Structure and Photophysical Properties of 2,6-Di-tert-Butyl-4-arylpyrylium 2-Naphthalenesulfonate Ion Pairs in Solution and in the Solid State

Abstract

2,6-Di-tert-butyl-4-arylpyrylium 2-naphthalenesulfonate salts form ion pairs in dimethylcarbonate solution that exhibit charge-transfer absorptions and result in the rapid quenching of the pyrylium fluorescence. Molecular mechanics calculations predict that these ion pairs exist in a T-shaped orientation, but X-ray structural analysis reveals a π face-to-face arrangement in the solid state. Nuclear Overhauser effect and time-resolved spectroscopic experiments carried out in solution are consistent with a T-shape for the ion pair, but these experiments do not prove that this structural hypothesis is correct