Quantum-chemical study of relation of spectral and luminescent properties of positively solvatochromic malononitrile-based merocyanine dyes with their structure

The electronic structure, the spectra, and the efficiency of photophysical processes of energy deactivation are calculated by a semiempirical method for three positively solvatochromic merocyanine dyes with different polymethine chain lengths. The electronic structure and spectra calculated by different modifications of the INDO method at different molecular geometries are compared, and the optimum geometry of the isolated molecule is chosen. The absorption spectra of dyes are interpreted, including the short-wave-length bands related to transitions to highest excited states. The possibility of a specific electrophilic solvation of these compounds in the ground and fluorescent states, as well as the contribution of specific intermolecular interactions to the total interaction with the medium, is estimated. The role played by the trans-cis isomerization of isolated merocyanine molecules in the deactivation of their excited states is considered.     

Computational study of new azo dyes with different anchoring groups for dye-sensitised solar cells

Some of new azo dyes with different anchoring groups, such as biscarbodithiolic acid, hydroxamic acid, phosphonic acid, carboxcylic acid and sulfonic acid have been investigated theoretically to evaluate the effects of various anchoring groups on the optical and electronic properties of the dyes in dye-sensitised solar cells. Optical and electronic properties, UV–Vis absorption spectra, light-harvesting efficiency, lifetime of the excited state, chemical hardness and lowest unoccupied molecular orbital (LUMO) orbital weight of the dyes on the anchoring groups, have been studied to shed light on how the various anchoring groups influence the properties of the dyes. The biscarbodithiolic acid-based dye shows the longest maximum absorption wavelength and the widest absorption spectra together with the highest light-harvesting efficiency, the longest lifetime of the excited state and the highest the LUMO orbital weight of the dye on the atoms of the anchoring group, suggesting the good ability in electron injection. Theoretical calculations have been also performed on the adsorption of these dyes on the TiO₂ anatase (101) surface. These results show that the biscarbodithiolic acid-based dye has the highest adsorption energy and the largest negative shift of the conduction band of TiO₂ due to the adsorption of the dye onto the TiO₂.     

Anisotropic and isotropic solvent effects on the dipole moment and photophysical properties of rhodamine dyes

Absorption and emission spectra of two rhodamine dyes with same molecular skeletons and different functional groups have been studied in various isotropic and anisotropic media. The solute photo-physical behavior depends strongly on the solvent–solute interactions and solvent microenvironment as well as resonance structures of the rhodamine dyes. In order to understand the effect of intermolecular interactions on spectral behaviors of these dyes and to conceive nature and extend of solvent–solute interactions the spectral variations were analyzed by the linear solvation energy relationships concept. In addition, by means of solvatochromic method the dyes dipole moments variations, from ground to excited states, were investigated in isotropic and anisotropic solvents media.     

Reaction kinetics and solubility in water‐organic binary solutions are governed by similar solvation equilibria

The solvation effects observed in water‐organic solutions were studied by combining data for reaction kinetics and dissolution equilibria by means of a linear free‐energy (similarity) analysis. Kinetic data for the pH‐independent hydrolysis of (4‐methoxyphenyl)‐2,2‐dichloroacetate measured in this work and solubility data for naphthalene, and other substrates of low polarity, in aqueous binary mixtures of methanol, ethanol, acetonitrile, dimethyl sulfoxide (DMSO), and 1,4‐dioxane were used. Linear similarity relationships were discovered for these data over the full range of solvent compositions studied. To gain insight into the similarities observed between these different phenomena, molecular dynamics simulations were carried out for naphthalene and an ester in water–acetonitrile solutions. The results revealed considerable preferential solvation of these substrates by the co‐solvent. Linear relationships between the experimental data and the mole fractions of acetonitrile in the solvation shells of substrates were found. Surprisingly, a linear relationship was found between the mole fractions of acetonitrile in the solvation shells of the ester and naphthalene. This linearity indicated that a similar solvation mechanism governs even such different phenomena as dissolution and reaction kinetics. The relationships between the experimental data and the results of the molecular dynamics calculations found in this work explained the solvent effect observed in water‐organic solutions on the molecular level. Copyright © 2015 John Wiley & Sons, Ltd.     

吡啶酮系偶氮染料腙式—偶氮式互变异构的研究——Ⅰ核磁共振波谱在构型测定中的应用

测定了七个吡啶酮系偶氮染料的~(13)C NMR波谱.借助于选择性非灵敏核极化转移增强法(SELINEPT)完成了谱带归属。从pH值对~(13)C化学位移的影响,~1H NMR谱和紫外-可见吸收光谱,指出这类染料的酸-碱变色现象是由腙式和偶氮式构型互变平衡的移动引起的.介质酸性或碱性的增强分别有利于染料以腙式或偶氮式的构型存在.不同结构的吡啶酮染料,其变色pH值是相当不同的.     

