INTRAMOLECULAR RELAXATION PROCESSES IN A SINGLET EXCITED NAPHTHALENE-ACRIDINE BICHROMOPHORIC MOLECULE IN SOLUTION AND IN A SUPERSONIC JET EXPANSION

Intramolecular electronic relaxation processes in a flexible naphthale ne-acridine bichromophoric molecule I were studied in solution and in a supersonic jet expansion. Intramolecular electronic energy transfer (intraEET) from the electronically excited naphthalene unit to the acr idine moiety and an additional non-radiative decay process, probably i ntramolecular electron transfer (intraELT) to the acridine unit, of th e excited naphthalene group was observed in solution. In a supersonic jet expansion, no indication for intraEET or other interchromophoric i nteractions was found. The relaxation of the excited naphthalene chrom ophore in I, under the conditions of supersonic jet expansion, is domi nated by intrachromophoric radiationless transitions. The dependence o f single vibronic fluorescence lifetimes of jet-cooled I on the excita tion frequency is discussed. (C) 1998 Elsevier Science B.V. All rights reserved.