2 GROUND-STATE CONFORMERS OF THE PROTON SPONGE 1,8-BIS(DIMETHYLAMINO)NAPHTHALENE REVEALED BY FLUORESCENCE SPECTROSCOPY AND AB-INITIO CALCULATIONS

The S-1<->S-0 transitions of the ''proton sponge'' 1,8-bis(dimethylami no)naphthalene have been studied by experiment and ab initio calculati ons. Fluorescence excitation and single vibronic level emission spectr oscopy on the sample seeded in a supersonic expansion lead to the conc lusion that the molecule can adopt two conformations in the ground sta te. This conclusion is supported by ab initio calculations at the HF/6 -31G level. The most stable conformer is shown to carry the spectrosc opic characteristics of the naphthalene chromophore, while torsional m otions of the dimethylamino groups dominate the spectroscopy of the ot her conformer.