Studies on metal carboxylates. Part III. Pyridine-2,6-dicarboxylates of the lanthanides. Synthesis and spectral studies and the X-ray photoelectron spectra of several pyridine carboxylate complexes

Abstract

The lanthanide(III) acetates react with aqueous solutions of pyridine-2,6-dicarboxylic acid (dipicolinic acid, dpcH₂) to afford two series of complexes, Ln(dpc)(dpcH),6H₂O (Ln = La, Ce, Pr, Nd, Sm, Gd, and Tb) and Ln(dpcH)₃,H₂O (Ln = Sm, Gd, Tb, Dy, Ho, or Yb). The samarium complex Sm(dpc)(dpcH),6H₂O was isolated in α- and β-forms. X-Ray powder data show that within each series the complexes are isostructural. The electronic absorption spectra of the complexes have also been recorded. The X-ray photoelectron spectra of the dehydrated species Ln(dpc)(dpcH)(Ln = Ce or Pr) and Dy(dpcH)₃ have been investigated and the C(1s), N(1s), and O(1s) binding energies measured. Attempts to determine the Ce, Pr, and Dy 4s binding energies were unsuccessful. Related measurements of the C(1s), N(1s), and O(1s) binding energies of several pyridine carboxylates of manganese(II), cobalt(II), nickel(II), and silver(II) are also described.