S TRUCTURE D ETERMINATION AND CH···F I NTERACTIONS IN H 2 C=CHF···H 2 C=CF 2 B Y F OURIER - T RANSFORM M ICROWAVE S PECTROSCOPY Rachel E. Dorris, Rebecca A. Peebles, Sean A. Peebles Department of Chemistry, Eastern Illinois University, Charleston, IL 61920

CH···F I NTERACTIONS 2 Christenholz, et al., J. Mol. Spec. 280 (2012) (5) Å 3.011(3) Å chlorofluoromethane (CFM)··· vinyl fluoride (VF) Christenholz, et al., J. Phys. Chem. A 118 (2014) (4) Å 2.521(27) Å difluoromethane (DFM)··· vinyl fluoride (VF) difluoroethylene (DFE)··· HF Leung, et al., J. Chem. Phys. 131 (2009) (4) Å (3) Å vinyl fluoride (VF)··· HF Cole, et al., Chem. Phys. Lett. 400 (2004) (14) Å Å vinyl fluoride (VF)··· difluoroethylene (DFE) TOP SIDE TOP

A B I NITIO S TRUCTURES VF···DFE 3 Perpendicular (side)Parallel (top) A / MHz B / MHz C / MHz µ a / D µ b / D µ c / D ΔE / cm Gaussian 03: MP2/ G(2d,2p)

E XPERIMENTAL H 2 C=CHF···H 2 C=CF 2 Scanned on 480 MHz CP-FTMW 7.5 – 19 GHz, 2000 shots Sample: ~1% each of vinyl fluoride and 1,1- difluoroethylene in He/Ne in 1 L tank – delivered at ~2.5 bar Cavity FTMW Confirmed assigned transitions from scan Measured four 13 C isotopes in natural abundance 4

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H 2 C 2 HF··· H 2 C 2 F 2 H 2 13 CCHF··· H 2 C 2 F 2 H 2 C 13 CHF··· H 2 C 2 F 2 H 2 C 2 HF··· H 2 13 CCF 2 H 2 C 2 HF··· H 2 C 13 CF 2 A / MHz (94) (47)6590.7(10) (70) (71) B / MHz (13) (37) (56) (63) (48) C / MHz (12) (40) (58) (54) (72) Δ J / kHz0.9088(20) Δ JK / kHz10.891(19) Δ K / kHz δ J / kHz0.0485(20) N RMS / kHz κ −0.9695−0.9705−0.9700−0.9682− P cc / u Å (1)1.904(3)1.895(1)1.889(5)1.866(5) S PECTROSCOPIC C ONSTANTS N ORMAL AND I SOTOPIC 6 PerpendicularParallel A / MHz B / MHz C / MHz

D IPOLE M OMENTS 7 PerpendicularParallel µ a / D µ b / D µ c / D a b μ a = (18) D μ a = 0.84 D μ b = (80) D μ b = 0.10 D Experiment Ab initio QSTARK: Kisiel, et al., Chem. Phys. Lett., 325, (2000), 523. Projected µ a = 0.80 D Induced dipole ~0.1 D

S TRUCTURE D ETERMINATION 8 Ab initio Inertial fit 2.43 Å 2.463(16) Å 2.52 Å 2.496(9) Å 152.3° 150.8(11)° 138.6° (19)° Adjusted Parameters R (C 1, C 4 )5.475(12) Å 7.220(66)° 85.01(52)° Structure fit used A and B rotational constants Tried all pairs of rotational constants Many ways of building the structure Varied parameters between carbon atoms Close to ab initio structure Z. Kisiel, J. Mol. Spectrosc. 218, (2003).

K RAITCHMAN C OORDINATES 9 Inertial fit Kraitchman Literature R (C 1, C 3 ) 4.160(12) Å 4.179(5) Å 1.559(23) Å 1.315(1) Å 1.306(3)Å 1.329(6) Å Lide, D. R.; Christenson, D.; Spectrochem. Act. 17 (1961) 665. Laurie, V. W.; Pence, D. T.; J. Chem. Phys. 38 (1963) a b

C OMPARISON WITH OTHER COMPLEXES (16) Å 2.496(9) Å VF···DFE Binding Energies E B (kJmol -1 ) # of “interactions” VF···CFM 8.66(4)3 VF···DFM 9.1(3)3 VF···DFE 5.3(2) (5)Å 3.011(3)Å VF···CFM 2.83(4) Å 2.521(27) Å VF···DFM Pseudo diatomic model Millen, D. J.; Can. J. Chem. 63 (1985) Balle, T. J.; Campbell, E. J.; Keenan, M. R.; Flygare, W. H. A.; J. Chem. Phys. 72 (1980) 922.

F UTURE W ORK Ab initio BSSE ZPE Very dense remaining spectrum Cut VF monomer, DFE···Ne, water dimer Other VF···DFE dimer VF dimer, VF···Ne, VF···H 2 O, DFE···H 2 O 11

A CKNOWLEDGMENTS NSF RUI program – grant CHE Previous group members: Ashley Anderton, Cori Christenholz, Anu Akmeemana, Nate Ulrich Current group members: Seri Kamari, Samee Dikkumbura 12

(16) Å 2.496(9) Å (105)° (19)° VF···DFE 2.764(5)Å 3.011(3)Å 95.37(4)° (12)° VF···CFM 2.83(4) Å 2.521(27) Å 90.6(3)° 124.2(7)° VF···DFM k s (Nm -1 ) VF···CFM 5.88(2) VF···DFM 6.8(1) VF···DFE 3.19(6)

(16) Å 2.496(9) Å (105)° (19)° VF···DFE difluoroethylene (DFE)··· HF Leung, et al., J. Chem. Phys. 131 (2009) (4) Å (3) Å ° vinyl fluoride (VF)··· HF Cole, et al., Chem. Phys. Lett. 400 (2004) (14) Å Å 121.4°

15 Frequency (MHz)

S CHEMATIC OF M ICROWAVE C IRCUIT AFG3251 Arbitrary Function Generator DC-240 MHz HP8673G MW Synthesizer GHz Amp RF amp Tektronix TDS5054B 500 MHz Oscilloscope Vacuum chamber LNA Molecular expansion Chirp 16

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18 VoltageFrequency VoltageFrequency lines read in 45 lines in the fit

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