2019, Liu, F., Velkos, G., Krylov, D.S., Spree, L., Zalibera, M., Ray, R., Samoylova, N.A., Chen, C.-H., Rosenkranz, M., Schiemenz, S., Ziegs, F., Nenkov, K., Kostanyan, A., Greber, T., Wolter, A.U.B., Richter, M., Büchner, B., Avdoshenko, S.M., Popov, A.A.

Engineering intramolecular exchange interactions between magnetic metal atoms is a ubiquitous strategy for designing molecular magnets. For lanthanides, the localized nature of 4f electrons usually results in weak exchange coupling. Mediating magnetic interactions between lanthanide ions via radical bridges is a fruitful strategy towards stronger coupling. In this work we explore the limiting case when the role of a radical bridge is played by a single unpaired electron. We synthesize an array of air-stable Ln 2 @C 80 (CH 2 Ph) dimetallofullerenes (Ln 2 = Y 2 , Gd 2 , Tb 2 , Dy 2 , Ho 2 , Er 2 , TbY, TbGd) featuring a covalent lanthanide-lanthanide bond. The lanthanide spins are glued together by very strong exchange interactions between 4f moments and a single electron residing on the metal–metal bonding orbital. Tb 2 @C 80 (CH 2 Ph) shows a gigantic coercivity of 8.2 Tesla at 5 K and a high 100-s blocking temperature of magnetization of 25.2 K. The Ln-Ln bonding orbital in Ln 2 @C 80 (CH 2 Ph) is redox active, enabling electrochemical tuning of the magnetism.

2018, Zhang, X., Li, W., Feng, L., Chen, X., Hansen, A., Grimme, S., Fortier, S., Sergentu, D.-C., Duignan, T.J., Autschbach, J., Wang, S., Wang, Y., Velkos, G., Popov, A.A., Aghdassi, N., Duhm, S., Li, X., Li, J., Echegoyen, L., Schwarz, W.H.E., Chen, N.

Unsupported non-bridged uranium-carbon double bonds have long been sought after in actinide chemistry as fundamental synthetic targets in the study of actinide-ligand multiple bonding. Here we report that, utilizing I h(7)-C80 fullerenes as nanocontainers, a diuranium carbide cluster, U=C=U, has been encapsulated and stabilized in the form of UCU@I h(7)-C80. This endohedral fullerene was prepared utilizing the Krätschmer-Huffman arc discharge method, and was then co-crystallized with nickel(II) octaethylporphyrin (NiII-OEP) to produce UCU@I h(7)-C80·[NiII-OEP] as single crystals. X-ray diffraction analysis reveals a cage-stabilized, carbide-bridged, bent UCU cluster with unexpectedly short uranium-carbon distances (2.03 Å) indicative of covalent U=C double-bond character. The quantum-chemical results suggest that both U atoms in the UCU unit have formal oxidation state of +5. The structural features of UCU@I h(7)-C80 and the covalent nature of the U(f1)=C double bonds were further affirmed through various spectroscopic and theoretical analyses.