A solvent adduct study of 1,4,8,11-tetraazacyclotetradecane nickel(II) perchlorate with the coordinating solvents acetonitrile, N,N-dimethylformamide (DMF), methyl sulfoxide (DMSO), and water by optical and nmr techniques is reported. The thermodynamic parameters ΔH°, ΔS°, and Keq for adduct formation are given for each solvent system. At 25 °C, the stability order is found to be DMF > CH3CN > DMSO > H2O. A comparison of the observed stability order and stabilities predicted by single optical measurements and solvent donicity is presented. © 1979.