Synthesis of polymethine dyes possessing nonlinear optical properties and preparation of photoconducting systems based thereupon

Reactions of 2,3,3-trimethyl-3H-indolium and 2-methylquinolinium quaternary salts with o- and p-hydroxybenzaldehydes afforded polymethine dyes (styryls) which were isolated for the first time as the corresponding tetrafluoroborates. The dyes can redily be deprotonated by the action of alkali to obtain neutral merocyanine species. Chemical, photophysical, and optical properties of the products were studied. All the obtained dyes were found to exhibit second-order nonlinear optical activity; in combination with 2,3-dimethyl-indole, they are also capable of photochemically generating mobile charge carriers.