Vibrational spectra and structure of diphenylacetilenes

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Vibrational Spectra and Structure of DiphenylacetilenesM. Alcolea Palafoxa

a Departamento de Química-Física I (Espectroscopia), Facultad de Ciencias Químicas, UniversidadComplutense, Madrid, SPAIN

To cite this Article Palafox, M. Alcolea(1996) 'Vibrational Spectra and Structure of Diphenylacetilenes', SpectroscopyLetters, 29: 2, 241 — 266To link to this Article: DOI: 10.1080/00387019608001600URL: http://dx.doi.org/10.1080/00387019608001600

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SPECTROSCOPY LETTERS, 29(2), 241-266 (1996)

VIBRATIONAL SPECTRA AND STRUCTURE OF DIPHENYLACETILENES

Key words: Vibrational frequencies, diphenylacetylene, infrared spectra, geometry optimization, scaling frequencies, AM1

M. Alcolea Palafox

Departamento de Quirmca-Fisica I (Espectroscopia), Facultad de Ciencias Quirmcas, Universidad Complutense, 28040- Madrid, SPATN

ABSTRACT

The vibrational spectra of diphenylacetylene and its deuterated forms were recorded, compared and their vibrations analysed. Using the AM 1 semiempirical method, the optimum geometric parameters of diphenylacetylene (tolane) and four halo-substituted were obtained, and the theoretical idiared spectra were calculated and compared. Several vibrational modes, especially in the low fiequency range, were established. A few thermodynamic parameters, net atomic charges and atomic electron density were computed.

INTRODUCTION

The molecular structure of diphenylacetylene (tolane) has been the subject of both experimental and theoretical studies. The molecule in the So state is known to be in a planar structure having D, symmetry in the crystalline state. The molecular structure has been studied by electron difiction in the gas phase at 150°C and by X-ray crystallography'4.

24 I

Copyright 0 1996 by Marcel Dekker, Inc.

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242 ALCOLEA PALAFOX

Theoretical calculations based on the two-dimensional Hiickel molecular orbital theory, as by CNDO methods, it has been determined that the planar structure of tolane is somewhat more stable than the perpendicular one, although by INDO and CNDO/2 semiempirical calculations2,6, the perpendicular form has been found to be more stable. The rotation potential has also been studied and it has been reported that its shape for an isolated molecule d y depends on conjugation between the unsaturated fiagments. Ab initio studies using h P 2 treatment of electron correlation, varying only the torsional angle corresponding to the C=C bond, show the two phenyl rings coplanar in the equilibrium geometry'. In view of the importance of the -C=C- bond and to understand the planarity of the structure, the present work shows the theoretical study with four halo-substituted in ortho position.

Concerning the fimdamental fiequencies of tolane, they have been identified with different force fields and with a normal coordinate treatmenP9. Also, the IR spectra of solid and solution samples have been reported", as well as the complete Raman spectra in solid and solution phases"', but many doubts yet remain in the assignment of the bands of their spectra, specially in the low fiequency range. The assignment shown in the present paper is based on the frequencies computed by the AM1 semiempirical method and correlations by scale factors with experimental fiequencies reported for benzene" and for other molecule^'^. Also correlations with the bands assigned in the spectrum of phenyl acetylene

methylacetylene (MA) and dunethylacetylene @MA)16, were carried out.

COMPUTATIONAL METJIODS

All the calculations were carried out with the AM1 semiempirical method from the AMPAC".'* and GAUSSIAN 9219 program packages. The optimum geometrical values were obtained without fixing any parameter, and with the keyword PRECISE in the M A C package and with the OPT=TIGHT convergence with GAUSSIAN 92 The vibrational fiequencies and intensities in this structure of minimum energy were calculated

The DRAW programZo was also used for graphical evaluation of the correctness of starting geometries prior to calculation, to review the resulting optimized geometries after the calculation, and to help in the identification of all the normal vibration modes obtained by M I . The drawings were observed in high- resolution graphics computer terminals, Tektronic 4 105 model


DIPHENY LACETILENES 243

EXPERIMENTAL

Tolane was purchased fiom Merck Ltd. and was used without hrther purification. Deuterated samples were prepared using a method similar to that previously reported2'. Infrared spectra were recorded on a Perkin Elmer 599 B spectrophotometer. Indene and polystyrene were used for instrument calibration. The infrared frequencies were accurate to 1 cm".

RESULTS AND DISCUSSION GEOMETRY OPTIMIZATION

The final structural parameters in tolane molecule computed by AMl, are listed in the second column of Tables 1-3: bond lengths, bond angles and torsional angles, respectively. The atom notation is shown in Fig. 1. Although the compiited data by AM1 correspond to a molecule isolated without the environment of the crystal structure, the results obtained are in agreement with the experimental ones, as discussed below.

