Microwave Spectroscopic Investigations of the C—H…p Containing Complexes CH2F2…
Propyne and CH2ClF…Propyne
Rebecca A. Peebles, Sean A. Peebles, Cori L. Christenholz, Yasser J. Dhahir,
Anthony A. ErnstDepartment of Chemistry, Eastern Illinois University,
Charleston, IL 61920
C—H…p Interactions
Cl
F
80.0(16)°
3.122(46) Å148.7(7)°
2.724(7) Å
Sexton, et al., Phys. Chem. Chem. Phys.,12 (2010), 14263.
3.207(22) Å
101.0(1)°
3.236(6) Å
Elmuti, et al., Phys. Chem. Chem. Phys., 13 (2011), 14043.
3.293(40) Å
2.670(8) Å
153.2(5)°
81.6(14)°
Obenchain, et al., J. Phys. Chem. A, 115 (2011), 12228.
2.84(6) Å
94.9(3)°
3.363(14) Å
Obenchain, et al., in preparation.
Propyne Complexes
• New considerations– Two inequivalent C—H bond donors in propyne– Internal rotation
Possible Structures
I II III IV V
A / MHz 4650.1 5870.8 5783.0 4516.8 6482.7
B / MHz 1572.5 1422.6 1362.3 1568.9 1063.4
C / MHz 1513.1 1162.0 1118.3 1495.1 924.3
ma / D 0.01 1.53 1.66 0.01 2.58
mb / D 1.24 0.75 0.71 1.23 1.32
mc / D 0.00 0.00 0.00 0.00 0.00
Pcc / u Å2 48.0 3.2 3.2 48.0 3.2
Relative Energy / cm-1
0 27 35 58 234
Gaussian 03: MP2/6-311++G(2d,2p)
Experimental
• CH2F2…Propyne– Scanned on 480 MHz CP-FTMW– Sample: ~1.8% each CH2F2 and propyne in He/Ne
pressurized to 5.2 bar in 1 L tank – delivered to nozzle at ~2 bar
– 2000 gas and microwave pulses per frequency step– Isotopes on cavity FTMW• Enriched: CH3CCD (98% D, CDN Isotopes)• All four carbons in natural abundance
J = 3 - 2 J = 4 - 3
J = 5 - 4J = 6 - 5
AABS: Z. Kisiel, L. Pszczolkowski, I. R. Medvedev, M. Winnewisser, F.C .De Lucia, C . E. Herbst, J.Mol.Spectrosc., 233, (2005), 231.PROSPE Web SITE: Z.Kisiel, in: J. Demaison, et al. (Eds.), Spectroscopy from Space, Kluwer Academic Publishers, Dordrecht, 2001, pp.91-106.
Spectroscopic Constants
propyne Pbb 1.59 u Å2
CH2F2 Paa 46.01 u Å2
CH2F2 Pbb 8.63 u Å2
CH2F2 Pcc 1.66 u Å2
CH2F2…
CH3CCH
CH2F2…
CH3CCD
CH2F2…
CH3C13CH
CH2F2...
CH313CCH
CH2F2...13CH3CCH
13CH2F2...
CH3CCH
A / MHz 5815.5858(34) 5412.3485(36) 5669.212(15) 5809.536(16) 5732.666(16) 5810.341(16)B / MHz 1341.1191(10) 1327.4534(11) 1326.3804(7) 1324.5778(7) 1322.0696(7) 1335.0765 (7)C / MHz 1099.2040(9) 1074.9320(11) 1084.0441(9) 1087.8428(9) 1083.4602(9) 1094.9527(9)
DJ / kHz 1.805(6) 1.760(7) 1.716(19) 1.782(19) 1.742(19) 1.824(19)
DJK / kHz 20.733(32) 20.348(45) 20.733 20.733 20.733 20.733
dJ / kHz 0.3192(46) 0.3486(54) 0.3192 0.3192 0.3192 0.3192
dK / kHz 13.64(33) 12.28(39) 13.64 13.64 13.64 13.64
Pcc / u Å2 1.9832(4) 1.9693(4) 1.9839(14) 1.9805(15) 1.9861(15) 1.9827(15)
rms / kHz 1.6 2.7 4.5 4.2 2.2 2.638 lines 29 lines 8 lines 8 lines 8 lines 8 lines
