1. ROTATIONAL SPECTRA OF THE TRIFLUORO ETHANOL (TFE) -WATER CLUSTERS AND THE TFE DIMERS Javix Thomas and Yunjie Xu Department of Chemistry, University of Alberta, Edmonton, Alberta, Canada, T6G 2G2.

2. 2 Motivation 1. Xu et al. J. Chem. Phys., 1995, 103, 9541. 2. Scharge et al. Z. Phys. Chem., 2008, 222, 1407.  TFE is an important organic solvent.  TFE and water are often used as co-solvents in the studies of protein folding process.  The interactions of TFE with itself and with water may play some significant roles molecular recognition of biomolcules.  The TFE monomer was extensively studied using rotational spectroscopy 1 and the TFE dimer was investigated using low resolution FTIR spectroscopy. 2

3. Related alcohols trans conformation gauche conformation Extra binding site Ethanol FE gauche conformation TFE

4. 4 4 Conformers of TFE dimer with O-H…O H-bond H-bond donor/acceptor: homo and het 2 Insertion into intra-ring: inserted or associatedX 2 O lone pairs of acceptor: compact or openX 2 = 8 1.80 2.52 2.11 2.52 associatedinserted 1.62 associated inserted 2.52 1.91 1.86 2.52 2.01 homo hetero

5. 5 MP2/6-311++g(d,p) level of theory Properties of the four conformers of the TFE dimer

6. 6 Searches were carried out using a chirp pulsed FTMW spectrometer. Final measurements were done with a cavity based FTMW spectrometer 0.3%~0.5% TFE (and water) in Neon or Helium backing gas ( 2~3 atm) Experimental details

7. Our chirp pulsed FTMW spectrometer G. G. Brown, B. C. Dian, K. O. Douglass, S. M. Geyer, S. T. Shipman and B. H. Pate, Rev. Sci. Inst., 2008, 79, 053103; S. Dempster, O. Sukhorukov, Q.-Y. Lei, W. Jäger, J. Chem. Phys., 2012, 137, 174303; J. Thomas, J. Yiu, J. Rebling, W. Jäger, Y. Xu, J. Phys. Chem. A., Online, Apr. 25, 2013, DOI: 10.1021/jp402552t.

8. Broadband spectrum of TFE+He

9. Assignment of the TFE dimer

10. 10 2.82 3.23 0 1.02 ichet ichom achom achet iohet iohom Relative energy / kJmol -1 MP2/aug-cc-pVTZ//MP2/6-311++G(d,p) The TFE dimer versus the 2-FE dimer X. Liu, N. Borho, Y. Xu, Eur. J. Chem. 2009, 15, 270. 0 0.76 ahet ihom ahom ihet Relative energy / kJmol -1 2.91 2.81 4.52 3.64 MP2/6-311++G(d,p)

11. 6 Conformers of the TFE-water dimer Do=0 Do=10.9Do=21.6 Do=22.3 MP2/6-311++G(d,p), ZPE corrected: kJ/mol 2.64 1.87 2.38 2.06 2.552.17 2.55 2.27 1.77 1.70 Do=9.0 Do=16.7

12. Broadband spectrum of TFE+water+He TFE+water+HeTFE+He

13. Assignment of the TFE-water spectrum Simulated spectrum of the TFE-water

14. 14 Semirigid rotor fits of the most stable TFE-water dimer Spec. Component 1 Component 12 Const. A 3.5428110(9) 3.542896(1) B 1.5504968(2) 1.5504926(2) C 1.3583053(2) 1.3582814(2) DJ 0.1299(2)E-05 0.1298(3)E-05 DJK -0.39(2)E-06 -0.37(2)E-06 DK 0.24(2)E-05 0.24(2)E-05 d1 -0.243(2)E-06 -0.241(2)E-06 d2 0.36(1)E-07 0.36(2)E-07 N4545 SD2.32.7

15. 15 Conclusion and future work ** Only the most stable conformer of the TFE dimer was identified, in contrast to the related ethanol and 2- fluoroethanol cases. ** Some unassigned lines may be attributed to the TFE trimer and perhaps even the TFE tetramer. ** Many strong unassigned lines in TFE+water+He are likely due to larger TFE-water clusters. Their assignments are in progress.

16. 16 Acknowledgement Funding: UofA, NSERC, CFI, AI, Petro-Canada.