Structure, Magnetism and Theory of a Family of Nonanuclear Cu(5)(II)Ln(4)(III)-Triethanolamine Clusters Displaying Single-Molecule Magnet Behaviour

Abstract

Synthesis, crystal structures and magnetic studies are reported for four new heterometallic CuII-LnIII clusters. The reaction of Cu(NO3)2̇3H2O with triethanolamine (teaH3), pivalic acid, triethylamine and Ln(NO3) 3̇6H2O (Ln=Gd, Tb, Dy and Ho) results in the formation of four isostructural nonanuclear complexes of general formula [Cu II5LnIII4O2(teaH) 4{O2CC(CH3)3}2(NO 3)4(OMe)4]̇2MeOḢ2Et2O [Ln=Gd (1), Tb (2), Dy (3) and Ho (4)]. The metal core of each cluster is made up of four face- and vertex-sharing tetrahedral units. Solid-state DC magnetic susceptibility studies reveal competing anti- and ferromagnetic interactions within each cluster leading to large-spin ground states for 1-4. Solid-state AC magnetic susceptibility studies show frequency-dependent out-of-phase (χ″ M) signals for 2-4 below 4 K, suggestive of single-molecule magnet behaviour. Ab initio calculations on one of the anisotropic examples (3) provided a rare set of J values for Dy-Cu and Cu-Cu exchange interactions (Dy-Dy zero), some ferro- and some antiferromagnetic in character, that explain its magnetic behaviour. © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.