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Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometry is applied to analyze the reactions of water cluster anions [([H.sub.2]O).sub.n.sup.-] where n ranges from 30 to 70, with hydrogen chloride. Results reveal that the [Cl.sup.-][(HCl).sub.4][([H.sub.2]O).sub.6] cluster symbolizes an example for supramolecular self-organization in the gas phase, which comprises of a tetrahedral [Cl.sup.-][(HCl).sub.4], linked on one side of the tetrahedron to a compact water hexamer.

The reaction of HNO3 with hydrated electrons (H2O)n- (n = 35-65) in the gas phase was studied using Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometry and ab initio molecular dynamics simulations. Kinetic analysis of the experimental data shows that OH−(H2O)m is formed primarily via a reaction of the hydrated electron with HNO3 inside the cluster, while proton transfer is not observed and NO3-(H2O)m is just a secondary product. The reaction enthalpy was determined using nanocalorimetry, revealing a quite exothermic charge transfer with −241 ± 69 kJ mol-1. Ab initio molecular dynamics simulations indicate that proton transfer is an allowed reaction pathway, but the overall thermochemistry favors charge transfer. [ABSTRACT FROM AUTHOR]

Infrared spectra of the hydrated vanadium cation (V+(H2O)n; n = 3–51) were measured in the O–H stretching region employing infrared multiple photon dissociation (IRMPD) spectroscopy. Spectral fingerprints, along with size-dependent fragmentation channels, were observed and rationalized by comparing to spectra simulated using density functional theory. Photodissociation leading to water loss was found for cluster sizes n = 3–7, consistent with isomers featuring intact water ligands. Loss of molecular hydrogen was observed as a weak channel starting at n = 8, indicating the advent of inserted isomers, HVOH+(H2O)n−1. The majority of ions for n = 8, however, are composed of two-dimensional intact isomers, concordant with previous infrared studies on hydrated vanadium. A third channel, loss of atomic hydrogen, is observed weakly for n = 9–11, coinciding with the point at which the H and H2O calculated binding energies become energetically competitive for intact isomers. A clear and sudden spectral pattern and fragmentation channel intensity at n = 12 suggest a structural change to inserted isomers. The H2 channel intensity decreases sharply and is not observed for n = 20 and 25–51. IRMPD spectra for clusters sizes n = 15–51 are qualitatively similar indicating no significant structural changes, and are thought to be composed of inserted isomers, consistent with recent electronic spectroscopy experiments. [ABSTRACT FROM AUTHOR]

The reactions and ligand exchange of hydrated silver cations Ag(super +)(H2O)(sub n) with NH3 as well as the complementary process, the reaction of large ammoniated silver cations Ag(super +)(NH3)(sub n) with H2O are examined in order to gain insight into the coordination chemistry of silver cations in mixed solvent systems. The experiments show that in mixed clusters the first and second ammonia ligand, however, are much more strongly bound than water because they cannot be exchanged.

Systematic study of the blackbody radiation induced fragmentation of size-selected ionic ammonia clusters are reported with its comparison with that of the corresponding hydrates. Experimental observations and DFT calculations of the cluster structures, harmonic frequencies and intensities depicted that the fragmentation rate constants of the ions solvated with ammonia exhibit overall linear dependence on the number of ligands n.

A new study investigates hypoidous acid as guest molecule in protonated water clusters, focusing on I(H2O)n+ (n= 3-15).

A collision complex of the metal cluster with a polyatomic molecule would be transiently stabilized by redistribution of the interaction energy, IVR. This energy redistribution results in heating of the collision complex to internal temperatures.

FT-ICR mass spectrometry can be used to assess the reactions of hydrated metal cations Ag+(H2O)n, n = 11-26, and Na+(H2O)n, n = 12-28, with HCl. It was established that an analogue to bulk precipitation reaction arises on a molecular level in clusters.

Hydrated aluminium cations have been investigated as a photochemical model system with up to ten water molecules by UV action spectroscopy in a Fourier transform ion cyclotron resonance (FT‐ICR) mass spectrometer. Intense photodissociation was observed starting at 4.5 eV for two to eight water molecules with loss of atomic hydrogen, molecular hydrogen and water molecules. Quantum chemical calculations for n=2 reveal that solvation shifts the intense 3s–3p excitations of Al+ into the investigated photon energy range below 5.5 eV. During the photochemical relaxation, internal conversion from S1 to T2 takes place, and photochemical hydrogen formation starts on the T2 surface, which passes through a conical intersection, changing to T1. On this triplet surface, the electron that was excited to the Al 3p orbital is transferred to a coordinated water molecule, which dissociates into a hydroxide ion and a hydrogen atom. If the system remains in the triplet state, this hydrogen radical is lost directly. If the system returns to singlet multiplicity, the reaction may be reversed, with recombination with the hydroxide moiety and electron transfer back to aluminium, resulting in water evaporation. Alternatively, the hydrogen radical can attack the intact water molecule, forming molecular hydrogen and aluminium dihydroxide. Photodissociation is observed for up to n=8. Clusters with n=9 or 10 occur exclusively as HAlOH+(H2O)n‐1 and are transparent in the investigated energy range. For n=4–8, a mixture of Al+(H2O)n and HAlOH+(H2O)n‐1 is present in the experiment. [ABSTRACT FROM AUTHOR]

Photochemical hydrogen evolution provides fascinating perspectives for light harvesting. Hydrated metal ions in the gas phase are ideal model systems to study elementary steps of this reaction on a molecular level. Here we investigate mass-selected hydrated monovalent vanadium ions, with a hydration shell ranging from 1 to 41 water molecules, by photodissociation spectroscopy. The most intense absorption bands correspond to 3d–4p transitions, which shift to the red from n = 1 to n = 4, corresponding to the evolution of a square-planar complex. Additional water molecules no longer interact directly with the metal center, and no strong systematic shift is observed in larger clusters. Evolution of atomic and molecular hydrogen competes with loss of water molecules for all V+(H2O)n, n ≤ 12. For n ≥ 15, no absorptions are observed, which indicates that the cluster ensemble is fully converted to HVOH+(H2O)n−1. For the smallest clusters, the electronic transitions are modeled using multireference methods with spin–orbit coupling. A large number of quintet and triplet states is accessible, which explains the broad features observed in the experiment. Water loss most likely occurs after a series of intersystem crossings and internal conversions to the electronic ground state or a low-lying quintet state, while hydrogen evolution is favored in low lying triplet states. [ABSTRACT FROM AUTHOR]

Density functional theory calculations were used to locate the transition state of the charge separation Co(H2O)4(super 2+) -> CoOH(H2O)2(super +) + H3O(super +). The transition stage was calculated to lie 166 kJ/mol kinetic energy release.

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