1. Weak Interactions and CO2  Microsolvation in the cis-1,2-difluoroethylene...CO2  Complex
Rebecca A. Peebles,a Prashansa B. Kannangara,a Brooks H. Pate,b William C. Trendell,a Sean A. Peeblesa
a Department of Chemistry, Eastern Illinois University, Charleston, IL, USA
b Department of Chemistry, University of Virginia, Charlottesville, VA, USA

2. Why CO2? Weak hydrogen bonding
Designing approaches to CO2 sequestration
Properties of supercritical fluid
Microsolvation
Trifluoroethylene
(TFE)
Difluoroethylene
(1,1-DFE)
Fluoroethylene (FE)
VF-CO2: C. L. Christenholz, et al., J. Phys. Chem. A, 118, (2014), 8765.
DFE-CO2: A. M. Anderton, et al., J. Phys. Chem. A, 120, (2016), 247.
TFE-CO2: R. Dorris, et al, J. Phys. Chem. A, 120, (2016), 7865.

3. Next Steps…
Additional dimers
Move towards larger clusters

4. Predicted DFE-CO2 Structure
Observed
side-bonded
structures
Initial prediction
for DFE-CO2
Gaussian 09: MP2/ G(2d,2p)

5. Oscilloscope (for data collection)
Tektronix TDS5054B
500 MHz Oscilloscope
AFG3251 Function
Generator (0-240 MHz)
HP8673G MW Synthesizer
GHz
Molecular Expansion
Vacuum Chamber
10 W Solid State Amp
Picoammeter
Gas sample injected
Electron gun
power
Diffusion
pump
Supersonic
nozzle
Oscilloscope (for data collection)
Reduced Bandwidth Chirped-Pulse Fourier-Transform Microwave (CP-FTMW) Spectrometer
480 MHz bandwidth, scan in 240 MHz steps
Calculate absolute frequencies and assemble into full 11 GHz spectrum using LabVIEW
Scan a full (10k average) spectrum in 1 day
D. A. Obenchain, A. A. Elliott, A.L. Steber, R. A. Peebles, S. A. Peebles, C. J. Wurrey, G. A. Guirgis, J. Mol. Spectrosc., 261, (2010), 35.

6. Assignment Process
Observed
“Stacked” prediction
“Side” prediction

7. Observed a c a c
Predicted a c
10000
9000
8000
Fitted

8. Fitted Constants 0+ 0- A / MHz 3810.154(14) 3809.984(14) B / MHz0+ 0-
A / MHz
(14)
(14)
B / MHz
(25)
(21)
C / MHz
(14)
(14)
DJ / kHz
3.490(10)
3.451(10)
DJK / kHz
14.940(67)
15.216(60)
DK / kHz
-12.02(41)
dJ / kHz
0.3322(70)
dK / kHz
-12.72(32)
Fac / MHz
(97)
DE / MHz
(19) N 51
RMS / kHz
2.2

9. Fitted Constants 0+ 0- A / MHz 3810.154(14) 3809.984(14) B / MHz0+ 0-
A / MHz
(14)
(14)
B / MHz
(25)
(21)
C / MHz
(14)
(14)
DJ / kHz
3.490(10)
3.451(10)
DJK / kHz
14.940(67)
15.216(60)
DK / kHz
-12.02(41)
dJ / kHz
0.3322(70)
dK / kHz
-12.72(32)
Fac / MHz
(97)
DE / MHz
(19) N 51
RMS / kHz
2.2

10. (Very) preliminary barrier = 42 cm-1
Fitted Constants 0+ 0-
A / MHz
(14)
(14)
B / MHz
(25)
(21)
C / MHz
(14)
(14)
DJ / kHz
3.490(10)
3.451(10)
DJK / kHz
14.940(67)
15.216(60)
DK / kHz
-12.02(41)
dJ / kHz
0.3322(70)
dK / kHz
-12.72(32)
Fac / MHz
(97)
DE / MHz
(19) N 51
RMS / kHz
2.2
(Very) preliminary barrier = 42 cm-1

11. Structure 0+ 0- A / MHz 3810.154(14) 3809.984(14) 3734.7 8002.30+ 0-
A / MHz
(14)
(14)
3734.7
8002.3
B / MHz
(25)
(21)
1559.1
868.2
C / MHz
(14)
(14)
1403.4
783.2
Paa / u Å2
(2)
(2)
274.5
582.1
Pbb / u Å2
83.259(2)
83.258(2)
85.6
63.2
Pcc / u Å2
49.382(2)
49.388(2)
49.7
0.0
ma / D
2.13(3)
2.2
0.02
mb / D
0.00
2.4
mc / D
1.13(4)
1.4
Gaussian 09: MP2/ G(2d,2p)

