the azo compounds. Based on the chemical shifts of the signals, it was established that these compounds are in the trans-form before UV irradiation. Spectra of the azo dyes before and after UV irradiation allowed assignment of the chemical shifts of the cis-isomers. In polar solvents these compounds undergo a hypochromic effect under heating or irradiation with UV light. Both compounds exhibit solvatochromism. The shifts in NMR signals caused by photoisomerization of the molecules were compared with the shifts in the NMR signals of other azo compounds such as Disperse Orange 3, Disperse Red 1 and azobenzene. [ABSTRACT FROM AUTHOR]

Luminescent polymer composites based on polystyrene and polycarbonate doped with boron difluoride curcuminoids containing various substituents in the phenyl ring have been synthesized. The effect of substituents, polymer matrix, and luminophore concentration on the spectral properties of the polymer composites has been studied. It has been found that the effect of the electron-donating force of luminophore substituents on the emission characteristics of the films is similar to the effect of solutions. The films doped with luminophores containing alkyl substituents (1a–5a) do not change their emission characteristics upon switching to another polymer matrix, while the 6a-doped composites are characterized by positive solvatochromism. A bathofluoric shift of luminescence with an increase in the luminophore concentration to 0.5% is observed for all the films. It has been found that the 6a-doped films exhibit delayed fluorescence. [ABSTRACT FROM AUTHOR]

Solvatochromism plays a pivotal role in various scientific and technological fields including those that explore molecular interactions, sensing technologies, and organic electronics. Notably, despite their ease of manipulation, direct visualization, and potential for single particle‐based sensing, micro‐sized solid particles have been the focus of a surprisingly low number of solvatochromism investigations. In this study, polydiacetylene (PDA) particles are synthesized and their solvatochromism is investigated at the single particle level using optical laser tweezers‐based methods. The findings reveal that unpolymerized monomers within PDA particles at the water/n‐decane interface undergo dissolution in the n‐decane phase to form internal voids in the particles. This phenomenon leads to structural deformation of the PDA which triggers a solvatochromic response. Studies that integrate this phenomenon with established particle‐based methodologies should provide deeper insights into diverse chromism behaviors and potential applications of solvatochromic materials. [ABSTRACT FROM AUTHOR]

A large series of previously unknown isoxazole containing difluoroboron β‐diketonate has been designed and synthesized from the available starting compounds. The photophysical properties of obtained compounds were studied, and the effects of the substituents in aromatic and isoxazole cycles of the BF2 complexes on the fluorescence were investigated. The effect of solvatochromism were demonstrated. Cytotoxic activity against MCF‐7 (breast carcinoma), HCT‐116 (colon carcinoma), A549 (pulmonary carcinoma) and WI38 (fibroblasts from lung tissue) cell lines was tested and moderate toxicity in the concentration range of 10–100 μM was found for several compounds. [ABSTRACT FROM AUTHOR]

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The influence of pure solvent and binary solvent mixtures on the optical properties of non-steroidal anti-inflammatory drug (NSAID) molecule, specifically flufenamic acid (FLA), has been studied using absorption and fluorescence spectroscopic techniques. A bathochromic shift is observed in the emission wavelength of FLA with an increase in the solvent polarity of pure solvents, attributed to the highest stability of the excited state. The spectral properties are correlated with Lippert–Mataga, solvent polarity parameter, Kamlet, and Catalan solvent polarity parameters, suggesting that both general and specific solvent effects influence the spectral properties, with general solvent effects dominating over specific solvent effects. Preferential solvation studies have been carried out in tetrahydrofuran (THF) and water solvent mixture, revealing variations in the preference for solvation of FLA as a function of the mole fraction of water. Solvatochromic data are utilized to estimate the excited state dipole moment in pure solvents using different solvatochromic methods, revealing that the excited state dipole moment of FLA is higher than its ground state counterpart. The increase in dipole moment in the excited state compared to the ground state is explained based on intramolecular charge transfer (ICT), with elaboration and discussion on the possible resonance structure corresponding to ICT, inferring the more polar nature of the excited state compared to the ground state. The effect of solute polarizability on the excited state dipole moment and change in dipole moment is also discussed. [ABSTRACT FROM AUTHOR]

