The crystal and molecular structure of (mu-4-amino-3,5-bis(pyridin-2-yl)-1,2,4-triazole-N’N-1,N-2,N") (mu-sulfato-O,O’)-[(sulfato-O)aquacopper(II)]triaquacopper hydrate, [Cu-2(abpt)(SO4)(2)(H2O)(4)]. H2O (1) (C12H20Cu2N6O13S2), in which abpt 4-amino-3,5-bis(pyridin-2-yl)-1,2,4-triazole, was determined by X-ray diffraction methods.; Crystal data for 1 : T = 298 K, monoclinic, space group = P2(1), with a = 9.9704(3) Angstrom, b 14.7093(3) Angstrom, c = 7.4034(6) Angstrom, beta = 96.8641(6)degrees, Z = 2 (dinuclear molecules), V = 1078 Angstrom(3). The least-squares refinement based on 2717 significant reflections [I > 2 sigma(I)] converged to R = 0.0410 and R(w) = 0.0500. The structure of 1 consists of asymmetric dinuclear units, in which the copper(II) ions are linked in the equatorial plane by an N-1,N-2 bridging chelating abpt ligand and a didentate bridging sulfate anion. The Cu-O(sulfate) distances are very short (1.937(4) and 1.908(5) Angstrom). The Cu(1)-Cu(2) distance is 4.415(1) Angstrom. The compound represents the first example of a dinuclear copper(II) compound having a single N-1,N-2 1,2,4-triazole bridge. Both Cu(II) ions have four short equatorial distances to the bridging sulfate, the bridging 1,2,4-triazole, the pyridyl group, and a monodentate sulfate (Cu(1)) or a water molecule (Cu(2)). Cu(1) has one additional apical water molecule, whereas Cu(2) has two additional . Hydrogen bonding appears to play an important role in the stabilization of the asymmetric dinuclear cluster. The magnetic susceptibility data (295-6 K) are interpreted on the basis of the spin Hamiltonian (H) over cap - 2J[(S) over cap(Cu(1)).((S) over cap(Cu(2))], yielding J = -34.5 cm(-1), g = 2.15, and p = 0.66%. The isotropic exchange constant is compared to the ones of doubly N-1,N-2 1,2,4-triazole bridged dinuclear copper(Il) compounds. : T = 298 K, monoclinic, space group = P2(1), with a = 9.9704(3) Angstrom, b 14.7093(3) Angstrom, c = 7.4034(6) Angstrom, beta = 96.8641(6)degrees, Z = 2 (dinuclear molecules), V = 1078 Angstrom(3). The least-squares refinement based on 2717 significant reflections [I > 2 sigma(I)] converged to R = 0.0410 and R(w) = 0.0500. The structure of 1 consists of asymmetric dinuclear units, in which the copper(II) ions are linked in the equatorial plane by an N-1,N-2 bridging chelating abpt ligand and a didentate bridging sulfate anion. The Cu-O(sulfate) distances are very short (1.937(4) and 1.908(5) Angstrom). The Cu(1)-Cu(2) distance is 4.415(1) Angstrom. The compound represents the first example of a dinuclear copper(II) compound having a single N-1,N-2 1,2,4-triazole bridge. Both Cu(II) ions have four short equatorial distances to the bridging sulfate, the bridging 1,2,4-triazole, the pyridyl group, and a monodentate sulfate (Cu(1)) or a water molecule (Cu(2)). Cu(1) has one additional apical water molecule, whereas Cu(2) has two additional . Hydrogen bonding appears to play an important role in the stabilization of the asymmetric dinuclear cluster. The magnetic susceptibility data (295-6 K) are interpreted on the basis of the spin Hamiltonian (H) over cap - 2J[(S) over cap(Cu(1)).((S) over cap(Cu(2))], yielding J = -34.5 cm(-1), g = 2.15, and p = 0.66%. The isotropic exchange constant is compared to the ones of doubly N-1,N-2 1,2,4-triazole bridged dinuclear copper(Il) compounds.