12. Structure Paa for DFE = 85.30534(4) u Å2 m for DFE = 2.42 D 0+ 0-0+ 0-
A / MHz
(14)
(14)
3734.7
8002.3
B / MHz
(25)
(21)
1559.1
868.2
C / MHz
(14)
(14)
1403.4
783.2
Paa / u Å2
(2)
(2)
274.5
582.1
Pbb / u Å2
83.259(2)
83.258(2)
85.6
63.2
Pcc / u Å2
49.382(2)
49.388(2)
49.7
0.0
ma / D
2.13(3)
2.2
0.02
mb / D
0.00
2.4
mc / D
1.13(4)
1.4
mtot / D
2.41(5)
Paa for DFE = (4) u Å2
m for DFE = 2.42 D
Monomer rotational constants: N. C. Craig, et al, Int. J. Quantum Chem., 95, (2003), 837.
Monomer dipole moment: V. W. Laurie, J. Chem. Phys., 34, (1961), 291.
Gaussian 09: MP2/ G(2d,2p)

13. What’s next? Larger clusters…
(d)
(e)
(a)
(b)
(c)
(i)
(h)
(f)
(g)
What’s next?
Symmetry adapted perturbation theory (SAPT)
Better understanding of energetics
Larger clusters…
Figure adapted from: R. Dorris, et al, J. Phys. Chem. A, 120, (2016), 7865.

14. Ees Eind Edisp Eex ESAPT EMP2 (BSSE)
X…CO [kJ mol-1 ]
X =
Ees
Eind
Edisp
Eex
ESAPT
EMP2 (BSSE)
FE (side)
–8.33 (52.0%)
–1.34 (8.3%)
–6.36 (39.7%)
8.33
–7.70
–6.41
FE (top)
–7.78 (49.7%)
–1.30 (8.2%)
–6.61 (42.1%)
8.03
–7.66
–6.30
FE (stacked)
–6.65 (42.5%)
–0.96 (6.1%)
–8.02 (51.3%)
8.43
–7.19
–6.44
1,1-DFE (top)
–5.69 (44.8%)
–1.00 (7.8%)
–6.02 (47.4%)
6.49
–6.22
–5.10
1,1-DFE (stacked)
–4.43 (34.8%)
–0.78 (6.1%)
–7.50 (59.1%)
7.35
–5.35
–4.86
cis-1,2-DFE (side)
–7.91 (51.0%)
–1.34 (8.6%)
–6.28 (40.5%)
7.99
–7.54
–6.33
cis-1,2-DFE (stacked)
–7.29 (44.6%)
–1.11 (6.8%)
–7.96 (48.7%)
8.38
–7.97
–6.81
TFE (side)
–7.61 (50.2%)
–1.30 (8.5%)
–6.23 (41.3%)
7.82
–7.32
–6.16
TFE (top)
–6.11 (45.7%)
–1.21 (9.0%)
–6.07 (45.3%)
6.78
–6.61
–5.39
TFE (stacked)
–5.84 (41.2%)
–0.87 (6.1%)
–7.47 (52.7%)
7.52
–6.66
–5.69
Table adapted from: R. Dorris, et al, J. Phys. Chem. A, 120, (2016), 7865.

15. Building up CO2 solvation shells
363 cm-1
0 cm-1
319 cm-1
24 cm-1
MP2/ G(2d,2p) using Gaussian 09

16. New Fluoroethylene-CO2 Scan – 1 million FIDs
FE-only lines cut

17. Top-stack
Side-stack
Stack
Side-top
A / MHz
1618.3
1734.3
2933.3
1626.8
B / MHz
1173.9
1107.4
643.5
922.9
C / MHz
881.2
808.4
609.4
588.8
Paa / u Å2
345.9
395.1
721.2
547.6
Pbb / u Å2
227.7
230.1
108.1
310.7
Pcc / u Å2
84.6
61.3
64.2
0.0
ma / D
1.1
0.8
0.03
mb / D
1.0
0.5
1.5
mc / D
0.7
DE / cm-1 24
319
363
(9)
(4)
(3)
(3)
(3)
(3)
Strongest
Less Strong
Weak
(1)
(1)
(1)
(7)
(7)
(7)
Medium
Stronger

18. Summary and Conclusions
cis-1,2-DFE-CO2 is nonplanar
CO2 inversion motion
Work using Meyer’s 1-dimensional model to determine barrier is in progress
Two VF-CO2-CO2 trimers observed
Nearly isoenergetic
Tetramers?

