Australian Journal of Chemistry Australian Journal of Chemistry Society
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Structural variations in the complete series of lanthanoid complexes of a calix[4]arene trisamide

Gareth Nealon , Matthew McIldowie , Brian Skelton , Mauro Mocerino , Massimiliano Massi , Mark Ogden

Abstract

Lanthanoid picrate complexes of 5,11,17,23-tetra-tert-butyl-25-hydroxy-26,27,28-tris(dieth- ylcarbamoylmethoxy)calix[4]arene (LH) have been synthesised and structurally characterised, to complete this series for all lanthanoids (other than promethium). From cerium to lutetium, three structural types are observed; Type I, [Ln(L)(O,O’-pic)](pic), Ln=Ce – Dy; Type II, [Ln(L)(O-pic)](pic), Ln=Tb, Ho; Type III, [Ln(L)(HOEt)](pic)2, Ln=Er – Lu. With lanthanum, three different 10-coordinate complexes were characterised; [Ln(L)(O,O’-pic)(HOEt)](pic), [Ln(L)(O,O’-pic)(OH2)](pic), and [Ln(L)(O,O’-pic)(HOMe)](pic). The crystallization of Type I and II observed for terbium shows that the stability of the different structures are sensitively poised at the transition points. Nevertheless, the structures show that the vacant space in the coordination sphere left by the trisamide L tends to reduce across the series as expected. It is occupied by a bidentate picrate anion and unidentate solvent molecule with lanthanum, a bidentate picrate anion for cerium to dysprosium (Type I), a unidentate picrate anion for terbium and holmium (Type II), and finally a unidentate solvent molecule from erbium to lutetium (Type III). The coordination number thus reduces from ten to eight across the series.

CH17484  Accepted 19 September 2017

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