Rossana R. Wright

Unexpected stability of [Cu⋅Ar]2+, [Ag⋅Ar]2+, [Au⋅Ar]2+, and their larger clusters

Experimental observations following the ionization of neutral group 11 metal/argon complexes have revealed the presence of doubly charged ions of the form [M . Ar-n](2+) for n in the range 1-6. Of particular interest are two features of the results. First, the unexpected stability of the dimer ions, [M . Ar](2+), since similar species involving a molecule rather than a rare gas atom are often unstable with respect to charge transfer. Ab initio calculations show the dimers owe their stability to a combination of a strong electrostatic interaction and the high ionization energy of argon. A second feature to the results is the high relative intensities of the [M . Ar-4](2+) and [M . Ar-6](2+) ions. Calculations show these complexes to consist of square-planar D-4h structures, with the additional two atoms in [M . Ar-6](2+) occupying axial sites, which are Jahn-Teller distorted. The calculated relative binding energies support the preferential stability of these two structures

Comment on “Do Cu2+NH3 and Cu2+H2O exist?: theory confirms yes!” (Chemical Physics Letters 318 (2000) 333–339)

Abstract Contrary to the theoretical results presented by El-Nahas et al. (Chem. Phys. Lett. 318 (2000) 333), we believe new experiments on [Cu·(H2O)n]2+ and [Cu·(NH3)n]2+ complexes suggest their minimum stable sizes are [Cu·(H2O)3]2+ and [Cu·(NH3)2]2+, respectively.

Cluster ion studies of Ho2+ and Ho3+ solvation in the gas phase

Abstract An attempt has been made to prepare triply charged ions of holmium in association with a range of solvent clusters. Neutral atoms of holmium are generated in the gas phase using an effusive oven and are crossed with a beam consisting of solvent/argon clusters. Collisions between the holmium atoms and the clusters lead to the formation of neutral metal–solvent complexes. Ionisation by electron impact in the source of a high resolution mass spectrometer enables measurements to be undertaken on the intensities and fragmentation patterns of the resultant ions as a function of size. Only singly and doubly charged complexes are observed when water and methanol are used as solvents. Stable triply charged complexes are formed with the solvents acetone and acetonitrile, and intensity measurements suggest the preferred coordination number in both cases is 6. Measurements following the collisional activation of the holmium/acetonitrile complexes show evidence of chemical reactivity.

The ultraviolet photofragmentation of doubly charged transition metal complexes in the gas phase: Initial results for [Cu.(pyridine)n]2+ and [Ag.(pyridine)n]2+ ions

Results are presented of a study of the UV photofragmentation patterns of the doubly charged complexes [Cu.(pyridine)n]2+ and [Ag.(pyridine)n]2+ for n=4–7. The two systems behave very differently, with Ag(II) being dominated by the presence of charge transfer products at small values of n. This ease of reduction of Ag(II) can be equated to behavior seen in the condensed phase. At all values of n both types of complex display a remarkable tendency to fragment to the most stable configuration, which can correspond to either a singly or doubly charged ion.

A systematic shift in the electronic spectra of substituted benzene molecules trapped in helium nanodroplets

Electronic spectra (S1<--S0) have been recorded from five separate substituted benzene derivatives trapped in helium nanodroplets. Each member of the series is found to exhibit a blueshift with respect to the equivalent transition in the gas phase. Taken together with previous results for benzene, the observed shifts show a remarkably good correlation with changes in electron density that occur within each of the aromatic rings as a result of electronic excitation.