The tolane conformation by AM1 was found to be planar, as in the crystal, and the deviations of the valence angles from 180" were not greater than *2". A review with the results fiom the structure refinements of the electron difiaction and X-ray data available in the literature has been reported'. The dimensions for the free molecule of tolane published more recently by X-ray dieaction are listed in the fourth column of Tables 1-2. In the crystal two crystallographically independent molecules, making an angle between their planes of 49.2", have been found with considerable structural Werences between them. The lengths and angles shown in the fourth column, are the average of the parameters of both molecules found in the crystal. The chemically equivalent atoms, but crystallographically independent parts of the molecule are also averaged'. When hydrogen atoms were involved, the crystallographic data were taken from ref. [2].

Taking into account the different physical meanings of structure parameters reported by electron &%action and by X-ray methods, the conformity of the results by Ah41 in tolane is fairly good. In an analysis of these values, the following is observed: All C-C distances in the phenyl ring calculated by Ah41 are larger than the main value of 1.392 A


244 ALCOLEA PALAFOX

Tablel'. Bond lengths in A optimized by AM1 in tolane and different halo- substituted derivatives, and mean molecular dimensions averaged over equivalent bonds reported in the aystal of tolane. Due to the symmetry of the molecule, only the values of ring I are shown

r C( 1 kC(2)

r C(2)-C(3)

r C(2)-CcI)

r C(3)-C(4)

r C(4)-C(S)

r C(5)-C(6)

r C(6)-C(7)

r C(3)-X(8)

r C(4)-H(9)

r C(5)-H(I0)

r C(7)-X(11)

r C(6)-H( 12)

r C( 1)42(13)

r C(3)-C(7)

r C(4)..*C(6)

r C(2)-C(5)

r C(2PC(14)

r C(5)-C(17)

r X(8)X(20)

r X( 1 1 pX(23)

AM1

1.4059

1.4053

1.4052

1.3928

1.3950

1.3950

1.3928

1.1Ooo

1.1001

1.0998

1 . 1 m

1.1001

1.2000

2.4268

2.4152

2.7998

4.01 18

9.61 16

4.3292

4.3315 -

X = H

AM1 rrmted 9 0 0

1.4063

1.4033

1.4075

1.3932

1.3942

1.3952

1.3921

-

1.1004

1.1001

1.0997

1.1002

1 .1001

1.1997

2.4228

2.41 35

2.8044

4.0129

9.6160

5.3491

5.2692 -

- 1.439

1.396

1.396

1.389

1.383

1.383

1.389

0.957'

0.92'

0.95'

0.9T

0.957'

1.192

2416'

2.43Y

2.795'

4.049"

9.638'

X = F

- 1.4013

1.4176

1.4193

1.4062

1.3901

1.3907

1.4067

1.3522

1.1OOo

1.1013

1.3520

1.0998

1.1999

2.4277

2.41 63

2.8284

4 0028

9.6561

4.1943

4.13% -

- x=c1

- 1.4040

1.4098

1.41 16

1.3973

1.3920

1.3933

1.3972

1.6973

1.1016

1.1003

1.6979

1.1012

1.1999

2.4181

2.41 13

2.82 12

4.0083

9.6468

3.8674

3.8013 -

X=Br

- 1.4049

1.4088

14115

1.3954

1.3940

1.3932

1.3964

1.8743

1.1022

1.1002

1.8747

1.1021

1.2000

2 4265

2.4 125

2.8125

4.0101

9.6299

3 7332

3.5613 -

X = l

- 14060

1 4051

14104

13930

I3938

13958

13935

2 0244

1 1022

11002

2 0241

11019

12003

2 4258

2 4147

2 8062

40129

9 6207

3 5448

3 4494 - ' In tables 1-3, the last digit shown in the calculated values is to aid in reproduction

According to of the results and is not thought to be physically meaningfbl. ref 4. 'Average value according to ref 2. "According to ref. 1.



Table 2. Comparison of the bond angles, in degrees, between the optimized structure of tolane by AM1 and X-ray data with those calculated in several halo-substituted derivatives. Due to the symmeq of the molecule, only the values of ring I are shown

Bond angles

L C(I)-C(2)-C(3)

L C(Z)-C(3)-C(4)

L C(3)-C(4)-C(S)

L C(2)-C(7)-C(6)

L C(4)-C(5)-C(6)

L C(I)-C(2)-C(7)

L C(3)-C(2)-C(7)

L C(S)-C(6)-C(7)

L C(2)-C(3)-X(8) L C(4)-C(3)-X(8)

L C(3)-C(4)-H(9)

L C(S)-C(4)-H(9)

L C(4)-C(S)-H(IO)

L C(6)-C(S)-H(IO)

L C(2)-C(7)-X( 11 )

L C(6)-C(7)-X( 1 1 )

L C(7)-C(6)-H(12)

L C( 5)-C(6)-H( 12)

