1. Microwave Spectrum of Hydrogen Bonded Hexafluoroisopropanol  water Complex Abhishek Shahi Prof. E. Arunan Group Department of Inorganic and Physical Chemistry Indian Institute of Science Bangalore-12, India.

2. Outline Introduction to the monomers and the complex Guess geometry and structure optimization Spectrum of complex and its isotopologues Assignment and Discussion Nature of interaction Conclusion

3. Complex under Study HFIPWater HFIP : HexaFluoroIsoPropanolWater : H 2 O

4. Introduction: HFIP-monomer Two conformers at room temperature (IR studies). Anti-periplanar (AP) is more stable than Synclinical (SC) in gas phase. Suhm M. Journal of Physical Chemistry A, 2000, 104(2), 265–274 Rotational Spectroscopy of monomer Complete structural determination of monomer. Microwave spectrum of 6 isotopologues (parent, two deuterated, three C-13) Only AP conformer could be seen in supersonic expansion. AP SC Abhishek Shahi and E. Arunan, Colloquium. and OSU-2013, http://hdl.handle.net/1811/55298

5. Monomer One of the most important molecules for life. A good H-bond acceptor as well as donor. Point Group: C 2v. Two non-equivalent lone pairs. Clusters Experimentally observed up to decamer. Titled complex always competed with water dimer. Introduction: Water

6. Binary aqueous solution of HFIP (fluoroalcohol) stabilizes α -helical structure of protein. HFIP is a commonly used solvent for dissolving polymer such as polyethylene terephthalate (PET), a normally difficult-to-dissolve polymer. HFIP can act as both H-bond donor as well as acceptor. IR, Raman, X-ray, NMR, MD simulation Studies are known for the HFIPwater complexes in liquid and gas phase. These studies suggest a very strong bond between HFIP and water. Czarnik-Matusewicz, B.; Pilorz, S.; Zhang, L.-P.; Wu, Y. J. Mol. Struct. 2008, 883-884, 195. Yoshida, K.; Yamaguchi, T. Chem. Phys. 2003, 119, 6132–6142. N. Hirota-Nakaoka and Y. Goto, Bioorg. Med. Chem. 1999, 7,67. R. Rajan and P. Balaram, Int. J. Pept. Protein Res. 1996, 48, 328. Introduction to the HFIP    H 2 O complex: Properties,usefulness and past studies

7. HFIP offers many possibilities for intermolecular interaction. Guess geometries and Structure optimization Different possible structures were considered for the optimization, which converged to three minima. HFIP Surface minima kcal/mol 13-6 14-6 15-6 16*-19 17-7 18-6 19-6 20-6 Surface maxima 2115 2220 23*36 24*56 2515 38 kcal/mol 46 kcal/mol

8. B3LYP/6-31G* MP2/6-311++G** Monomer studies: SC conformer does not exist in supersonic expansions. These structures have high binding energy but there is conformational instability 34 kJ/mol38 kJ/mol 0.6 kJ/mol 29 kJ/mol 34 kJ/mol Guess geometries and Structure optimization

9. MD studies suggest one more minimum for the HFIPwater complex. Exhibits two H-bonding interactions. C-H group acts as hydrogen bond donor. Formation of five-membered ring. AP conformer of HFIP is involved. Therefore, finally two structures were considered for the search of rotational transitions. Guess geometries and Structure optimization

10. At LC-wPBE/6-311++G**Structure 1Structure 2 Binding Energy (kJ/mol) 31.817.6 Dipole moment ( μ a, μ b, μ c ) in Debye 0.5, 1.8, 1.51.9, 0.2, 1.5 Rotational Constants (A, B, C) in MHz 1147.98 986.89 709.22 1053.48 980.63 676.24  0.270.61 The two most stable structures and their properties

11. On the basis of calculated rotational constants, search was started for following sets of lines. At the end, 46 transitions were observed and could be fitted within experimental uncertainty using a semi-rigid rotor Hamiltonian. TransitionsCalculated (MHz)Observed (MHz) 5, 0, 5 <-- 4, 1, 47427.037401.5900 5, 1, 5 <-- 4, 0, 47429.157403.1100 6, 0, 6 <-- 5, 1, 58843.638812.6180 6, 1, 6 <-- 5, 0, 58843.958812.8320 7, 0, 7 <-- 6, 1, 610259.5510223.1295 7, 1, 7 <-- 6, 0, 610259.6010223.1685 8, 0, 8 <-- 7, 1, 711675.3811633.5880 8, 1, 8 <-- 7, 0, 711675.3911633.5880 Search for rotational transitions

