Three new dinuclear copper(II) compounds: [Cu-2(dpyam)(2)(mu(1.1)-N-3)(2)(O2CH)(2)] (1), [Cu-2(dpyam)(2)(mu(1.1)-N-3)(2)(O2CCH3)(2)](2) and [Cu-2-(dpyam)(2)(mu(1.1)-N-3)(2)(O2CCH2CH3)(2)](3) have been synthesized and characterized crystallographically and spectroscopically. Compounds 1, 2 and 3 consist of a dinuclear unit in which both Cu(II) ions are connected through two end-on azido bridges providing a distorted square pyramidal geometry with a CuN4O chromophore. The (CuCu)-Cu-. . . separations are 3.195, 3.200 and 3.247 angstrom for compounds 1, 2 and 3, respectively. The magnetic properties have been measured in the range from 5 to 300 K and correlated with the molecular structures. All three compounds show a medium to weak ferromagnetic exchange interactions between the Cu(II) ions dominated by the bridging azido ligands, with a singlet-triplet splitting (J) of 63.3, 63.8 and 5.1 cm(-1), for compounds 1, 2 and 3, respectively. A large zero-field splitting of about 0.4 cm(-1) is observed in the EPR for compounds 1 and 2. (c) 2006 Elsevier Ltd. All rights reserved.