The azomethine TPA-(BTZ)3-TPA with a donor–acceptor–acceptor–acceptor–donor structure has been synthesized and characterized. Azomethine TPA-(BTZ)3-TPA exhibited luminescence properties and a positive solvatochromic effect. Electropolymerization on terminated triphenylamine groups was used to obtain a thin layer of the polyazomethine poly-[TPA-(BTZ)3-TPA]. Further investigation of oxidation/reduction properties of poly-[TPA-(BTZ)3-TPA] via cyclic voltammetry showed that the polymer undergoes two reversible oxidation/reduction processes due to the presence of tetraphenylbenzidine moieties. Electrochromic properties of the polyazomethine poly-[TPA-(BTZ)3-TPA] were investigated via spectroelectrochemistry. It was observed that the polymer in its neutral state is orange, and the color changes to green upon electro-oxidation. The stability of the polymer during multiple oxidation/reduction cycles, response times, and coloration efficiency were also investigated. [ABSTRACT FROM AUTHOR]

Polarizable continuum methods (PCM) have been widely employed for simulating solvent effects, in spite of the fact that they either ignore specific interactions in solution or only partially reproduce non-specific contributions. Examples of three solvatochromic dyes with a negative, a positive and a reverse behavior illustrate the achievements and shortcomings of PCM calculations and the causes for their variable success. Even when qualitatively mimicking non-specific solvent effects, departures of calculated values from experimental data may be significant (20–30%). In addition, they can utterly fail to reproduce an inverted behavior that is caused by significant specific contributions by the solvent. As shown through a theoretical model that rationalizes and predicts the solvatochromism of phenolate merocyanines based on DFT (Density Functional Theory) descriptors in the gas phase, PCM shortcomings are to be held responsible for its eventual failure to reproduce experimental data in solution. [ABSTRACT FROM AUTHOR]

The development of multi‐stimuli‐responsive (MSR) materials is a tempting yet intriguing challenge due to the absence of a defined design approach. In this study, we designed and synthesised two compounds based on triphenylamine, namely, TPA‐Tz1 and TPA‐Tz2. The photoluminescent investigations reveal the MSR behaviour of both compounds. TPA‐Tz1 shows reversible mechanochromism with a blue‐shifted emission due to changes in intermolecular interactions. Furthermore, both compounds exhibit solvatochromism in solvents of varying polarity. Detailed studies suggest that solvatochromism in TPA‐Tz1 can be attributed to twisted intramolecular charge transfer (TICT), while in TPA‐Tz2, it is due to intramolecular charge transfer (ICT). Additionally, both compounds display acidochromic properties in solution as well as in the solid state due to the protonation of the triazole ring. All changes in emissions are corroborated through theoretical calculations. The results provide insights into the intricate interplay of molecular interactions and structural rearrangements that contribute to the compound's multifaceted responsiveness. [ABSTRACT FROM AUTHOR]

Stimuli‐responsive materials based on π‐conjugated donor‐acceptor systems have great potential for sensing applications in solution and solid state. The photophysical properties of an oligo(p‐phenylenevinylene) series consisting of five push‐pull type molecules were systematically investigated to switch their absorption and emission properties by using trifluoroacetic acid as a specific external analyte. During the trifluoracetic acid sensing, the terminal pyridine units of the molecules undergo the protonation and lead to the broader absorption band at a longer wavelength region owing to the π‐π* characteristics of molecules. Upon exposing solid samples to the trifluoracetic acid vapors, the initial color of solid samples changed from yellow to orange for three‐ring system‐based molecules and brick red to wine red color for five‐ring system‐based molecules with the shifting of emission band to the longer wavelength region. Furthermore, exposing the trifluoracetic acid‐fumed solid samples to triethylamine vapors, the color of the solid samples reverted to their original colors and emission properties. The DFT analysis indicated a decreased energy band gap for the protonated molecules compared to the neutral molecules, suggesting a redshift in both the absorption and emission spectra of the protonated molecules. Thus, all the molecules of an Oligo(p‐phenylenevinylene) series can be utilized effectively for volatile acid detection. [ABSTRACT FROM AUTHOR]

A new method was developed for the synthesis of ethyl 3,6-diamino-4-aryl-5-cyanothieno[2,3-b]pyridine-2-carboxylates by the reaction of 4-aryl-2-amino-6-chloropyridine-3,5-dicarbonitriles with ethyl 2-mercaptoacetate. The synthesized compounds exhibit fluorescence both in solution and in the solid state. The emission maxima in benzene solution depend on the substituent and are in the range of 503–531 nm or from 498 to 541 nm in the solid state. For photoluminescence of ethyl 3,6-diamino-4-aryl-5-cyanothieno[2,3-b]pyridine-2-carboxylates, large Stokes shifts were observed: from 214 nm (13106 cm–1) in chloroform to 251 nm (14433 cm–1) in methanol. [ABSTRACT FROM AUTHOR]

