1. Internal Rotation in CF 3 I  NH 3 and CF 3 I  N(CH 3 ) 3 Probed by CP-FTMW Spectroscopy Nicholas R. Walker, Susanna L. Stephens, Anthony C. Legon 66 th OSU International Symposium on Molecular Spectroscopy 1 19 th June, 2011.   R cm N I Engineering and Physical Sciences Research Council

2. Introduction 1)Halogen bond describes attractive interaction between electron donor (e.g. NH 3 ) and a halogen atom. 2)Significance of I  N interaction in solid-state technology exploiting halogen bonds. Iodoperfluoroalkanes are standard “building blocks” because electron-withdrawing CF 2 units allow stronger interactions of the iodine atom. 3) CF 3 I  NH 3 and CF 3 I  N(CH 3 ) 3 excellent targets for CP-FTMW spectroscopy. Extensive hyperfine structure, many bands between 8-18 GHz.

3. Power divider SPST switch Mixer Low noise amplifier Pin diode limiter Adjustable attenuator 5W Power amplifier AWG (0.5-12 GHz) Oscilloscope (0-12 GHz) 10 MHz reference frequency PDRO (19.00 GHz) 7.0-18.5 GHz 7.0-18.5 GHz 12.2 GHz Low-pass band filter CP-FTMW Spectrometer 300 W TWT Amplifier

4. OCS Multi-chirp excitation

5. CF 3 I CF 3 I  NH 3 ?? CF 3 I  NH 3

6. [1] G. T. Fraser, F. J. Lovas, R. D. Suenram, D. D. Nelson, Jr. and W. Klemperer, J. Chem. Phys. 1986, 84, 5983-5988. [2] G. Valerio, G. Raos, S. V. Meille, P. Metrangolo and G. Resnati, J. Phys. Chem. A, 2000, 104, 1617-1620. C 3v Symmetric top ? Internal rotation? The Hamiltonian

7. 138501386013870 Energy/MHz Exp. Sim. [80 kHz FWHM] Energy/MHz 138501385513860138651387013875 A species sim. E species sim. Total (A and E) sim. Simulation and fitting using PGOPHER (2010, version 7.0.103), a Program for Simulating Rotational Structure, C. M. Western, University of Bristol, http://pgopher.chm.bris.ac.uk. http://pgopher.chm.bris.ac.uk CF 3 I  14 NH 3

8. 10150 10160 10170 Energy/MHz Exp. Sim. CF 3 I  15 NH 3

9. A species CF 3 I  15 NH 3 CF 3 I  14 NH 3 / MHz 848.26550(19) a 866.68032(21) D J / kHz 0.1041(15)0.0988(17) D JK / kHz 1.230(37)1.531(16) / MHz  2229.944(77)  2230.241(90) / MHz  3.337(51) N 76189  r.m.s / kHz 6.711.6 E species / MHz 848.26550 b 866.68032 c D J / kHz 0.1060(12)0.0931(12) D JK / kHz 1.285(31)1.489(33) D Jm / kHz 36.81(34)39.76(38) D JKm / kHz 11.204(36)11.365(39) / MHz  2230.186(66)  2230.124(75) / MHz  3.151(42) N 154282  r.m.s /kHz 7.411.1 a Numbers in parentheses are one standard deviation in units of the last significant figure. b Fixed to the value of B 0 determined for CF 3 I  15 NH 3. c Fixed to the value of B 0 determined for CF 3 I  14 NH 3.

10. A speciesCF 3 I  15 N(CH 3 ) 3 CF 3 I  14 N(CH 3 ) 3 CP-FTMW ( < 10 GHz) / MHz 437.88712(19) a 440.74496(11)440.74496 b D J  10 2 / kHz 2.793(37)2.950(30) 2.950 b / MHz  2240.40(20)  2241.61(17)  2241.61 b / MHz  4.761 c  4.761(88) N 318452 74  r.m.s / kHz 32.218.9 11.8 E species / MHz 437.88712 d 440.74496 e D J  10 2 / kHz 2.96(10)2.891(58) D Jm / kHz 29.06(49)29.71(31) D JKm / kHz 1.691(45)1.698(38) / MHz  2240.70(50)  2241.62(47) / MHz  4.761 c N 147201  r.m.s /kHz 26.322.3 a Numbers in parentheses are one standard deviation in units of the last significant figure. b Fixed to the values determined by fitting all transitions in the broadband spectrum. c Fixed to =  4.761 MHz, determined by fitting to selected transitions below 10 GHz.

11. 3.054 Å > r N  I > 3.034 Å for CF 3 I  NH 3 where 30  >  >0  and 8  >  >0  2.790 Å > r N  I > 2.769 Å for CF 3 I  N(CH 3 ) 3 where 30  >  >0  and 8  >  >0  Structure implies  = 20.5(12)  for CF 3 I  NH 3 and  = 16.2(20)  for CF 3 I  N(CH 3 )

12. V. Amico, S. V. Meille, E. Corradi, M. T. Messina and G. Resnati, J. Am. Chem. Soc. 1998, 120, 8261- 8262. E. Corradi, S. V. Meille, M. T. Messina, P. Metrangolo and G. Resnati, Tetrahedron Lett. 1999, 40, 7519-7523. r N  I =2.84(3) Å. r N  I close to 2.80 Å. 2.790 Å > r N  I > 2.769 Å for CF 3 I  N(CH 3 ) 3 where 30  >  >0  and 8  >  >0  3.054 Å > r N  I > 3.034 Å for CF 3 I  NH 3 where 30  >  >0  and 8  >  >0  Correspondence with solid state

13. Acknowledgements University of Bristol Susanna Stephens Tony C. Legon Ruth Oval Colin M. Western University of Virginia Brooks H. Pate Stephen T. Shipman Financial Support Engineering and Physical Sciences Research Council University of Sheffield Michael Hippler

14. CF 3 I  14 N(CH 3 ) 3 CF 3 I 879088008810882088308840 Energy/MHz Exp. A and E species sim. CF 3 I  14 N(CH 3 ) 3