Syntheses and Crystal Structures of Mn(II), Ni(II) and Cu(II) Coordination Compounds Assembled by Maleato and Dimethyl-2,2′-bipyridines

Abstract

Three complexes: {[Mn(H2O)(mal)(5dmb)·H2O}n] (1); [ Ni2(H2O)6(mal)2(4dmb)2]·3H2O (2); [ Cu2(mal)2(4dmb)2]·3H2O (3); where mal = maleato, 4dmb = 4,4′-dimethyl-2,2′-bipyridine, and 5dmb = 5,5′-dimethyl-2,2′-bipyridine; have been synthesized, using self-assembly solution reactions at ambient conditions. Crystallographic studies show that 1 crystallizes in an orthorhombic system, space group Pna21, with a = 17.4067(4) Å, b = 11.9672(2) Å, c = 8.2075(2) Å; V = 1709.70(6) Å3. Complex 2 has a monoclinic system, space group C2/c, with a = 21.206(8) Å, b = 7.523(3) Å, c = 25.399(10) Å; β = 109.755(8)°; V = 3813(2) Å3. Complex 3 crystallizes in a monoclinic system, space group C2/c, with a = 14.6976(12) Å, b = 11.3849(10) Å, c = 22.1638(18) Å; β = 101.2998(17)°; V = 3636.8(5) Å3. Complex 1 is a one-dimensional (1D) polymer, where the Mn centers are six-coordinated in a distorted octahedral geometry. 2 is a dinuclear complex, generated by supramolecular interactions, where Ni ions are six-coordinated in a distorted octahedral geometry. 3 is a dinuclear complex with five-coordinated Cu ions having a distorted square pyramidal geometry. All three complexes exhibit hydrogen bonding interactions, which generate 2D supramolecular structures in 1 and 2, whereas in complex 3 a 3D supramolecular array is formed. These novel complexes prove that the self-assembly of a dicarboxylate ligand (mal) with three different first-row transition metals, can afford coordination compounds with diverse structural characteristics and dimensionality, which can be attributed to the different ligand coordination modes and the coordination properties of the employed metals.