3,1'-BRIDGED 2-[2'-(4''-DIALKYLAMINOPHENYL)ETHENYL] PYRYLIUM AND 1-BENZOPYRYLIUM DYES - SYNTHESIS AND VIS NIR ABSORPTION/EMISSION BEHAVIOR/

A series of new 3,1'-bridged 2-[2'-(4 ''-dialkylaminophenyl)ethenyl]-4 ,6-diarylpyrylium perchlorates (3), 2-[2'-(4 minophenyl)ethenyl]-7-die thylamino-1-benzopyrylium perchlorates 5-8, 2-[4'-(4 ''-dialkylaminoph enyl)butadien-1',3'-yl]-, and 2-[2'-(7 ''-diethylaminocoumar-3 ''-yl)e thenyl]-7-diethylamino-1-benzopyrylium perchlorates 10-12 were synthes ized and characterized by means of elemental analysis, m.p., Vis/NIR, and H-1 NMR spectra. Semiempirical MO calculations were performed to e lucidate the essential features of the chromophores. The size of the b ridging ring strongly affects the geometry of the chromophores which, in turn, determines the extent of charge transfer of the longest wavel ength electronic transition. Increasing deviation from planarity cause s the polymethine-like chromophore to become more polyene-like.