The rotational spectrum of pyridazine (o-C4H4N2), the ortho disubstituted nitrogen analog of benzene, has been measured and analyzed in the gas phase. For the ground vibrational state of the normal isotopolog, over 2000 individual rotational transitions have been identified between 238 and 360 GHz and have been fit to 13 parameters of a 6th-order centrifugal distortion Hamiltonian. All transitions in this frequency region can now be predicted from this model to near experimental accuracy, i.e., well enough for the purpose of any future radio-astronomical search for this species. Three isotopologs, [3-13C]-C4H4N2, [4-13C]-C4H4N2, and [1-15N]-C4H4N2, have been detected in natural abundance, and several hundred lines have been measured for each of these species and fit to 6th-order Hamiltonians. Ten additional isotopologs were synthesized with enhanced deuterium substitution and analyzed to allow for a complete structure determination. The equilibrium structure (Re) of pyridazine was obtained by correcting the experimental rotational constants for the effects of vibration-rotation coupling using interaction constants predicted from CCSD(T) calculations with an ANO0 basis set and further correcting for the effect of electron mass. The final Re structural parameters are determined with excellent accuracy, as evidenced by their ability to predict 28 independent moments of inertia (Ia and Ib for 14 isotopologs) very well from 9 structural parameters. The rotational spectra of the six lowest-energy fundamental vibrational satellites of the main isotopolog have been detected. The rotational spectra of the five lowest-energy vibrational satellites have been assigned and fit to yield accurate rotational and distortion constants, while the fit and assignment for the sixth is less complete. The resultant vibration-rotation interaction (α) constants are found to be in excellent agreement with ones predicted from coupled-cluster calculations, which proved to be the key to unambiguous assignment of the satellite spectra to specific vibration modes.

1.
V. M.
Bierbaum
,
V.
Le Page
, and
T. P.
Snow
, “
PAHs and the chemistry of the ISM
,”
Eur. Astron. Soc. Publ. Ser.
46
,
427
440
(
2011
).
2.
E.
Ye
,
R. P. A.
Bettens
,
F. C.
De Lucia
,
D. T.
Petkie
, and
S.
Albert
, “
Millimeter and submillimeter wave rotational spectrum of pyridine in the ground and excited vibrational states
,”
J. Mol. Spectrosc.
232
(
1
),
61
65
(
2005
).
3.
Z.
Kisiel
,
L.
Pszczółkowski
,
J. C.
López
,
J. L.
Alonso
,
A.
Maris
, and
W.
Caminati
, “
Investigation of the rotational spectrum of pyrimidine from 3 to 337 GHz: Molecular structure, nuclear quadrupole coupling, and vibrational satellites
,”
J. Mol. Spectrosc.
195
(
2
),
332
339
(
1999
).
4.
W.
Werner
,
H.
Dreizler
, and
H. D.
Rudolph
, “
Zum mikrowellenspektrum des pyridazins
,”
Z. Naturforsch., A: Phys. Sci.
22
(
4
),
531
543
(
1967
).
5.
J. C.
López
,
A.
de Luis
,
S.
Blanco
,
A.
Lesarri
, and
J. L.
Alonso
, “
Investigation of the quadrupole coupling hyperfine structure due to two nuclei by molecular beam Fourier transform microwave spectroscopy: Spectra of dichlorofluoromethane and pyridazine
,”
J. Mol. Struct.
612
(
2–3
),
287
303
(
2002
).
6.
J.
Kraitchman
, “
Determination of molecular structure from microwave spectroscopic data
,”
Am. J. Phys.
21
(
1
),
17
24
(
1953
).
7.
F. C.
De Lucia
, “
The submillimeter: A spectroscopist's view
,”
J. Mol. Spectrosc.
261
(
1
),
1
17
(
2010
).
8.
J. R.
Schmidt
and
W. F.
Polik
, WebMO Enterprise, v. 13.0, WebMO LLC, Holland, MI,
2013
; www.webmo.net.
