ABSTRACT
Since the first indication of the existence of endohedral metallofullerenes (EMFs) reported in 1985, the nature of the interaction between endohedral metal atoms and the host carbon cage has been recognized as one of the crucial points of EMF research. With the isolation of the first bulk amounts of EMFs in early 1990s, electron spin resonance (ESR) spectroscopic studies of paramagnetic mono-metallofullerenes Y@C82 and La@C82 showed that metal atoms transfer their valence electrons to the carbon cage.1,2 X-ray photoelectron spectroscopy (XPS) studies also showed that the spectra in the range of metal-based transition levels correspond well with the spectra of metal oxides in the corresponding oxidation states.3 Hence, the electronic structure of EMFs can be formally described as M3+@C823− and metal-cage interactions are understood as ionic bonding. Ionic conjecture is also supported by frontier molecular orbital (MO) analysis, which shows that the MOs of the EMFs can be described as MOs of the fullerene cores with additional electrons borrowed from
3.1 Bonding Interactions in Endohedral Metallofullerenes ................................. 67 3.1.1 Metal-Cage Electron Transfer and Bonding Interactions .................. 67 3.1.2 Metal-Metal Bonding ......................................................................... 70 3.1.3 Bonding between Metal and Nonmetal Atoms .................................. 72
3.2 Molecular Structures of Endohedral Metallofullerenes ................................. 73 3.2.1 Charge Transfer and Carbon-Cage Isomerism ................................... 73 3.2.2 Cage Form Factor and Strain in the Endohedral Cluster ................... 76
3.3 Dynamics of Encapsulated Species in Endohedral Fullerenes ...................... 81 3.3.1 Dynamics from Static Calculations .................................................... 81 3.3.2 Molecular Dynamics Simulations ...................................................... 83
3.4 Concluding Remarks ......................................................................................86 References ................................................................................................................87
