ROTATIONAL SPECTRA OF THE TRIFLUORO ETHANOL TFE WATER

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, T 6 G 2 G 2.

Motivation 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 1. Xu et al. J. Chem. Phys. , 1995, 103, 9541. 2. Scharge et al. Z. Phys. Chem. , 2008, 222, 1407. 2

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

4 Conformers of TFE dimer with O-H…O H-bond donor/acceptor: homo and het Insertion into intra-ring: inserted or associated O lone pairs of acceptor: compact or open hetero homo associated inserted 1. 91 associated inserted 2. 52 2. 01 1. 80 1. 86 2. 52 2 X 2 =8 2. 52 1. 62 2. 11 2. 52 4

Properties of the four conformers of the TFE dimer MP 2/6 -311++g(d, p) level of theory ΔDo Confs k. J/mol i/hom 0 A B C GHz μ a, μ b, μ c 1. 61147 0. 43043 0. 41144 -2. 43, -0. 13, -1. 26 a/hom 2. 82 1. 62591 0. 39955 0. 38001 1. 43, 2. 34, -3. 32 i/het 0. 756 1. 51552 0. 44402 0. 40357 3. 12, 1. 13, 0. 25 a/het 3. 226 1. 83234 0. 35243 0. 34739 -1. 28, 0. 38, -3. 81 5

Experimental details • 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) 6

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/jp 402552 t.

Broadband spectrum of TFE+He

Assignment of the TFE dimer

The TFE dimer versus the 2 -FE dimer Relative energy / k. Jmol-1 MP 2/aug-cc-p. VTZ//MP 2/6 -311++G(d, p) 4. 52 3. 64 iohet iohom 2. 91 2. 81 achet achom 1. 02 ichom 0 Relative energy / k. Jmol-1 MP 2/6 -311++G(d, p) 3. 23 2. 82 0. 76 ahet 0 ihom ichet X. Liu, N. Borho, Y. Xu, Eur. J. Chem. 2009, 15, 270. ihet ahom 10

6 Conformers of the TFE-water dimer MP 2/6 -311++G(d, p), ZPE corrected: k. J/mol 2. 06 2. 64 2. 38 2. 55 1. 87 2. 17 Do=10. 9 2. 55 Do=21. 6 Do=0 2. 55 2. 27 1. 70 1. 77 Do=9. 0 Do=16. 7 Do=22. 3

Broadband spectrum of TFE+water+He TFE+He

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

Semirigid rotor fits of the most stable TFE-water dimer Spec. Const. Component 12 A B C 3. 5428110(9) 1. 5504968(2) 1. 3583053(2) 3. 542896(1) 1. 5504926(2) 1. 3582814(2) DJ DJK DK d 1 d 2 0. 1299(2)E-05 -0. 39(2)E-06 0. 24(2)E-05 -0. 243(2)E-06 0. 36(1)E-07 0. 1298(3)E-05 -0. 37(2)E-06 0. 24(2)E-05 -0. 241(2)E-06 0. 36(2)E-07 N SD 45 2. 3 45 2. 7 14

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. 15

Acknowledgement Funding: Uof. A, NSERC, CFI, AI, Petro-Canada. • Questions? 16