OBSERVATION OF C-H · · · π INTERACTIONS: MICROWAVE SPECTRA AND STRUCTURES

OF THE CH2FX···HCCH (X=F, Cl) WEAKLY BOUND

COMPLEXESLena F. Elmuti, Daniel A. Obenchain, Don L. Jurkowski, Cori L. Christenholz,

Amelia J. Sanders, Rebecca A. Peebles, Sean A. Peebles Department of Chemistry, Eastern Illinois University,

600 Lincoln Avenue, Charleston, IL 61920

Amanda L. Steber, Justin L. Neill, Brooks H. PateDepartment of Chemistry, University of Virginia,

McCormick Rd., PO Box 400319, Charlottesville, VA 22904

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Recent work in C-H···π Interactions

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CHClF2···HCCHa

CH2F2···HCCH

CH2ClF···HCCH

aElmuti, L. F.; Peebles, R. A.; Peebles, S. A.; Steber, A. L.; Neill, J. L.; Pate, B. H. J. Phys. Chem. Chem. Phys. 2011, DOI 10.1039/c1cp20684b

Cl

F

3.061(38) Å

2.730(6) Å

Cl

F

3

CH2ClF···HCCH ab initio Structures MP2/6-311++G(2d,2p) level

A /MHz 5120

B /MHz 1625

C /MHz 1243

EZPE /cm-1 0

A /MHz 9652

B /MHz 1204

C /MHz 1078

EZPE /cm-1 26

a

b

Chlorine out structureChlorine in structure

b

a

4

CH2ClF ··· HCCH Spectrum Measurement

CP-FTMW (University of Virginia)a

7.0-18.0 GHz 350,000 averages 0.75% CH2ClF/ 1.0% HCCH diluted in He, P= 2 atm Fit using AABS package from Kisielb and SPFIT/SPCAT softwarec

Less intense transitions and 13C isotopologues measured on the Balle-Flygare cavity FTMW (Eastern Illinois University)d, e

1.0% CH2ClF/ 1.0% HCCH diluted in He/Ne (17.5%/82.5%) P=2.0-2.5 atm

a Brown, G. G.; Dian, B. C.; Douglass, K. O.; Geyer, S. M.; Shipman, S. T.; Pate, B. H. Rev. Sci. Instrum. 2008, 79, 053103bKisiel, Z.; Pszczolkowski, L.; Medvedev I.R.; Winnewisser, M.; De Lucia, F. C.; Herbst, C. E. J. Mol. Spec. 2005, 233, 231-243cPickett, H. M. J. Mol. Spec. 1991, 148, 371dBalle, T. J.; Flygare, W. H. Rev. Sci. Instrum. 1981, 52, 33e Newby, J. J.; Serafin, M. M.; Peebles, R. A.; Peebles, S. A. Phys. Chem. Chem. Phys. 2005, 7, 487

5

CH2ClF 111 ← 202

5/2 ← 7/2S/N ≈ 2800

CH2ClF···HCCH303 ← 202

9/2 ←7/2S/N ≈ 250

CH235ClF···HCCH

303-202

CH237ClF···HCCH

322-221

CH2ClF···HCCH Spectrum

6

CH2ClF· · ·HCCH Constants  

Ab initio Chlorine in

CH235ClF···

H12C12CHCH2

37ClF··· H12C12CH

CH235ClF···

H13C13CH CH2

37ClF··· H13C13CH

A / MHz 5120 5262.899(14) 5139.79(12) 5229.361(21) 5108.535(24)B / MHz 1625 1546.8071(10) 1538.2279(15) 1471.2616(11) 1462.4085(11)C / MHz 1243 1205.4349(7) 1193.6843(10) 1157.3986(7) 1145.9242(8)χaa / MHz 24.19 28.497(5) 22.270(7) 28.362(8) 22.096(8)χbb / MHz –60.13 –65.618(13) –51.496(22) –65.474(21) –51.337(20)χcc / MHz 35.94 37.121(8) 29.226(14) 37.112(13) 29.240(12)χab / MHz –22.2007 –22.2007 –18.1583 –22.2007 –18.1583

Na – 71 39 46 43Δνrms/ kHzb – 5.5 5.8 2.8 4.5

Pcc / uÅ2 1.565 1.7502(4) 1.7478(15) 1.7461(5) 1.7426(5)

a number of fitted transitionsb Δνrms=√(∑(νobs-νcalc)2/N)c Blanco, S.; Lesarri. A.; López, J. C.; Alonso, J. L.; Guarnieri, A. J. Mol. Spec. 1995, 174, 397

