THE MICROWAVE SPECTRA OF THE LINEAR OC HCCCN,

OC DCCCN, AND THE T-SHAPED HCCCN CO2 COMPLEXES

The 62nd. International Symposium on Molecular Spectroscopy, RG 09

LU KANGDepartment of Natural Sciences, Union College, Barbourville, KY 40906

STEWART E. NOVICKDepartment of Chemistry, Wesleyan University, Middletown, CT 06459

General Introduction

IR study of the OC---HCCCN, and the HCCCN---CO2

X. Yang, R.Z. Pearson, G. Scoles; Chem. Phys. Lett., 204(12), p145, 1993X. Yang, R.Z. Pearson, and G. Scoles; J. Mol. Spectrosc., 180(1), p1, 1996

Rotational spectroscopy study of the OC---HCNE. J. Goodwin, A. C. Legon; Chem. Phys., 87, p81, 1984

Both Linear and T-shaped HCN---CO2 exist

T. D. Klots, R. S. Ruoff, H. S. Gutowsky; J. Chem. Phys., 90(8), p4216, 1989K. R. Leopold, G. T. Fraser, W. Klemperer; J. Chem. Phys., 80(3), p1039, 1984

Complete rotational spectroscopy investigations of the weakly bound Ng---HCCCN van der Waals complexes He---HCCCN: W. C. Topic, W. Yäger; J. Chem. Phys.,123(6), p064303/1, 2005 Ne---HCCCN: A. Huckauf, W. Yäger; manuscript in preparation. Ar---HCCCN: A. Huckauf, W. Yäger, P. Botschwina, R. Oswald; J. Chem. Phys., 119(15), p7749, 2003

Thorough understanding of the subunits: CO and HCCCNCO: F. J. Lovas, P. H. Krupenie; J. Phys. Chem. Ref. Data, 3(1), p245, 1974HCCCN: W. J. Lafferty, F. J. Lovas; J. Phys. Chem. Ref. Data, 7(2), p441, 1978

Experiment

Balle-Flygare Type Fourier transform microwave spectrometer (FTMW) at Wesleyan University Molecular beam pulsed-nozzle (~3 K) Cover 3.7 – 26.5 GHz ~ 1 kHz frequency resolution

The synthesis of Ethyl cyanide (Cyanoacetylene), HCCCN. C. Moureu, J. C. Bongrand; Ann. Chim. (Paris), 14, p47, 1920. Propiolamide is commercially available (Acme Bioscience Inc.)

Deuterated sample, DCCCN was also made! 0.5% HCCCN (DCCCN) + 7.5% CO / Ar or Ne carrier gas 0.5% HCCCN (DCCCN) + 10% CO2 / Ar or Ne carrier gas

H C C C

O

NH2

H C C C N120 - 140 oC

+ P2O5sand

Spectrum

Spectrum

Hamiltonian

H = HR + HQ

HR: the effective Hamiltonian for the vibrational ground state semi-rigid linear molecules

HR = B0J2 – D0J4 + H0J6

EJ = B0J(J+1) – D0J2(J+1)2 + H0J3(J+1)3

J+1→J = 2B0(J+1) – 4D0(J+1)3 + H0(J+1)3[(J+2)3-J3]

HQ: the nuclear quadrupole coupling interactions between the molecular rotation angular momentum, J, and the nuclear spin angular momentum, I.

HQ = The nuclear spin of Nitrogen atom is1, hence, J + I(N) = F

EQ :6

1

Spectroscopic constants

Table-1: the rotational constants, centrifugal distortion constants, and the nuclear quadrupole coupling constants of the OC---HCCCN isotopomers Molecular Species

(Hydrogenated) B0

(MHz) D0

(kHz) H0

(Hz) eqQ(14N) (MHz)

σ (kHz) / # of lines

18OC --- HCCCN 591.143890(36) 0.29866(29) -0.386(67) -4.2097(19) 1.4 / 32

O13C --- HCCCN 611.097110(30) 0.31732(21) -1.52(49) -4.2085(10) 1.0 / 44

OC --- HCCCN 619.521775(21) 0.32577(11) -0.39(18) -4.20865(55) 0.74 / 72

OC --- H13CCCN 619.376060(39) 0.32520(28) -0.47(55) -4.2123(19) 1.0 / 32

OC --- HC13CCN 617.799558(32) 0.32443(23) -1.10(47) -4.2085(15) 1.0 / 37

OC --- HCC13CN 613.348720(32) 0.31871(23) -0.05(47) -4.2096(20) 0.72 / 38

OC --- HCCC15N 607.553100(56) 0.30901(23) -0.70(68) N/A 0.85 / 14

Spectroscopic constants

Table-1: the rotational constants, centrifugal distortion constants, and the nuclear quadrupole coupling constants of the OC---DCCCN isotopomers

