Three new polynuclear copper(II) complexes with the symmetric [Cu(μ1,1-N3)2Cu]2+ core and pyridine derivatives:: Syntheses, structure, and magnetic behavior

Three new polynuclear copper(II) complexes, derived from the end-on azido bridging ligand and pyridine derivatives, have been synthesized, and their crystal structures have been determined by X-ray diffraction methods; they are the dinuclear compounds [Cu-2(mu(1,1)-N-3)(2)(4-Etpy)(4)(mu-NO3)(2)] (1), and [Cu-2(mu(1,1)-N-3)(2)(3-ampy)(4)(mu-NO3)(2)]. C2H5OH (2), and the trinuclear [Cu-3(mu(1,1)-N-3)(4)(N-3)(2)(Meinic)(2)(DMF)(2)] (3). 4-Etpy is 4-ethylpyridine, 3-ampy is 3-aminopyridine, and Meinic is methylisonicotinate. Compound 1, C28H36Cu2N12O6, crystallized in the monoclinic system, space group P2(1)/n, with a = 12.355(9) Angstrom, b = 12.474(4) Angstrom, c = 12.854(6) Angstrom, beta = 117.68(4)degrees, and Z = 2. Compound 2, C22H30Cu2N16O7, crystallized in the triclinic system, space group (P) over bar 1 with a = 9.695(2) Angstrom, b = 10.895(2) Angstrom, c = 7.909(2) Angstrom, alpha = 96.81(3)degrees, beta = 96.40(3)degrees, gamma = 96.56(3)degrees and Z = 1. Compound 3, C20H28Cu3N22O6, crystallized in the monoclinic system, space group P2(1)/n, with a = 7.755(2) Angstrom, b = 14.680(5) Angstrom, c = 15.810(5) Angstrom, beta = 102.81(2)degrees, and Z = 2. 1-3 have the symmetric [Cu(mu(1,1)-N-3)(2)Cu](2+) core and structural parameters outside the previously reported range. Magnetic susceptibility data, measured from 2 to 300 K, show strong ferromagnetic coupling for the dinuclear end-on compounds 1 and 2 and bulk moderate ferromagnetic coupling for the trinuclear compound 3. These data were fitted to the appropriate equations derived from the Hamiltonian H = -JS(1)S(2) for 1 and 2 and from the Hamiltonian H = -J(1)(SA1SB + SA2SB) - J(2)S(A)1.S-A2 for 3, giving the parameters J = 230.1 (1) cm(-1), g = 2.17(0.01) for 1, J = 223.2(2) cm(-1), g = 2.16(0.01) for 2, and J(1) = 47.3(2) cm(-1), J(2) = -22.5(1) cm(-1), g(A) = 2.26(0.02), g(B) = 2.07(0.03) for 3. The magnetic susceptibility data can be correlated with the structural parameters.