Modeling the Structure of Endohedral Eu@C60 and (Eu@C60)2 Metallofullerenes

Abstract

The structural parameters of Eu@C60 isomers and the squared electron spin have been calculated using the quantum-chemical DFT (U)PBE0 method with variable quantum numbers MS. The (C2v) isomer (MS = 7/2, = 15.76 a. u.) includes a triatomic EuC2 fragment with a degraded C=C bond (2.565 A), common for two 6-atom cycles. Two (C3v) isomers (MS = 7/2±1, = 17.76±7.01 a. u.) include the hexagonal pyramid EuC6. The energies of the isomers differ by no more than 0.046 eV. The energy barriers allow pseudo-rotation of the molecule. The Eu endo atom increases the reactivity of the carbon shell of C60 and stabilizes the (Eu@C60)2 nano-dumbbell. The values are 56 and 90 a. u. for the structures of similar energy, (Ci)-(Eu@η2-C60)2 and (Ci)-(Eu@η6-C60)2, with Eu∙∙∙Eu distances of 10.35 and 10.08 A, respectively.