Pcc (CH2ClF) = 1.6092(1) uÅ2 c

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CH2ClF···HCCH StructureInertial Fit

“Best” a

Ab initio

Chlorine in

R|||…C / Å3.605(4) 3.476

θC–|||…C / °73.9(9) 73.6

θ|||…C–Cl / °91.87(27) 94.3

RCl…H / Å 3.207(22) 3.138

R|||…H / Å 3.236(6) 3.101

θC–H…||| / ° 101.0(1) 101.2

θC–H…Cl / ° 109.0(1.0) 110.1

3.207(22) Å

RH…p = 3.236(6) ÅqC-H…p = 101.0(1)°

91.87(27)°

73.9(9)°

3.605(4) Å

109.0(10)°

85.2(22)°

Cl

F

a average of the structures produced by fitting (Ia, Ib, Ic), (Ia, Ib), (Ia, Ic), and (Ib, Ic) in STRFITQ bΔνrms=√(∑(νobs-νcalc)2/N)

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CH2F2···HCCH Predictions

A /MHz 11211

B /MHz 1703

C /MHz 1493

EZPE /cm-1 0

A /MHz 8121

B /MHz 2067

C /MHz 1838

EZPE /cm-1 64

A /MHz 10588

B /MHz 1498

C /MHz 1323

EZPE /cm-1 165

MP2/6-311++G(2d,2p) level

1 imaginary frequency 1 imaginary frequency

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CH2F2···HCCH Spectrum Measurement

CP-FTMW at Eastern Illinois University1.5% CH2F2/ 1.5% HCCH in 5 bar He/Ne, 1.6 atm backing pressure480 MHz Chirp, 1000 averages7.0 -15.6 GHz

Balle-Flygare FTMW Spectrometer at Eastern Illinois Universitya

aObenchain, D.A.; Elliott, A.A.; Steber, A.L.; Peebles, R.A.; Peebles, S.A. Wurrey, C.J.; Guirgis, G.A. J. Mol. Spec. 2010, 261, 35-40

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CH2F2···HCCH Spectrum

CH2F2···HCCHCH2F2···H2Oa

(CH2F2)3b

(CH2F2)2c

a Caminati,W.; Melendra, S; Rossi, I.; Favero, P. G. J. Am. Chem. Soc. 1999, 121, 10098b Blanco, S.; Melandri, S.; Ottaviani, P. Caminati, W. J. Am. Chem. Soc. 2007, 129 (9), 2700c Blanco, S.; López, J. C.; Lesarri, A.; Alonso, J. L. J. Mol. Struct. 2002, 612, 255

1000 avg scan1.5% CH2F2

1.5% HCCH in 5 bar He/Ne

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From the original 1000 average scan

Only a-types were visible in the original scan

Potential b-type transitions were found in a 2000 average scan with a smaller chirp

(80-120 MHz)

13CH2F2···HCCH Isotopologue

12CH2F2···H12C12CH303-202

13CH2F2···H12C12CH303-202

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CH2F2···HCCH ConstantsParameter

Ab initio MP2/

6-311++G(2d,2p)CH2F2···HCCH 13CH2F2···HCCH CH2F2···H13C13CH

A /MHz 11211 11716.8028(18) 11687.6000(24) 11555.6991(20)

B /MHz 1704 1624.083(5) 1619.8958(8) 1553.561(5)C /MHz 1493 1440.007(5) 1436.3245(8) 1381.977(5)

Δνrms /kHza - 2.18 2.86 3.44

Nb - 29 12 29

Paa /uÅ2 295.0 309.5006(14) 310.29879(25) 323.6311(16)

Pbb /uÅ2 43.42 41.4554(14) 41.55697(25) 42.0617(16)

Pcc /uÅ2 1.655 1.6774(14) 1.68365(25) 1.6724(16)

Pcc (CH2F2) = 1.6512(1) uÅ2 c

aΔνrms=√(∑(νobs-νcalc)2/N)bnumber of fitted transitionscHirota, E.; Tanaka, T.; Sakakibara, A.; Ohashi, Y.; Morino, Y. J. Mol. Spec. 1970, 34, 222

