BORONYL MIMICS GOLD: A PHOTOELECTRON SPECTROSCOPY STUDY Tian Jian, Gary V. Lopez, Lai-Sheng Wang Department of Chemistry, Brown University International Symposium on Molecular Spectroscopy 70 TH MEETING JUNE 22-26, 2015 CHAMPAIGN-URBANA, ILLINOIS
Outline Background and Motivation Experimental Principle and Setup Results and Summary Acknowledgement
I) Boronyl as a monovalent σ ligand: BO/BO − versus CN/CN − and CO Zhai, H. J. et al., Acc. Chem. Res. 2014, 47, 2435−2445 Background 1222143212221432
II) BO/Au analogy in B 13 O − and B 12 Au − Optimized anion global-minimum structures for (a) B 12 O - (16) and (b) B 12 Au - (1) at the B3LYP/B,O/6-311G(d,p)/Au/Stuttgart_rsc_1997_ecp+2f1g level AdNDP analyses for the chemical bonding in (a) B 12 O - (16) and (b) B 12 Au - (1) (a)(b) (d) Bai, H. et al., Phys. Chem. Chem. Phys., 2013, 15, 9646
Optimized anion global-minimum structures of B 3 (BO) n − and B 3 Au n − (n = 1, 2) clusters and their neutrals at the B3LYP/B,O/aug-cc-pVTZ/Au/Stuttgart_rsc_1997_ecp+2f1g level. BO/Au analogy in B 3 (BO) n − and B 3 Au n − (n = 1, 2) Selected molecular orbitals of B 3 (BO) n − and B 3 Au n − (n = 1, 2) that are responsible for the delocalized σ and π bonding in the B3 core, and the B−Au and B−(BO) σ single bonds Chen, Q. et al., J. Chem. Phys. 2013, 139,
Motivation The BO group demonstrates structural and chemical robustness in boronyl clusters, suggesting its potential as new inorganic ligands and building blocks in chemistry. Although boronyl (BO/BO − ) are isovalent to CN/CN − and CO, the chemistry of boronyl has remained relatively unknown until recently. Braunschweig, H. et al., Science. 2010, 328, 345 X-ray molecular structure of trans- [(Cy3P)2BrPt(BO)] (2) (left) and -MOs of the model complex trans- [(Me3P)2BrPt(BO)] (2′) (right).
Photoelectron Spectroscopy Principle M–M– M
Experimental Setup Wang, L.S. et al., J. Chem. Phys. 1995, 102,
Photoelectron spectra of BiBO − at three different photon energies: a)532 nm, b)355 nm, c)266 nm, and d)193 nm. Photoelectron spectra of BiAu − at three different photon energies: a)532 nm, b)355 nm, c)266 nm, and d)193 nm. Photoelectron spectra of BiAu − and BiBO − B O Å Å BiBO ─ C V ( 2 Π) EA= 1.84 ± 0.03 eV Au Å BiAu ─ C V ( 2 Π) EA= 1.38 ± 0.04 eV
Features VDE (eV) a Exptl. Final State and electronic configuration BiAu − X1.43(4) 3 Σ - …1σ 2 2σ 2 1π 2 A2.14(4) 1 Δ …1σ 2 2σ 2 1π 2 B2.72(2) 1 Σ + …1σ 2 2σ 2 1π 2 C3.97(2) 3 Π …1σ 2 2σ 1 1π 3 D4.10(2) 1 Π …1σ 2 2σ 1 1π 3 E4.44(5) F4.65(5) G4.94(6) H5.14(5) I5.48(5) J5.84(5) K6.02(5) a 3.42(3) b1 Σ + …1σ 2 1π 4 b 3.52(3) b1 Σ + …1σ 2 1π 4 c 3.62(3) b1 Σ + …1σ 2 1π 4 BiBO − X1.84(3) 3 Σ - …1σ 2 2σ 2 1π 2 A2.47(3) 1 Δ …1σ 2 2σ 2 1π 2 B3.10(3) 1 Σ + …1σ 2 2σ 2 1π 2 C5.52(5) 3 Π …1σ 2 2σ 1 1π 3 D5.66(5) 1 Π …1σ 2 2σ 1 1π 3 a 4.38(5) c1 Σ + …1σ 2 1π 4 a Numbers in the parentheses present experimental uncertainties in the last digit. b,c These electronic states are due to two electron processes. Molecular orbital energy diagram for BiAu − Complete list of the observed VDEs including Photoelectron spectra of BiAu − at 193 nm
BiBO ─ 323 (30) cm (50) cm -1 Vibrational structure of BiBO DescriptionExperimental (cm -1 )Theoretical (cm -1 )* B-O stretching1855 (50)1815 Bi-B stretching323 (30)354 *PW91/B,O/aug-cc-pVTZ/Bi/SDD
Summary Anions of Gold-Bismuth and Boronyl-Bismuth clusters have been observed in laser vaporization experiments. Well-resolved photoelectron spectra were obtained at various photon energies and the electron affinities and low-lying electronic excited states of the neutral BiAu and BiBO clusters were reported. BiAu and BiBO show similar PES patterns, due to the fact that Au and BO are both monovalent σ ligands. BiAu − and BiBO − clusters can be considered to be isostructural and isovalent. We confirm that the boronyl unit does mimic the gold atom when interacting with Bi atom.
Acknowledgement Brown University Prof. Lai-sheng Wang Dr. Gary V. Lopez, Tengteng Chen All Wang group members
Thank you! Questions?
Molecular orbitals for BiAu − and BiBO − * * at PW91/B,O/aug-cc-pVTZ/Au, Bi/SDD