Inversion of states in two conformers of 1,8-bis(dimethylamino) naphthalene - the proton sponge

The S-1 <-> S-0 transitions of two conformers of 1,8-bis(dimethylamino) naphthalene, the "proton sponge", have been studied by semiempirical AM1 calculations. They reveal that "inversion of states" occurs in the asymmetric conformer DMAN-2, which in the gas phase may be emitted from the L-1(a) state in comparison to the L-1(b) State in symmetric DMAN-1. It was also concluded that because of the mixed character of the HOMO-1 orbital in both conformers, a certain CT contribution to the S-0 <-> S-1 transition has to be taken into account. The calculated maxima of absorption and emission have been compared to those experimentally obtained in supersonic expansion. (C) 2000 Elsevier Science B.V. All rights reserved.