9.
J.
Cernicharo
,
A. M.
Heras
,
A. G. G. M.
Tielens
,
J. R.
Pardo
,
F.
Herpin
,
M.
Guélin
, and
L. B. F. M.
Waters
, “
Infrared space observatory's discovery of C4H2, C6H2, and benzene in CRL 618
,”
Astrophys. J. Lett.
546
(
2
),
L123
L126
(
2001
).
10.
H. S. P.
Müller
,
F.
Schlöder
,
J.
Stutzki
, and
G.
Winnewisser
, “
The cologne database for molecular spectroscopy, CDMS: A useful tool for astronomers and spectroscopists
,”
J. Mol. Struct.
742
(
1–3
),
215
227
(
2005
).
11.
H. S. P.
Müller
,
S.
Thorwirth
,
D. A.
Roth
, and
G.
Winnewisser
, “
The cologne database for molecular spectroscopy
,”
CDMS. Astron. Astrophys.
370
(
3
),
L49
L52
(
2001
).
12.
S. L. W.
Weaver
,
A. J.
Remijan
,
R. J.
McMahon
, and
B. J.
McCall
, “
A search for ortho-benzyne (o-C6H4) in CRL 618
,”
Astrophys. J. Lett.
671
(
2
),
L153
(
2007
).
13.
M. N.
Simon
and
M.
Simon
, “
Search for interstellar acrylonitrile, pyrimidine, and pyridine
,”
Astrophys. J.
184
,
757
762
(
1973
).
14.
S. B.
Charnley
,
Y.-J.
Kuan
,
H.-C.
Huang
,
O.
Botta
,
H. M.
Butner
,
N.
Cox
,
D.
Despois
,
P.
Ehrenfreund
,
Z.
Kisiel
,
Y.-Y.
Lee
,
A. J.
Markwick
,
Z.
Peeters
, and
S. D.
Rodgers
, “
Astronomical searches for nitrogen heterocycles
,”
Adv. Space Res.
36
(
2
),
137
145
(
2005
).
15.
M.
Frenklach
and
E. D.
Feigelson
, “
Formation of polycyclic aromatic hydrocarbons in circumstellar envelopes
,”
Astrophys. J.
341
,
372
384
(
1989
).
16.
N. R.
Hore
and
D. K.
Russell
, “
Radical pathways in the thermal decomposition of pyridine and diazines: A laser pyrolysis and semi-empirical study
,”
J. Chem. Soc., Perkin Trans. 2
1998
,
269
275
.
17.
E.
Kraka
and
D.
Cremer
, “
Ortho-, meta-, and para-benzyne. A comparative CCSD(T) investigation
,”
Chem. Phys. Lett.
216
(
3–6
),
333
340
(
1993
).
18.
R. C.
Woods
and
T. A.
Dixon
, “
A computer controlled microwave spectrometer system
,”
Rev. Sci. Instrum.
45
(
9
),
1122
1126
(
1974
).
19.
R. H.
Petrmichl
,
K. A.
Peterson
, and
R. C.
Woods
, “
The microwave spectrum of SiF+
,”
J. Chem. Phys.
89
(
9
),
5454
5459
(
1988
).
20.
LabVIEW 2010, 10.0 (32-bit),
2010
.
21.
Z.
Kisiel
,
L.
Pszczółkowski
,
B. J.
Drouin
,
C. S.
Brauer
,
S.
Yu
,
J. C.
Pearson
,
I. R.
Medvedev
,
S.
Fortman
, and
C.
Neese
, “
Broadband rotational spectroscopy of acrylonitrile: Vibrational energies from perturbations
,”
J. Mol. Spectrosc.
280
(
0
),
134
144
(
2012
).
22.
H.-Q.
Do
,
R. M. K.
Khan
, and
O.