Motivated by the scarcity of prior research, in this study we report the synthesis and photophysical characteristics of newly obtained benzanthrone ethynyl derivatives. Fourier-transform infrared spectroscopy, 1H and 13C nuclear magnetic resonance spectroscopy and high-resolution mass spectrometry elucidated the structures of the compounds. To study photophysical characteristics, absorbance and emission spectra were measured in solvents with different polarities. Photofading proved high stability of the synthesized compounds (up to 96% of initial absorption after irradiation for 4 h). The analyzed compounds are fluorescent (quantum yields from 0.01 to 0.74 in ethanol) with a significant solvatochromic effect (from 466 nm in benzene to 720 nm in dimethyl sulfoxide). Based on these findings, there is a correlation between the electronic nature of substituents and photophysical parameters. Hence, these compounds could find applications as probes in fluorescence microscopy and sensors to detect polarity variations. [ABSTRACT FROM AUTHOR]

In this study, we have successfully designed and synthesized two novel dual‐emission emitters featuring phenothiazine‐5‐oxide and phenothiazine‐5,5‐dioxide motifs, characterized by highly lopsided and asymmetric conformational states. Through rigorous spectral examinations and DFT calculations, the compounds exhibit distinctive ICT phenomena, coupled with efficient emission in solid states and AIEE characteristics under high water fractions in DMF/H2O mixtures. These non‐planar luminogens exhibit vibrant green and blue solid‐state luminescence, with fluorescence quantum yields of 24.1 % and 15.21 %, respectively. Additionally, they both emit green fluorescence in THF solution, with notable emission quantum yields (QYs) 36.4 % and 30.4 %. Comprehensive theoretical investigations unveil well‐defined electron cloud density separation between the energies of HOMO/LUMO levels within the two luminogens. Notably, the targeted molecule harboring the phenothiazine‐S,S‐dioxide motif also demonstrates remarkable reversible mechanofluorochromic properties. Moreover, we testify their potential in applications such as solid‐state rewritable information storage and live‐cell imaging in solution states. Through theoretical calculations and comparative studies, we have explored the intrinsic relationship between molecular structure and performance, effectively screening and identifying new fluorescent molecules exhibiting outstanding luminescent attributes. These discoveries establish a robust theoretical and technical foundation for the synthesis and application of efficient DSE‐based MFC materials, opening new avenues in the realm of advanced luminescent materials. [ABSTRACT FROM AUTHOR]

This work includes synthesis of the novel azo compound, which consists of diazotization of 3-nitroaniline followed by reaction with 4-hydroxybenzaldehyde in presence of sodium carbonate. The syanthesized azo compound was confirmed by characterization, using FT-IR, ¹HNMR, 13CNMR and GC-MS spectra. The azo compound was screened for solvatochromism, Halochromism using UV-Vis spectrophotometer, and found that the azo compound exhibited low solvatochromic and good Halochromic properties. While the dying study (Dye-doped Polymer Films), Poly ethylene was found the best polymer dyed by azo compound and showed good absorbance in the UV region. All fabrics were dyed with a yellow color except the cotton exhibiting a light brown color. [ABSTRACT FROM AUTHOR]

Polydiacetylenes (PDA) are highly regarded for their unique colorimetric and fluorescent responses, making them ideal for sensor development. Despite their potential, conventional methods for fabricating biocompatible PDA‐encapsulated hydrogel sensor beads often fail to offer precise control over bead size and morphology. This study introduces a coflow gas‐shearing microfluidic system that effectively overcomes these limitations, enabling the controlled production of polydiacetylene/alginate (PDA/Alg) and polydiacetylene/polydimethylsiloxane/alginate (PDA/PDMS/Alg) microbeads. Through systematic variation of gas pressure, liquid flow rates, and nozzle sizes, the mechanisms of droplet breakup and generation are explored. This process is validated through numerical modeling based on the Weber number, which enhances our understanding of droplet size distribution and flow regimes. The solvatochromic properties of PDA/Alg microbeads are assessed, highlighting their potential as polar solvent sensors and discussing the solvatochromic mechanism in terms of intermolecular interactions and the dissolution of unpolymerized monomers. Additionally, PDA/PDMS/Alg microbeads exhibit a semireversible thermochromic response under repeated cycles of heating, cooling, and UV exposure. This response is attributed to the formation of new PDA domains inside the PDMS phase upon UV exposure onto the red‐phase microbeads. Overall, this study successfully demonstrates a straightforward and effective microfluidic approach for producing well‐defined stimulus‐responsive PDA–hydrogel microbeads.

