title: Pentacoordinated Cu(II)/Zn(II) complexes bearing macrocyclic skeleton: synthesis, spectroscopic and molecular structure optimization studies.
abstract: 2,6-Diacetylpyridine and 1,2-diaminoethane in the presence of copper(II) and zinc(II) chlorides containing a few drops of acetic acid were condensed into compositions [CuLH2]2.2HCl.H2O (1), [Cu2LPyz]2.2HCl.4CH3COCH3 (2) [CuZnLPyz]2.2HCl.2CH3COCH3.10H2O (3) and [ZnL'Cl]3.3HCl.3H2O (4) substantiated by elemental analyses, IR, UV-vis, 1H NMR and FAB mass spectral data. Demetallation of a Ni(II) complex (isolated as above) afforded macrocyclic skeleton LH4, whereas L' symbolizes a skeleton of the ligand containing only ethylenediamine and 2,6-diacetylpyridine. Molecular structure optimization using MM2 force field calculations for the complexes revealed distorted square pyramidal geometry around Cu(II) centers in complexes 1 and 2 and tetrahedral geometry around Cu(II) and Zn(II) centers with different degrees of distortion in complex 3 whereas three Zn(II) atoms (each in distorted square pyramidal geometry) attached via Cl bridges form a cyclic structure in complex 4. In complexes 1 and 2,Cu-Cu = 2.63-2.66 angstroms indicated the possibility of coupling between the two Cu(II) centers which has been supported by lower magnetic moment as well as ESR spectra showing half-field signal.
authors.affiliation: Department of Chemistry, Banaras Hindu University, Varanasi 221005, India. lmishrabhu@yahoo.co.in
authors.forename: Lallan
authors.initials: L
authors.lastname: Mishra
authors.forename: Kumari
authors.initials: K
authors.lastname: Bindu
authors.forename: Subrato
authors.initials: S
authors.lastname: Bhattacharya
mesh_terms: D003198:Computer Simulation; D003300:Copper / Q000737:chemistry*; D004578:Electron Spin Resonance Spectroscopy; D047028:Macrocyclic Compounds / Q000138:chemical synthesis / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy; D008280:Magnetics; D013058:Mass Spectrometry; D008958:Models, Molecular; D013057:Spectrum Analysis; D015032:Zinc / Q000737:chemistry*
chemical_list: D047028:Macrocyclic Compounds; D003300:Copper; D015032:Zinc