Excited state dynamics of 4-pyrrolidino pyridine in different solvents

Photophysical properties of 4-Pyrrolidino Pyridine (PP) have been delineated from the absorption, steady state and time-resolved spectroscopy in different solvents. Preferential hydrogen bonding of PP with water and also protonation with acid at intercyclic (pyrrolidino) nitrogen lone pair site could be observed. The intramolecular exciplex as predicted from semi-empirical calculations controls the photophysics in weakly polar and nonpolar solvents. In water, a ground-state pretwisted pyrrolidino group forms hydrogen-bonded complex that dominates over the intramolecular exciplex and this H-bonded exciplex acts as a quenching channel for the dual fluorescence. Intermolecular exciplexes of PP were found to form in binary and ternary solutions with polar solvent containing N-atom. Fluorescence in beta-cyclodextrin cavity resembles intramolecular exciplex in ethanol with high quantum yield. (C) 1998 Elsevier Science S.A. All rights reserved.