title: Oxidation of substituted phenols using copper(II) metallatriangles formed through ligand sharing.
abstract: Reaction of N(2),N(2')-bis-[(1-butyl-benzimidazol-2yl)methyl]biphenyl-2,2'-dicarboxamide (L) with CuX2⋅nH2O in methanol leads to the assembly of four trinuclear Cu(II) complexes with the general formula [Cu3(L)3X3]⋅3X⋅nH2O⋅mMeCN, where X=Cl(-), Br(-), NO3(-) and C6H5COO(-) and n=0-5, m=0-8 (compounds 1-4, respectively). The structure of one of the complex contains three Cu(II) metal ions at the corners of an equilateral triangle. Each of the copper(II) are coordinated through two benzimidazolyl imine N-atoms and two amide carbonyl O-atoms and the apical position is occupied by an anionic nitrate ion, leading to a distorted square pyramidal environment. The magnetic susceptibility data were analyzed through Hamiltonian H=-J (S1S2+S2S3+S1S3) obtaining -J=0.16, 0.12, 0.15 and 0.14cm(-1) for 1-4, respectively. X-Band EPR spectra typically show a broad single line at 120K with g∼2.11. Oxidation of phenols was studied homogeneously using copper(II) metallatriangles (1-3) as catalyst in acetonitrile. The oxidation of 2,4,6-tri-tert-butyl phenol yields the corresponding quinone after oxidative dealkylation. The oxidation of 2-amino-5-methyl phenol yields the corresponding phenoxazinone while the oxidation of 2-amino-4-tert-butyl phenol yields the phenoxazine instead of phenoxazinone. The products so obtained were analyzed by NMR and X-ray single crystallography.
authors.affiliation: Department of Chemistry, University of Delhi, Delhi 110007, India.
authors.forename: Kuldeep
authors.initials: K
authors.lastname: Mahiya
authors.affiliation: Department of Chemistry, University of Delhi, Delhi 110007, India.
authors.forename: Ravinder
authors.initials: R
authors.lastname: Kumar
authors.affiliation: Instituto de Ciencia Molecular (ICMol), Universidad de Valencia, C/Catedratico Jose Beltran 2, 46980 Paterna, Valencia, Spain.
authors.forename: Francisco
authors.initials: F
authors.lastname: Lloret
authors.affiliation: Department of Chemistry, University of Delhi, Delhi 110007, India. Electronic address: pavanmat@yahoo.co.in.
authors.forename: Pavan
authors.initials: P
authors.lastname: Mathur
mesh_terms: D001562:Benzimidazoles / Q000737:chemistry*; D003300:Copper / Q000737:chemistry*; D003958:Diamide / Q000737:chemistry*; D004578:Electron Spin Resonance Spectroscopy; D008024:Ligands; D008280:Magnetics; D008958:Models, Molecular; D010084:Oxidation-Reduction; D010636:Phenols / Q000737:chemistry*
chemical_list: D001562:Benzimidazoles; D008024:Ligands; D010636:Phenols; D003958:Diamide; D003300:Copper
keywords: Benzimidazole diamide; EPR; Magnetism; Phenol oxidation; Trinuclear copper(II)