THE QUINTESSENTIAL BOND OF MODERN SCIENCE THE DETECTION
THE QUINTESSENTIAL BOND OF MODERN SCIENCE. THE DETECTION AND CHARACTERIZATION OF DIATOMIC GOLD SULFIDE, Au. S. DAMIAN L KOKKIN, RUOHAN ZHANG, TIMOTHY STEIMLE AND BRADLEY W PEARLMAN, IAN A WYSE, THOMAS D. VARBERG.
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.
Spectroscopy of Au. S Three previous experimental studies undertaken on the Au. S 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
Counts Mirror Grating λem Ablation laser 10 cm Excitation laser Gold rod ablated in the presence of OCS (5%) in Argon buffer gas (300 psi)
LIF was collected through a redpass cut-off filter chosen to block discharge emission to the blue of the laser and focused onto a side-on PMT. Excitation laser Au Cathode Laser Beam Au. S in Ar Plasma Slit Insulating Cap Slit Anode (225 V) Low Vacuum (~2 torr) Au Cathode (0 V) Excitation bands arising from the n = 0– 4 levels of the X 12 P 3/2 state were recorded, as well as from the n = 0 and 1 levels of the X 22 P 1/2 state, which lies 1319 cm– 1 above the ground state. Insulting Disc Carrier Gas (5% OCS in Ar)
Excitation Spectra Macalester T≈500 K ASU T≈50 K Measured approximately 100 red-degraded vibrational bands covering the range 1350022700 cm-1 resulting from excitation out of both spin components of the ground state.
What the heck are we seeing? • • The ground state electronic configuration of Au. S is (1 s)2(1 p)4(1 d)4(2 s)2(2 p*)3, which gives rise to just one state, the inverted 2 P ground state. From this ground electronic configuration, one would expect the lowest energy transitions to correspond to an electronic promotion of either 2 s 2 p* or 2 p* 3 s*, which lead to a total of five excited electronic states, as follows: • (1 s)2(1 p)4(1 d)4(2 s)1(2 p*)4 A 2 S+ • (1 s)2(1 p)4(1 d)4(2 s)2(2 p*)2(3 s*)1 a 4 S, B 2 S-, C 2 D, D 2 S+
Excitation Spectra A B C D Measured approximately 100 red-degraded vibrational bands covering the range 1350022700 cm-1 resulting from excitation out of both spin components of the ground state.
Dispersed Fluorescence Spectra
Dispersed Fluorescence Spectra
Excitation Spectra A B C D Measured approximately 100 red-degraded vibrational bands covering the range 1350022700 cm-1 resulting from excitation out of both spin components of the ground state.
Dispersed Fluorescence Spectra
Dispersed Fluorescence Spectra
Lifetime Measurements State A 2Σ+1/2 B 2Σ– 1/2 C 2 D 5/2 C 2 D 3/2 t (ns) 1329± 29 841± 22 1758± 67 1189± 32
Global Fit Measurements A global fit was undertaken of all the observed band positions for Au. S, with the predicted band origins and determined ground and excited state vibrational parameters given below. State Te SD ωexe SD X 2Π 3/2 0. 00 - 410. 04 0. 47 1. 63 0. 11 X 2Π 1/2 1318. 85 1. 08 400. 20 1. 99 2. 40 0. 78 a 4 S-3/2 13583. 94 0. 49 334. 23 0. 46 2. 73 0. 09 A 2Σ+1/2 15572. 01 1. 06 386. 19 1. 25 1. 65 0. 42 B 2Σ– 1/2 16329. 84 0. 76 331. 85 0. 55 3. 04 0. 10 C 2 D 5/2 18508. 20 1. 07 336. 44 0. 97 4. 06 0. 19 C 2 D 3/2 19013. 00 1. 24 347. 55 1. 76 2. 89 0. 72 Liang Y. -N. , Wang F. Acta Phys. –Chim. Sin. 30 (8) 14472014 406 395 374 ωeye SD -0. 09 0. 04 -0. 42 0. 08
Bond Strength of Au-S • The standard formula for the dissociation energy of a rigid rotor assuming a Morse potential: – De=ωe 2/4ωexe • De = 73. 7(12) kcal/mol (3. 20(5) e. V or 25800(400)cm-1). – Kraka et al. , Croat. Chem. Acta. 82, 233 2009, calculated 60 kcal/mol-1 • Much stronger then the other coinage metal sulfides. Ag-S is 60 kcal/mol (2. 6 e. V) a. • Comparison to the larger systems where the Au-S bond is utilized: – Au-S-CH 3 53 kcal/mol b – Au surface – thiolate 40 kcal/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
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 Au. S.
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