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CH2F2···HCCH Stark Effects

Transition 105 x (Δν/E2) obs.105 x (Δν/E2)

calc.202←101 |M|= 0 -3.3840 -3.4079

202←101 |M|= 1 2.5522 2.5175

303←202 |M|= 0 -4.4624 -4.4315

303←202 |M|= 1 -3.6005 -3.5966

303←202 |M|= 2 -1.0932 -1.0918

111←000 |M|= 0 6.7099 6.7261

313←212 |M|= 1 -2.9271 -2.9439This Study Ab initioμa /D 1.511(3) 1.68

μb /D 1.2246(19) 1.29

μtotal /D 1.9452(26) 2.12

c

a

b

μtotal (CH2F2) = 1.97(2) Da

a Lide, D. R. Jr. J. Am. Chem. Soc. 1952, 74 (14) 3548

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Inertial Fit“Best”a

Ab initioStructure

R |||···C /Å 3.625(9) 3.51

θC-|||···C/° 70.2(28) 66.5

θ|||···C-F/° 80.0(8) 83.7

RF···H /Å 2.84(6) 2.68

RH···||| /Å 3.363(14) 3.22

Rcm /Å 4.033(1) 3.937

θC-H···|||/° 94.9(3) 96.2

θC-H···F/° 105(3) 111

θC-F···H/° 104.5(13) 99.7

CH2F2···HCCH Structure

3.625(9) Å

RH···||| = 3.363(14) ÅθC-H…||| = 94.9(3)°

70.2(28)°

80.0(8)°

104.5(13)°

105(3)°

2.84(6) Å

  a /Å b /Å

Substitution -0.90101(11) -0.33033(2)

Inertial fit (Ia, Ic) -0.9264 -0.3089

Ab initio structure

-0.8788 -0.2956

a average of the structures produced by fitting (Ia, Ib, Ic), (Ia, Ib), (Ia, Ic), and (Ib,Ic) in STRFITQ

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HCCH complex

ks /N m-1 Eb / kJ mol-1

CH2F2 2.85(3) 3.88(6)

CH2ClF 3.46(2) 4.75(4)

CHClF2a 3.7(5)

[3.7(5)]b

4.9(5)[5.0(5)]b

CHBrF2c 1.82(1) 2.46(3)

Force Constants and Binding Energies

aElmuti, L. F.; Peebles, R. A.; Peebles, S. A.; Steber, A. L.; Neill, J. L.; Pate, B. H. Phys. Chem. Chem. Phys. 2011. DOI 10.1039/c1cp20684bbStrucure refit using a refined CHClF2 monomer structure. Vincent, M. A.; Hillier, I. H. Phys. Chem. Chem. Phys. 2011, 13, 4388cObenchain D. A.; Bills, B. J.; Christenholz, C. L.; Peebles, R. A.; Peebles, S. A.; Neill, J. L.; Pate, B. H. Manuscript in preparation

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C-H···π InteractionsCH2F2···HCCH CH2ClF···HCCH CHClF2···HCCHa CHBrF2···HCCH

R|||-C /Å 3.625(9) 3.605(4)3.710(4)[3.676]

3.683(7)

R|||-H /Å 3.363(14) 3.236(1)2.730(6)[2.655]

2.670(8)

θ|||···C-X /˚ 80.0(8) 91.87(27)88.0(5)[87.7]

91.71(94)

RC-C/ Å 3.468(37) 3.487(10)3.563(16)

[3.500]3.540(14)

a Strucure refit using a refined CHClF2 monomer structure. Vincent, M. A.; Hillier, I. H. Phys. Chem. Chem. Phys. 2011, 13, 4388

Distributed Multipole AnalysisUp to quadrupole terms considered

GDMA 2.2Anthony Stonea

MIN16Buckingham-Fowler modelb,c

PROSPE websited,e

Electrostatic Interactions

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Lowest Energy Highest Energy

Buckingham-Fowler Model

Ab initioMP2/

6-311++G(2d,2p)

a Stone, A. J. J. Chem Theory Comp. 2005, 1, 1128b Buckingham A. D.; Fowler P. W. J.Chem.Phys. 1983, 79, 6426c Buckingham A. D.; Fowler P. W. Can.J.Chem. 1985, 63, 2018d Kisiel Z.; Fowler, P. W.; Legon A.C. J. Chem. Phys. 1990, 93, 3054e Kisiel Z. MIN16, PROSPE. www.ifpan.edu.pl/~kisiel/prospe.htm

