Shape-adaptive single-molecule magnetism and hysteresis up to 14 K in oxide clusterfullerenes DyO@C and DyO@C with fused pentagon pairs and flexible Dy-(μ-O)-Dy angle.

Dysprosium oxide clusterfullerenes DyO@C(10528)-C and DyO@C(13333)-C 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 DyO cluster, which is bent in DyO@C but linear in DyO@C. 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. DyO@C exhibits zero-field quantum tunneling of magnetization and magnetic hysteresis up to 14 K, the highest temperature among Dy-clusterfullerenes.