Daugulis
, “
A general method for copper-catalyzed arylation of arene C−H bonds
,”
J. Am. Chem. Soc.
130
(
45
),
15185
15192
(
2008
).
23.
A. R.
Katritzky
,
B. E.-D. M.
El-Gendy
,
B.
Draghici
,
D.
Fedoseyenko
,
A.
Fadli
, and
E.
Metais
, “
1H, 13C, and 15N NMR spectra of some pyridazine derivatives
,”
Magn. Reson. Chem.
48
(
5
),
397
402
(
2010
).
24.
Z.
Kisiel
,
PROSPE—Programs for ROtational SPEctroscopy
, see http://info.ifpan.edu.pl/~kisiel/prospe.htm.
25.
J. F.
Stanton
,
J.
Gauss
,
M. E.
Harding
,
P. G.
Szalay
with contributions from
A. A.
Auer
,
R. J.
Barlett
,
U.
Benedikt
,
C.
Berger
,
D. E.
Bernholdt
,
Y. J.
Bomble
,
L.
Cheng
,
O.
Christiansen
,
M.
Heckert
,
O.
Heun
,
C.
Huber
,
T.-C.
Jagau
,
D.
Jonsson
,
J.
Jusélius
,
K.
Klein
,
W. J.
Lauderdale
,
D. A.
Matthews
,
T.
Metzroth
,
L. A.
Mück
,
D. P.
O’Neill
,
D. R.
Price
,
E.
Prochnow
,
C.
Puzzarini
,
K.
Ruud
,
F.
Schiffmann
,
W.
Schwalbach
,
S.
Stopkowicz
,
A.
Tajti
,
J.
Vázquez
,
F.
Wang
,
J. D.
Watts
and the integral packages MOLECULE (
J.
Almlöf
and
P. R.
Taylor
), PROPS (
P. R.
Taylor
), ABACUS (
T.
Helgaker
,
H. J. Aa.
Jensen
,
P.
Jørgensen
, and
J.
Olsen
), and ECP routines by A. V. Mitin and C. van Wüllen, see http://www.cfour.de.
26.
A. D.
Becke
, “
Density-functional thermochemistry. III. The role of exact exchange
,”
J. Chem. Phys.
98
,
5648
5652
(
1993
).
27.
C.
Lee
,
W.
Yang
, and
R. G.
Parr
, “
Development of the Colle-Salvetti correlation-energy formula into a functional of the electron density
,”
Phys. Rev. B: Condens. Matter
37
(
2
),
785
789
(
1988
).
28.
W. J.
Hehre
,
R.
Ditchfield
, and
J. A.
Pople
, “
Self-consistent molecular orbital methods. XII. Further extensions of Gaussian—Type basis sets for use in molecular orbital studies of organic molecules
,”
J. Chem. Phys.
56
,
2257
2261
(
1972
).
29.
T. H.
Dunning
, “
Gaussian basis sets for use in correlated molecular calculations. I. The atoms boron through neon and hydrogen
,”
J. Chem. Phys.
90
,
1007
1023
(
1989
).
30.
M.
Head-Gordon
,
J. A.
Pople
, and
M. J.
Frisch
, “
MP2 energy evaluation by direct methods
,”
Chem. Phys. Lett.
153
(
6
),
503
506
(
1988
).
31.
M. J.
Frisch
,
G. W.
Trucks
,
H. B.
Schlegel
 et al, Gaussian 09, Revision B.1, Gaussian, Inc., Wallingford, CT,
2009
.
32.
M. H.
Palmer
,
R.
Wugt Larsen
, and
F.
Hegelund
, “
Comparison of theoretical and experimental studies of infrared and microwave spectral data for 5- and 6-membered ring heterocycles: The rotation constants, centrifugal distortion and vibration rotation constants
,”
J. Mol. Spectrosc.
252
(
1
),
60
71
(
2008
).
33.
J. A.
Pople
,
M.
Head-Gordon
, and
K.
