Mahdi Kamaee and Jennifer van Wijngaarden - PowerPoint Presentation

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

C1C21.381(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

C1C5

1.450(3)1.455(6)

1.443(5)

1.435(C1

C2C3)

118.1(5)119.4(4)

119.5(3)119.5

(C2C3

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)

C1C2

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

C1C5

1.443(5)1.430(3)

-0.009

(C1C2C3)

119.5(3)121.1(2)

+1.4

(C2C3

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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