Synthesis and Characterization of Four Cu(II) Coordination Polymers Based on Glutarate and 3,3′-Dimethylglutarate Ligands

Abstract

Four new Cu(II) coordination polymers, namely [Cu(mu -glu)(mim)(2)](n) (1), {[Cu(mu -glu)(emim)(2)]<middle dot>H2O}(n) (2), [Cu(mu (3)-dmg)(im)(2)](n) (3) and [Cu-4(mu (4)-dmg)(2)(pyz)](n) (4), where H(2)glu: glutaric acid, H(2)dmg: 3,3 '-dimethyl glutaric acid, im: imidazole, mim: 2-methyl imidazole, emim: 2-ethyl-4-methyl imidazole, pyz: pyrazine, have been successfully synthesized and structurally characterized by elemental analysis, IR and UV-Vis spectra, single crystal X-ray diffraction, powder X-ray diffraction (PXRD), and magnetic properties. X-ray diffraction studies have revealed that complexes 1 and 2 crystallize in the orthorhombic system, with space groups P2(1)2(1)2(1) (1) and Pbca (2), respectively, while compounds 3 and 4 crystallize in the monoclinic system, with space groups P2(1)/n (3) and C2/c (4), respectively. In compounds 1 and 2, the glu ligands adopt a bis(bidentate) bridging coordination mode, linking Cu(II) ions to form a one-dimensional linear chain. In compounds 3 and 4, the dmg ligands act as bridging linkers, adopting mu-eta(2):eta(0):eta(1):eta(0) and mu(4)-eta(1):eta(1):eta(1):eta(1) coordination modes, respectively, to construct 2D coordination polymer networks. Topological analysis results of complexes 3 and 4 show that complex 3 forms a 5-connected uninodal 2D framework with a Shubnikov plane net (3(3).4(3).5(4)) topology, while complex 4 forms a 6-connected uninodal 2D framework with a SP 2-periodic net (3(6).4(6).5(3)) topology. Moreover, thermal and optical absorption properties were studied. The thermal stability of the hydrated complexes follows order: 4 (200 degrees C) >3 (197 degrees C) > 1 (190 degrees C) > 2 (177 degrees C) in static air atmosphere. The optical absorption studies revealed that the calculated band gap values of complexes 1-4 are related to the type and structure of the ligands.