Infrared and electronic spectra of microhydrated para-dichlorobenzene cluster cations

Microhydrated para-dichlorobenzene cation clusters, pDCB+(H2O)n with n = 1 and 2, were characterised in the electronic ground state by infrared photodissociation spectroscopy in the O–H and C–H stretch ranges and B3LYP/6–311++G∗∗ calculations. The intermolecular pDCB+H2O potential features at least two nonequivalent minima with charge-dipole configuration and comparable binding energies. The pDCB+(H2O)2 spectrum reveals the presence of two types of isomers, in which either a (H2O)2 dimer or two single H2O ligands are attached to pDCB+. The detected pDCB+(H2O)1,2 complexes are unreactive with respect to nucleophilic substitution. This conclusion is supported for pDCB+H2O by the electronic spectrum of its B ← X transition.