Three novel end-to-end single azido-bridged ferromagnetic copper(II) chains: Synthesis, crystal structure, and magnetic behavior

Three new single end-to-end azido-bridged copper(II) chains [Cu(L1)(N₃)]_n(C1O₄)_n (1), [Cu(L2)(N₃)]_n(C1O₄)_n (2), and [Cu(L3)(N₃)]_n(C1O₄)_n (3) using three different tridentate Schiff bases L1, L2, and L3, obtained from condensation of pyridine-2-carbaldehyde with N,N-dimethylethane-1,2-diamine, N,N-diethylethane-1,2-diamine, and 4-(2-amino-ethyl)morpholine, respectively, have been synthesized, and their crystal structures have been determined by X-ray diffraction methods. Complex 1, C₁₀H₁₅CuN₆C1O₄, crystallizes in an orthorhombic system, space group P2₁2₁2₁, with a = 7.434(3), b = 12.047(4), c = 17.404(6) Å, and Z = 4; complex 2, C₁₂H₁₉CuN₆C1O₄, crystallizes in an orthorhombic system, space group Pna2₁, with a = 14.723(5), b = 13.829(5), c = 8.002(5) A, and Z = 4 and complex 3, C₁₂H₁₇CuN₆C1O₅, crystallizes in an orthorhombic system, space group Pna2₁, with a = 13.837(15), b = 14.804(2), c = 8.050(4) Å, and Z = 4. Each structure consists of a single end-to-end azido-bridged copper(II) 1D chain where each copper(II) center possesses a square pyramidal geometry. Magnetic susceptibility data, measured from 4 to 300 K, show weak ferromagnetic interaction through the end-to-end bridging azido pathway in all the complexes. The magnetic data were fitted to a high temperature series-expansion for a one-dimensional system with S = 1/2 local spin based on the Hamiltonian H = - JSS_i·S_i+1 for all the complexes, giving the parameters J = +2.15 cm^-1, g = 2.23 for 1, J = +3.61 cm^-1, g = 2.16 for 2, and J = +2,06 cm^-1, g = 2.17 for 3. This unusual magnetic behavior through the end-to-end bridging azido pathway has been correlated to the structural parameters.© Wiley-VCH Verlag GmbH, 69451 Weinheim, Germany, 2002.