This study delves into the intricate electronic and photophysical properties of copper (II) complexes and their ligands, shedding light on their behavior under varying conditions. UV–Vis absorption spectroscopy unveils significant insights, revealing absorption peaks attributed to ligand–metal charge transfer transitions (LMCT) and π → π* transitions of C = N bonds. The solvent’s polarity dictates the absorption peak positions, indicating a pronounced solvatochromic effect. Molar extinction coefficients underscore the complexes’ high absorption efficiency across different solvents. Density Functional Theory (DFT) calculations provide a theoretical framework, elucidating electronic transitions observed experimentally. While HL1 exhibits a single peak, HL2 displays two peaks, findings supported by calculated transition energies and oscillator strengths.Moreover, the oxidation processes of copper complexes with iodide salt and triethylamine unveil favorable electron transfer mechanisms, as corroborated by cyclic voltammograms and free energy change values. Photolysis experiments underpin the complexes’ behavior under light irradiation, revealing reversible photoreduction processes and the formation of novel photoproducts. Notably, the addition of triethylamine influences photolysis kinetics, elucidating complex interactions. Furthermore, fluorescence experiments unveil the fluorescent behavior of bidentate copper (II) complexes and their ligands. Fluorescence emission peaks, observed around 475–550 nm for complexes and 400–550 nm for ligands, are influenced by solvent polarity, indicating solvent effects on fluorescence deactivation pathways. Overall, this comprehensive investigation provides valuable insights into the electronic and photophysical characteristics of copper (II) complexes, paving the way for their potential applications in diverse fields, including materials science, catalysis, and photochemistry.

The effect of changing carbonyl group to methylidenepropanedinitrile moiety onto electronic absorption and fluorescence spectra was analyzed theoretically within DFT / TD-DFT scheme. Chalcone (1,3-diphenylpropeneone) was chosen as a model molecular system of this investigation. Methylidenepropanedinitrile moiety was characterized as more suitable for obtaining bright fluorescent products, however, its electron accepting ability was lower compared to carbonyl group, contrary to widespread insights.

The electronic absorption spectral characteristics of cycloimmonium ylids with a zwitterionic structure have been analyzed in forty-three solvents with different hydrogen bonding abilities. The two ylids lack fluorescence emission but are very dynamic in electronic absorption spectra. Using the maximum of the ICT band, the goal was to establish an accurate relationship between the shift of the ICT visible band and the solvent parameters and to estimate two of the descriptors of the first (the) excited state: the dipole moment and the polarizability. Two procedures were involved: the variational method and the relationships of the Abe model. The results indicate that the excited state dipole moment of the two methylids decreases in the absorption process in comparison with the ground state. The introduction of a correction term in the Abe model that neglects the intermolecular H-bonding interactions leads to a more accurate determination of the two descriptors. The strong solvatochromic response of both ylids has been further applied in distinguishing the solvents as a function of their specific parameters. Principal component analysis was applied to five selected properties, including the maximum of the charge transfer band. The results were further applied to discriminate several binary solvent mixtures. [ABSTRACT FROM AUTHOR]

Pyrene derivatives bearing substituents at positions 1, 3, 6, and 8 find numerous applications, as exemplified by their use in lasers, sensors, and bioimaging probes. However, these derivatives typically have point‐symmetric or short‐axially symmetric structures, whereas long‐axially symmetric derivatives remain underexplored because of the difficulty in obtaining their precursor, 1,3‐dibromopyrene. To address this problem, we herein synthesized 1,3‐dibromopyrene from 1‐methoxypyrene in an overall yield (71 % over four steps) considerably exceeding those of existing methods. 1,3‐Dibromopyrene was converted into 13OPA, a long‐axially symmetric pyrene dye with electron‐donor (alkoxy) groups at positions 1 and 3 and electron‐acceptor (formyl) groups at positions 6 and 8. 13OPA exhibited photophysical properties distinct from those of its point‐symmetric and short‐axially symmetric isomers, featuring a broad and strongly redshifted absorption, strong fluorescence with reduced sensitivity to protic solvents, and small dipole moment change upon photoexcitation. The derivatization of 13OPA into a Schiff base and its functionalization via Lewis acid‐base pairing were also demonstrated. Thus, our work expands the design scope of pyrene‐based molecules, particularly those used as emitters. [ABSTRACT FROM AUTHOR]