Effect of solvent polarity on the yield of twisted intramolecular charge transfer (TICT) emission. Competition between formation and nonradiative decay of the TICT state

Abstract

The fluorescence quantum yield of the dual emission of dimethylaminobenzonitrile (DMABN) has been measured in a series of isoviscous mixtures of n-octane and propionitrile of differing polarity. With increase in solvent polarity, the yield of the TICT emission initially rises to a maximum and then decreases. Contrary to this, the yield of “nonpolar” emission monotonically decreases with increase in the polarity. This is explained in terms of the competition between the formation, and nonradiative decay of the TICT state, both of which are accelerated with increase in solvent polarity.