Theoretical Study On The Structures And Absorption Spectra For Some Styryl Dyes And On The Reaction Mechanism Of Small Radicals

Styryl dyes with a good and wide bands in UV-Vis region are among the most important organic functional dyes. They are widely used in the areas of photographic industry, optical recording materials, laser technology, fluorescent chemosensor, solar cell and fluorescent probes. With the development of quantum mechanical theory and computer technology, the methods of quantum chemistry have become the potentest tool to design dye molecules. Density Functional Theory (DFT) and Time Dependent Density Functional Theory (TDDFT) with a high accuracy and economical computing resources have been used broadly by chemists.In this paper, the structure and quality of styryl dyes as well as their new applications are introduced. The increasing theoretical studies on the electric structures and spectrum properties for kinds of dyes are briefly reviewed. Theoretical studies on series of styryl dyes with quinoline nucleus and 2-styryl-β-naphthathiazole dyes were carried out to obtain optimized equilibrium structure and absorption spectra using TDDFT. The substituting effects on the intramolecular charge transfer, energies of frontier molecular orbitals and UV-Vis absorption spectra were investigated. Moreover, the electronic transition of the first singlet excited state was discussed. Polar continuum model (PCM) of the self-consistent reaction field (SCRF) method was selected for taking into account solute-solvent interactions. 2-Substituted styryl benzimidazole and some hemicyanine dyes with pyridine nucleus were studied by PCM/TDDFT. The nature of the common influences of the substituting groups and N-heterocyclic moiety on their absorption maxima (λ_max) in methanol was explored. Regression analysis was used for studying the relationship of theoretical values with experimental results ofλ_max in different solvent. Compared with experimental data, the calculations all provided a correct description on the molecular geometries and the UV-Vis spectra of these dye molecules.The process of chemical reaction is an advanced research shot topics in theoretical studies. The reaction includes reactants, intermediates, transition-state, products and one or more paths. The information of some intermediates and transition-state with relatively short lifetime is difficult to obtain by experimentation. In present study, the reaction mechanism of C₂H₃ radical with NO₂ was investigated by DFT method. The study shows that the reaction is multi-channel in the single state and triplet state. The potential energy surfaces of the reaction in the singlet state are lower than that in the triple state. NO is confirmed to be the primary product of reaction on the ground-state singlet. OH, HCO and HCN are proved the products of reaction on the triplet state.