EXCITED-STATE DYNAMICS OF 4-PYRROLIDINO PYRIDINE IN DIFFERENT SOLVENTS

Photophysical properties of 4-Pyrrolidino Pyridine (PP) have been deli neated from the absorption, steady state and time-resolved spectroscop y in different solvents. Preferential hydrogen bonding of PP with wate r and also protonation with acid at intercyclic (pyrrolidino) nitrogen lone pair site could be observed. The intramolecular exciplex as pred icted from semi-empirical calculations controls the photophysics in we akly polar and nonpolar solvents. In water, a ground-state pretwisted pyrrolidino group forms hydrogen-bonded complex that dominates over th e intramolecular exciplex and this H-bonded exciplex acts as a quenchi ng 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 E lsevier Science S.A. All rights reserved.