Microsolvation of Zn cations: infrared multiple photon dissociation spectroscopy of Zn+(H2O)n (n=2-35)

The structures, along with solvation evolution, of size-selected Zn+(H2O)(n) (n = 2-35) complexes have been determined by combining infrared multiple photon photodissociation (IRMPD) spectroscopy and density functional theory. The infrared spectra were recorded in the O-H stretching region, revealing varying shifts in band position due to different water binding motifs. Concordant with previous studies, a coordination number of 3 is observed, determined by the sudden appearance of a broad, red-shifted band in the hydrogen bonding region for clusters n > 3. The coordination number of 3 seems to be retained even for the larger clusters, due to incoming ligands experiencing significant repulsion from the Zn+ valence 4s electron. Evidence of spectrally distinct single- and double-acceptor sites are presented for medium-sized clusters, 4 <= n <= 7, however for larger clusters, n >= 8, the hydrogen bonding region is dominated by a broad, unresolved band, indicative of the increased number of second and third coordination sphere ligands. No evidence of a solvated, six-fold coordinated Zn2+ ion/solvated electron pair is present in the spectra.

Automated summary

This study determined the structures and solvation evolution of size-selected Zn+(H2O)(n) (n = 2-35) complexes using infrared multiple photon photodissociation (IRMPD) spectroscopy and density functional theory. The coordination number of 3 was observed, even for larger clusters, due to repulsion from the Zn+ valence 4s electron. Spectrally distinct single- and double-acceptor sites were found for medium-sized clusters, while larger clusters showed increased second and third coordination sphere ligands in the hydrogen bonding region. No evidence of a solvated, six-fold coordinated Zn2+ ion/solvated electron pair was present in the spectra.