Spin-orbit ab initio and density functional theory investigation of bismuth monoboronyl, BiBO

The molecular properties of bismuth monoboronyl, BiBO, were investigated using high-level ab initio and density functional theory calculations by including the effect of spin-orbit coupling (SOC). SOC does not cause any change in the BiB bond length of BiBO, by contrast it causes significant elongation of the BiB bond of BiBO⁻, by ∼0.03 Å. The BiB bond length of BiBO⁻ that is calculated by considering SOC is almost identical to that of BiBO; this result is consistent with a recent experimental study. The term values of excited states of BiBO calculated by including SOC are in good agreement with the experimental results. One excited state which was not assigned in the previous experimental study is the Ω = 0⁺ state generated by strong SOC. In the theoretical calculations on molecules containing 6p-block elements, including SOC is crucial for obtaining results that are consistent with the corresponding experimental results.