Molecular Species (Deuterated)

B0 (MHz)

D0 (kHz)

H0 (Hz)

eqQ(14N) (MHz)

# of lines / σ (kHz)

18OC --- DCCCN 591.397792(45) 0.28887(37) 2.76(92) -4.354(65) 3.0 / 28

O13C --- DCCCN 611.289802(30) 0.30730(29) -0.02(65) -3.928(35) 1.9 / 36

OC --- DCCCN 619.654917(32) 0.31430(25) -0.58(58) -4.21113(66) 1.8 / 57

OC --- D13CCCN N/A N/A N/A N/A N/A

OC --- DC13CCN 617.915477(39) 0.31292(29) -1.85(66) -4.244(35) 1.7 / 33

OC --- DCC13CN 613.442390(39) 0.30814(30) 1.45(67) -4.125(35) 2.3 / 35

OC --- DCCC15N 607.631979(78) 0.30238(72) 0.0102(20) N/A 3.5 / 11

Spectroscopic constants of HCCCN---CO2

Table-3: The spectroscopic constants of the T-shaped HCCCN---CO2 dimer

Constants * A / MHz 11824 B / MHz 764.597(3) C / MHz 715.745(2) ΔJ / kHz 0.5006(7)

ΔJK / kHz 120.89(4) δJ / kHz 0.0425(11) δK / kHz 0.0653(6) HJ / kHz 1.2(11) 10-6

HJK / kHz 0.03488(9) HKJ / kHz -0.683(3) HK / kHz 2.52779(5) χaa / MHz -4.1293(3)

χbb – χcc / MHz 0.10(8) σ / kHz 1.5

# of lines 214 *: The standard deviations are put in the ( ). : Fixed to HCN---CO2 value, 0.394406 cm-1.

The observed spectra agree with the T-shaped structure.

IR spectroscopy determined rotational constants:

B” = 0.0254463(59) cm-1

i.e., 762.9(19) MHz

C” = 0.0254463(59) cm-1

i.e., 715.5(18) MHz

X. Yang, R. Z. Pearson, G. Scoles;

J. mol. Spectro.180, p 1-6, 1996 The obtained rotational constants

from the microwave spectroscopy are in good agreement with the IR values.

Structural Analysis: Linear Model

a C O C C C H N

a

r c .m .

r c - c

rO C - - - H C

b

b

IR spectroscopy determined rOC-HC = 2.615Å for OC---HCCCN complex Yang, et. al., Chem. Phys. Lett., 204(12), p145-151, 1993. Microwave spectroscopy determined rOC-HC = 2.577Å for OC---HCN Goodwin, et. al., Chem. Phys., 87, p81-92, 1984.

Structural Analysis: Linear Model

How to find a distance that can best descrbe the complex?Table-4: Various distances related to the linear model of OC---HCCCN and OC---DCCCN*

Molecular Species rc.m. (Å) rc-c (Å) rOC-HC (Å)

OC---HCCCN 6.2048 3.6610 2.6035 18OC---HCCCN 6.2361 3.6600 2.6024

O13C---HCCCN 6.1827 3.6613 2.6038

OC---H13CCCN 6.1687 3.6615 2.6040

OC---HC13CCN 6.1916 3.6611 2.6036

OC---HCC13CN 6.2179 3.6608 2.6034

OC---HCCC15N 6.2401 3.6609 2.6034

OC---DCCCN 6.1443 3.6575 2.6005 18OC---DCCCN 6.1756 3.6564 2.5994

O13C---DCCCN 6.1222 3.6578 2.6007

OC---D13CCCN N/A N/A N/A

OC---DC13CCN 6.1324 3.6576 2.6006

OC---DCC13CN 6.1588 3.6579 2.6008

OC---DCCC15N 6.1800 3.6574 2.6004

*Kisiel’s STRFIT program gives us rOC-HC = 2.6018(5) Å

Structural Analysis: Procession Model

The description of the procession model: E. J. Goodwin & A. C. Legon; Chem. Phys., 87, p81 – 92, 1984

