Counterpoise corrected geometries, absolute energies, and vertical detachment energies of the ClO- center dot (H2O)(n) n = 1-4 clusters were determined for the first time using high-level ab initio [up to CCSD(T)] and density functional theory calculations. For the n > 1 clusters, a number of low-energy, isomeric structures are obtained. The global minima structures are characterized by water hydrogen bonds to the oxygen of ClO-, with the CI protruding from the cluster surface. By contrast, the neutral ClO center dot (H2O)(n) n = 1-4 cluster structures are controlled by water-water interactions, with ClO being only weakly bound. Implications for the atmospheric chemistry and photodetachment spectroscopy of these species are briefly discussed. (c) 2006 Elsevier B.V. All rights reserved.