Photoelectron Spectroscopy of BiAu^– and BiBO^–: Further Evidence of the Analogy between Au and Boronyl

Abstract

Boronyl (BO) is a monovalent σ radical with a B≡O triple bond. Its chemistry has remained relatively unknown, though analogy has been established for BO with monovalent atoms, such as H or Au. Here we report a photoelectron spectroscopic study of BiAu(-) and BiBO(-), showing further evidence of the analogy between Au and BO. The photoelectron spectra of BiAu(-) and BiBO(-) are found to be similar, suggesting that they possess similar electronic structure and chemical bonding. The electron affinities of BiAu and BiBO are measured to be 1.38(4) and 1.84(3) eV, respectively. The ground states of both BiAu and BiBO are shown to be a triplet (X (3)Σ(-)). In addition, vibrational structures are resolved in the spectra of BiBO(-). Two vibrational frequencies at 320(30) and 1860(50) cm(-1) are measured for the ground state of BiBO, corresponding to the Bi-B and B-O stretching modes, respectively. The low-lying electronic excited states of BiAu and BiBO are also found to be similar: their first four excited states are A (1)Δ, B (1)Σ(+), C (3)Π, and D (1)Π, with excitation energies at 0.71, 1.29, 2.54, and 2.67 eV for BiAu and 0.63, 1.26, 3.68, and 3.82 eV for BiBO, respectively, above the (3)Σ(-) ground state. Weak photoelectron features related to two-electron detachment transitions are also observed for both anions because of strong electron correlation effects in the ground state of the anions.

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

“…The molecular structures of the 3 Σ − , 1 Δ, 1 Σ + , 3 Π(1), and 1 Π(1) states of BiBO and 2 Π state of BiBO − are optimized using the MRCI + Q method and their optimized geometrical parameters are summarized in Table . As predicted by the previous PES study, the ground state of BiBO − is the 2 Π state . The ejection of an electron from the π Bi and σ orbitals (see Figure ) of BiBO − generates the 3 Σ − , 1 Δ, and 1 Σ + states, and the 3 Π(1) and 1 Π(1) states, respectively.…”

“…As shown in Table , the molecular structure of BiBO differs from that of BiBO − ; the BiB bond length of the 3 Σ − state of BiBO is ∼0.03 Å larger than that of the 2 Π state of BiBO − . This result contradicts a recent experimental study suggesting that the molecular structures of BiBO and BiBO − are similar to each other . The DFT and SODFT calculations of the ground state of BiBO and BiBO − were performed to clarify this discrepancy and the calculated results are summarized in Table .…”

“… The experimentally observed BiB stretching and BO stretching modes are 320(30) and 1860(50) cm −1 , respectively (see Ref. [ ]).…”

“…The electronic configurations of those electronic states were suggested in that study except for one electronic state (a state, see Ref. ). No detailed theoretical investigation has been performed to support the experimental results.…”

“…The recent PES study on bismuth monoboronyl anion (BiBO − ) revealed the various electronic states of BiBO . The electronic configurations of those electronic states were suggested in that study except for one electronic state (a state, see Ref.…”