Comparative studies of H+(C6H6)(H2O)1,2 and H+(C5H5N)(H2O)1,2 by DFT calculations and IR spectroscopy

Protonated benzene - water and pyridine - water complexes have been investigated by density functional theory (DFT) calculations and infrared (IR) spectroscopy. The calculations performed at the B3LYP/6 - 31+ G* level predict that there exist several stable isomers for H+(C6H6)(H2O)(1,2) with two distinct ion cores, C6H7+ and H3O+. In contrast, only the C5H5NH+-centred form can be found for H+(C5H5N)(H2O)(1,2), arising from the higher proton affinity of pyridine compared to that of benzene and water. Vibrational predissociation spectroscopic measurements of H+(C6H6)(H2O)(2) and H+(C5H5N)(H2O)(2) support the predictions.