Persistence of a Delocalized Radical in Larger Clusters of Hydrated Copper(II) Hydroxide, CuOH(HO).

The structures, vibrational spectra, and electronic properties of copper hydroxide hydrates CuOH(HO) were investigated with quantum chemistry computations. As a follow-up to a previous analysis of CuOH(HO), this investigation examined the progression as the square-planar metal coordination environment was filled and as solvation shells expanded. Four-, five-, and six-coordinate structures were found to be low-energy isomers. The delocalized radical character, which was discovered in the small clusters, was found to persist upon continued hydration, although the hydrogen-bonded water network in the larger clusters was found to play a more significant role in accommodating this spin. Partial charges indicated that the electronic structure includes more Cu···OH character than was observed in smaller clusters, but this structure remains decidedly mixed with Cu···OH configurations and yields roughly half-oxidation of the water network in the absence of any electrochemical potential. Computed vibrational spectra for = 3 showed congruence with spectra from recent predissociation spectroscopy experiments, provided that the role of the D tag was taken into account. Spectra for = 4-7 were predicted to exhibit features that are reflective of both the mixed electronic character and proton-/hydrogen-shuttling motifs within the hydrogen-bonded water network.