Department of Chemistry University of Manitoba Microwave Spectra and Molecular Geometries of Benzonitrile and Pentafluorobenzonitrile 1 2 2 Fluorine substituted benzonitriles trifluoro ID: 230599
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Slide1
Mahdi Kamaee and Jennifer van WijngaardenDepartment of Chemistry, University of Manitoba
Microwave Spectra and Molecular Geometries of Benzonitrile and Pentafluorobenzonitrile
1Slide2
2
2
Fluorine substituted
benzonitriles
trifluoro
difluoro
monofluoro
perfluoroSlide3
3
Geometry trends in the ring backbone
At site of fluorination:
C-C bonds shorten 0.005 – 0.008 Å
Ring angle increases by >2
o
Neighbour
vs
non-neighbour substituents
neighbour
: shared bond shortens ~0.010
Å
No large angle changes
n
on-neighbour
:
similar to single F case
All C-C bonds shorten 0.003 – 0.009 Å
Ring angle at C1 decreases by ~2
o
MP2/6-311G++(2d,2p)Slide4
4
Geometry trends near CN substituent
MP2/6-311G++(2d,2p)Slide5
Extensive MW studies (3-160 GHz)G. Erlandsson
, J. Chem. Phys. 22, 1152 (1954).14N hfsDreizler and coworkers, Z. Naturforsch
.
26a, 1124 (1981); 43a, 283 (1988).
Dipole momentK. Wolfhart et al.,
J. Mol.
Spectrosc
.
247
, 119 (2008).
13
C isotopologuesBak
et al., J. Chem. Phys., 37, 2027 (1962).
Dreizler and coworkers, Ber. Bunsenges. Phys. Chem.
98, 970 (1994).5
Benzonitrile: Previous work
µ
a
=4.5152(68) DSlide6
6
MW study (18-26 GHz)
Sharma and
Doraiswamy
, Proc. Ind. Acad. Sci.
67a
, 12 (1968).
14
N
hfs
(7-13 GHz)
Krüger and Dreizler, Z.
Naturforsch. 47a, 865 (1992).
No isotopic studiesPerfluorobenzonitrile: Previous work
µa
=2.79 DMP2/6-311G++(2d,2p)Slide7
7
Balle-Flygare FTMW instrument
4-26 GHz
FWHM ~7kHz
Useful for:
14
N
hfs
resolved
13
C in natural abundance
Sample prep:
1-2
atm
of Ne/Ar bubbled through liquid sampleSupersonic jetSlide8
8
Sample FTMW spectrum of PFBN14N hyperfine structureSlide9
9
Chirped pulse FTMW instrument
8-18
GHz
6 GHz bandwidth
FWHM ~100kHz
Useful for:
Identifying
isotopologue
transitions
Sample prep:
1
atm
of Ne/
Ar bubbled through liquid sampleSupersonic jetSlide10
10
Sample cp-FTMW spectrum of PFBNSlide11
11
Parent BN
C1
C2
C3
C4
C5
Rotational Constants /MHz
A
5655.264(5)
5655.496(4)
5563.914(4)
5565.666(4)
5655.453(5)
5655.237(3)
B
1546.8758(10)
1545.55191(6)
1546.80335(5)
1535.71300(5)
1523.65521(6)
1528.64085(6)
C
1214.40407(9)
1213.60148(6)
1210.08975(4)
1203.37301(4)
1200.05798(6)
1203.13679(4)
Centrifugal Distortion Constants /kHz
Δ
J
0.0450(4)
0.0450
0.0450
0.0450
0.0450
0.0450
Δ
JK
0.9373(19)
0.9373
0.9373
0.9373
0.9373
0.9373
Δ
K
-0.5(18)
-0.5
-0.5
-0.5
-0.5
-0.5
δ
J
0.0112(3)
0.01122
0.01122
0.01122
0.01122
0.01122
δ
K
0.59(4)
0.59
0.59
0.54
0.59
0.59
14
N Nuclear
Quadrupole
Coupling Constants /MHz
1.5
χ
aa
-6.3560(8)
-6.344(9)
-6.367(8)-6.366(8)-6.348(15)-6.359(16)0.25(χbb-χcc)0.0848(3)0.073(6)0.070(5)0.068(5)0.074(5)0.076(2)rms /kHz0.951.21.11.11.01.1no. lines1775163634239
BN Spectroscopic constants
Pickett’s SPFIT program, Watson A-reduction,
