Internal Rotation in CF3INH3 and CF3I N(CH3)3

Probed by CP-FTMW SpectroscopyNicholas R. Walker, Susanna L. Stephens, Anthony C. Legon

66th OSU International Symposium on Molecular Spectroscopy

1

19th June, 2011.

Rcm

N I

Engineering and Physical Sciences Research Council

Introduction

1) Halogen bond describes attractive interaction between electron donor (e.g. NH3) and a halogen atom.

2) Significance of IN interaction in solid-state technology exploiting halogen bonds. Iodoperfluoroalkanes are standard “building blocks” because electron-withdrawing CF2 units allow stronger interactions of the iodine atom.

3) CF3INH3 and CF3IN(CH3)3 excellent targets for CP-FTMW spectroscopy. Extensive hyperfine structure, many bands between 8-18 GHz.

Power divider

SPST switch

MixerMixer

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

OCS

590 790 990 1190 Units are microsecondstime

FID intensity

Multi-chirp excitation

8000 10000 12000 14000 16000 18000Energy/MHz

13840 13860 13880 13900Energy/MHz

CF3I

CF3INH3 ??

8000 10000 12000 14000 16000 18000Energy/MHz

13840 13860 13880 13900Energy/MHz

CF3INH3

Rcm

N I

[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.

C3v Symmetric top ?Internal rotation?

22220R )1())1()(( JJDJJKmDmDKDBH JJKmmJJΚ

The Hamiltonian

13850 13860 13870

Energy/MHz

Exp.

Sim. [80 kHz FWHM]

Energy/MHz13850 13855 13860 13865 13870 13875

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.

CF3I14NH3

10370 10380 10390

Energy/MHz

Sim.

Exp.

CF3I14NH3

10150 10160 10170

Energy/MHz

Exp.

Sim.

CF3I15NH3

A species CF3I15NH3 CF3I14NH3

/ MHz 848.26550(19)a 866.68032(21)DJ / kHz 0.1041(15) 0.0988(17)

DJK / kHz 1.230(37) 1.531(16) / MHz 2229.944(77) 2230.241(90) / MHz 3.337(51)N 76 189r.m.s/ kHz 6.7 11.6E species / MHz 848.26550b 866.68032c

DJ / kHz 0.1060(12) 0.0931(12)

DJK / kHz 1.285(31) 1.489(33)

DJm / kHz 36.81(34) 39.76(38)

DJKm / kHz 11.204(36) 11.365(39) / MHz 2230.186(66) 2230.124(75) / MHz 3.151(42)N 154 282r.m.s/kHz 7.4 11.1

(I)aa(N)aa

(N)aa

0B

(I)aa

0B

a Numbers in parentheses are one standard deviation in units of the last significant figure. b Fixed to the value of B0 determined for CF3I

15NH3. c Fixed to the value of B0 determined for CF3I

14NH3.

A species CF3I15N(CH3)3 CF3I14N(CH3)3 CF3I14N(CH3)3CP-FTMW CP-FTMW CP-FTMW

( < 10 GHz) / MHz 437.88712(19)a 440.74496(11) 440.74496b

DJ 102 / kHz 2.793(37) 2.950(30) 2.950 b

/ MHz 2240.40(20) 2241.61(17) 2241.61 b

/ MHz 4.761c 4.761(88)N 318 452 74r.m.s/ kHz 32.2 18.9 11.8

E species / MHz 437.88712d 440.74496e

DJ 102 / kHz 2.96(10) 2.891(58)

DJm / kHz 29.06(49) 29.71(31)

DJKm / kHz 1.691(45) 1.698(38) / MHz 2240.70(50) 2241.62(47) / MHz 4.761c

N 147 201r.m.s/kHz 26.3 22.3

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.

0B

(I)aa(N)aa

0B

(I)aa(N)aa

Rcm

N I

2ICF

2ICF

2NH

2NH

2 sin2

cos12

sin2

cos12

3333aabbccbb

cmSbb

IIIIRMI

3.054 Å > rNI > 3.034 Å for CF3INH3 where 30>>0 and 8>>0

2.790 Å > rNI > 2.769 Å for CF3IN(CH3)3 where 30>>0 and 8>>0

Structure

(N)aa implies = 20.5(12) for CF3INH3 and = 16.2(20) for CF3IN(CH3)

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.

rNI=2.84(3) Å.

rNI close to 2.80 Å.

2.790 Å > rNI > 2.769 Å for CF3IN(CH3)3 where 30>>0 and 8>>0

3.054 Å > rNI > 3.034 Å for CF3INH3 where 30>>0 and 8>>0

Correspondence with solid state

Acknowledgements

University of BristolSusanna StephensTony C. LegonRuth OvalColin M. Western

University of VirginiaBrooks H. PateStephen T. Shipman

Financial Support

Engineering and Physical Sciences Research Council

University of SheffieldMichael Hippler

8000 10000 12000 14000 16000 18000Energy/MHz

CF3I14N(CH3)3

CF3I

8790 8800 8810 8820 8830 8840Energy/MHz

Exp.

A and E species sim.

CF3I14N(CH3)3