Singly charged zinc-water cations are produced in a pulsed supersonic expansion source using laser vaporization. Zn(+)(H2O)n (n = 1-4) complexes are mass selected and studied with infrared laser photodissociation spectroscopy, employing the method of argon tagging. Density functional theory (DFT) computations are used to obtain the structures and vibrational frequencies of these complexes and their isomers. Spectra in the O-H stretching region show sharp bands corresponding to the symmetric and asymmetric stretches, whose frequencies are lower than those in the isolated water molecule. Zn(+)(H2O)nAr complexes with n = 1-3 have O-H stretches only in the higher frequency region, indicating direct coordination to the metal. The Zn(+)(H2O)2-4Ar complexes have multiple bands here, indicating the presence of multiple low energy isomers differing in the attachment position of argon. The Zn(+)(H2O)4Ar cluster uniquely exhibits a broad band in the hydrogen bonded stretch region, indicating the presence of a second sphere water molecule. The coordination of the Zn(+)(H2O)n complexes is therefore completed with three water molecules.

Singly charged aluminum-benzene cation complexes are produced by laser vaporization in a pulsed supersonic expansion. The Al(+)(benzene)n (n = 1-4) ions are mass selected and investigated with infrared laser photodissociation spectroscopy. Density functional theory (DFT) is employed to investigate the structures, energetics and vibrational spectra of these complexes. Spectra in the C-H stretching region exhibit sharp multiplet bands similar to the pattern known for the Fermi triad of the isolated benzene molecule. In the fingerprint region, strong bands are seen corresponding to the ν19 C-C ring motion and the ν11 out-of-plane hydrogen bend. The hydrogen bend is strongly blue-shifted compared to this vibration in benzene, whereas the ν19 carbon ring distortion is only slightly shifted to the red. Computed structures and energetics, together with experimental fragmentation and vibrational patterns, indicate a primary coordination of three benzene molecules around the central Al(+) cation. The n = 4 complex contains one second-sphere solvent molecule.