title: Water Adsorption on Free Cobalt Cluster Cations.
abstract: Cationic cobalt clusters complexed with water Con(+)-H2O (n = 6-20) are produced through laser ablation and investigated via infrared multiple photon dissociation (IR-MPD) spectroscopy in the 200-1700 cm(-1) spectral range. All spectra exhibit a resonance close to the 1595 cm(-1) frequency of the free water bending vibration, indicating that the water molecule remains intact upon adsorption. For n = 6, the frequency of this band is blue-shifted, but it gradually converges to the free water value with increasing cluster size. In the lower-frequency range (200-650 cm(-1)) the spectra contain several bands which show a very regular frequency evolution, suggesting that the exact cluster geometry has little effect on the water-surface interaction. Density functional theory (DFT) calculations are carried out at the OPBE/TZP level for three representative sizes (n = 6, 9, 13) and indicate that the vibrations responsible for the resonances correspond to bending and torsional modes between the cluster and water moieties. The potential energy surfaces describing these interactions are very shallow, making the calculated harmonic frequencies and IR intensities very sensitive to small geometrical perturbations. We conclude that harmonic frequency calculations on (local) minima structures provide insufficient information for these types of cluster complexes and need to be complemented with calculations that provide a more extensive sampling of the potential energy surface.
authors.affiliation: Radboud University , Institute for Molecules and Materials, FELIX Laboratory, Toernooiveld 7, 6525 ED Nijmegen, The Netherlands.
authors.forename: Denis M
authors.initials: DM
authors.lastname: Kiawi
authors.affiliation: Radboud University , Institute for Molecules and Materials, FELIX Laboratory, Toernooiveld 7, 6525 ED Nijmegen, The Netherlands.
authors.forename: Joost M
authors.initials: JM
authors.lastname: Bakker
authors.affiliation: Radboud University , Institute for Molecules and Materials, FELIX Laboratory, Toernooiveld 7, 6525 ED Nijmegen, The Netherlands.
authors.forename: Jos
authors.initials: J
authors.lastname: Oomens
authors.forename: Wybren Jan
authors.initials: WJ
authors.lastname: Buma
authors.affiliation: Department of Physical Chemistry, Chemistry and Chemical Engineering Research Center of Iran , P.O. Box 14335-186, Tehran, Iran.
authors.forename: Zahra
authors.initials: Z
authors.lastname: Jamshidi
authors.affiliation: Amsterdam Center for Multiscale Modeling Section Theoretical Chemistry, VU University Amsterdam , De Boelelaan 1083, 1081 HV Amsterdam, The Netherlands.
authors.forename: Lucas
authors.initials: L
authors.lastname: Visscher
authors.affiliation: SRON Netherlands, Sorbonnelaan, Utrecht, The Netherlands.
authors.forename: L B F M
authors.initials: LB
authors.lastname: Waters