Geometries,spectra and photoelectric properties of trifluorenylamine-based photoactive layer

The ground-state geometries, electronic structures, spectra and photoelectric properties of two dyes (JA1 and JA2) used for dye-sensitised solar cells (DSSCs) have been investigated with density functional theory (DFT) and time-dependent density functional theory (TDDFT). For simulation of the realistic environment, we calculated the energy levels of molecular orbitals and absorption spectra in solvent, and the different electric fields have been considered. For interpreting the difference of photoelectric properties, we assessed the energy levels and energy gaps of frontier molecular orbitals, electron density, absorption, the total static first hyperpolarisability and driving force of electron injection. The relationship between structure and performance should be established. Furthermore, 24 dyes were designed on the basis of JA1 and JA2 to improve optical response and electron injection. The results of molecular modelling would provide the optional approach for improving performance of photoelectric materials.     

Application of power ultrasound for azo dye degradation

Power ultrasound of 850 kHz at 60, 90 and 120 W was used for the degradation of industrial azo dyes Acid Orange 5 and 52, Direct Blue 71, Reactive Black 5 and Reactive Orange 16 and 107. The results show that power ultrasound is able to mineralize azo dyes to non-toxic end products, which was confirmed by respiratory inhibition test of Pseudomonas putida. All investigated dyes have been decolorized and degraded within 3-15 h at 90 W and within 1-4 h at 120 W, respectively. Mass spectrometric investigations show, that hydroxyl radicals attack azo dyes by simultaneous azo bond scission, oxidation of nitrogen atoms and hydroxylation of aromatic ring structures. A volumetric scale-up showed a correlation between the energy input and the absolute amount of degraded dye. Up to an energy input of about 90 W no enzymatic deactivation of laccase was observed which might be helpful for a simultaneous action of sonochemical and enzymatic treatments.     

Molecular organization and aggregation in Langmuir and Langmuir-Blodgett films of azo dye/liquid crystal mixtures

A study of azo dye/liquid crystal mixtures in monolayers formed at air-water (Langmuir films) and air-solid substrate (Langmuir-Blodgett films) interfaces was performed. Three azo dyes with various molecular structure and two liquid crystal materials: 4-octyl-4′-cyanobiphenyl (8CB) and trans-4-octyl(4′-cyanophenyl)-cyclohexane (8PCH) were used. The morphology of Langmuir films was monitored by means of a Brewster angle microscope (BAM). Moreover, a surface pressure and electronic absorption spectra of the monolayer spread on the water surface of dye/liquid crystal mixtures as a function of a mean molecular area were simultaneously recorded. In addition, the absorption for Langmuir-Blodgett films deposited on quartz plates was measured. Information about intermolecular interactions in the mixtures of the nonamphiphilic dye and the liquid crystal with polar terminal group was obtained. Conclusions about the formation of self-aggregates between dye molecules have been drawn. The influence of the dye molecular structure and its concentration on aggregates’ geometry was found.     

Red Emitting Coumarin—Azo Dyes : Synthesis,Characterization, Linear and Non-linear Optical Properties-Experimental and Computational Approach

The coumarin molecules with 7-(N,N-diethylamino) substitution and aryl azo (Ar–N=N-) at 3-position were synthesized, by reacting diazonium salt of substituted amines and 7-(N, N-diethylamino)-4-hydroxy coumarin under basic conditions. They were found to be fluorescent despite the presence of azo group. The azo group rotation was blocked by complexing with -BF₂, so as to get a red shift in absorption. The azo molecules show charge transfer, whereas BF₂-complexes do not. The dipole moment ratios between the ground and excited states calculated suggest highly polar excited state and an intra-molecular charge transfer at the excited state in the case of azo dyes. The NLO properties were calculated by solvatochromic method and computationally. Second order hyperpolarizability was found to be 46 to 1083 times more than urea. DFT and TDTDF calculations were performed to understand the electronic properties of the molecules at the ground as well as excited states.     

