CHARGE-TRANSFER INTERACTIONS IN 1-CYANONAPHTHALENE VANDERWAALS COMPLEXES WITH ALIPHATIC-AMINES - DEPENDENCE OF EXCITED-STATE DYNAMICS ON DONOR IONIZATION-POTENTIAL

The exciplex formation reaction that occurs within the initially excited van der Waals complexes of 1-cyanonaphthalene with a variety of aliphatic amines has been studied as a function of the ionization potential (IP) of the amines and the excess vibrational energy of the electronically excited complexes. In all cases, the fluorescence excitation spectra are composed of only narrow-band features originating from local excitations of the acceptor chromophore. While complexes involving amines of high IP are inefficient in producing exciplexes, those with amines of low IP give rise to exciplex fluorescence from the charge-transfer state. The tributylamine complex, unlike the others, undergoes the exciplex formation upon excitation into its S1 origin. These results are interpreted in terms of the crossing of the initially excited van der Waals state and the charge-transfer state.