Nuclear magnetic shift and relaxation effects resulting from complexation of lanthanide ions with endo-cis-bicyclo[2.2.1]hept-5-ene-2,3-dicarboxylic acid

Abstract

The effects on the n.m.r. spectrum of binding various lanthanide complexes to the title dicarboxylic acid in aqueous solution have been studied. It is shown using relaxation-time measurements that all lanthanides and complexes form similar adducts with the acid. The magnetic susceptibility tensor, which determines the shifts induced by a lanthanide, is not related simply to the geometry of the adduct. Rather, an averaged tensor is observed, whose symmetry is close to axial for lanthanides in the first half of the series, but often far from axial for those later in the series. It is proposed that this type of behaviour is general for lanthanide complexes in water.