Bhowmick Rina, Roy Chowdhury Sabyasachi, Vlaisavljevich Bess
Department of Chemistry, University of South Dakota, Vermillion, South Dakota 57069, United States.
Inorg Chem. 2023 Aug 28;62(34):13877-13891. doi: 10.1021/acs.inorgchem.3c01779. Epub 2023 Aug 17.
Copper corroles are known for their unique multiconfigurational electronic structures in the ground state, which arise from the transfer of electrons from the π orbitals of the corrole to the d-orbital of copper. While density functional theory (DFT) provides reasonably good molecular geometries, the determination of the ground spin state and the associated energetics is heavily influenced by functional choice, particularly the percentage of the Hartree-Fock exchange. Using extended multireference perturbation theory methods (XMS-CASPT2), the functional choice can be assessed. The molecular geometries and electronic structures of both the unsubstituted and the -triphenyl copper corroles were investigated. A minimal active space was employed for structural characterization, while larger active spaces are required to examine the electronic structure. The XMS-CASPT2 investigations conclusively identify the ground electronic state as a multiconfigurational singlet (S) with three dominant electronic configurations in its lowest energy and characteristic saddled structure. In contrast, the planar geometry corresponds to the triplet state (T), which is approximately 5 kcal/mol higher in energy compared to the S state for both the bare and substituted copper corroles. Notably, the planarity of the T geometry is reduced in the substituted corrole compared with that in the unsubstituted one. By analyzing the potential energy surface (PES) between the S and T geometries using XMS-CASPT2, the multiconfigurational electronic structure is shown to transition toward a single electron configuration as the saddling angle decreases (i.e., as one approaches the planar geometry). Despite the ability of the functionals to reproduce the minimum energy structures, only the TPSSh-D3 PES is reasonably close to the XMS-CASPT2 surface. Significant deviations along the PES are observed with other functionals.
铜卟吩因其基态独特的多构型电子结构而闻名，这种结构源于电子从卟吩的π轨道转移到铜的d轨道。虽然密度泛函理论（DFT）能提供相当不错的分子几何结构，但基态自旋态和相关能量的确定受泛函选择的影响很大，尤其是哈特里 - 福克交换的百分比。使用扩展多参考微扰理论方法（XMS - CASPT2），可以评估泛函选择。研究了未取代和 - 三苯基铜卟吩的分子几何结构和电子结构。在结构表征中采用了最小活性空间，而研究电子结构则需要更大的活性空间。XMS - CASPT2研究最终确定基态电子态为多构型单重态（S），在其最低能量状态下有三种主要电子构型且具有特征性的鞍形结构。相比之下，平面几何结构对应于三重态（T），对于裸铜卟吩和取代铜卟吩，三重态的能量比单重态大约高5千卡/摩尔。值得注意的是，与未取代的卟吩相比，取代卟吩中T几何结构的平面性有所降低。通过使用XMS - CASPT2分析S和T几何结构之间的势能面（PES），结果表明随着鞍形角减小（即当接近平面几何结构时），多构型电子结构会向单一电子构型转变。尽管这些泛函能够重现最低能量结构，但只有TPSSh - D3势能面与XMS - CASPT2表面相当接近。使用其他泛函时，沿势能面会观察到显著偏差。
