Vu Khanh, Pandian Joshua, Zhang Boyi, Annas Christina, Parker Anna J, Mancini John S, Wang Evan B, Saldana-Greco Diomedes, Nelson Emily S, Springsted Greg, Lischka Hans, Plasser Felix, Parish Carol A
Department of Chemistry, Gottwald Center for the Sciences, University of Richmond, Richmond, Virginia 23173, United States.
Department of Chemistry and Biochemistry, Texas Tech University, Lubbock, Texas 79409, United States.
J Phys Chem A. 2024 Sep 19;128(37):7816-7829. doi: 10.1021/acs.jpca.4c04099. Epub 2024 Sep 6.
The diradical benzyne isomers are excellent prototypes for evaluating the ability of an electronic structure method to describe static and dynamic correlation. The benzyne isomers are also interesting molecules with which to study the fundamentals of through-space and through-bond diradical coupling that is important in so many electronic device applications. In the current study, we utilize the multireference methods MC-SCF, MR-CISD, MR-CISD+Q, and MR-AQCC with an (8,8) complete active space that includes the σ, σ*, π and π* orbitals, to characterize the electronic structure of and -benzyne. We also determine the adiabatic and vertical singlet-triplet splittings for these isomers. MR-AQCC and MR-CISD+Q produced energy gaps in good agreement with previously obtained experimental values. Geometries, orbital energies and unpaired electron densities show significant through-space coupling in the - and -benzynes, while -benzyne shows through-bond coupling, explaining the dramatically different singlet-triplet gaps between the three isomers.
双自由基苯炔异构体是评估电子结构方法描述静态和动态相关性能力的优秀原型。苯炔异构体也是有趣的分子，可用于研究在许多电子器件应用中很重要的空间和键间双自由基耦合的基本原理。在当前研究中，我们使用多参考方法MC-SCF、MR-CISD、MR-CISD+Q和MR-AQCC，其具有包含σ、σ*、π和π*轨道的(8,8)完全活性空间，来表征邻位和间位苯炔的电子结构。我们还确定了这些异构体的绝热和垂直单重态-三重态分裂。MR-AQCC和MR-CISD+Q产生的能隙与先前获得的实验值吻合良好。几何结构、轨道能量和未成对电子密度表明，邻位和间位苯炔中存在显著的空间耦合，而对位苯炔表现出键间耦合，这解释了三种异构体之间单重态-三重态能隙的巨大差异。
