Synthesis,spectroscopy, electrochemistry,and molecular structure of tetrakis{(E)-2-((pyridin-2-ylimino)methyl)phenolato}(hydroxido)0.5(nitrato)1.5-tetracopper(II) nitrate hydroxide

Abstract

Reaction between (E)-2-((pyridin-2-ylimino)methyl)phenol (HL) and copper(II) nitrate provides tetrakis{(E)-2-((pyridin-2-ylimino)methyl)phenolato}(hydroxido)_0.5(nitrato)_1.5-tetracopper(II) nitrate hydroxide, (CuL)₄(NO₃)_1.5(OH)_0.5](NO₃)(OH) (1 (a) J. Miao, Z. Zhao, H. Chen, D. Wang, Y. Nie. Acta Cryst., E65, m904 (2009); (b) A. Castineiras, J.A. Castro, M.L. Duran, J.A. Garcia-Vazquez, A. Macias, J. Romero, A. Sousa. Polyhedron, 8, 2543 (1989); (c) I.S. Vasil'chenko, A.S. Antsyshkina, D.A. Garnovskii, G.G. Sadikov, M.A. Porai-Koshits, S.G. Sigeikin, A.D. Garnovskii. Koord. Khimiya, 20, 824 (1994).Crossref], Web of Science ®] , Google Scholar], Google Scholar], Google Scholar]). ESI-mass spectra show the ion peaks for the dinuclear species at m/z 565 for (CuL)₂(HCO₂)]⁺ and 521 for (CuL)₂+H]⁺ and the mononuclear species at m/z 260 for (CuL)]⁺. Vibrational spectra show very strong bands at 1604/1546?cm^?1 for ν(C?=?N/C?=?C) and at 1384, 1351?cm^?1 for ν(NO₃^–). Cyclic voltammograms demonstrate an irreversible redox processes for the Cu(II)/Cu(I) and Cu(I)/Cu(0) couples in acetonitrile. X-ray molecular structure determination explores the formation of a cationic tetranuclear copper(II)-complex, in which a deprotonated ligand molecule chelates to one copper ion with the phenolate-O and imino-N atoms. In addition, a phenolate-O atom bridges between two neighboring copper ions and a pyridine-N atom coordinates to a third copper ion, so that each ligand bridges among three copper ions in a κ²N,O:κO:κN' coordination sphere. Thus, the four copper ions and four chelating-bridging ligands assemble primarily into a cationic (CuL)₄]⁴⁺ complex. The two copper ions are further coordinated by either a nitrate anion (75% occupancy) or a hydroxide anion (25% occupancy) and form the core of a tetranuclear (CuL)₄(NO₃)_1.5(OH)_0.5]²⁺ cation.