Molecular models of the form (H2O)(n) ... Cu+... X, where n = 1, 2, 3 and X = CO, 2(CO), NO, (NO)(2), and H2O are employed to investigate the catalytically active copper sites in Cu+-ZSM-5 zeolite. Structures, binding energies and vibrational frequencies are calculated for these molecular models by density functional theory with gradient-corrected functionals. The calculated vibrational frequencies are compared to experimental infrared spectra of CO and NO adsorbed in Cu+-ZSM-5 for each n value. The absence (presence) of an unpaired electron in the CO (NO) molecule is found to have effects in the structures, binding energies, and vibrational frequencies of the adsorbed species. Upon adsorption at a copper cation site, we find that, in agreement with experiment, (1) the stretching frequency of CO undergoes a small blue shift whereas that of NO is red shifted; (2) the formation of adsorbed dicarbonyl species is not as favored as the formation of adsorbed dinitrosyl species; and (3) the frequency separation between the antisymmetric and symmetric stretching modes is much smaller in the dicarbonyl species than in the dinitrosyl species. The choice of gradient-corrected functionals and the basis set used in this study is found to reproduce accurately the successive binding energies of (H2O)(n) ... Cu+ when three or more Ligands to the copper cation are present.