Coordination and solvation structures of the Cu+(H2O)(n) ions with n = 1-4 are studied by infrared photodissociation spectroscopy and density functional theory calculations. Hydrogen-bonding between H2O molecules is detected in Cu+(H2O)(3) and Cu+(H2O)(4) through a characteristic change in the position and intensity of OH-stretching transitions. The third and fourth waters prefer hydrogen-bonding sites in the second solvation shell rather than direct coordination to Cu+. The infrared spectroscopy verifies that the gas-phase coordination number of Cu+ in Cu+(H2O)(n) is two and the resulting linearly coordinated structure acts as the core of further solvation processes. (c) 2006 Elsevier B.V. All rights reserved.