Shape-adaptive single-molecule magnetism and hysteresis up to 14 K in oxide clusterfullerenes Dy(2)O@C(72) and Dy(2)O@C(74) with fused pentagon pairs and flexible Dy–(μ(2)-O)–Dy angle

Dysprosium oxide clusterfullerenes Dy(2)O@C(s)(10528)–C(72) and Dy(2)O@C(2)(13333)–C(74) 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 Dy(2)O cluster, which is bent in Dy(2)O@C(72) but linear in Dy(2)O@C(74). 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. Dy(2)O@C(74) exhibits zero-field quantum tunneling of magnetization and magnetic hysteresis up to 14 K, the highest temperature among Dy-clusterfullerenes.