硼/氮掺杂富勒烯C20的结构和稳定性

应用密度泛函理论(DFT)的B3LYP/6-31G*方法, 对C_20-2nX_2n(X=B, N; n=1、2、3、4)各异构体进行几何构型全优化和振动频率计算, 确定了基态结构, 对它们的取代方式、电子结构、张力和芳香性进行了研究. 氮掺杂不能显著降低分子的张力, C₁₂N₈的张力甚至比C₂₀的还要大, 极不稳定. C₁₈B₂的两个最稳定异构体1,14-C₁₈B₂和1,3-C₁₈B₂都有比较大的能隙和结合能, 具有很强的芳香性, 其张力与C₂₀的相比均显著降低. 1,14-C₁₈B₂ 和1,3-C₁₈B₂具有较高的稳定性, 可以用红外光谱区分这两个构型异构体.

Structures and Stabilities of Boron/Nitrogen-Doped Fullerene C20

The geometries of various isomers of heterofullerenes C20-2nX2n (X=B,N; n=1,2,3,4) were fully optimized at the B3LYP/6-31G density functional level of theory,and the corresponding frequency calculations at the same level were used to characterize the ground state structures. The substitutional patterns,electronic structure,strain,and aromaticity of these heterofullerenes have been investigated. In general,nitrogen doping could not significantly decrease the strain of the cage. The strain of C12N8 was even larger than that of C20,this nitrogen analogue was extraordinarily unstable. The two most stable isomers of C18B2,1,14-C18B2 and 1,3-C18B2,both have large HOMO-LUMO gaps and binding energies. They were highly aromatic. The strains of these two molecules were very small,compared with that of C20. 1,14-C18B2 and 1,3-C18B2 were predicted to be highly stable small heterofullerenes,these two configurational isomers could be distinguished from each other by their IR spectra.