Carbon cage isomers and magnetic Dy amp; 8943;Dy interactions in Dy2O C88 and Dy2C2 C88 metallofullerenes

Three isomers of Dy2O C88 and two isomers of Dy2C2 C88 were synthesized and structurally characterized by single crystal X ray diffraction, vibrational spectroscopy, and DFT calculations. Both types of clusterfullerenes feature 4 fold electron transfer to the carbon cage, thus resulting in the same carbon cage isomers identified as C1 26 , Cs 32 , and D2 35 . The studies of Dy amp; 8943;Dy superexchange interactions in Dy2O and Dy2C2 clusters revealed that the O2 amp; 8722; bridge favors antiferromagnetic coupling whereas the acetylide group C22 amp; 8722; supports ferromagnetic coupling of Dy magnetic moments. The strength of the coupling showed a considerable variability in different cage isomers. All metallofullerenes exhibited slow relaxation of magnetization and magnetic hysteresis. In Dy2O C88 isomers the hysteresis remained open up to 7 9 K, while in Dy2C2 C88 the hysteresis loops were closed already at 2.5 K. This study demonstrated that both the endohedral bridge between metal atoms and the fullerene cage play an important role in magnetic interactions and relaxation of magnetizatio