Structure I: 1.59 + 46.01 = 47.60 u Å2
Structure II: 1.59 + 1.65 = 3.24 u Å2
I II
I II III
A / MHz 4650.1 5870.8 5783.0
B / MHz 1572.5 1422.6 1362.3
C / MHz 1513.1 1162.0 1118.3
ma / D 0.01 1.53 1.66
mb / D 1.24 0.75 0.71
mc / D 0.00 0.00 0.00
Pcc / u Å2 48.0 3.2 3.2
Relative Energy / cm-1
0 27 35
CH2F2-Propyne Structure
r0 rs re
3.497(1) Å3.480(2) Å3.388 Å
85.56(9)°85.84(23)°84.7°
89.61(4)°85.0°
1.060(2) Å1.060(1) Å
1.2073(10) Å1.212(5) Å
1.4596(10) Å1.452(5) Å
Lit. rs
J. L. Duncan, et al., J. Mol. Spectrosc. 46 (1973) 232.
3.170(1) Å3.097 Å
3.109(4) Å2.875 Å
r0 re
Dipole moment|M |′ |M″| Number of Measurements
313←212 0 0 9303←202 0 0 1
1 1 63 2 9
312←211 0 0 91 1 5
414←313 0 0 71 1 72 3 5
404←303 0 0 81 1 82 2 83 3 4
Dnrms = 4.1 kHz ma = 1.568(2) D mb = 0.587(2) D mc = 0.00 D mtot = 1.674(1) D
a
b 1.97 D
0.7804 D
ma = 1.568(2) Dma = 1.434 D
mb = 0.587(2) Dmb = 0.656 D
mtot = 1.674(1) Dmtot = 1.577 D
measuredprojectedmonomers
QSTARK: Kisiel, et al., Chem. Phys. Lett., 325, (2000), 523.
Next Step – CH2ClF…Propyne
I II III IV V
A / MHz 3337.7 3738.8 5715.2 3841.1 5112.4
B / MHz 1328.0 1273.5 973.5 1044.8 808.1
C / MHz 1255.2 961.5 840.6 830.0 704.0
caa / MHz 30.1 29.8 -65.7 2.2 -48.9
cbb / MHz -43.5 -65.3 29.7 -38.1 12.7
ccc / MHz 9.8 35.5 36.1 35.9 36.2
ma / D 0.26 1.90 1.38 2.59 2.24
mb / D 0.17 0.34 0.72 0.56 1.58
mc / D 1.04 0.00 0.00 0.00 0.00
Pcc / u Å2 64.7 3.2 3.2 3.2 3.2
Relative Energy / cm-1
0 116 181 310 370
Experimental
• CH2ClF…Propyne– ~1.7% of each component in He/Ne, delivered at 1.5 –
2.5 atm– Original scan on CP-FTMW – a few very weak candidate
lines– Checked these on cavity FTMW – identified a few
transitions– Further cavity FTMW searching led to assignment– Very weak transitions – seem to get weaker and weaker– Only 35Cl and 37Cl assigned
220 - 110 221 - 111
Spectroscopic ConstantsCH2
35ClF...CH3CCH Ab Initio CH237ClF...CH3CCH
A / MHz 3423.636(8) 3337.7 3385.8964(8)
B / MHz 1253.7572(25) 1328.0 1238.0102(4)
C / MHz 1200.4850(19) 1255.2 1181.5034(15)
DJ / kHz 4.61(5) -- 4.61#
DJK / kHz 10.70(11) -- 10.70#
DK / kHz -10.5(16) -- -10.5#
1.5caa 43.639(9) 45.2 33.640(18)
0.25(cbb – ccc) -11.4869(23) -13.3 -9.257(5)
cbc -40.178(20) -34.4 -31.23(10)
cab -21.913* -21.9 -19.128*
cac -10.378* -10.4 -8.742*
Pcc / u Å2 34.8637(9) 64.7 64.8683(4)
rms / kHz 7.2 (35 lines) -- 13.0 (18 lines)
Chlorine atom coordinates (Å)Ab initio:a = 1.5246 b = 0.9575 c = 0.0287Kraitchman:a = ±1.6106(9) b = ±0.9235(16) c = ±0.051(30)
Comparison of Alkyne Complexes
Cl
F
Fitted:R(≡… C) = 3.706(4) Åf(C–≡…C) = 71.1(16)°q(Cl–C…≡) = 88.3(5)°
80.0(16)°
3.122(46) Å148.7(7)°
2.724(7) Å
3.293(40) Å
2.670(8) Å
153.2(5)°
81.6(14)°
Fitted:R(≡… C) = 3.683(7) Åf(C–≡…C) = 73.9(14)°q(Br–C…≡) = 91.7(4)°
3.207(22) Å
101.0(1)°
3.236(6) Å
Fitted:R(≡… C) = 3.605(4) Åf(C–≡…C) = 73.9(9)°q(Cl–C…≡) = 91.9(3)°
2.84(6) Å
94.9(3)°
3.363(14) Å
Fitted:R(≡… C) = 3.625(9) Åf(C–≡…C) = 70.2(28)°q(F–C…≡) = 80.0(8)°
Fitted:R(≡…C) = 3.497(1) Åf(C–≡…C) = 85.56(9)°q(F–C…≡) = 89.61(4)°
3.109(4) Å
3.170(1) Å
98.2(5)°
To be determined?
What’s Next?• Complexes with aromatic p systems– Next talk! Including benzene…HCCH
Acknowledgements• Ashley Elliott, Dan Obenchain• Current Peebles group: Anu Akmeemana,
Ashley Anderton, Cori Christenholz, Rachel Dorris, Nate Ulrich
• NSF grants: RUI-0809387, RUI-1214070