title: Synthesis and spectral studies of copper complexes using a N-octylated bis benzimidazole diamide ligand.
abstract: Monomeric Cu(II) and Cu(I) complexes bound to a tetradentate bis-benzimidazole diamide ligand N,N'-bis(N-octyl benzimidazolyl-2yl)(methyl)pentane diamide (O-GBGA) have been isolated and characterized. X-Band EPR spectra of the copper(II) complexes in CH2Cl2 were recorded in a frozen solution as solvent at liquid nitrogen temperature. Solution spectra typically indicate a d(x2-y2) ground state (g||>g⊥>2.0023) and show less than four nuclear hyperfine lines with broadening of g⊥ line in some cases, thus indicating distorted tetragonal geometry. One of the copper(II) complexes shows a five line N-SHF structure (16±1G) implying the binding of imine nitrogen of the benzimidazole to copper ion. α2 ranges from 0.57-0.97 indicating considerable amount of covalent character in Cu-L bond. Anodic shifts in E1/2 values indicate the retention of anion in the coordination sphere of Cu(II), E1/2 values becoming anodic in the order C6H5COO-<SCN-<Cl-. The fluorescence quantum yield of complexes was found to be lower than that of the ligand O-GBGA (Φ=0.029) and the relative fluorescence data reveals that fluorescence of such compounds could distinguish between small and large anions.
authors.affiliation: Department of Chemistry, University of Delhi, Delhi 110007, India. subashcm@gmail.com
authors.forename: Subash Chandra
authors.initials: SC
authors.lastname: Mohapatra
authors.forename: Pavan
authors.initials: P
authors.lastname: Mathur
mesh_terms: D001562:Benzimidazoles / Q000737:chemistry*; D003300:Copper / Q000737:chemistry*; D003958:Diamide / Q000737:chemistry*; D055664:Electrochemical Techniques; D004578:Electron Spin Resonance Spectroscopy; D004583:Electrons; D008024:Ligands; D009682:Magnetic Resonance Spectroscopy; D013050:Spectrometry, Fluorescence; D013055:Spectrophotometry, Infrared
chemical_list: D001562:Benzimidazoles; D008024:Ligands; D003958:Diamide; C009712:bis-benzimidazole; D003300:Copper