Design of high-dimensional copper(II) malonate complexes with exo-polydentate N-donor ligands

Two polymeric malonato-bridged copper(II) complexes of formulas {(H(2)bpe)[Cu(mal)(2)]}(n).4nH(2)O (1) and [Cu-4(mal)(4)(bpe)(3)](n).6nH(2)O (2) [mal = malonate dianion; bpe = 1,2-bis(4-pyridyl)ethylene] have been synthesized and characterized by X-ray diffraction. Complex 1 crystallizes in triclinic space group P (1) over bar, Z = 1, with unit cell parameters a = 4.8831(10) Angstrom, b = 9.585(2) Angstrom, c = 11.813(2) Angstrom, alpha = 77.29(3)degrees, beta = 82.18(3)degrees, and gamma = 84.92(3)degrees, whereas complex 2 crystallizes in the monoclinic space group P2(1)/n, Z = 4, with unit cell parameters a = 13.462(3) Angstrom, b = 10.275(5) Angstrom, c = 19.579(4) Angstrom, and beta = 105.21(3)degrees. The structure of 1 consists of anionic malonato-bridged uniform copper(II) chains which are connected through hydrogen bonds involving malonate-oxygen atoms, noncoordinated water molecules, and H(2)bpe(2+) cations. The intrachain copper-copper separation through carboxylate-malonate bridge in the anti-syn conformation is 4.8831(10) Angstrom. Complex 2 possesses a three-dimensional structure made up of neutral corrugated malonated-bridged copper(II) layers linked through bis-monodentate bpe molecules. The copper(II) atoms within each layer are bridged by a double mu-oxo and four carboxylato-malonate bridges with copper-copper separations of 3.4095(7) Angstrom (through oxo) and 4.9488(11)-6.5268(13) Angstrom (through carboxylato). The shortest interlayer copper-copper separation across bridging bpe is 13.434(3) Angstrom. Variable-temperature magnetic measurements (2-290 K) show an overall ferromagnetic behavior for both compounds. The magnetic pathway of complex I is through a single carboxylate-malonate bridge connecting apical and equatorial positions of adjacent copper(II) atoms, and the value of the magnetic coupling (J) for 1 through a numerical expression for a ferromagnetic uniform chain of interacting local doublets is J = +0.049(1) cm(-1). The values for the magnetic couplings through the main intralayer exchange pathways in 2 which correspond to carboxylate-malonate bridges connecting equatorial-equatorial (J(1)) and equatorial-apical (J(2)) coordination sites and to the double mu-oxo bridge linking equatorial-apical (J(5)) positions have been determined through a simplified model. The three magnetic couplings are weak, two of them being ferromagnetic (J(1) = +23(1) cm(-1) and J(2) = +6.5(1) cm(-1)) and the other one antiferromagnetic [zJ = -1.0(1) cm(-1)]. The values of the magnetic couplings in 1 and 2 compare well with those previously reported for similar malonato-bridged copper(II) complexes of different dimensionalities.