Schoendorff George, Ruedenberg Klaus, Gordon Mark S
Department of Chemistry, Virginia Military Institute, Lexington, Virginia 24450, United States.
Department of Chemistry and Ames Laboratory, Iowa State University, Ames, Iowa 50011-3111, United States.
J Phys Chem A. 2021 Jun 10;125(22):4836-4846. doi: 10.1021/acs.jpca.1c02860. Epub 2021 May 27.
The bonding structures of the ground state and the lowest five excited states of rhodium monoboride are identified by determining the quasi-atomic orbitals in full valence space MCSCF wave functions and the interactions between these orbitals. A quadruple bond, namely two π-bonds and two σ-bonds, is identified and characterized for the XΣ ground state, in agreement with a previous report (Cheung . 2020, 11, 659-663). However, in all excited states, the bonding is predicted to be weaker because, in these states, one of the σ-bonding interactions has a small magnitude. In the aΔ and AΔ states, the bond order is between a triple and quadruple bond. In the bΣ state, the Rh-B linkage is a triple bond. In the cΠ and BΠ states, the atoms are linked by a double bond due to an additional weakening of the two π-bonds. The decreases in the predicted bond strengths are reflected in the decreases of the predicted binding energies and in the increases of the predicted bond lengths from the XΣ ground state to the cΠ and the BΠ excited states. Notably, the 5pσ orbital of rhodium, which is vacant in the ground state of the atom, plays a significant role in the molecule.
通过确定全价空间MCSCF波函数中的准原子轨道以及这些轨道之间的相互作用，确定了一硼化铑基态和最低五个激发态的键合结构。对于XΣ基态，确定并表征了一个四重键，即两个π键和两个σ键，这与之前的报告一致（Cheung. 2020, 11, 659 - 663）。然而，在所有激发态中，预计键合较弱，因为在这些状态下，其中一个σ键相互作用的强度较小。在aΔ和AΔ态中，键级在三重键和四重键之间。在bΣ态中，Rh - B键是一个三重键。在cΠ和BΠ态中，由于两个π键的进一步减弱，原子通过双键相连。预测的键强度的降低反映在预测的结合能的降低以及从XΣ基态到cΠ和BΠ激发态预测的键长的增加上。值得注意的是，铑的5pσ轨道在原子基态中是空的，但在分子中起着重要作用。
