Examining the Electronic Structures of Monouranium Endohedral Metallofullerenes: Solution Versus Solid-State Effects in U@C82

In uranium endohedral metallofullerenes, cage isomer dependent oxidation states have been theoretically deter-mined for U3+@C2v(9)-C823- and U4+@C2(5)-C824+. Solution phase EPR supports this assessment; however, in the solid-state, EPR, SQUID magnetometry, and XANES suggest both isomers adopt a common metal-oxidation state. This inves-tigation shows the redox active uranium center may be sensitive to changes at the carbon cage, demonstrating that solution versus solid-state factors is a possible consideration when determining the electronic structure and reactivity of these unique systems.