Structure and properties of some lanthanoid(III) perchlorates with the cryptand 4,7,13,16,21,24-hexaoxa-1,10-diazabicyclo[8.8.8]hexacosane

Abstract

Some complexes of lanthanoid(III) perchlorates with the title ligand (L) have been prepared in methyl cyanide. Three series have been obtained with formulae (i) Ln[ClO₄]₃·L·MeCN (Ln = Pr, Nd, or Eu), (ii) Ln[ClO₄]₃·L·H₂O·0.5MeCN (Ln = La, Ce, Sm, Eu, Dy, or Ho), and (iii) Ln[ClO₄]₃·L·MeCONH₂(Ln = Er or Yb). The crystal and molecular structure of the Eu[ClO₄]₃·L·MeCN complex has been determined from X-ray diffractometric data. Crystals are orthorhombic, space group P2₁2₁2₁, with a= 33.567(4), b= 10.646(2), c= 8.821 (2)Å, and Z= 4. The structure has been refined by least-squares techniques to R 0.072 for 1 037 reflections. The europium(III) ion is ten-co-ordinated to the eight donor atoms of L and to two oxygen atoms of a [ClO₄]^– ion. The co-ordination polyhedron can be described as a bicapped square antiprism. The i.r. and electronic spectra of the cryptates are discussed. The complexes of Sm, Eu, and Yb exhibit electron-transfer transitions in agreement with the optical electronegativity value of 3.0 for the cryptand.