The first dinuclear orotate complex: Syntheses, spectral, thermal and structural characterization of supramolecular orotate complexes of nickel(II) and copper(II) with 2-hydroxyethylpyridine

Two novel orotate complexes, mononuclear [Ni(HOr)(H2O)(2)(etpy)]center dot H2O (1) and dinuclear [Cu(mu-HOr) (etpy)](2) (2) (etpy = 2-hydroxyethylpyridine, HOr(2-) = dianionic orotate), have been prepared and characterized by elemental analyses, spectroscopic (IR, UV-vis), thermal, magnetic and single crystal X-ray diffraction studies. The mononuclear Ni(II) complex crystallizes in the triclinic space group Pi and the dinuclear copper(H) complex crystallizes in the monoclinic space group P2(1)/c. The mononuclear complex consists of individual units in which nickel(II) lies on the inversion center and has octahedral coordination by bidentate HOr(2-), bidentate etpy and two aqua ligands. The dinuclear copper(II) complex composed of a double-orotate bridge and bidentate etpy ligands. Each HOr(2-) ligand simultaneously exhibits chelating bidentate and bridging coordination modes. HOr(2-) is tricoordinated to one copper atom through N3 atom of pyrimidine ring, one oxygen atom of the carboxylate group as a bidentate ligand and to the other copper ion via the other oxygen of the carboxylate group. The structural units are joined into the framework by the hydrogen bonds in 1 and 2. (C) 2008 Elsevier B.V. All rights reserved.