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

Abstract

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