INTRAMOLECULAR CHARGE-TRANSFER PROPERTIES OF DICYANOVINYL-SUBSTITUTED AROMATICS

A series of five dicyanovinyl (DCV)-substituted aromatic compounds (referred to collectively as Ar-DCV, where Ar = 1-phenyl, 1-napthyl, 9-anthracenyl, 9-phenanthrenyl, and 1-pyrenyl) were prepared and their ground- and excited-state properties were examined. Solvent-dependent NMR studies indicate that the ground state of the Ar-DCV compounds is polar. Strong intramolecular charge transfer (ICT) absorption bands were observed for each compound. The position of the ICT absorption is nearly independent of solvent polarity and the molar absorptivity is related to the twist angle between the aromatic donor and the DCV acceptor. The fluorescence spectra are highly solvatochromatic and the fluorescence energy correlates with the solvent polarity parameter-DELTA-f in a variety of solvents. The fluorescence quantum yields are low and no emission was observed from phenyl-DCV. An excited-state model is proposed which explains the solvent dependence of the ICT absorption and emission of the series of Ar-DCV compounds.