Self-assembly, structures, and magnetic properties of ladder-like copper(II) coordination polymers

Two novel ladder-like copper(II) compounds, [Cu-2(histamine)(2)(C2O4)(ClO4)(2)] (1) and [Cu-2(histamine)(2)(C2O4)(H2O)(2) (NO3)(2)] (2), are prepared. Compound 1 crystallizes in the triclinic space group P (1) over bar, with a = 7.450(4) Angstrom, b = 7.519(7) Angstrom, c = 9.646(5) Angstrom, alpha = 85.78(7)degrees, beta = 88.60(4)degrees, gamma = 76.78(7)degrees, V = 524.5(6) Angstrom(3), and Z = 1 with R = 0.0789 (all data). In 1, the dinuclear units of [Cu-2(histamine)(2)(C2O4)](2+) are linked together by the perchlorate anions to form a ladder-like chain. The chains interact each other by the pi-pi stacking interactions via the imidazole groups. Compound 2 crystallizes in the triclinic space group P (1) over bar, with a = 7.579(2) Angstrom, b = 8.133(1) Angstrom, c = 9.161(3) Angstrom, alpha = 77.06(2)degrees, beta = 89.23(2)degrees, gamma = 82.54(1)degrees, V = 545.6(2) Angstrom(3), and Z = 1 with R = 0.0751 (all data). In 2, each dinuclear unit [Cu-2(histamine)(2)(C2O4)](2+) is coordinated with a nitrate anion and a water molecule, and they are held together by the hydrogen bonding interactions to form a ladder-like chain. The magnetic susceptibility data of 1 and 2 measured in 2-300 K provide the magnetic parameters, g = 2.08, J = -166 cm(-1), J' = 6.46 cm(-1), rho = 0.0026, N alpha = 155 x 10(-6) cm(3) mol(-1), and R = 1.03 x 10(-3) (g = 2.05, J = -162 cm(-1), J' = 10.5 cm(-1), rho = 0.0029, and R = 2.95 x 10(-3) with the fixed value of N alpha = 120 x 10(-6) cm(3) mol(-1)) for 1 and g = 2.00, J = -158 cm(-1), J' = 26.5 cm(-1), rho = 0.0020, N alpha = 136 x 10(-6) cm(3) mol(-1), and R = 7.31 x 10(-4) (g = 2.01, J = -157 cm(-1), J' = 25.0 cm(-1), rho = 0.0021, and R = 1.32 x 10(-3) with the fixed value of N alpha = 120 x 10(-6) cm(3) mol(-1)) for 2. These indicate that very strong antiferromagnetic interactions occur along the rungs of the ladder via the oxalate bridge and weak ferromagnetic interactions along the chains. (C) 2000 Academic Press.