Structure, Magnetism and Theory of a Family of Nonanuclear Cu $^II$ $_5$ Ln $^III$ $_4$ –Triethanolamine Clusters Displaying Single‐Molecule Magnet Behaviour

Abstract Synthesis, crystal structures and magnetic studies are reported for four new heterometallic Cu II –Ln III clusters. The reaction of Cu(NO 3 ) 2 ⋅ 3H 2 O with triethanolamine (teaH 3 ), pivalic acid, triethylamine and Ln(NO 3 ) 3 ⋅ 6H 2 O (Ln=Gd, Tb, Dy and Ho) results in the formation of four isostructural nonanuclear complexes of general formula [Cu II 5 Ln III 4 O 2 (teaH) 4 O 2 CC(CH 3 ) 3 2 (NO 3 ) 4 (OMe) 4 ] ⋅ 2 M eOH ⋅ 2Et 2 O [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 ( textbackslashchi textasciicircumtextbackslashprimetextasciicircumtextbackslashprimetextbackslashrmM ) 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.