Exploiting complementary ligands for the construction of square antiprismatic monometallic lanthanide SMMs

The methylation of p-tert -butylcalix[4]arene in the distal 1,3-phenolic sites provides the ligand H 2 L = { p-tert -butylcalix[4](OMe) 2 (OH) 2 arene} that enables construction of heteroleptic mononuclear lanthanide complexes. The reaction of (N( n Bu) 4 )(acac) (Hacac = acetylacetone), M III Cl 3 and H 2 L under Schlenk conditions results in the formation of a family of (N( n Bu) 4 )[M III L(acac) 2 ] complexes where M = Y ( 1 ), Gd ( 2 ), Tb ( 3 ) and Dy ( 4 ). The metal ions are eight-coordinate in distorted square-antiprismatic coordination geometries, resulting in slow relaxation of the magnetisation for the Tb derivative. (N( n Bu) 4 )[M III L(acac) 2 ], M = Y, Gd, Tb and Dy, have been constructed by combination of two O donor ligands, bidentate acetylacetone and tetradentate p-tert -butylcalix[4]arene.