Crystal Structure and Magnetic Characterization of a Building Block for Quasi One-Dimensional Heterobimetallic Polymeric Complexes Bridged by 2,2′-Bibenzimidazolate Ligands

Abstract

We have synthesized ⁶³Cu(bbim)₂](ⁿBu₄N)₂(1)by 2,2′bibenzimidazolate ligands (bbim) with multi-proton donor property as a building block of models for quasi one-dimensional heterobimetallic polymeric complexes with dp-pp interaction. The study of the molecular and electronic structures of 1 and the non-deprotonated form of 1, in terms of crystal structure analysis and magnetic characterization by single-crystal ESR spectroscopy, has been carried out. The angular dependence of the Cu(II) hyperfine ESR spectra of 1 showed that the parallel orientation (B₀ || c axis) gave both the maximum copper hyperfine splitting (84 × 10⁻⁴cm⁻¹) and the maximum anisotropic g value (g _|| =2.218). The findings show that the copper(II) ion is bound at the site of a tetragonally distorted tetrahedral field, being in accord with the molecular structure of the donor site with the distorted tetrahedral symmetry as obtained by the X-ray crystal analysis. Superhyperfine structures due to the nitrogen atoms of bbim²⁻ dianion were detected in the g₁ region of the ESR spectrum of [⁶³Cu(bbim)₂](ⁿBu₄N)₂ in a frozen glass.