Chemistry Department and Institute of Soft Matter, Georgetown University, 37th and O Streets, NW, Washington, District of Columbia 20057-1227, United States.
Department of Chemistry and Biochemistry, Texas Tech University, Lubbock, Texas 79409, United States.
J Phys Chem A. 2023 May 25;127(20):4440-4454. doi: 10.1021/acs.jpca.3c01209. Epub 2023 May 11.
A number of conjugated molecules are designed with extremely long single C-C bonds beyond 2.0 Å. Some of the investigated molecules are based on analogues to the recently discovered molecule by Kubo et al. These bonds are analyzed by a variety of indices in addition to their equilibrium bond length including the Wiberg bond index, bond dissociation energy (BDE), and measures of diradicaloid character. All unrestricted DFT calculations indicate no diradical character supported by high-level multireference calculations. Finally, was computed through fractional orbital density (FOD) calculations and used to compare relative differences of diradicaloid character across twisted molecules without central C-C bonding and those with extremely elongated C-C bonds using a comparison with the C-C bond breaking in ethane. No example of direct C-C bonds beyond 2.4 Å are seen in the computational modeling; however, extremely stretched C-C bonds in the vicinity of 2.2 Å are predicted to be achievable with a BDE of 15-25 kcal mol.
设计了许多具有超长单 C-C 键的共轭分子，超过 2.0 Å。所研究的分子中的一些基于 Kubo 等人最近发现的分子的类似物。除了平衡键长外，还通过多种指标分析这些键，包括 Wiberg 键指数、键离解能 (BDE) 和自由基特征度量。所有非限制的 DFT 计算都表明，高水平的多参考计算不支持自由基特征。最后，通过分数轨道密度 (FOD) 计算来计算 ，并用于比较无中心 C-C 键的扭曲分子和具有极长 C-C 键的分子之间的自由基特征的相对差异，使用与乙烷中 C-C 键断裂的比较。在计算建模中没有看到超过 2.4 Å 的直接 C-C 键的例子；然而，预测在附近具有 2.2 Å 的极拉伸 C-C 键可以实现 15-25 kcal mol 的 BDE。
