1. JASPER R. CLARKSON AND TIMOTHY S. ZWIER Funding: National Science Foundation Petroleum Research Fund, Type AC Purdue Research Foundation CONFORMATIONAL ISOMERIZATION BARRIERS AND DYNAMICS OF PHENOL-ETHANOLAMINE CLUSTERS.

2. How does solvent bind at a specific site affect the barriers to conformational isomerization of the flexible molecule? Studying Clusters Shuttling a water molecule between remote H-bonding sites on the same ‘solute’ molecule The effect of H-bonded water on an intramolecular isomerization barrier Measuring the barrier to moving from one lone pair to the other in an OH--OH H-bond TI11 TODAY, 4:36 PM 1015 McPHERSON JCP 122, 214312 (2005)

3. Pulsed valve To Roots pump PMT Carrier gas y x z Lens Mirror Expansion CCD SPEX Monochromator 0.75 m grating S0S0 S1S1 Zero-point Level C A B IV. UV Probe III. Collisional Cooling II. UV Dump I. UV Pump Excited Vibrational Level B*B* Expt’l protocol: 1.Cool 2.Pump 3.Dump 4.Re-cool 5.Probe A C A A B C C A B B B B B B B B C A* B* C C B A* A A A A C C A A C C B B SEP excites single conformation C A C A A B C C A B B B B B B B B C A* B* C C B A* A A A A C C A A C C B B C Experimental Setup 1. 2-3. 4. 5.

4. Macleod and Simons PCCP, 2003, 5, 1123-1129 Complex A 0.00 kcal/mol Complex B 0.51 kcal/mol Complex C 0.73 kcal/mol Phenol-(2-aminoethanol) 1

5. Complex BComplex C ~200 cm -1 H O R.. C ↔ B isomerization pathway: The barrier between lone pairs on the acceptor oxygen

6. Complex C origin Complex B originComplex A origin 2 nd order cluster (D) LIF Phenol-(2-Aminoethanol) 1 Clusters Wavenumbers(cm -1 ) Intensity (arb. units)

7. 10008006004002000 Energy above ZPL (cm -1 ) next slide Gains = 20 + 10 Hz fluorescence Dips = SEP SEP C SEP-PT C-->B SEP-PT C-->C 0-10-20 Hz Holeburning Intensity (arb. units) Overview SEP-PT Spectra Phenol-(2-Aminoethanol) 1 C

8. intensity (arbitrary units) ? Upper bound 206 cm -1 Lower bound 136cm -1 400350300250200150100 Energy above ZPL (cm -1 ) SEP C SEP-PT C-->B SEP-PT C-->C 0-10-20 Hz Holeburning SEP-PT Spectra Phenol-(2-Aminoethanol) 1 C  B Intensity (arb. units)

9. SEP-PT Spectra Phenol-(2-Aminoethanol) 1 B  C Intensity (arb. units) 5004003002001000 Energy above ZPL (cm -1 ) SEP-PT B  C Upper Bound 520 cm -1 180 cm -1 Lower Bound 140 cm -1 SEP-PT B  B

10. SEP-PT Spectra Phenol-(2-Aminoethanol) 1 C  A SEP C SEP-PT C  A SEP-PT C  B Intensity (arb. units) 1600 1500 1400 130012001100 Energy above ZPL (cm -1 ) 1700

11. Why can’t we pump into and out of A? 136-206 cm -1 Bounds on the barriers to isomerization Computed Barriers A 140-520 cm -1 ?? B C 320 cm -1 260 cm -1 1850 cm -1 322 cm -1 134 cm -1 1790 cm -1 A B C A B C

12. Black – DF Complex A Red – DF tuned out of gas pulse Short S 1 lifetime Broad, red-shifted fluorescence Population transfer out of A: Competition with H-atom transfer in the S1 state?

13. Conclusions: Measuring the barrier to moving from one lone pair to the other in an OH…OH H-bond: ~200 cm -1 Measuring the relative energies between Complex C and B Locating minimum energy pathways Observing possible H-atom transfer

14. B3LYP/6-31+G* full optimizations of minima and optimization of TS using QST3 G03. TS verified with imaginary frequency. 707 cm -1 IPA(A)-gauche1  IPA(B)-gauche1 425 cm -1 IPA(A)-gauche1  IPA(A)-gauche2 238 cm -1 IPA(A)-gauche1  IPA(A)-anti Intramolecular isomerization: Higher barrier Solvent isomerization: Lower barrier, energy flow from indole through H-bonds to ethanol torsion ‘Solute’ isomerization in competition with ‘solvent’ isomerization: IPA-ethanol

15. Acknowledgements Collaborators: Professor Ken Jordan Professor David Wales Dr. Dave Evans Funding: National Science Foundation Petroleum Research Foundation Purdue Research Foundation Professor Tim Zwier Zwier Group Esteban Baquero Alvin Shubert Jaime Stearns Talitha Selby Tracy LeGreve Nathan Pillsbury Bill James Josh Newby