Popov Alexey A, Dunsch Lothar
Chemistry Department, Moscow State University, Moscow 119992, Russia.
J Am Chem Soc. 2008 Dec 31;130(52):17726-42. doi: 10.1021/ja804226a.
DFT calculations of Sc(3)N@C(80) in the neutral and anionic states are performed which revealed that in the neutral state of the nitride clusterfullerene the lowest energy structure has C(3) symmetry, while in the anionic and dianionic states the C(3v) conformer has the lowest energy. Barriers to the cluster rotation inside the cage are also found to increase in the charge states. The (45)Sc hyperfine slitting constant, a(Sc), in Sc(3)N@C(80) anion radical is calculated by different theoretical approaches and in different conformations of Sc(3)N cluster. It is found that a(Sc) is strongly dependent on the cluster orientation with respect to the cage, covering a range form -10 to +25 Gauss at the B3LYP/6-311G*//PBE/TZ2P level of theory. A thorough analysis of the computed values as well as comparison of unrestricted and orbital-restricted calculations revealed that the polarization contribution to a(Sc) is about -10 Gauss and does not depend on the cluster orientation. Dependence of the predicted a(Sc) values on the density functional form (LSDA, BP, PBE, BLYP, OLYP, TPSS, B3LYP, and TPSSh), the basis set, as well as on the scalar-relativistic and spin-orbit corrections were investigated. The analysis of the charge distribution in the Sc(3)N@C(80)(-) anion radical revealed an interesting peculiarity of its electronic structure: while the spin density mostly resides on the cluster, only a slight decrease of its charge is found using both Bader and Mulliken definitions of atomic charges. A set of other endohedral metallofullerenes, including nitride clusterfullerenes Sc(3)N@C(2n) (2n = 68, 70, 78) and Y(3)N@C(2n) (2n = 78-88), carbide clusterfullerenes Sc(2)C(2)@C(68), Sc(2)C(2)@C(82), Sc(3)C(2)@C(80), Ti(2)C(2)@C(78), Y(2)C(2)@C(82), and dimetallofullerenes Sc(2)@C(76), Y(2)@C(82), La(2)@C(2n) (2n = 72, 78, 80), was also studied in the neutral and anionic state, and a spatial charge-spin separation is found to be a general rule for all endohedral fullerenes with high contribution of metal atoms to the LUMO.
对中性和阴离子态的Sc(3)N@C(80)进行了密度泛函理论（DFT）计算，结果表明，在氮化物团簇富勒烯的中性态下，能量最低的结构具有C(3)对称性，而在阴离子态和二阴离子态下，C(3v)构象体能量最低。还发现笼内团簇旋转的势垒随电荷态增加。通过不同的理论方法和Sc(3)N团簇的不同构象，计算了Sc(3)N@C(80)阴离子自由基中的(45)Sc超精细分裂常数a(Sc)。发现在B3LYP/6 - 311G*//PBE/TZ2P理论水平下，a(Sc)强烈依赖于团簇相对于笼的取向，范围从 - 10到 + 25高斯。对计算值的深入分析以及无限制和轨道限制计算的比较表明，a(Sc)的极化贡献约为 - 10高斯，且不依赖于团簇取向。研究了预测的a(Sc)值对密度泛函形式（LSDA、BP、PBE、BLYP、OLYP、TPSS、B3LYP和TPSSh）、基组以及对标量相对论和自旋轨道校正的依赖性。对Sc(3)N@C(80)(-)阴离子自由基中电荷分布的分析揭示了其电子结构的一个有趣特性：虽然自旋密度主要位于团簇上，但使用Bader和Mulliken原子电荷定义时，仅发现其电荷略有减少。还研究了一组其他内包金属富勒烯，包括氮化物团簇富勒烯Sc(3)N@C(2n)（2n = 68、70、78）和Y(3)N@C(2n)（2n = 78 - 88）、碳化物团簇富勒烯Sc(2)C(2)@C(68)、Sc(2)C(2)@C(82)、Sc(3)C(2)@C(80)、Ti(2)C(2)@C(78)、Y(2)C(2)@C(82)以及双金属富勒烯Sc(2)@C(76)、Y(2)@C(82)、La(2)@C(2n)（2n = 72、78、80）的中性态和阴离子态，发现空间电荷 - 自旋分离是所有金属原子对最低未占分子轨道（LUMO）贡献较大的内包富勒烯的普遍规律。
