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

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.

Next Steps… Additional dimers Move towards larger clusters

Predicted DFE-CO2 Structure Observed side-bonded structures Initial prediction for DFE-CO2 Gaussian 09: MP2/6-311++G(2d,2p)

Oscilloscope (for data collection) Tektronix TDS5054B 500 MHz Oscilloscope AFG3251 Function Generator (0-240 MHz) HP8673G MW Synthesizer 2-26.5 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.

Assignment Process Observed “Stacked” prediction “Side” prediction

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

Fitted Constants 0+ 0- A / MHz 3810.154(14) 3809.984(14) B / MHz   0+ 0- A / MHz 3810.154(14) 3809.984(14) B / MHz 1614.4404(25) 1614.4991(21) C / MHz 1456.786(14) 1456.867(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 167.828(97) DE / MHz 333.2433(19) N 51 RMS / kHz 2.2

Fitted Constants 0+ 0- A / MHz 3810.154(14) 3809.984(14) B / MHz   0+ 0- A / MHz 3810.154(14) 3809.984(14) B / MHz 1614.4404(25) 1614.4991(21) C / MHz 1456.786(14) 1456.867(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 167.828(97) DE / MHz 333.2433(19) N 51 RMS / kHz 2.2

(Very) preliminary barrier = 42 cm-1 Fitted Constants   0+ 0- A / MHz 3810.154(14) 3809.984(14) B / MHz 1614.4404(25) 1614.4991(21) C / MHz 1456.786(14) 1456.867(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 167.828(97) DE / MHz 333.2433(19) N 51 RMS / kHz 2.2 (Very) preliminary barrier = 42 cm-1

Structure 0+ 0- A / MHz 3810.154(14) 3809.984(14) 3734.7 8002.3   0+ 0- A / MHz 3810.154(14) 3809.984(14) 3734.7 8002.3 B / MHz 1614.4404(25) 1614.4991(21) 1559.1 868.2 C / MHz 1456.786(14) 1456.867(14) 1403.4 783.2 Paa / u Å2 263.655(2) 263.637(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: MP2/6-311++G(2d,2p)

Structure Paa for DFE = 85.30534(4) u Å2 m for DFE = 2.42 D 0+ 0-   0+ 0- A / MHz 3810.154(14) 3809.984(14) 3734.7 8002.3 B / MHz 1614.4404(25) 1614.4991(21) 1559.1 868.2 C / MHz 1456.786(14) 1456.867(14) 1403.4 783.2 Paa / u Å2 263.655(2) 263.637(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 = 85.30534(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: MP2/6-311++G(2d,2p)

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.

Ees Eind Edisp Eex ESAPT EMP2 (BSSE) X…CO2 [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.

Building up CO2 solvation shells 363 cm-1 0 cm-1 319 cm-1 24 cm-1 MP2/6-311++G(2d,2p) using Gaussian 09

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

  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 1552.1048(9) 1169.4589(4) 847.2575(3) 351.5135(3) 244.9746(3) 80.6342(3) Strongest Less Strong Weak 1660.3513(1) 1109.7647(1) 785.7775(1) 397.08505(7) 246.07289(7) 58.30788(7) Medium Stronger

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?

Acknowledgements National Science Foundation Pate Group (UVa) RUI1214070 (2012-2017) RUI1664900 (2017-2020) Pate Group (UVa) Eastern Illinois University spcat 

TRIMER2 – prelim fit 10000 A / /MHz 1660.35130(13) 1 20000 B / /MHz 1109.76472(10) 2 30000 C / /MHz 785.77746(10) 3 200 DJ / /MHz -0.0015444(41) 4 1100 DJK / /MHz 0.0003469(68) 5 2000 DK / /MHz -0.004195(14) 6 40100 dj / /kHz -0.37274(76) 7 41000 dk / /kHz -1.4705(55) 8 TRIMER1 – prelim fit 10000 A / /MHz 1552.10482(85) 1 20000 B / /MHz 1169.45892(35) 2 30000 C / /MHz 847.25746(28) 3 200 DJ / /MHz -0.002092(10) 4 1100 DJK / /MHz 0.003866(54) 5 2000 DK / /MHz -0.00724(17) 6 40100 dj / /kHz -0.5918(76) 7 Trimer spectra uncut

  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

Trimer! I II Observed A / MHz 1623.4 1626.8 1552.10482(85) B / MHz   I II Observed A / MHz 1623.4 1626.8 1552.10482(85) B / MHz 1171.2 922.9 1169.45892(35) C / MHz 881.4 588.8 847.25746(28) Paa / u Å2 346.8 547.6 351.51351(25) Pbb / u Å2 226.6 310.7 244.97460(25) Pcc / u Å2 84.7 0.0 80.63421(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

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. 15. e Ref. 16. 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