Crystal Structures of Dyes Composed of an Aniline Donor and a Pyrroline-Type Acceptor

Abstract

Single crystals of 3-[4-(dibutylamino)phenyl]-4-cyano-5-dicyanomethylene-2-oxo-3-pyrroline 1a and its derivatives with 1-butyl (1b), 1-hexyl (1c) and 1-(2-[2-(acryloyloxy)ethoxy])ethyl (1e) groups were prepared and their X-ray crystallographic analyses were performed. These dyes have a common π-conjugation system terminated by donor and acceptor groups, and they can be applied to use as electrooptic chromophores. Their absorption of the crystals were discussed in relation to the chromophore alignment in the crystals. Antiparallel interaction between the π-conjugated systems, whether face-to-face or side-by-side, caused absorption shifts to shorter wavelengths. Absorption at the longest wavelength was observed for 1e, whose π-conjugated systems were separated by the substituents resulting in almost no interaction among the adjacent π-conjugated systems.