| Budget Amount *help |
¥13,700,000 (Direct Cost: ¥13,700,000)
Fiscal Year 1998: ¥2,800,000 (Direct Cost: ¥2,800,000)
Fiscal Year 1997: ¥10,900,000 (Direct Cost: ¥10,900,000)
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| Research Abstract |
1. Structures, Electronic States, and Bonding Features of Endohedral Metallofullerenes
The endohedral structures of monometallofullerenes M@C_<82>(M=Ca, Sc.Y.La, Ce, Pr, Nd, Eu, Gd, Yb, and Lu) and dimetallofullerenes Sc_2@C_<84> and La_2@C_<80> have been disclosed through a close interplay between theoretical prediction and experiment. In addition, a topological analysis of electron density and its Laplacian has been carried out to reveal the general features of chemical bonding in metallofullerenes. The structural and bonding study of the trimetallfullerene Sc_3@C_<82> is still in progress.
2. The Dynamic Behaviors of Encapsulated Metal Atoms
From the variable-temperature 13CNMR measurement of La_2@C_<80>, it has been for the first time found that the two La atoms circulate with +3 charge inside the round C_<80> cage even at room temperature. This finding has been also confirmed by the variab1e-temperature 139La NMR measurement and theoretical calculations.
3. Unconventional Cage Structures of Endohedral Metallofullerenes
Metal atoms can stabilize unconventional structures which violate the isolated pentagon rule established in fullerene chemistry and contain heptagonal rings (thereby not obeying the traditional definition of fullerenes), during growth and annealing processes. This has been shown for Ca@C_<72> and Sc_2@C_<74>, as representative examples.
4. Endohedrallly Metal-Doped Heterofullerenes.
An experimental attempt to substitute one cage carbon in La@C_<82> and La_2 by one nitrogen atom has been performed to prepare La@C_<81>N and La_2@C_<79>N.it is noteworthy that these La-doped heterofullerenes have no significant radical character on the cages, unlike C_<81>N and C_<79>N.
5. Summary
The cage structures of metallofullerenes do not necessary coincide with those of the most stable fullerene isomers, because of significant electron transfer from metal to carbon cages. Most Probably, endohedral structures are formed during the annealing process.
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