Quantum Chemical Study Of The Structure And Properties Of A Number Of Indigoid Compounds

Indigoids , an important part of the reduce dyes , have being widely used in the industrial fields of dying and foods. They are also used in storing and using solar energy and in information recording. In this thesis, a relatively high level theoretical investigation has been performed using the density functional theory (DFT) and time-dependent density functional theory (TD-DFT) methods to study the structures and properties of a series of indigoids and chromophores. The relationship between structure and property was discussed.First, calculations have been carried out on indigo and chromophores of thioindigo using different theoretical methods. The calculated results of various methods are compared and the reliability of the results is tested. It is found that the semiempirical PM3 and Hartree-Fock ab initio methods are not suitable for calculating indigoids, while the results at the B3LYP/6-31G* level are quite good and are linearly correlated with the experimental results. Moreover, the CPU tune and computer resource desired by the B3LYP/6-31G* calculation are much less than the B3LYP/6-311G**, therefore it can be adopted to accurately calculate the title compounds. The results at the B3LYP/3-21G level are somewhat poorer than that of the B3LYP/6-31G*, however, considering the less computer resource desirement, this method was choosed for studing series and relatively large systems , such as the benzene-substituted derivatives and the dinner of indigo .Then, Indigo and its 4,4'-, 5,5' -, 6,6'-, and 7,7'-substituted derivatives with F, C1, Br, NO2, CH3O, and CH3 groups and monobromo-substituted derivatives have been studied at the B3LYP/6-31G*(or 3-21G) level of density functional theory(DFT). The substitution effects of the electron-donating and electron-accepting groups at various positions on the geometry structures , electronic structures, and the electronic spectrum have been investigated, and quite good results are achieved compared with the experimental results: substitution mainly affects the geometrical parameters and charge distributions near the substitution position. The changes in the frontier molecular orbital energy caused by different position substitution have the similar trend, viz. the electron-accepting groups decrease while the electron-donating groups increase the frontier MOs energy. For the frontier MOs energy gaps (Es) and the absorption maxima (max), 4,4'- and 6,6'-, and 5,5'- and 7,7'- substituted derivatives have the same trend, respectively. Moreover, substitutions with the strong electron-accepting and electron-donating groups haveopposite effects on Es and max. Substitutions on benzene rings bring about 10~70nm changes in electronic absorption spectrum. Except the substitution with NOa, 5,5' - and 7,7'-substitution cause a red-shift of max, and 6,6'- substitution causes a blue-shift, but there are no obvious regular change for 4,4'- substitution.The indigo dimer, the polymer of indigo and solvent (e.g. CH3COOH), and N,N' -diacetylindigo were calculated too. The characters and properties of intra- and intermolecular hydrogen bonds were discussed.In addition, the geometry structures , electronic structures, and the electronic spectrum of oxindigo, thioindigo, and selenoindigo were calculated and discussed. Except for the bonds including electron-donating groups (X), the other lengths change little. The increasing in the electron-donating capabilities causes a red-shift of max. The first excited singled states (S1) have the Bu symmetry, and are originated from the HOMO LUMO electron transition.Finally, the structures and spectral properties of indigoids chromophores were calculated .The effects of the electron-donating groups and the extension of chromophores on the electronic spectrum have been investigated, and good results are achieved compared with the experimental results of indigoids. The nature of emission of indigoids was further clarified.