dispersed fluorescence spectroscopy of jet-cooled p-aminotoluene 61 st osu isms 2006 partha biswas,...

Dispersed Fluorescence Spectroscopy of Jet-Cooled p-Aminotoluene

61st OSU ISMS 2006

Partha Biswas,a) Montu Kumar Hazra a) and

Tapas Chakraborty a,b)

a) Department of Chemistry, Indian Institute of Technology Kanpur, UP 208016, india

b) Department of Physical Chemistry, Indian association for the Cultivation of Science, Jadavpur, Calcutta 700032, india

Yan, S.; Spangler, L. H. J. Chem. Phys. 1992, 96, 4106.

p-Aminotoluene

Methyl –internal rotationAmine –umbrella-type inversion and torsional motion

.

Yan, S.; Spangler, L. H. J. Chem. Phys. 1992, 96, 4106 Tan, X. Q.; Pratt, D. W. J. Chem. Phys. 1994, 100, 7061

How these two moieties interact with each other through the aromatic ring and what is the consequence of that?

p-Aminotoluene is an ideal system to investigate the ring-mediated coupling between the large-amplitude motions associated with methyl and amine

0 200 400 600 800 1000 1200

1263

1255

1207

8868

688

29

820774

730

438

b. p-Fluoroaniline

14

a. p-Fluorotoluene

12631230

1206

1026

855

803

719

561

412407

308

289

255

219

171

132

108

7453

1247

1194

1169

1192

899864

816

792

737,7

44

711,7

25

429

374

293

52

83

c. p-AminotolueneIn

ten

sity

Wavenumber(cm-1)

Fluorescence excitation spectra of a.p-Fluorotoluene b.p-Fluoroaniline and c.p-Aminotoluene

Ju, Q..; Parmenter, C.S..; Stone, T.A.; Zhao, Z-Q. Israel J. Chem. 1997, 37, 379.

d-s

ub

stitu

tion

0 -500 -1000 -1500

0 -50 -100 -150 -200 -250156

278

214

178

80

52

Wavenumber(cm-1)

386

b. p-Fluoroaniline

460

539 1356

1310

12941

281

1240

898

851

755

480

440

350

I0 2X

c. p-Aminotoluene

a. p-Fluorotoluene

1304

1240

902

848

725

637

456

281

244

1378

1356

1304

1272

1225

1191,1

203

1181

1076

926

895

841 (

1)

811

744 (

12 )

711

649

539

464 ( 6a)

435 (

I0 2 )

Inte

nsity

Wavenumber(cm-1)

I0 2( N

H2)0 2

Y0 1

X=

CH 3 ,

F

Mode Y : out-of-plane methyl bending

Dispersed Fluorescence spectra exciting the origin bands of a.p-Fluorotoluene

b.p-Fluoroaniline and c.p-Aminotoluene

Ju, Q..; Parmenter, C.S..; Stone, T.A.; Zhao, Z-Q. Israel J. Chem. 1997, 37, 379.

Comparison of Dispersed Fluorescence spectra exciting the 6a mode

of p-Aminotoluene and p-Fluoroaniline

0 -500 -1000 -1500

0 -50 -100-150-200-250-300

278

214

80

52

464

811

435

0DF exciting the (00+429) cm-1 band of p-Aaminotoluene

1378

1356

13111281

1240

969

918

898

851

755

4804

60

440

386

1082

1181

1390

895

841

841

1226

464

464

841

744

539

4644

35

350

0DF exciting the (00+438) cm-1 band of p-Fluoroaniline

Inte

nsity

Wavenumber(cm-1)

6a

0 -500 -1000 -1500

I0 2

Y

0 1

53

9

13

51

12

01

10

91

85

1

75

5

46

0

14

31

89

5

13

50

13

03

12

23

43

5

10

76

10

29

46

44

64

84

1

74

4

50

746

4DF exciting the (00

0+730)cm-1 of p-Fluoroaniline

DF exciting the (00

0+711)cm1 p-Aminotoluene

Inte

nsity

Wavenumber(cm-1)

Mode Y : out-of-plane methyl bending

Comparison of Dispersed Fluorescence spectra exciting the 711 and 730 cm-1 band

of p-aminotoluene and p-fluoroaniline respectively

Comparison of Dispersed Fluorescence spectra exciting the Inversion mode

of p-Aminotoluene and p-Fluoroaniline

0 -500 -1000 -1500

I20 9b0

1CH

3)

I2 2

(CH3)I2

0 16a0

2CH

3)

84

1

435 464

13

55

13

31

13

10

12

94

12

13

10

89

10

63

10

32

96

993

991

989

885

2

75

5

48

04

60

44

0

14

52

13

78

13

56

84

1

12

59

10

76

10

19

99

29

61

92

7

46

48

41

82

3

74

4

63

753

9

46

44

35

24

0

0DF exciting the (00+774)cm-1 of p-Fluoroaniline

DF exciting the (00+737)cm-1 of p-Aminotoluene

Inte

nsity

Wavenumber(cm-1)

or

6a

Theoretical prediction is indicating the amino torsion (mode 44) mixed with out-of-plane mode 39 and mode 41 and in-plane mode 42 upon electronic excitation but not with mode 45 (methyl torsion) of

p-Aminotoluene

Q'39 =-0.949Q"38 + 0.285Q"39 + 0.120Q"40

Q'40 =-0.275Q"38 -0.942Q"39 - 0.177Q"44

Q'41 =-0.109Q"40 + 0.634Q"41 - 0.760Q"42

Q'42 = 0.996Q"43

Q'43 = 0.165Q"39 + 0.161Q"41 + 0.128Q"42 -

0.960Q"44

Q'44 =-0.747Q"41 - 0.630Q"42 - 0.179Q"44

Q'45 =-0.996Q"45

Mode-39 Frequency-527 cm-1

16b


16a


9b

Normal modes in the S0 state those are mixed with amino torsion mode-44

S1 modes Expansion in S0 modes

Limitation of the calculation in harmonic limit !!!