EZPE= 0 cm-1 EZPE= 34 cm-1 EZPE= 64 cm-1 EZPE= 165 cm-1

1 imaginary frequency 1 imaginary frequency

Electrostatic InteractionsLowest Energy Highest Energy

Buckingham-Fowler Model

Ab initioMP2/

6-311++G(2d,2p)

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EZPE= 0 cm-1 EZPE= 13 cm-1 EZPE= 26 cm-1 EZPE= 231 cm-1

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Conclusions Assigned the spectrum of CH2ClF···HCCH (4

isotopologues) and CH2F2···HCCH (3 isotopologues)Structure fits

○ Similar RC-C distance for analog HCCH complexes

Dipole moments of CH2F2···HCCH○ Agree with ab initio to within expected deviation○ No enhancement of the dipole moment from the measured

monomer valueForce constants and binding energies

○ Appears that the chlorine containing halomethanes are more strongly bound to acetylene than the other halomethanes studied thus far

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Conclusions

Intermolecular InteractionsElectrostatic model can be used to predict

possible asymmetric structures ○ Preference of the lowest energy structure cannot be

determined by only an electrostatic model ○ Orient a

Additional studies are still needed to reliably determine the types of intermolecular interactions that are influencing the structures of these complexes

a Stone, A. J.; Dullweber, A.; Engkvist, O.; Fraschini, E.; Hodges, M. P.; Meredith, A. W.; Nutt, D. R.; Popelier, P. L. A.; Wales, D. J. 2002, ‘Orient:

a program for studying interactions between molecules, version 4.5,’ University of Cambridge, Enquiries to A. J. Stone, ajs1@cam.ac.uk

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Current Projects CH2ClF

Vinyl Fluoride

Vinyl Fluoride

CH2=CH2

CH2=CH2

CO2

CO2

CH2F2

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Support

NSF Research at Undergraduate Institutions CHE-0809387

Professor Kuczkowski for the H13C13CH sample

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Ia, Ib, Ic a Ia, Ib

a Ia, Ic a Ib, Ic

a “Best” b Ab initio

Structure I

R|||…C / Å 3.605(3) 3.608(3) 3.600(3) 3.606(3)3.605(4) 3.476

θC–|||…C / ° 74.10(5) 74.93(5) 73.43(5) 73.47(5)73.9(9) 73.6

θ|||…C–Cl / ° 91.82(21) 91.71(21) 92.19(22) 91.72(21)91.87(27) 94.3

RCl…H / Å c 3.210(2) 3.232(2) 3.198(2) 3.190(2)3.207(22) 3.138

R|||…H / Å c 3.237(16) 3.240(16) 3.229(18) 3.238(16)3.236(6) 3.101

θC–H…||| / ° c 100.9(7) 100.9(7) 101.1(7) 100.9(7)101.0(1) 101.2

θC–H…Cl / ° c 108.8(1) 107.8(1) 109.6(1) 109.5(1)109.0(1.0) 110.1

rms / u Å2 d 0.107 0.049 0.047 0.067– –

CH2ClF···HCCH Structure

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  CH235ClF–H12C12CH CH2

37ClF–H12C12CH CH235ClF–H13C13CH CH2

37ClF–H13C13CH Ab initio Chlorine in

A / MHz 5262.899(14) 5139.79(12) 5229.361(21) 5108.535(24) 5120

B / MHz 1546.8071(10) 1538.2279(15) 1471.2616(11) 1462.4085(11) 1625

C / MHz 1205.4349(7) 1193.6843(10) 1157.3986(7) 1145.9242(8) 1243

DJ / kHz 3.308(12) 3.158(34) 3.287(19) 3.163(18)–

DJK / kHz 14.03(8) 14.63(12) 11.95(11) 12.66(14)–

DK / kHz –402(14) –439(46) –598(22) –583(24)–

dJ / kHz 0.830(15) 0.874(25) 0.929(15) 0.784(17)–

caa / MHz 28.497(5) 22.270(7) 28.362(8) 22.096(8)24.19

cbb / MHz –65.618(13) –51.496(22) –65.474(21) –51.337(20)–60.13

ccc / MHz 37.121(8) 29.226(14) 37.112(13) 29.240(12)35.94

cab / MHz –22.2007 –18.1583 –22.2007 –18.1583–22.2007

Pcc / u Å2 1.7502(4) 1.7478(15) 1.7461(5) 1.7426(5) 1.5646

N c 71 39 46 43–

Dnrms/ kHz 5.5 5.8 2.8 4.5–

CH2ClF···HCCH Constants

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CH2F2···HCCH StructureIa, Ib, Ic Ia, Ib Ia, Ic Ib, Ic “Best” Ab initio