12. TransitionsObservedObs-Calc 2, 0, 2 <- 1, 1, 13062.6515-0.0029 2, 1, 2 <- 1, 0, 13250.33600.0080 3, 0, 3 <- 2, 1, 24556.34600.0031 3, 1, 3 <- 2, 0, 24607.49750.0089 4, 0, 4 <- 3, 1, 35987.3295-0.0025 4, 1, 4 <- 3, 0, 35996.9975-0.0008 5, 0, 5 <- 4, 1, 47401.5900-0.0005 5, 1, 5 <- 4, 0, 47403.1100-0.0069 5, 2, 4 <- 4, 1, 38139.86600.0052 5, 2, 3 <- 4, 3, 28434.56100.0015 4, 4, 1 <- 3, 3, 08760.1525-0.0008 4, 4, 0 <- 3, 3, 08799.4635-0.0050 6, 0, 6 <- 5, 1, 58812.61800.0044 6, 1, 6 <- 5, 0, 58812.8320-0.0001 4, 4, 1 <- 3, 3, 18852.7780-0.0031 8, 0, 8 <- 7, 1, 7 11633.58800.0019 8, 1, 8 <- 7, 0, 7 11633.5880-0.0019 7, 3, 4 <- 6, 4, 3 12015.09960.0000 8, 1, 7 <- 7, 2, 6 12333.25350.0002 8, 2, 7 <- 7, 1, 6 12333.63450.0016 9, 0, 9 <- 8, 1, 8 13044.02700.0005 9, 1, 9 <- 8, 0, 8 13044.02700.0001 10, 0, 10 <- 9, 1, 9 14454.4560 0.0002 10, 1, 10 <- 9, 0, 9 14454.4560 0.0001 4, 3, 1 <- 3, 2, 28988.1890-0.0072 5, 3, 3 <- 4, 2, 29126.4780-0.0030 6, 1, 5 <- 5, 2, 49507.5520-0.0004 6, 2, 5 <- 5, 1, 49521.1735-0.0104 6, 2, 4 <- 5, 3, 310103.42650.0029 7, 0, 7 <- 6, 1, 610223.1295-0.0038 7, 1, 7 <- 6, 0, 610223.16850.0058 5, 4, 2 <- 4, 3, 110257.78750.0013 5, 3, 2 <- 4, 2, 210264.5755-0.0022 6, 3, 4 <- 5, 2, 310354.04350.0022 5, 2, 3 <- 4, 1, 310397.9045-0.0002 5, 1, 4 <- 4, 0, 410516.29250.0016 5, 4, 1 <- 4, 3, 110523.6245-0.0001 5, 2, 4 <- 4, 1, 410526.53650.0058 5, 3, 3 <- 4, 2, 310539.29200.0022 5, 4, 2 <- 4, 3, 210715.22700.0041 7, 1, 6 <- 6, 2, 510922.3905-0.0010 7, 2, 6 <- 6, 1, 510924.7730-0.0064 5, 5, 1 <- 4, 4, 011066.96350.0009 5, 5, 0 <- 4, 4, 011081.86050.0032 5, 5, 1 <- 4, 4, 1 11106.2760-0.0018 5, 5, 0 <- 4, 4, 1 11121.17250.0000 b-type signals were stronger than c-type. a-type signals were absent. Kisiel’s programs were used for fitting.

