A hydrogen bonded Co(ii) coordination complex and a triply interpenetrating 3-D manganese(ii) coordination polymer from diaza crown ether with dibenzoate sidearms

Abstract

The diaza crown ether dicarboxylate ligand, 4,4′-((1,7-dioxa-4,10-diazacyclododecane-4,10-diyl)bis(methylene)dibenzoate), L, forms a monomeric coordination complex of Co(II) ions, CoL(H2O)2·2H2O, 1, and a coordination polymer (MnL·H2O)n, 2, with Mn(II) ions under hydrothermal conditions. The monomeric coordination complex (structure 1) is polar with mirror symmetry and crystallizes in the non-centrosymmetric space group Cm. The mirror plane bisects the complex at the six-coordinate Co(II) ion, the two oxygen atoms of the crown moiety and the two oxygen atoms from coordinated water molecules. The coordinated water molecules take part in strong, linear hydrogen bonds with carboxylate oxygens provided by neighboring Co(II)–crown complexes resulting in a three-dimensional (1 : 1)n polar network in which the topology of the underlying 8-coordinated net is sqc3. The structure of 2 crystallizes in the orthorhombic Fdd2 space group as an infinite, polar triply interpenetrating three-dimensional network. The eight-coordinate Mn(II) ion coordinates two oxygen and two nitrogen atoms of the crown moiety, as well as single carboxylate O atom from each of two neighboring ligands. In both structures, the ligand assumes a flexed-wing bird shape, with the two benzoate sidearms of the crown moiety locked in a syn orientation. The metal ion elevated above the plane of the diaza-crown oxygen and nitrogen atoms. The diaza-crown moiety with its two benzoate sidearms has the peculiar property of forming an oriented crystal structure where the metal-crown vectors are oriented parallel to each other in the crystal. However, the structures are achiral, but the rigid crystal lattice prevents re-orientation of the structure through inversion. The coordination polymer (MnL·H2O)n, 2, is a 3-center uninodal net with ths (ThSi2) topology. Computational results using the density functional theory (DFT) calculations explain why the flexed-wing bird shape is the preferred and most stable ligand conformation for metal ion binding. Both structures demonstrate magnetic properties that are characteristics of the respective non-interacting isolated paramagnetic transition metal ions that are present.