Low-coordinate mononuclear lanthanide complexes as molecular nanomagnets

Abstract

The discovery that some bis-(phthalocyaninato)lanthanide complexes are molecular magnets triggered interest in lanthanide ion complexes. Theoretical and experimental observations have shown that the magnetization dynamics of such complexes can be tailored by tuning the coordination geometry and ligand-field around the metal centres. In particular, low-coordinate Ln(III) complexes seem to be quite attractive as molecular magnets, some of them displaying significantly large energy barriers for magnetization reversal with high blocking temperatures. In this review article, a concise but comprehensive introductory section to the basics of the magnetic anisotropy of the lanthanide ions is portrayed along with the conventional classifications and quality-check parameters of the molecular nanomagnets. We have elaborated with examples the magneto-structural correlation in various lanthanide-based molecular complexes with coordination numbers ranging from one to seven, and have highlighted the most promising systems as nanomagnets. We have also reviewed various examples of low-coordinate lanthanide-based molecular nanomagnets that are encapsulated inside fullerene cages of various sizes. A short section dealing with the lanthanide ions-based magnetic systems exhibiting slow relaxation of magnetization is also included. A special attention is also paid to the magneto-structural correlation of the lanthanide-based half-sandwich, pseudo-sandwich and a special class of sandwich complexes.