13. Experimental Calculated Structure 1 Calculated Structure 2 A/MHz 1134.53898(77)1147.981053.72 B/MHz 989.67594(44)986.88980.53 C/MHz 705.26602(20)709.22675.98 D J /kHz -0.0876(51)-0.02910.6130 D JK /kHz 2.230(39)1.541-2.232 D K /kHz -1.805(29)-1.2023.046 d 1 /kHz 0.0092(27)0.0015-0.242 d 2 /kHz -0.0738(18)-0.05020.03902 RMS (MHz)0.0041 No. of transitions 46 b- & c-type only Dipole Moment b-type transitions were stronger than c-type 0.5, 1.8, 1.51.9, 0.2, 1.5 No a-type transitions (WHY ?) Results and comparisons with theory

14. I.HFIPD 2 O II.HFIPHOD Two isotopologues could be observed Isotopologues Sample preparation of HOD by mixing H 2 O and D 2 O in 1:1 ratio

15. HFIPH 2 O Parent HFIPD 2 O (I) HFIPHOD (II) A /MHz1134.53898(77)1075.1262(10)1110.15554(67) B /MHz 989.67594(44) 983.0710(16) 986.0420(17) C /MHz 705.26602(20) 683.64615(22) 696.72950(21) D J /kHz -0.0876(51) -0.148(25) -0.1737(74) D JK /kHz 2.230(39) 2.43(16) 3.526(89) D K /kHz -1.805(29) -1.91(14) -2.977(86) d 1 /kHz 0.0092(27) 0.029(11)[0.0092] d 2 /kHz -0.0738(18) -0.0861(57) -0.1214(39) RMS /MHz0.00410.0035 0.0042 Transition4630 33 Both the hydrogens of water are identical. Rotational Constants of the isotopologues

16. Both hydrogens are identical ! Vib. Freq. 75 cm-1 ZPE = 0.46 kJ/mol Barrier Height = 0.24 kJ/mol Absence of a-type transition

17. Exp= 3.19588(83) Å Kraitchman’s analysis and the ‘experimental’ structure

18. 18 Exp= 3.88827(70) Å DistancesExperimentalStructure 1Structure 2 CM-H 1 3.19588(83) Å3.1873.229 CM-H 2 3.88827(70) Å3.7124.303 Kraitchman’s analysis and the ‘experimental’ structure

19. Theoretical prediction ExperimentStrucure 1Cal-ExpStrucutre 2Cal-Exp HFIP---H 2 O1134.538981147.98131053.32-81 989.67594986.89-3980.76-9 705.26602709.234676.1-29 HFIP---HOD1110.155541123.34131031.45-79 986.042983.08-3979.95-6 696.7295700.834666.98-30 HFIP---D 2 O1075.12621090.89161000.28-75 983.071981.97973.35-10 683.64615688.14651.5-32

20. ExperimentMP2mp2=fullb2plypB2plypdLC-wPBECAM-B3LYPwB97XD A1134.53898(77)1148.31151.01142.91170.21148.01164.71165.4 B 989.67594(44)986.2988.5977.9979.8986.9982.9977.3 C 705.26602(20)710.5712.4704.9719.3709.2715.2714.1 D J -0.0876(51)-0.007 0.005-0.004-0.0290.010-0.010 D JK 2.230(39)1.1441.1351.1161.0071.5421.0181.142 D K -1.805(29)-0.869-0.864-0.795-0.800-1.203-0.756-0.865 d 1 0.0092(27)-0.003 -0.0040.0010.002-0.005-0.0001 d 2 -0.0738(18)-0.038 -0.037-0.030-0.050-0.033-0.035 Which one is better ? Ab initio Calculations

21. A very strong Hydrogen Bonding Structure 1 Structure 2 AIM analysis There is linear correlation between Electron density at intermolecular BCP (green dots) and binding energy 0.0132 0.0137 0.0348

22. One H-bond in Structure 1 Overlapping of Oxygen’s lone pair of water with O-H(  *) of HFIP stabilize the complex by 21.2 kcal/mol. Two H-bonds in Structure 2 Overlapping of Oxygen’s lone pair of water with C-H(  *) of HFIP stabilize the complex by 1.8 kcal/mol. Overlapping of Oxygen’s lone pair of HFIP with O-H(  *) of HFIP stabilize the complex by 0.88 kcal/mol. NBO analysis A very strong Hydrogen Bonding

23. Rotational spectra of HFIP---water and its two isotopologues have been observed and fitted within experimental uncertainty. The fitted rotational constants confirm that the HFIP---water complex exists as structure 1. A very strong H-bounded complex. Summary

24. Acknowledgements: All labmates. Funding: