Virant Miha, Štrbac Petar, Krawczuk Anna, Milašinović Valentina, Stanić Petra, Lozinšek Matic, Molčanov Krešimir
Jožef Stefan Institute, Jamova Cesta 39, SI-1000 Ljubljana, Slovenia.
Rud̵er Bošković Institute, Bijenička 54, HR-10000 Zagreb, Croatia.
Cryst Growth Des. 2024 Jul 22;24(15):6187-6195. doi: 10.1021/acs.cgd.4c00342. eCollection 2024 Aug 7.
The dimer of the tetracyanoethylene (TCNE) radical anions represents the simplest and the best studied case of two-electron multicenter covalent bonding (2e/mc or ). The model compound, -methylpyridinium salt of TCNE, is diamagnetic, meaning that the electrons in two contiguous radicals are paired and occupy a HOMO orbital which spans two TCNE radicals. Charge density in this system is studied as a benchmark for comparison of charge densities in other pancake-bonded radical systems. Two electrons from two contiguous radicals indeed form a bonding electron pair, which is distributed between two central ethylene groups in the dimer, i.e., between four carbon atoms. The topology of electron density reveals two bond critical points between the central ethylene groups in the dimer, with maximum electron density of 0.185 e Å; the corresponding theoretical value is 0.118 e Å.
四氰基乙烯（TCNE）自由基阴离子二聚体代表了双电子多中心共价键合（2e/mc或 ）最简单且研究最充分的案例。模型化合物TCNE的 -甲基吡啶鎓盐是抗磁性的，这意味着两个相邻自由基中的电子成对，并占据跨越两个TCNE自由基的最高已占分子轨道（HOMO）。该系统中的电荷密度作为比较其他薄饼状键合自由基系统中电荷密度的基准进行研究。来自两个相邻自由基的两个电子确实形成了一个成键电子对，该电子对分布在二聚体中的两个中心乙烯基之间，即在四个碳原子之间。电子密度拓扑结构显示二聚体中中心乙烯基之间有两个键临界点，最大电子密度为0.185 e Å；相应的理论值为0.118 e Å。
