1. Reactive Intermediates in 4 He Nanodroplets: Infrared Laser Stark Spectroscopy of Dihydroxycarbene Bernadette M. Broderick, Chris Moradi, Laura McCaslin, John F. Stanton, Gary Douberly 25jun15

2. Carbenes C R”R” R’R’ singlettriplet

3. Carbenes C R”R” R’R’ Organometallic chemistry, Fischer and Schrock Key synthetic agents Smaller carbenes relevant to atmospheric, combustion, pre-biotic earth chemistry

4. Carbenes in Spectroscopy

5. dihydroxycarbene Schreiner, Peter R., et al. Science 332.6035 (2011): 1300-1303. P. R. Schreiner, H. P. Reisenauer, F. C. Pickard, A. C. Simmonett, W. D. Allen, E. Mátyus, and A. G. Császár, Nature 453, 906 (2008). C. M. Leavitt, C. P. Moradi, J. F. Stanton, and G. E. Douberly, J. Chem. Phys. 140, 171102 (2014)

8. P. R. Schreiner and H. P. Reisenauer, Angew. Chem. Int. Edit. 47, 7071 (2008)

9. ~ 2 h ~ 1 h

10. Dihydroxycarbene in 4 He Nanodroplets

11. “pick-up cells” laser spectroscopy mass spectrometry Trapping potential depth ~ 100 K Molecular degrees of freedom are brought into thermal equilibrium with the helium droplet at 0.4 K The HENDI Technique ~10 11 molecules·cm -3 Cooling timescale < 1 ns, pick-up timescale ~10  s 10000 He atoms can dissipate ~6 eV (~140 kcal/mol) 30 bar 15 K Pickup Chamber Stark Chamber

12. Laser-Induced Depletion Signal Infrared cw-OPO Tunable from 4100 to 2570 cm -1 with >1 Watt output power. IR excitation of dopant Vibrational excitation quenched through loss of several thousand He atoms Reduced ionization efficiency of MS leads to depletion signal hν IR The HENDI Technique

13. X Droplet beam Rough Pump Gate Valve AirVacuum O-ring seal Water cooled copper electrodes Ta filament / Quartz tube Oxalic Acid Pyrolysis Source HOCOH + CO 2 + H 2

14. Dihydroxycarbene & Mass Spectra

19. IR Laser Spectroscopy of Dihydroxycarbene

20. Arrows: dihydroxycarbene band origins from previous Ar-matrix spectra (Schriener et al.) Sticks: VPT2 calculations McCaslin, Stanton

21. b a b a (b2)(b2) (a1)(a1) (a)(a)

22. Dihydroxycarbene & Stark Spectroscopy

23. Electric field lifts the rotational state degeneracy (2J+1)  M = ±1 E laser E Stark E laser E Stark or  M = 0

24. Stark Spectroscopy of trans,cis-dihydroxycarbene b a Parallel polarization  M = ±1 E laser E Stark E laser E Stark or  M = 0

25. Stark Spectroscopy of trans,trans-dihydroxycarbene Parallel polarization b a  M = ±1 E laser E Stark E laser E Stark or  M = 0

26. Summary

29. Dihydroxycarbene was generated in the gas-phase via pyrolysis of oxalic acid Two of the three rotamers are unambiguously identified as trans,trans and cis,trans Band origins and vibrationally averaged dipole moments obtained in He droplets agree with those predicted by VPT2 calculations Observance of cis,trans and trans,trans implies that our pyrolysis temperature is incapable of both fragmenting the precursor and surmounting the rotamerization barrier to generate the cis,cis conformer

30. Acknowledgements Financial Support: Department of Energy

31. Thank you!

32. Carbenes in Spectroscopy