Two- and three-dimensional mixed-valence Cu(I)-Cu(II) coordination polymers:: Syntheses and characterization of α-, β-[Cu2X(C5H3N2O2)2(H2O)] (X= Cl, Br)

Novel mired valence compounds with the formula alpha-[Cu2X(C5H3N2O2)(2)(H2O)](n) [X = Cl(1), Br(3), C5H3N2O2 = 2-pyrazinecarboxylate] and their isomers beta-[Cu2X(C5H3N2O2)(2) (H2O)](n) [X = Cl(2), Br(4)] have been synthesized and structurally characterized, Crustal data: 1, orthorhombic, Pbca, a = 12.8040(7), b = 7.7323(4), c = 26.104(1) Angstrom, V = 2584.4(2) Angstrom(3), Z = 8, R1 = 0.0559; 2, triclinic, P (1) over bar, a = 6.1908(7), b = 7.7246(8), c = 13.968(2) Angstrom, alpha = 78.853(2), beta = 81.455(2), gamma = 78.036(2)degrees, V = 637.0(1) Angstrom(3), Z = 2, R1 = 0.0592; 3, orthorhombic, Pbca, a = 12.7082(6), b = 7.7676(4), c = 26.1548(12) Angstrom, V = 2581.8(2) Angstrom(3), Z = 8, R1 = 0.0257; 4, triclinic, P (1) over bar, a = 6.2462(5), b = 7.7568(6), c = 14.1121(10) Angstrom, alpha = 78.082(1), beta = 81.702(1), gamma = 79.096(1)degrees, V = 652.97(9) Angstrom(3), Z = 2, R1 = 0.0290. The alpha-isomers 1 and 3 have two-dimensional layer structures which are composed of mired valence chains of [(CuCuII)-Cu-I(C5H3N2O2)(2)(H2O)] and chains of corner-sharing {(CuN2X2)-N-I} tetrahedra. The beta-isomers 2 and 4, however, have three-dimensional structures with the [(CuCuII)-Cu-I(C5H3N2O2)(2)] chains interconnected by an alternative arrangement of {(CuN2O4)-N-II} octahedra, {(CuN2OX)-N-I} tetrahedra and {(CuN2O2X2)-N-II} octahedra. The spectroscopic and magnetic properties have been investigated. (C) 2000 Academic Press.