19. Acknowledgements National Science Foundation Pate Group (UVa)
RUI ( ) RUI ( )
Pate Group (UVa)
Eastern Illinois University
spcat 

20. TRIMER2 – prelim fit
A / /MHz (13)
B / /MHz (10)
C / /MHz (10)
DJ / /MHz (41)
DJK / /MHz (68)
DK / /MHz (14)
dj / /kHz (76)
dk / /kHz (55)
TRIMER1 – prelim fit
A / /MHz (85)
B / /MHz (35)
C / /MHz (28)
DJ / /MHz (10)
DJK / /MHz (54)
DK / /MHz (17)
dj / /kHz (76)
Trimer spectra uncut

21. I
Side-top II
End-top
III
Stack IV
Side-end
A / MHz
1618.3
1734.3
2933.3
1626.8
B / MHz
1173.9
1107.4
643.5
922.9
C / MHz
881.2
808.4
609.4
588.8
Paa / u Å2
345.9
395.1
721.2
547.6
Pbb / u Å2
227.7
230.1
108.1
310.7
Pcc / u Å2
84.6
61.3
64.2
0.0
ma / D
1.1
0.8
0.03
mb / D
1.0
0.5
1.5
mc / D
0.7
DE / cm-1 24
319
363

22. Trimer! I II Observed A / MHz 1623.4 1626.8 1552.10482(85) B / MHzI II
Observed
A / MHz
1623.4
1626.8
(85)
B / MHz
1171.2
922.9
(35)
C / MHz
881.4
588.8
(28)
Paa / u Å2
346.8
547.6
(25)
Pbb / u Å2
226.6
310.7
(25)
Pcc / u Å2
84.7
0.0
(25)
ma / D
1.2
0.03
Strongest
mb / D
1.0
1.5
Less Strong
mc / D
0.7
Weak
DE / cm-1
363 I II

23. Table 4 SAPT interaction energy decomposition resultsa (kJ mol–1) and percentage contribution to the attractive interaction (in parentheses) for fluorinated ethylene complexes with CO2. Also included are supermolecular interaction energies (EMP2) and pseudodiatomic approximation (EB) values (where available from experimental studies). See Figure 3 for structures.
a Ees is the electrostatic, Eind the induction, Edisp the dispersion and Eex the exchange-repulsion contributions to the overall SAPT interaction energy (ESAPT). b EMP2 is the BSSE corrected supermolecular interaction energy: EMP2 = E(A…B) – E(A) – E(B), where the energy values are for the dimer and isolated monomers, respectively. c EB is an estimate of the binding energy from spectroscopic data using the pseudodiatomic approximation; see text for details. d Ref e Ref f Currently in progress in our lab; the observed rotational spectrum appears to be consistent with a stacked structure. g The trans-1,2-DFE…CO2 rotational spectrum is expected to be weak since it is formed from two non-polar monomers. h This work.
X…CO2
X =
𝐸 es
𝐸 ind
𝐸 disp
𝐸 ex
𝐸 SAPT a
EMP2b (BSSE)
EBc
VF (side)
–8.33 (52.0%)
–1.34 (8.3%)
–6.36 (39.7%)
8.33
–7.70
–6.41
–5.80(20)d
VF (top)
–7.78 (49.7%)
–1.30 (8.2%)
–6.61 (42.1%)
8.03
–7.66
–6.30
–6.13(10)d
VF (stacked)
–6.65 (42.5%)
–0.96 (6.1%)
–8.02 (51.3%)
8.43
–7.19
–6.44 –
1,1-DFE (top)
–5.69 (44.8%)
–1.00 (7.8%)
–6.02 (47.4%)
6.49
–6.22
–5.10
–5.80(1)e
1,1-DFE (stacked)
–4.43 (34.8%)
–0.78 (6.1%)
–7.50 (59.1%)
7.35
–5.35
–4.86
cis-1,2-DFE (side)
–7.91 (51.0%)
–1.34 (8.6%)
–6.28 (40.5%)
7.99
–7.54
–6.33 –f
cis-1,2-DFE (stacked)
–7.29 (44.6%)
–1.11 (6.8%)
–7.96 (48.7%)
8.38
–7.97
–6.81
– f
trans-1,2-DFE (side)
–7.61 (50.6%)
–1.21 (8.1%)
–6.23 (41.3%)
7.87
–7.18
–6.03
– g
trans-1,2-DFE (top)
–7.99 (49.5%)
–1.42 (8.8%)
–6.74 (41.7%)
8.28
–7.87
–6.45
TFE (side)
–7.61 (50.2%)
–1.30 (8.5%)
7.82
–7.32
–6.16
–7.12(15)h
TFE (top)
–6.11 (45.7%)
–1.21 (9.0%)
–6.07 (45.3%)
6.78
–6.61
–5.39
TFE (stacked)
–5.84 (41.2%)
–0.87 (6.1%)
–7.47 (52.7%)
7.52
–6.66
–5.69