Infrared spectra of Cl−–(C6H6)m m = 1, 2

The Cl−–(C6H6)Arn n = 0, 1, 2 and Cl−–(C6H6)2 complexes are investigated using photodissociation infrared spectroscopy in the CH stretch region and through ab initio calculations at the MP2/aug-cc-pVDZ level. The results indicate that Cl−–C6H6 possesses a planar structure in which the benzene molecule is attached to the Cl− anion by a double hydrogen bond. The calculations predict that Cl−–(C6H6)2 has a C2 symmetry structure in which the two face-to-face benzene molecules are attached to the Cl− anion by double hydrogen bonds. This structure is compatible with the measured Cl−–(C6H6)2 infrared spectrum.