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

Two novel ladder-like copper(II) compounds, [Cu₂(histamine)₂(C₂O₄)(ClO₄)₂] (1) and [Cu₂(histamine)₂(C₂O₄)(H₂O)₂ (NO₃)₂] (2), are prepared. Compound 1 crystallizes in the tri clinic space group P1, with a = 7.450(4) Å, b = 7.519(7) Å, c = 9.646(5) Å, α = 85.78(7)°, β = 88.60(4)°, γ = 76.78(7)°, V = 524.5(6) ų, and Z = 1 with R = 0.0789 (all data). In 1, the dinuclear units of [Cu₂(histamine)₂(C₂O₄)]²⁺ are linked together by the perchlorate anions to form a ladder-like chain. The chains interact each other by the π-π stacking interactions via the imidazole groups. Compound 2 crystallizes in the triclinic space group P1, with a = 7.579(2) Å, b = 8,133(1) Å, c = 9.161(3) Å, α = 77.06(2)°, β = 89.23(2)°, γ = 82.54(1)°, V = 545.6(2) ų, and Z = 1 with R = 0.0751 (all data). In 2, each dinuclear unit [Cu₂(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, ρ = 0.0026, Nα = 155 x 10^-6 cm³ mol^-1, and R = 1.03 x 10^-3 (g=2.05, J = -162 cm^-1, J' = 10.5cm^-1, ρ = 0.0029, and R = 2.95 x 10^-3 with the fixed value of Nα = 120 x 10^-6 cm³ mol^-1) for 1 and g = 2.00, J = -158 cm^-1, J' = 26.5 cm^-1, ρ = 0.0020, Nα = 136 x 10^-6 cm³ mol^-1, and R = 7.31 x 10^-4 (g=2.01, J = -157 cm^-1, J' = 25.0 cm^-1, ρ = 0.0021, and R = 1.32 <x> 10^-3 with the fixed value of Nα = 120 x 10^-6 cm³ 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.