(ab initio calculations are performed in CASSCF(8,7)/6-311g** level)

0

0

0

0

00

0

0

0

0

-3000-2000-10000-3000-2000-10000

p-fluoroanilinep-aminotoluene

00- cm-1 excitation

(00+1255) cm-1 excitation




00- cm-1 excitation





Inte

nsi

ty

Wavenumber(cm-1)

00

0 - excitation 00

0 - excitation

0 -1000 -2000 -3000-3000-2000-10000

p-vinylfluorobenzene

(00

0 +507) cm-1 excitation (00

0 +507) cm-1 excitation

(00



(00



(00



p-vinyltoluene

Wavenumber (cm-1)

Dispersed Fluorescence spectral signatures of excited state IVR

Interact with each other via aromatic ring

p-vinyltoluene

Biswas, P.; Panja, S. S.; Manogaran, S.; Chakraborty, T. J. Phys. Chem. A 2005, 109, 3225.

Fluorescence excitation spectra of a. p-vinylfluorobenzene b. toluene and

c. p-vinyltoluene,

0 200 400 600 800 1000 1200

1263

1193997

988

9669

35

915

864

809754

736

613

532

462

457

372332

55

b. toluene

796

801

1206

1202

949

954

842

805

500

507

4323

92

348

360

3072

392

21

706 1

202

11897

96772

507

450

417

369335

315

235

214

53

33

18

a. p-vinylfluorobenzene

c. p-vinyltoluene

Inte

nsity

Wavenumber (cm-1)

Hickman, C.G.; Gascooke, J.R. ; Lawrence, W.D. J. Chem. Phys. 1996, 104, 4887.

0 -500 -1000 -1500

(49

)2 1(5

0)0 1(5

1)1e

2e

(49

)0 2(5

0)0 2(5

1)0a1

3a1

13

6

1206

644

267

173

414

822

1182

1206

644

822

190

267

19

084

267

1465

1206

414

173

644

822

53

841

8209

1646

1628

1640

1465

1032

1206

822

644

535

525

414

209

173

84

53

18

(00


(00


00

0 - excitation

Inte

nsity

Wavenumber (cm-1)

(49

)0 2(5

0)0 2

Dispersed fluorescence spectra following excitations of the origin band , 214 &

235 cm-1 vibronic bands of the fluorescence excitation spectrum of p-vinyltoluene

Mode 49 – vinyl bending ;Mode 50 – vinyl torsion ;Mode 51-methyl torsion

0 -500 -1000 -1500

*

**

**

**190

173

136

84 4

14

644

822

1206

330

535

800

695

644

644

822

822

800

695

535

583

(00


644

822

644

822

426

535

414

330

265

173

84

1206

822

644

525

414

8453

18

525

53

1206

822

644

414

18

350

(00


(00


(0 0


Inte

nsity

Wavenumber (cm-1)

* Appearance of these bands are indicative of partial mixing of in-plane and out of plane modes involving the methyl torsional mode upon electronic excitation

Dispersed fluorescence spectra following excitations of the 335, 417, 450 and 507 cm-1 vibronic bands of the fluorescence excitation spectrum of p-

vinyltoluene

Theoretical prediction is indicating the Duschinsky mixing of methyl torsion (mode 51) with vinyl torsion (mode 50) and out-

of-plane vinyl bending (mode 49) modes upon electronic excitation of p-vinyltoluene

Q47

’ = 0.139 Q46’’ - 0.960 Q47

’’ - 0.161 Q48’’

Q48’ = -0.129 Q46

’’ - 0.215 Q47’’ + 0.944 Q48

’’ - 0.139 Q50’’

Q49’ = -0.111 Q47

’’ - 0.204 Q48’’ - 0.760 Q49

’’ - 0.562 Q50’’ -

0.213 Q51’’

Q50’ = -0.610 Q49

’’ + 0.732 Q50’’ + 0.282 Q51

’’

Q51’ = 0.360 Q50

’’ - 0.932 Q51’’

S1 modes Expansion in S0 modes

Mode-50 Frequency-12 cm-1 Mode-49 Frequency-141 cm-1

Mode-48 Frequency-305 cm-1 Mode-47 Frequency- 431 cm-1 Mode-46 Frequency- 486 cm-1

Mode-51 Frequency- 15 cm-1

Normal modes in the ground electronic state(ab initio calculations are performed in CASSCF(8,8)/6-31g** level)

In p-Aminotoluene…….

The features of our measured dispersed fluorescence spectra presented here bear signatures of coupling of amine inversion and torsion with low-energy modes involving the methyl group. Specifically, the dispersed fluorescence spectrum measured following excitation of a vibronic band of 711 cm-1 excess energy reveal coupling of amine torsion with the mode corresponds to methyl motion of out-of-plane bending type. Furthermore , dispersed fluorescence spectral features for excitation with 737 cm-1 excess energy shows that amine inversion motion is coupled with ring vibration of 16a type with methyl torsion as well as out-of-plane methyl bending vibration. The details of the analysis will be published elsewhere.

Summary and Conclusion:

Labmates: Chayan K. Nandi, Sujit S. Panja, V. Ramanathan,

Amit Samanta, Prasenjit Pandey, Biman Bandopadhay

Prof. S. Manogaran ,IIT Kanpur, India

Indian Institute of Technology Kanpur, INDIA

Department of Science and Technology, Govt. of India.

Acknowledgement

dispersed fluorescence spectroscopy of jet-cooled p-aminotoluene 61 st osu isms 2006 partha biswas,...

Documents