1. THE QUINTESSENTIAL BOND OF MODERN SCIENCE. THE DETECTION AND CHARACTERIZATION OF DIATOMIC GOLD SULFIDE, AuS. DAMIAN L KOKKIN, RUOHAN ZHANG, TIMOTHY STEIMLE AND BRADLEY W PEARLMAN, IAN A WYSE, THOMAS D. VARBERG.

2. Gold-Sulfur Bonding Au-S bonding Au-S cites Many reviews have appeared describing the study and use of the gold-thiol systems in molecular biology, inorganic chemistry, self-assembled monolayers and molecular electronics. Much of this work has been done to understand the interaction only on the nanoscale.

3. Spectroscopy of AuS Three previous experimental studies undertaken on the AuS anion via photoelectron spectroscopy (PES) have been reported. Theoretically a number of papers have been reported primarily on the ground state or couple to understanding the PES results. The most recent two studies by Wang, who with the combination of experiment and theory were able to confirm the previous experimental results, in addition to determining the excitation energy to a number of low lying electronic states in the neutral in addition to vibrational properties. H. T. Liu, D.-L. Huang, Y. Liu, L.-F. Cheung, P. D. Dau, C.-G. Ning, and L.-S. Wang, J. Phys. Chem. Lett., 2015, 6, 637−642. H. J. Zhai, C. Bürgel, V. Bonacic-Koutecky and L.-S. Wang, J. Am. Chem. Soc., 2008, 130, 9156–9167 T. Ichino, A. J. Gianola, D. H. Andrews and W. C. Lineberger, J. Phys. Chem. A, 2004, 108, 11307-11313

4. Experimental Approach 10cm Ablation laser Excitation laser Counts λ em Grating Mirror Cold molecular beam source 0.67m McPherson monochromator with Andor iStar cooled intensified CCD camera. Gold rod ablated in the presence of OCS (5%) in Argon buffer gas (300psi)

5. Experimental Approach Slit AuS in Ar Plasma Low Vacuum (~2 torr) Anode (225V) Au Cathode (0V) Insulting Disc Carrier Gas (5% OCS in Ar) Laser Beam Insulating Cap Au Cathode Excitation laser LIF was collected through a red-pass cut-off filter chosen to block discharge emission to the blue of the laser and focused onto a side-on PMT. Excitation bands arising from the = 0–4 levels of the X 1    state were recorded, as well as from the = 0 and 1 levels of the X 2    state, which lies 1319 cm –1 above the ground state. Slit

6. Excitation Spectra Measured approximately 100 red-degraded vibrational bands covering the range 13500- 22700cm -1 resulting from excitation out of both spin components of the ground state. Macalester T≈500K ASU T≈50K

7. What the heck are we seeing? The ground state electronic configuration of AuS is            , which gives rise to just one state, the inverted   ground state. From this ground electronic configuration, one would expect the lowest energy transitions to correspond to an electronic promotion of either    or    , which lead to a total of five excited electronic states, as follows:                                  a       C   D   

8. Excitation Spectra Measured approximately 100 red-degraded vibrational bands covering the range 13500- 22700cm -1 resulting from excitation out of both spin components of the ground state. AB C D

9. Dispersed Fluorescence Spectra

11. Excitation Spectra Measured approximately 100 red-degraded vibrational bands covering the range 13500- 22700cm -1 resulting from excitation out of both spin components of the ground state. AB C D

12. Dispersed Fluorescence Spectra

15. Lifetime Measurements State  (ns) A 2 Σ + 1/2 1329 ± 29 B 2 Σ – 1/2 841 ± 22 C 2  5/2 1758 ± 67 C 2  3/2 1189 ± 32

16. Global Fit Measurements StateTeTe SDωeωe ωexeωexe ωeyeωeye X 2 Π 3/2 0.00-410.040.471.630.11 X 2 Π 1/2 1318.851.08400.201.992.400.78 a 4   3/2 13583.940.49 334.230.462.730.09 A 2 Σ + 1/2 15572.011.06386.191.251.650.42-0.090.04 B 2 Σ – 1/2 16329.840.76331.850.553.040.10 C 2  5/2 18508.201.07336.440.974.060.19 C 2  3/2 19013.001.24347.551.762.890.72-0.420.08 A global fit was undertaken of all the observed band positions for AuS, with the predicted band origins and determined ground and excited state vibrational parameters given below. Liang Y.-N., Wang F. Acta Phys. –Chim. Sin. 30 (8) 14472014 406 395 374

17. Bond Strength of Au-S The standard formula for the dissociation energy of a rigid rotor assuming a Morse potential: – D e =ω e 2 /4ω e x e D e = 73.7(12) kcal/mol (3.20(5) eV or 25800(400)cm -1 ). – Kraka et al., Croat. Chem. Acta. 82, 233 2009, calculated 60kcal/mol -1 Much stronger then the other coinage metal sulfides. Ag-S is 60kcal/mol (2.6eV) a. Comparison to the larger systems where the Au-S bond is utilized: – Au-S-CH 3 53kcal/mol b – Au surface – thiolate 40kcal/mol c a. V. Gupta, F. J. Mazzotti, C. A. Rice, R. Nagarajan and J. P. Maier, J. Mol. Spec., 2013, 286, 52-55 b. D. Jiang and S. Dai, J. Phys. Chem. C, 2009, 113, 3763–376 c. D. G. Castner, K. Hinds and D. W. Grainger, Langmuir, 1996, 12, 5083-5086

18. Acknowledgements National science foundation, division of chemistry, CHE-1265885 (ASU) and CHE- 1265741 (Macalester) Metal Containing Thursday morning and listen to Ruohan speak on the hyperfine and dipole moment of AuS.