Determination of intermolecular copper–copper distances from the EPR half-field transitions and their comparison with distances from X-ray structures: applications to copper(II) complexes with biologically important ligands

摘要: An EPR method involving measurement of half-field transitions was applied to determine the intermolecular Cu–Cu distances in copper(II)-carboxylate complexes with biologically important ligands. The experimental powder spectra are composed allowed (ΔM S  = ±1) centered at ~3,200 Gauss and weak intensity, nominally forbidden,  = ±2) peaks observable ~1,600 Gauss. Values average interspin distance for each complex were determined from ratios integrated forbidden peak areas using several methods. calculated correlated copper–copper experimentally obtained by X-ray crystallography. agree well values when crystallographic value one member a series is used calibrate series. Less satisfactory agreement found methods based on Cu-spin-label systems used.