1. Victoria P. Barber and Josh J. Newby TK14 Department of Chemistry and Biochemistry, Swarthmore College Swarthmore, PA 19081 Spectroscopic characterization of a natural product: anethole

2. Motivation Natural products Low amplitude motions Complete the spectroscopy

3. Early work (Grassian et al.) Syn Anti R2PI Grassian et al. J. Phys. Chem. 1989, 93 3470-3474

4. Cools gas phase molecules to effective temperatures of a few degrees Kelvin Boltzmann distribution of conformations Collisional cooling Jet-cooled spectroscopy Buffer gas A A A B B BB B B A A B A AA B B B B B A A B B A A A B B B B B A A B B Isolated, cold molecules High Pressure (1 bar)Low Pressure (10 -7 bar)

5. Excited Fluorescence spectroscopy Ground 1.LIF Tune laser, measure total fluorescence Excited state vibrations 2.SVLF Park laser, disperse fluoresce Ground state vibrations

6. LIF spectrum of anethole

7. SynAnti Bands separated by 70 cm -1

8. Origin SVLF spectra Two conformers confirmed SVLF Anti Syn

9. Computation AntiSyn (wavenumbers) B3LYP/6-311++G(d,p) Grassian assignments confirmed

10. Detect total fluorescence Probe (20 Hz) Conformer A(S 0, ZPL) HB (10 Hz) UVHB UV Hole-burn laser fixed UV probe laser tuned UVHB Hole-burning of anethole (Purdue) A (S 1 ) Syn Anti

11. (a)Warm conditions (b) Cold Conditions 10 psi 30 psi v = 0 v = 1 v = 0 v = 1 v = 2 v = 3 S1S1 S0S0 Pressure study (a) (b)

12. Origin SVLF spectra (Purdue) Anti Syn

13. Syn SVLF (in plane) Simple false origin SVLF of in plane IVR

14. Syn SVLF (out of plane) Significant Duschinsky mixing of out of plane modes

15. Syn Hot bands SVLF Identical absolute frequency implies same upper state

16. Anti SVLF

17. FCF of ν 39 Conformations differ in displacement

18. MOs of anethole MeO orientation tweaks MO geometry

19. Syn/Anti Isomerization

20. Isomerization

21. (a)Warm conditions (b) Cold Conditions 10 psi 30 psi v = 0 v = 1 v = 0 v = 1 v = 2 v = 3 S1S1 S0S0 Pressure study (a) (b)

22. SVLF spectra of Syn origin and Syn+58 Similar structure New low frequency bands Implies VDW cluster Syn 0 0 Syn +58

23. SVLF spectra of Syn origin and Anti+51 Similar structure New low frequency bands Implies VDW cluster Anti 0 0 Anti +51

24. LIF of water clusters ‘Neat’ sample has water clusters! Neat +H 2 O

25. Spontaneous Emulsion (Ouzo Effect) Ouzo Absinthe

26. Styrene : water Origin shift n=1 => 21.5 cm -1 n=2 => 46.5 cm -1 anisole : water Origin shift n=1 => 118 cm -1 n=2 => 107 cm -1 Water cluster comparison Reimann et al. J. Chem. Phys. 117(19) 2002 8805 Mahmoud et al. Chem. Phys. Lett. 356 2002 91

27. LAM Comparison Syn Anti

28. Two conformations (syn/anti) Similar with key differences (ν 63, ν 39 ) Styrene like vibrational characteristics OMe is sneaks in Readily clusters with water Trimers form without much effort? Key points

29. Swarthmore Prof. Thomas A. Stephenson Victoria P. Barber Madeleine Amodio Purdue Prof. Timothy S. Zwier Deepali N. Mehta-Hurt Acknowledgements