Synthesis,Characterization and Fluorescence Studies of Novel Tetrachloroperylene-Azo Hybrid Dyes

Novel rylene-azo hybrid dyes have been synthesized by condensation of azo-dyes with tetrachloroperylene dianhydride, possessing stupendous thermal, chemical and photochemical stability. Phenolic azo dyes are used for the nucleophilic replacement of chlorine substituents at 1,6,7,12-positions of perylene 3,4,9,10-dianhydride system. The absorption maxima (?_max) of these dyes have been determined in diverse solvents such as water, ethanol, methanol, ethyl acetate and N, N-dimethylformamide. Fluorescence spectra are taken in water and highest fluorescence was exhibited by dyes containing carboxylic groups. The ?_max and fluorescence of these dyes is greatly affected by polarity of solvents. The structures of newly synthesized rylene-azo hybrid dyes have been confirmed by UV, FTIR and ¹HNMR spectroscopy.     

Impacts of pH and molecular structure on ultrasonic degradation of azo dyes

Sonochemical bleaching of monoazo dyes was investigated by irradiating 30 microM solutions of two "aryl-azo-naphthol" type model dyes in acidic, neutral and basic conditions using a 300 kHz emitter. It was found that the rate of bleaching in all cases was first order with respect to the maximum absorption of the dye in the visible band, and accelerated with increased acidity. The inhibition observed at alkaline conditions was attributed to the formation of anionic dye structures and their competition with the dye and its intermediate oxidation products for hydroxyl radicals, which are the major precursors of azo dye oxidation in sonicated water. Decolorization of the dyes was also related to the size of the molecule and the type or position of substituents about azo bonds. Comparison of color decay rates at similar conditions showed that the dye with a simple structure, low molecular mass and one ortho-substituent (hydroxyl) about the azo bond bleached considerably faster than the one having a more complicated structure (higher mass) and an additional o-substituent to the azo bond other than the OH group.     

蓝光存储偶氮染料及偶氮金属染料的研究进展

综述了可用于新一代高密度光盘的蓝光存储偶氮染料和偶氮金属染料的研究进展,重点阐述了蓝光存储偶氮染料和偶氮金属染料的结构、性能和应用,并对其发展趋势作了展望。     

NLO characteristics of D-π-A coumarin-thiophene bridged azo dyes by Z-scan and DFT methods

ABSTRACT

The structural, electronic, intramolecular charge transfer (ICT) and nonlinear optical (NLO) properties of the donor-π-acceptor (D-π-A) azo linked dyes bearing coumarin thiophene bridge with different acceptors were inspected by Z-scan and DFT methods. The dye 3a exhibits bathochromic absorption maxima (649 and 650?nm) in the near IR region in DMF and DMSO. The dye 3a holds low HOMO–LUMO gap elucidated by CV and DFT indicating strong ICT character. The thermal stability is high for 3a and it shows enhanced NLO property by Z-scan and DFT methods as predicted in both global and range-separated hybrid functionals. The molecular geometry was optimised using B3LYP/6-311?+?g(d,p). The ICT characteristics are correlated with NLO properties obtained by Z-scan and DFT techniques.     

分子轨道法计算三苯二恶嗪类分子的电子光谱

采用改进的半经验分子轨道法 (PPP SCF MO)计算了 15种三苯二恶嗪类染料分子的电子结构和电子光谱 ,计算得到的最大吸收峰波长与实验值较好的一致 ,计算得到的荧光跃迁能 ΔEfl 与荧光峰波数νfl 存在如下关系 :νfl =11 6 837ΔEfl+3 34 85 (k·cm- 1 ) ,r=0 95 47,并讨论了电子结构与光谱性能的关系。     

Photophysics of the analogs of pyrromethene PM 567

The spectral and luminescence properties of a number of pyrromethene (PM) dyes have been investigated. The absorption and luminescence spectra of PM molecules in different solvents are measured. The electronic structure and electronic excited states are calculated by the method of intermediate neglect of differential overlap with special spectroscopic parameterization. The rate constants of photophysical processes are estimated, and the fluorescence quantum yields are calculated. The fluorescence quantum yields of PM I and PM II molecules are found to decrease upon their excitation to the second short-wavelength absorption band. This phenomenon is interpreted.     

Novel Thiazole Based Styryl Dyes with Benzimidazole Unit - Synthesis,Photophysical and TD-DFT Studies

Three new Y-shaped styryl dyes were designed and synthesized from thiazole carbaldehyde with different active methylene compounds as acceptor moieties. All the dyes were characterized by IR, ¹HNMR, MS/LCMS/HRMS. Spectroscopic properties and non-linear optical properties styryl derivatives were analyzed and the effect of change in solvent polarity on their absorption and emissive properties has been investigated. The dye with (1-phenylethylidene) propanedinitrile unit shows red shift absorption/emission profile among all the dyes. Density Functional Theory and Time Dependent-Density Functional Theory computations have been used for comparative study with the experimental data and also to understand the structural, molecular, electronic and photophysical parameters of the styryl dyes. The computational method was also employed to investigate the nonlinear optical properties of the styryl dyes in different organic solvent. The unsubstituted benzimidazolyl thiazole styryl dyes possess good non-linear optical properties.     

