An investigation of the ¹H nmr isotropic shifts for some methyl-substituted bipyridine complexes with Ni(II) and Co(II)

Abstract

In order to extend existing ideas on isotropic spin transfer mechanisms in bipyridine–metal complexes, a series of unsymmetrical methyl-substituted bipyridine ligands, and their nickel(II) and cobalt(II) complexes, have been prepared, and their 1 H nmr isotropic shifts measured experimentally. Simulating different electron spin density transfer mechanisms, from direct σ-electron density transfer to indirect π-mechanisms involving spin polarization or hyperconjugation, various INDO calculations have been performed on model cations and anions of the free ligand, producing good agreement with the experimental results.