Two new tetranuclear μ4-carbonato copper(II) complexes. Syntheses, crystal structure and magnetic behaviour of [(μ4-CO3)(μ-Br)2 {Cu4(bapa)4}]Br4 and [(μ4-CO3)(μ-Cl)2 {Cu4(bapma)4}]Cl4 ·12H2O [bapa = bis(aminopropyl)amine and bapma = bis(aminopropyl)methylamine]

Publisher Website
Google Scholar
Abstract
The syntheses, by fixation of atmospheric CO 2 , and the crystal structures of the new tetranuclear µ 4 -CO 3 2- compounds [(µ 4 -CO 3 )(µ-Br) 2 {Cu 4 (bapa) 4 }]Br 4 1 and [(µ 4 -CO 3 )(µ-Cl) 2 {Cu 4 (bapma) 4 }]Cl 4 ·12H 2 O 2, [bapa and bapma are bis(3-aminopropyl)amine and bis(3-aminopropyl)methylamine respectively] are reported. Crystallographic data for 1 space group C2/c, a = 14.928(5), b = 19.010(3), c = 17.337(4) Å, β = 92.75(4)°, U = 4914(2) Å 3 and Z = 4, for 2 space group P2 1 /n, a = 14.947(6), b = 13.047(4), c = 16.084(5) Å, β = 104.75(5)°, U = 3033(2) Å 3 and Z = 2. The analogous compound [(µ-CO 3 )(µ 4 -Cl) 2 {Cu 4 (bapa) 4 }]Cl 4 3 has been also prepared for comparative purposes; 1–3 show very strong antiferromagnetic coupling. According to the molecular structures, the experimental data were fitted to the expression derived from the Hamiltonian H = -2J 12 S 1 ·S 2 - 2 J 13 (S 1 ·S 3 + S 2 S 4 ) - 2 J 14 (S 1 ·S 4 + S 2 ·S 3 ) - 2J 34 S 3 ·S 4 , which corresponds to a rectangular array of spins. The best fit parameters were for 1–3 respectively: 2J 12 = -275(14), -390(12), -212(8); 2J 34 = -31(4), -26(7), -26(3); 2J 14 = -57(10), -10(12), -72(9); 2J 13 = -8(8), 22(10), -20(7) cm -1 ; g = 2.03(1), 2.09(1) and 2.12(1).