The pyridazine (pdz) complexes [Cu(pdz)(3)(NO3)(3)]Cu-2, 1, [Cu(pdz)(3)(NO3)(2)], 2, [Cu(pdz)(4)(NO3)(2)] 3, and [Cu(pdz)(4)(NO3)][NO3], 4, have been prepared and characterized by spectroscopic methods, magnetic susceptibility measurements and, for 1 and 4, by single crystal X-ray diffraction. 1 crystallizes in the monoclinic space group P2(1)/n, with a = 8.938(1) Angstrom, b = 13.6677(6) Angstrom, c = 14.933(2) Angstrom, beta = 96.03(1)degrees and Z = 2. 4 crystallizes in the monoclinic space group P2(1)/c, with a = 10.6425(9) Angstrom, b = 16.442(1) Angstrom, c = 11.9930(6) Angstrom, beta = 98.225(6)degrees and Z = 4. Both structures were solved by the Patterson method and refined by full-matrix least-squares procedures to R = 0.029 and 0.034 for 3026 and 3572 reflections with I greater than or equal to 3 sigma(I), respectively. 1 has a linear trimetallic structure and exhibits strong antiferromagnetic coupling. Analysis of powder susceptibility data according to a Heisenberg model yields a J value of -139 cm(-1). The remaining three compounds have monometallic structures and are magnetically dilute.