Stable Red-Emissive Cationic Dithienotropylium Dyes

摘要

A series of thiophene-fused tropylium ions, containing various electron-donating amino groups at the terminal positions, was synthesized. The fusion of the thiophene rings, as well as the presence of the terminal amino groups endows the cationic tropylium ion with excellent stability and high pK(R)(+) values. X-ray crystallographic analysis of these compounds revealed a pronounced quinoidal character for the amino-substituted dithienotropylium skeletons. These compounds exhibit attractive photophysical properties such as strong absorption in the visible region combined with red fluorescence. Theoretical calculations suggested that the 3,3'-bithiophene substructure should be crucial for attaining these photophysical properties.