Structural changes of triplet states of hydrogen bonded hexagonal dimers upon ionization and electron capture

Abstract

The dimers of the S=1/2 radicals, HO 2 and N 2H 3, are investigated by ab initio quantum chemical geometry optimizations. Several isomers of the dimers are found. The main emphasis in this investigation is on dimers consisting of two monomers, hydrogen bonded head to tail in a hexagonal ring with two hydrogen bonds of equal length. The electronic wave function for these dimers is a spin triplet. The geometries of the cations and anions pertaining to the hexagonal dimers are likewise determined by the geometry optimizations in order to investigate the structural changes upon ionization and electron capture. The main structural change can be described as a migration of H/H + from one monomer to the other while the overall hexagonal form is conserved. In order to have a standard of comparison a similar investigation is performed for the spin triplet state of the hexagonal dimer of C 2H 5. The findings in this case are consistent with the expected low capacity for hydrogen bonding for the C 2H 5 radical.