Structure

R |||···C /Å 3.625(2) 3.625(7) 3.617(12) 3.631(11) 3.625(9) 3.51

θC-|||···C/° 70.5(38) 70.5(36) 66(6) 74(7) 70.2(28) 66.5

θ|||···C-F/° 79.9(11) 79.9(11) 81.3(19) 79.1(16) 80.0(8) 83.7

RF···H /Å 2.84(11) 2.84(1) 2.75(16) 2.92(19) 2.84(6) 2.68

RH···||| /Å 3.365(4) 3.364(15) 3.346(19) 3.377(18) 3.363(14) 3.22

Rcm /Å 4.033(18) 4.033(9) 4.033(17) 4.033(15) 4.033(1) 3.937

θC-H···|||/° 94.9(5) 94.9(5) 95.4(8) 94.5(7) 94.9(3) 96.2

θC-H···F/° 105(5) 105(5) 110(7) 101(7) 105(3) 111

θC-F···H/° 104.7(14) 104.7(12) 102.4(24) 106.1(20) 104.5(13) 99.7

Rms/ uÅ2 0.05 0.045 0.054 0.062 - -

3.59(7) Å

RH···||| = 3.63(11) ÅθC-H…||| = 94.9(3)°

70.2(28)°

80.0(8)°

104.5(13)°

105(3)°

2.84(6) Å

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Instruments

CH2ClF···HCCHCP-FTMW at the University of Virginia

CH2F2···HCCHCP-FTMW at Eastern Illinois University

Balle-Flygare FTMW at Eastern Illinois UniversityUsed to measure transitions of both speciesWeak components of parent species and

isotopologues

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CH2F2···HCCH CH2F2 CHF3 CHF3 CH2ClF CHClF2 CHBrF2

Acetyleneks /N m-1 2.85(3) - - 3.46(2) 3.7(5) 1.82(1)

Eb /kJ mol-1 3.88(6) - - 4.75(4) 4.9(5) 2.46(3)

Carbonyl Sulfide

ks /N m-1 2.1(1) 1.2(1) 3.25(7) - - -Eb /kJ mol-1 2.1(1) 1.6(1) 3.5(1) - - -

Carbon Dioxide

ks /N m-1 - 1.4(2) - - - -Eb /kJ mol-1 - 1.6(4) - - - -

Waterks /N m-1 7.7 - - - 5.3(2) -

Eb /kJ mol-1 7.5 - - - 5.5(2) -

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CH2F2···HCCH ConstantsParameter ab initio

MP2/(6-311++G(2d,2p))CH2F2···HCCH 13CH2F2···HCCH CH2F2···H13C13CH

A /MHz 11210.613 11716.8028(18) 11687.6000(24) 11555.6991(20) B /MHz 1703.614 1624.083(5) 1619.8958(8) 1553.561(5) C /MHz 1493.338 1440.007(5) 1436.3245(8) 1381.977(5) ΔJ /kHz - 5.22(12) 5.216(26)a 4.819(12) ΔJK /kHz - -33.51(8) -33.51a -32.74(8) δJ /kHz - 0.8593(32) 0.8593a 0.774(3) δK /kHz - 20.2(23) 20.2a 2.02(24)Δνrms /kHz - 2.18 2.86 3.436 Nc - 29 12 29 Paa /uÅ2 294.9966 309.5006(14) 310.29879(25) 323.6311(16) Pbb /uÅ2 43.4258 41.4554(14) 41.55697(25) 42.0617(16) Pcc /uÅ2 1.6546 1.6774(14) 1.68365(25) 1.6724(16)

Pcc (CH2F2) = 1.651(1) uÅ2

Electrostatic Interactions

Relative energy -0.0268668 -0.0172967

Dipole-Quadrapole -0.0302364 -0.0157568

Quadrapole-Quadrapole 0.0024266 -0.0020474

Electrostatic InteractionsLowest Energy Highest Energy

Buckingham-Fowler Model

Ab initioMP2/

6-311++G(2d,2p)

30

EZPE= 0 cm-1 EZPE= 13 cm-1 EZPE= 26 cm-1