1. Michal M. Serafin, Sean A. Peebles
C-H HYDROGEN BONDING INTERACTIONS IN THE CARBONYL SULFIDE-TRIFLUOROMETHANE DIMER
Michal M. Serafin, Sean A. Peebles
Department of Chemistry, 600 Lincoln Avenue, Eastern Illinois University, Charleston, IL USA

2. Introduction
Systematic study of HCF3 complexes to characterize weak intermolecular forces
Complex splitting pattern in HCCH-HCF3 dimer not fully understood
OCS-HCF3 is a less complex system since carbonyl sulfide is not symmetric – possibly providing a simpler spectrum

3. Ab Initio Structure
2.62Å
3.48 Å
60.8
74.8
MP2/ G(2d,2p)

4. Theoretical Results
Theoretical rotational constants and dipole data provided by Gaussian 98
Near prolate asymmetric top =
Theoretical Rotational Constant (MHz)
Theoretical Dipole Moment Components (Debye)
A= 4637
μa= 0.84
B= 861
μb= 0.88
C= 834
μc= 0.00
μtot=1.21

5. Experimental Details
Balle-Flygare type Fourier transform microwave (FTMW) spectrometer, General Valve (series 9), operating on the 6-15GHz region
Sample contains approx. 1.5% of both OCS and HCF3 filled to a backing pressure of ~2-2.5 bar of He/Ne
Stark effect experiments performed to acquire dipole data

6. Spectroscopic Constants
Parameter
Experimental Value
Theoretical
A / MHz
(25)
4637
B / MHz
(27)
861
C / MHz
(27)
834
∆J / kHz
(30)
∆JK / kHz
(22)
∆K / kHz
88.8 (5)
J / kHz
(20)
K / kHz
-57.0 (14) N 44
∆υrms / kHz
2.1

7. Dipole Data & Planar Moments
Dipole Component
Experimental Value (Debye)
Theoretical Value (Debye) μa
0.827 (4)
μa= 0.84 μb
0.858 (7)
μb= 0.88 μc
0.000
μc= 0.00
μtot
1.192 (6)
μtot=1.21
Planar Moment
Experimental Value
Paa / amu Å2
(22)
Pbb / amu Å2
(22)
Pcc / amu Å2
(22)
Pbb(HCF3 monomer) = 44.5 amu Å2

8. Isotopic Results
O13CS-HCF3
OC34S-HCF3
OCS-H13CF3
A / MHz
(25)
(16)
(12)
B / MHz
(5)
(8)
(7)
C / MHz
(4)
(7)
(4)
∆J / kHz
2.887 (6)
2.852 (8)
2.907 (6)
∆JK / kHz
-2.14 (4)
-3.18 (21) a)
∆K / kHz
88.8 (5)
88.8 a)
J / kHz
0.279 (4)
0.262 (7)
0.284 (5)
K / kHz
-57.0 a) N 30 15
∆υrms / kHz
2.1
3.0
2.7
Pcc / amu Å2
(7)
(6)
(5)
a) Constants fixed at the value obtained for the normal isotopomer

9. Structure 80(8) 74.8 60.2(4) 60.8 3.63 (5) Å 3.48 Å
MP2/ G(2d,2p) values

10. Conclusion Complex splitting pattern not observed
Observed spectrum consistent with ab initio structure
Next project: DFM-OCS dimer

11. OCS-H2CF2: Ab initio structure
MP2/ G(2d,2p)
3.45Å
2.65Å
74.9
63.8 

12. OCS-H2CF2: Experimental Results
Parameter
MP2 Normal Isotope
OCS-H2CF2
O13CS-H2CF2
OC34S-H2CF2
A / MHz
4480
(27)
(9)
(18)
B / MHz
1332
(27)
(7)
(9)
C / MHz
1265
(27)
(7)
(7) N -- 42 25 15
∆υrms / kHz
1.7
3.0
Pcc / u Å2
(18)
(2)
(3)
Paa H2CF2 / u Å2
46.066
Dipole Data
Theoretical Dipole
Normal Isotope
μa / Debye
1.18
(16)
μb / Debye
0.52
0.492 (6)
μc / Debye
0.00
μtot / Debye
1.29
1.236 (3)

13. Acknowledgements
American Chemical Society, Petroleum Research Fund, No GB6
Dr. E. M. Treadwell