Raghavachari
, “
Quadratic configuration interaction. A general technique for determining electron correlation energies
,”
J. Chem. Phys.
87
(
10
),
5968
5975
(
1987
).
34.
J.
Almlof
and
P. R.
Taylor
, “
General contraction of Gaussian basis sets. I. Atomic natural orbitals for first- and second-row atoms
,”
J. Chem. Phys.
86
(
7
),
4070
4077
(
1987
).
35.
G. E.
Scuseria
, “
Analytic evaluation of energy gradients for the singles and doubles coupled-cluster method including perturbative triple excitations: Theory and applications to FOOF and Cr2
,”
J. Chem. Phys.
94
(
1
),
442
447
(
1991
).
36.
T. J.
Lee
and
A. P.
Rendell
, “
Analytic gradients for coupled-cluster energies that include noniterative connected triple excitations: Application to cis- and trans-HONO
,”
J. Chem. Phys.
94
(
9
),
6229
6236
(
1991
).
37.
J. F.
Stanton
,
C. L.
Lopreore
, and
J.
Gauss
, “
The equilibrium structure and fundamental vibrational frequencies of dioxirane
,”
J. Chem. Phys.
108
(
17
),
7190
7196
(
1998
).
38.
I. M.
Mills
,
Infrared Spectra. Vibration-Rotation Structure in Asymmetric- and Symmetric-Top Molecules
(
Academic
,
1972
), pp.
115
140
.
39.
R. J.
McMahon
,
M. C.
McCarthy
,
C. A.
Gottlieb
,
J. B.
Dudek
,
J. F.
Stanton
, and
P.
Thaddeus
, “
The radio spectrum of the phenyl radical
,”
Astrophys. J. Lett.
590
(
1
),
L61
(
2003
).
40.
W.
Gordy
and
R. L.
Cook
,
Microwave Molecular Spectra
, 3rd ed. (
Wiley
,
New York
,
1984
).
41.
J. F.
Stanton
,
J.
Gauss
, and
O.
Christiansen
, “
Equilibrium geometries of cyclic SiC3 isomers
,”
J. Chem. Phys.
114
(
7
),
2993
2995
(
2001
).
42.
W. H.
Flygare
, “
Magnetic interactions in molecules and an analysis of molecular electronic charge distribution from magnetic parameters
,”
Chem. Rev.
74
(
6
),
653
687
(
1974
).
43.
J.
Gauss
,
K.
Ruud
, and
M.
Kállay
, “
Gauge-origin independent calculation of magnetizabilities and rotational g tensors at the coupled-cluster level
,”
J. Chem. Phys.
127
(
7
),
074101
(
2007
).
44.
J.
Vázquez
,
J. J. L.
Gozález
,
F.
Márquez
, and
J. E.
Boggs
, “
Vibrational spectrum of pyridazine
,”
J. Raman Spectrosc.
29
(
6
),
547
559
(
1998
).
45.
Y.
Ozono
,
Y.
Nibu
,
H.
Shimada
, and
R.
Shimada
, “
Polarized Raman and infrared spectra of [1H4]- and [2H4]-pyridazines
,”
Bull. Chem. Soc. Jpn.
59
(
10
),
2997
3001
(
1986
).
46.
H. D.
Stidham
and
J. V.
Tucci
, “
Vibrational spectra of pyridazine, pyridazine-d4, pyridazine-3,6-d2, and pyridazine-4,5-d2
,”
Spectrochim. Acta, Part A
23
(
8
),
2233
2242
(
1967
).
47.
See supplementary material at http://dx.doi.org/10.1063/1.4832899 for summaries of geometry optimizations, harmonic vibrational frequency, and anharmonic vibrational frequency calculations from Gaussian09 and CFOUR. Comparisons of isotopolog constants from Ref. 4 and our work and theoretical calculations. Theoretical predictions of the vibration-rotation interaction at various levels of theory. A full list of measured and fit lines for all species in the ASFIT output format.

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