Design of Polycyclic Molecules of Group 15 Elements and Pentagon Stability

结果表明，五元环是由15个基团元素组成的单环分子（XH）n （XN，P,As）和设计的低应变单环和多环分子中最稳定的。由于孤对原子的n轨道和相邻X-X键的σ^*轨道的相位是连续的，所以15族原子的孤对以循环方式离域。键模型分析表明，n-σ^*相互作用对X= n的稳定没有显著贡献，但对X=P和As的稳定有显著贡献。当X=N时，五元环的应变比六元环大。令我们惊讶的是，五元环（X=P和As）具有负应变能，并且比六元环的应变要小。根据五边形稳定性，设计了低应变的P和As多环分子。我们展示了化学物质铝阴离子、碳烯、硅烯和二甲苯的五边形稳定性，其中环戊烷的一个碳原子被相应的原子取代。化学反应的过渡态具有五边形稳定性。例如，环戊烷去质子化反应的活化能（4.25 kcal/mol）低于环己烷去质子化反应的活化能（4.52 kcal/mol）。

We showed that the five-membered ring is the most stable of the monocylic molecules (XH)n (XN,P,As) composed of the 15 group elements and designed mono-and polycyclic molecules with low strains.A lone pair of an atom in the 15 group delocalize in a cyclic manner since the phase of the n-orbital for the lone pairs and the σ^*-orbitals of the vicinal X-X bonds is continuous. The bond model analysis showed that n-σ^* interaction does not contribute to significant stabiizization for X=N but for X=P and As. The five membered ring is more strained than the six-membered ring for X=N. To our surprise, the five-membered rings (X=P and As) have negative strain energies, and are less strained than the six-membered rings. According to the pentagon stability, we designed polycycic molecules of P and As with low strains.We showed the pentagon stability of the chemical species, aluminum anion, carbene, silylene, and germylene, where an carbon atom of cyclopentane is replaced by the corresponding atom.The pentagon stability is shown for the transition states of chemical reactions. For example, the activation energy (4.25) kcal/mol) of the deprotonation from cyclopentane is lower than that (4.52 kcal/mol) from cyclohexane.