Further Investigation on the Action of 60Co-γ-Rays on the Stability of some New Azo-Dyes

A number of 1,3-diphenyl-2-thiohydantoin azo dyes were purely prepared and characterized by spectroscopic analyses. Then the azo dyes were subjected to γ-radiation doses of up to 10⁹ rd. Results obtained indicated that the spectral bands of the investigated azo dyes suffer shifts, changes in intensity, broadening, creation of new bands and/or completely disappearance of others as a result of radiation damage. Furthermore a sequence for the relative stability of the different dyes towards gamma radiation damage was put forward.     

General solvation motifs of a charged linear macroion in an aqueous droplet

ABSTRACT

We explore the solvation patterns of a charged rigid and semi-rigid linear macroion in an aqueous droplet. The solvation patterns are summarised in an empirical ‘phase diagram’ on the parameter space defined by the length of the macroion and its charge density. In the study, we employ molecular dynamics and atomistic modelling. The macroion is represented by a positively charged carbon nanotube. Linear macroion-solvent interactions in droplets are distinct from those of spherical ions because of the interplay among several factors such as the tendency of the solvent to form spherical droplets in order to minimise the surface energy, the constraint on the charge of a spherical droplet imposed by the Rayleigh limit, the solvation energy of the macroion and its length. The combination of all these factors may lead to a variety of solvent distributions along the rigid rod such as asymmetric solvation of the linear macroion, formation of spiky ‘star’-like distribution of solvent, partial wetting of the rod by a droplet. The study provides insight into the solvation of macroions in droplets with applications in electrosprayed macroions and atmospheric aerosols. We also propose a possible path of generating a sequence of nanoparticles of different shapes (spheres, multi-point stars) along a linear macromolecule by exploiting the various solvation patterns.     

Red Emitting Monoazo Disperse Dyes with Phenyl(1H-benzoimidazol-5-yl) Methanone as Inbuilt Photostabilizing Unit: Synthesis,Spectroscopic, Dyeing and DFT Studies

Synthesis of three novel phenyl(1H-benzoimidazol-5-yl)methanone based fluorescent monoazo disperse dyes and their characterization by spectroscopic methods (¹H NMR, ¹³C NMR, IR and MS) are presented. Insertion of phenyl(1H-benzoimidazol-5-yl)methanone moiety bring about induced fluorescence properties and enhanced photostability as compared to the previously reported analogues (CI Solvent Yellow 14, 4-diethylamino-2-hydroxy-1-diazobenzene and 7-(diethylamino)-4-hydroxy-3-(phenyldiazenyl)-2H-chromen-2-one). Synthesized phenyl(1H-benzoimidazol-5-yl)methanone based dyes exhibited red-shifted absorption maxima (497–516 nm), high molar extinction coefficients and are emitting in the far-red region (565–627 nm). Moreover, naphthalene-comprising dyes showed negative solvatochromism while N,N-diethylamine comprising dyes showed positive solvatochromism and are in good agreement with solvent polarity graphs and the computed energy levels of highest occupied and lowest unoccupied molecular orbitals. Synthesised dyes have better photostability (light fastness) and sublimation fastness on dyed polyester and nylon compared to reported analogues. DFT calculated energies, electrophilicity index and Frontier Molecular Orbitals (FMO’s) enabled to evaluate the stabilities of azo and hydrazone forms of the dyes.     

Experimental determination of the solvation shifts of purely electronic spectra and their Franck-Condon components

The possibilities of using resonance spectra to determine the solvation shifts of purely electronic bands of organic luminophores in solutions and the contributions to these shifts from Franck-Condon components arising due to relaxation of solvation shells are discussed. It is shown that, upon a change in the solvation conditions, the relaxation processes accompanying the purely electronic transition of organic luminophores in solutions can significantly contribute to the solvation shifts of absorption and luminescence bands. Therefore, for the spectroscopic analysis of intermolecular interactions in solutions to be correct, the contribution from the Franck-Condon components should be quantitatively taken into account. Using carbazole and N-methyl carbazole as an example of luminophores with identical chromophore nuclei, it is found that intermolecular hydrogen bonds do not manifest themselves in the relaxation of the solvation environment, while the contribution from intermolecular interactions of a universal (van der Waals) character to the solvation shifts of such systems is the same.