Model Systems for Probing Metal Cation Hydration:  The V⁺(H₂O) and ArV⁺(H₂O) Complexes

Abstract

In support of mass-selected infrared photodissociation (IRPD) spectroscopy experiments, coupled-cluster methods including all single and double excitations (CCSD) and a perturbative contribution from connected triple excitations [CCSD(T)] have been used to study the V+(H2O) and ArV+(H2O) complexes. Equilibrium geometries, harmonic vibrational frequencies, and dissociation energies were computed for the four lowest-lying quintet states (5A1, 5A2, 5B1, and 5B2), all of which appear within a 6 kcal mol(-1) energy range. Moreover, anharmonic vibrational analyses with complete quartic force fields were executed for the 5A1 states of V+(H2O) and ArV+(H2O). Two different basis sets were used: a Wachters+f V[8s6p4d1f] basis with triple-zeta plus polarization (TZP) for O, H, and Ar; and an Ahlrichs QZVPP V[11s6p5d3f2g] and Ar[9s6p4d2f1g] basis with aug-cc-pVQZ for O and H. The ground state is predicted to be 5A1 for V+(H2O), but argon tagging changes the lowest-lying state to 5B1 for ArV+(H2O). Our computations show an opening of 2 degrees -3 degrees in the equilibrium bond angle of H2O due to its interaction with the metal ion. Zero-point vibrational averaging increases the effective bond angle further by 2.0 degrees -2.5 degrees, mostly because of off-axis motion of the heavy vanadium atom rather than changes in the water bending potential. The total theoretical shift in the bond angle of about +4 degrees is significantly less than the widening near 9 degrees deduced from IRPD experiments. The binding energies (D0) for the successive addition of H2O and Ar to the vanadium cation are 36.2 and 9.4 kcal mol(-1), respectively.

H 2 production from reactions between water and small molybdenum suboxide cluster anions

“…22 Armentrout and co-workers used collision induced dissociation techniques to determine bond energies and reactions between water and transition metal cations 23 and metal sulfide cations. 24,25 Duncan and co-workers [26][27][28][29] used IR spectroscopy to characterize complexes formed between a number of transition metal cations and dications and water, including the observation of solvation effects.…”

Reactivity of Hydrated Monovalent First Row Transition Metal Ions M+(H2O)n, M = V, Cr, Mn, Fe, Co, Ni, Cu, Zn, toward Molecular Oxygen, Nitrous Oxide, and Carbon Dioxide

“…Infrared spectroscopy by Duncan and co-workers revealed structural features of M + (H 2 O), M = V, Cr, Mn, Fe, − as well as V 2+ (H 2 O) . Larger clusters were studied for Ni + (H 2 O) n , n ≤ 25, indicating that all water molecules are involved in hydrogen bonding by n = 10.…”

Photodissociation and photochemistry of V+(H2O)n, n = 1–4, in the 360–680 nm region

“…Their properties have been investigated in considerable detail, with a wide range of experimental techniques, as reviewed recently [2][3][4][5][6][7]. Photodissociation in the O-H stretch region of the infrared, often coupled with tagging with a weakly bound species like Ar, is the most widely used spectroscopic method [8][9][10][11][12][13][14] [15] were characterized with infrared spectroscopy by Duncan and coworkers. For V + (H 2 O) n , n ≤ 8, a square-planar configuration was observed by Ohashi and coworkers, with four water molecules directly coordinated to V + [13].…”