An investigation of structures and stabilization energies of copper water complexes is presented. Possible cluster geometries of [Cu(H2O)(n)](2 divided by) for n = 1-8 were optimized using HF/6-31G(d,p), and energies were determined at the MP2/6-31G(d,p) and B3LYP/6- 31G(d,p) levels of theory. In addition, for n = 6, 7, and 8 geometry optimizations at MP2/6-311g(d,p) have been carried out. The basis set effect on stabilization energies was also considered by performing MP2 with 6-31 ++G(d,p), 6-311 G(d,p) and 6-311 G(2df,p) single point energy calculations. Only five- and six-fold coordination complexes were obtained with square pyramid (spy) and octahedral (oct) copper coordination as their most stable structures. The hydrogen bonds which form between water molecules in the first and second solvation shell play an important role for the stabilities of the complexes. (c) 2007 Elsevier B.V. All rights reserved.