富勒烯C_(36)等电子体C_(34)BN异构体的结构及其相对稳定性理论研究

用半经验的AM1和MNDO方法优化了富勒烯C_(36)的等电子体C_(34)BN所有可能 异构体的构型，分析了各异构体相对稳定性与杂原子取代位置间的关系。另外，比 较了C_(36)碳笼上同位置地取代杂原子形成的C_34BN,C_(34)B_2和C_(34)N_2间的 电子结构，并分析了C_(34)BN最稳定异构体的振动模型。结果表明以C_(36):A (D_(6h))为母体形成的最稳定C_(34)BN异构体对应于碳笼赤道位置六元环中1，4- 取代产物，而以C_(36):B(D_(2d))为母体形成的最稳定C_(34)BN异构体对应于碳笼 近赤道位置的1，2-取代产物.C_(34)BN各异构体的稳定性可能主要由体系的共轭性 质决定。前线轨道能级表明B，N原子取代所得异构体的氧化-还原活性按以下顺序 递增：C_(34)B_2

Theoretical Studies on Structures and Stabilities of C_(34)BN Isomers

The possible stable structures of substituted fullerenes C 34 BN formed on the initial C 36 cages of D 6 h and D 2 d symmetries have been systematically investigated at the AM1 and MNDO levels. The relationship between the stabilities of the C 34 BN isomers and the sites where boron or nitrogen atoms dope at the C 36 cage has been discussed. The results show that for the C 36 cage with D 6 h symmetry, the most stable isomer of C 34 BN derivative is formed by boron and nitrogen atoms doping at the 1,4 sites in the six membered ring which locates at the equatorial belt of C 36 cage. While for C 36 cage with D 2 d symmetry, the most stable isomer of C 34 BN derivative is formed by boron and nitrogen atoms doping at the sites near equatorial belt of C 36 cage, which corresponds to 1,2 substitution pattern. It seems that the stabilities of C 34 BN isomers are mainly determined by the conjugate effect of the cage. The activity of the redox of the C 34 XY (X, Y=B, N) isomers increases in the following order: C 34 B 2