C

N

C

C

H

C

O

a a

b

b rc.m.

rOC--HC

rc-c

θ

HCCCNCO

HCCCNCO

HCCCNb

CObmcbb

MM

MM

IIrI

222.. cos1

2

1cos1

2

1

Structural Analysis: Procession Model

Average effect of the procession around the a-axis

The geometry of the complex is determined by rc.m. and θ, , µ,

can be obtained from the experiment.

can be obtained from the quadrupole coupling constant of 14N

222..

exp cos12

1cos1

2

1 HCCCN

bCObmcbbb IIrII

expb

HCCCNb

COb I,I,I

1cos32

1 20 aa

1

)(

)(2

3

1cos

140

142

N

Naa

1

)(

)(2

3

1arccos

140

14

N

Naa

02

020

21

2

2

ddd aaaaaa

Structural Analysis: Procession Model

For example, OC---HCCCN, aa(14N)=-4.20865(55)MHz, and the 0(14N) for free HCCCN is: 0(14N)=-4.31806(38)MHz, then: OC---HCCCN: =7.468(1)

For other isotopomers: OC---DCCCN: =7.31(4)18OC---HCCCN: =7.432(3) 18OC---DCCCN: N/AO13C---HCCCN: =7.473(1) O13C---DCCCN: =14.17(2)OC---H13CCCN: =7.341(3) OC---D13CCCN: N/AOC---HC13CCN: =7.473(1) OC---DC13CCN: =6.05(6)OC---HCC13CN: =7.435(1) OC---DCC13CN: =9.89(3)OC---HCCC15N: N/A OC---DCCC15N: N/A

= 7.44(5) ↔ OC---HCN = 13-14

Structural Analysis: Procession Model

Ibb is determined by the (θ, r2c.m.½) pair, how do we estimate θ?

Note that rc-c is almost isotropically invariant, and, (θ, rc-c) can also be used to determine Ibb, i.e., Ib

exp

Construct a set of (θ, rc-c) pairs from the main isotopomer and use them to reproduce Ibbs for other isotopomers, and find the best matched (θ, rc-c) pair to get the answer.

Examples: 18OC---HCCCN: O13C---HCCCN:

comparing with 18OC---HCN: ~ 15º O13C---HCN: ~ 10º

The procession model does not work very well for HCCCN isotopomers! ~ 0º - 90º (similar to the OC---HCN when use this model to handle HCN isotopomers!)

MHz144.591Bexp0 MHz140.591B 16

0

MHz097.611Bexp0 MHz100.611B 8

0

Conclusion

1. The rotational spectra of the weakly bound van der Waals complex dimers, including, OC---HCCCN, OC---DCCCN, and HCCCN---CO2 are observed.

2. All 13C (1.07%), 15N (0.37%), and 18O (0.205%) isotopomers are found in natural abundance!

3. The obtained results are in good agreement with previous studies

4. OC---HCCCN / OC---DCCCN is linear shaped. The procession model is effective to describe this system.

5. The T-shaped HCCCN---CO2 has been observed. We tried, but the linear shaped CO2---HCCCN was not found yet!

6. Why the procession model failed to reproduce the geometry of the OC---HCCCN complex when the HCCCN subunit is substituted by 13C or 15N isotopes?

Future Plan

1. Try to improve the quality of the data for OC---DCCCN by observing low frequency transitions. (get the eqQ for D).

2. Try to get the nuclear quadrupole coupling splittings due to the 13C of O13C-HCCCN. (can help us figure out very accurately)

3. Keep searching for the linear shaped CO2---HCCCN dimer.

4. We already observed N2---HCCCN.

5. We already observed HCCCN---HCCCN, HCCCN---DCCCN, DCCCN---HCCCN, and DCCCN---DCCCN dimers (The low frequency data will really help!).

6. Searching for NO---HCCCN complex.

Acknowledgement

Andrea Meini Department of Chemistry, Wesleyan University

Dr. Steven Shipman, Justin Neill, University of Virginia

Professor Wallace PringleDepartment of Chemistry, Wesleyan University

Union College, and Professor Brooks Pate, University of Virginia.