Shape-adaptive single-molecule magnetism and hysteresis up to 14 K in oxide clusterfullerenes Dy2O@C72 and Dy2O@C74 with fused pentagon pairs and flexible Dy–(μ2-O)–Dy angle

Abstract

Dysprosium oxide clusterfullerenes Dy₂O@C_s(10528)–C₇₂ and Dy₂O@C₂(13333)–C₇₄ are synthesized and characterized by single-crystal X-ray diffraction. Carbon cages of both molecules feature two adjacent pentagon pairs. These pentalene units determine positions of endohedral Dy ions hence the shape of the Dy₂O cluster, which is bent in Dy₂O@C₇₂ but linear in Dy₂O@C₇₄. Both compounds show slow relaxation of magnetization and magnetic hysteresis. Nearly complete cancelation of ferromagnetic dipolar and antiferromagnetic exchange Dy⋯Dy interactions leads to unusual magnetic properties. Dy₂O@C₇₄ exhibits zero-field quantum tunneling of magnetization and magnetic hysteresis up to 14 K, the highest temperature among Dy-clusterfullerenes.