Synthesis and crystal structures of di- and tetra-nuclear dicarboxylate-bridged copper(II) complexes

Three new Cu(II) complexes, [Cu2(C3H2O4)(phen)2(H2O)3](NO3)2(H2O)2 (1) (C3H2O4 = malonate, phen = 1,10-phenanthroline), [Cu2(C4H4O4)(phen)2(H2O)2](NO3)2 (2) (C4H4O4 = succinate), and {[Cu2(phen)2(H2O)(NO3)]2(C5H6O4)2}(NO3)2 (3) (C5H6O4 = glutarate) have been synthesized and characterized by elemental analysis, infrared spectroscopy, thermogravimetric analysis, and single crystal X-ray diffraction. The X-ray analysis reveals that the structures of 1 and 2 are of dinuclear copper(II) complexes bridged by malonate and succinate dianions, respectively, and 3 is a tetranuclear species formed by two {[Cu2(phen)2(H2O)(NO3)](C5H6O4)} fragments. The copper ions in 1 and 3 show square-pyramidal coordination geometry, while the copper ions in 2 exhibit a square planar geometry. In each complex, the dicarboxylate ligand is coordinated to copper ions as a chelate and monodentate (1), bis-monodentate (2), and bis-bridging ligand toward the copper ions with syn–syn coordination mode (3).