I
r
representation
CD constants fixed to those of parent speciesSlide12
12
C1C21.381(6)1.390(4)
1.392(3)
1.401
C2
C3
1.415(12)
1.381(5)
1.376(4)
1.393
C3
C4
1.396(1)
1.404(2)
1.395(2)1.396
C1C5
1.450(3)1.455(6)
1.443(5)
1.435(C1
C2C3)
118.1(5)119.4(4)
119.5(3)119.5
(C2C3
C4)
120.2(1)
119.8(6)120.0(4)
120.1
(C3
C4
C3)
120.1(1)
120.2(6)
120.1(2)
120.2
(
C2
C1
C2)
123.3(6)
121.5(6)
120.8(5)
120.5
r
s
r
o
r
e
SE
r
e
BN Geometry
r
s
,
r
o
and
r
e
SE
geometries calculated using KRA and STRFIT programs
(http://info.ifpan.edu.pl/~kisiel/prospe.htm)
r
o
geometry using B and C constants
only
r
e
SE
:
rovibrational corrections were calculated at B3LYP/6-31G(d,p)re were calculated at MP2/6-311G++(2d,2p)Slide13
13
PFBN Spectroscopic constants
Parent PFBN
C1
C2
C3
C4
C5
Rotational Constants /MHz
A
1029.36864(3)
1029.4002(3)
1026.38600(17)
1026.3606(2)
1029.4046(3)
1029.3699(4)
B
764.595288(9)
762.9252(2)
764.32975(6)
763.68959(11)
761.7224(2)
756.6354(2)
C
438.721848(6)
438.17764(10)
438.092216(9)
437.877115(9)
437.781210(10)
436.089680(11)
Centrifugal Distortion Constants /kHz
Δ
J
0.006169(18)
0.006169
0.006169
0.006169
0.006169
0.006169
Δ
JK
0.04498(7)
0.04498
0.04498
0.04498
0.04498
0.04498
Δ
K
-0.0284(3)
-0.0284
-0.0284
-0.0284
-0.0284
-0.0284
δ
J
0.00237(10)
0.00237
0.00237
0.00237
0.00237
0.00237
δ
K
0.02955(7)
0.02955
0.02955
0.02955
0.02955
0.02955
14
N Nuclear Quadrupole Coupling Constants /MHz
1.5
χ
aa
-6.5807(12)
-6.58(4)
-6.574(19)
-6.58(2)
-6.59(4)-6.63(4)0.25(χbb-χcc)0.1080(7)0.105(3)0.111(3)0.108(3)0.108(3)0.108(3)rms /kHz0.7871.2031.1791.1671.2011.355no. lines7538199968178
Pickett’s SPFIT program, Watson A-reduction,
I
r
representation
CD constants fixed to those of parent speciesSlide14
14
rsr
o
reSE
r
e
PFBN Geometry
r
o
geometry using A, B and C constants
r
e
SE
:
rovibrational
corrections were calculated at B3LYP/6-31G(
d,p
)
re were calculated at
MP2/6-311G++(2d,2p)
C1C2
1.400(2)
1.394(2)1.389(2)
1.398
C2
C3
1.360(4)
1.373(2)
1.373(3)
1.388
C3
C4
1.391(1)
1.390(1)
1.383(2)
1.392
C1
C5
1.436(1)
1.438(2)
1.430(3)
1.426
(C1
C2
C3)
121.6(2)
121.1(2)
121.1(2)
120.9
(C2
C3
C4)
119.8(1)
119.7(2)
119.6(3)
119.6
(C3
C4
C3)
119.8(1)
120.1(1)
120.3(3)
120.4
(
C2
C1
C2)117.5(2)118.4(2)118.3(2)118.6Slide15
15
Geometry comparison of BN and PFBN
C1
C2
1.392(3)
1.389(2)
-0.003
C2
C3
1.376(4)
1.373(3)
-0.005
C3
C4
1.395(2)1.383(2)
-0.004
C1C5
1.443(5)1.430(3)
-0.009
(C1C2C3)
119.5(3)121.1(2)
+1.4
(C2C3
C4)
120.0(4)119.6(3)
-0.4
(C3
C4
C3)
120.1(2)
120.3(3)
+0.2
(
C2
C1
C2)
120.8(5)
118.3(2)
-1.9
r
e
SE
r
e
SE
r
e
(PFBN-BN)
Ab initio
calculations predict:
All C-C bonds shorten 0.003 – 0.009 Å
Ring angle at C1 decreases by ~2
oSlide16
16
Geometry comparison with benzeneSlide17
17
Monofluorinated BN
μ
b
μ
μ
a
μ
b
μ
μ
a
µ
a
=5.44 D
µ
b
=0.64 D
(calc.)
µ
a
=3.29 D
µb=2.38 D
(calc.)Slide18
18
Acknowledgements
Mahdi Kamaee
Dr. Ming Sun
Questions???
vanwijng@cc.umanitoba.ca
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