The structure and bonding of mixed component radical cation clusters

Basin hopping in conjunction with second order Møller–Plesset perturbation theory is used to characterise the lowest energy isomers of mixed component radical cation clusters of the form [H2O-X]+, [(H2O)2-X]+ and [H2O-X2]+, where X = PH3, H2S and HCl, with the relative energies refined using coupled cluster theory calculations. For the dimers where X = H2S or HCl, a proton transfer based structure comprising H3O+ and SH or Cl radicals has the lowest energy structure whereas for X = PH3 a hemibonded structure is most stable. For the trimers, a much wider range of possible isomers based upon both proton transfer and hemibonded structural motifs is observed.