Obernikhina N. Electronic and spectral properties of the donor-acceptor polymethine dyes

Dissertation deals with systematic quantum-chemical and spectral studies of structure and the nature of electron transitions of neutral donor-acсeptor polymethine dyes. The polyene-like electron structure and molecular geometry of the cyanine bases and merocyanines have been explained by the calculations. It has been shown that at the critical length the chromophor the bi-radical state emerges in which atomic charges as well as bond lengths are equalized. For the explanation of deep color and fluorescence of merocyanines, the scheme of the interaction of the quasi-local chromophores was proposed. Such chromophores include the conjugating system of terminal groups with the polymethine chain. On the basis of nonlinear optical studies, it was established that increasing the basicity of the terminal groups in the unsymmetrical cyanine bases is accompanied by a regular increase of the hyperpolarizibilities. That's why these compounds are promising for the creation of organic materials for nonlinear optics.