L C(Z)-C(I).C( 13) L C(I)=C(13)-C( 14)

Ah41 - 121.28

120.05

120.28

120.32

119.92

119.26

1 19.04

120.28

119.73

120.22

119.74

1 19.98

120.04

120.04

119.73

120.22

119.75

119.98 I

X = H

AM1 d 90'

121 70

120 28

120 30

120 26

11982

1 I9 22

11907

120 26

11965

120 06

11967

120 03

120 11

120 07

11961

120 13

11976

11998

179.99 ~ 17981 179.98 ~ 17993

X-ray

120 2

1199

120 3

1199

120 0

120 2

1197

120 3

1 I9 55-

120 3*

118 72'

120 97'

119Y

1199'

1 I9 55'

120 3'

118 72-

120 97-

=

X = F

121 70

120 92

119 94

120 93

120 67

120 61

11768

11985

120 09

11898

119 17

I20 88

11967

1 I9 66

120 11

1 I8 97

11923

120 92

I79 90 I80 00

- x =c1 - 121 70

120 74

120 35

I21 02

11993

120 33

11798

120 00

I20 44

1 I8 82

1 I9 74

11991

120 03

120 04

120 40

11859

I1995

120 05

I80 O(1

179 83 -

X = Br

= 121 70

120 34

120 40

I20 36

1 I9 89

11957

11872

120 28

I20 73

11893

120 16

11944

120 02

120 09

120 91

1 I8 73

120 20

I1952

179 68 I79 65

121 70

120 27

120 38

120 29

11991

119 30

1 I8 99

120 16

120 88

11885

120 19

1 I9 43

120 08

120 01

120 92

118 78

I20 38

1 I9 35

179 75 I79 90 -

'According to ref. 4. * Average value according to ref. 2


246 ALCOLEA PALAFOX

Table 3. Final torsional angles L in degrees using AM 1 in tolane and different halo- substituted derivatives. The other dihedral angles not listed in this table are planar. Due to the symmetry of the molecule, only the values of ring I are shown.

Torsional angles

L C(2)-C(3)-C(4)-C(S)

L C(2)-C(7)-C(6)-C(5)

L C( I)-C(2)-C(7)-C(6)

L C(3)-C(z)-C(7)-C(6)

L C(3)-C(4)-C(S)-C(6)

L C(4)-C(S)-C(6)-C(7)

L C(4)-C(3)-C(2)-C(7)

L C( I)-C(?)-C(3)-X(8)

L C(S)-C(4)-C(3)-X(S)

L C(7)-C(2)-C(3)-X(8)

L C(2)-C(3)-C(4)-H(9)

L C(6)-C(S)-C(4)-H(9)

L X(S)-C(3)-C(4)-H(9)

L C(7)-C(6)-C(S)-H(IO)

L H(9)-C(4)-C(S)-H( 10)

L C(1 )-C(2)-C(7)-X(I I )

L C(3)-C(2)-C(7)-X(I 1)

L C(5)-C(6)-C(7)-X(I I )

L C(Z)-C(7)-C(6)-H(12)

L C(4)-C(S)-C(6)-H(12)

L H(IO)-C(j)-C(6)-H(12)

L X( 1 1 )-C(7)-C(6)-H( 12)

L C(3)-C(2,-C( l ) = C ( 13)

L C(7)-C(2)-C(1)~C(13)

L C(2)-C( 1) = C( 1 3)-C( 14)

/ C( I).C(I 3)-C( 14)-C( 15)

L C( 1 ).C( 13)-C( 14)-C( 19)

X = H - planar -

-0 02

000

180 0

-0 02

0 01

0 01

0 02

0 02

17999

-17997

179 98

18000

-0 01

180 00

0 01

-0 02

179 99

179 99

18000

18000

0 00

0 0 0

I9 87

5 42

80 05

60 44

-1 17 -

rotated 90"

0 0

0 0

180 0

0 0

0 0

0 0

0 0

0 0

180 0

I80 0

180 0

I80 0

0 0

I80 0

0 0

0 0

180 0

I80 0

I80 0

180 0

0 0

0 0

-178 57

1 4 3

-2 05

90 52

-89 48 -

=

X = F

- -0 09

0 03

-179 91

0 02

0 15

-0 12

0 01

-0 12

I79 %

179 95

179 95

-179 90

0 01

179 98

0 00

0 12

-179 95

-17999

179 99

179 91

0 01

-0 02

18000

-0 08

-7 29

-173 01

6 96 -

=

x = CI

- 0 02

0 01

180 00

-0 02

-0 03

0 01

0 0 0

0 02

I79 99

-17996

-179 %

I79 95

0 01

179 99

-0 03

-0 0 3

179 95

-179 96

-179 99

-179 99

-0 01

0 04

-14 04

165 94

I03 61

-89 97

90 03 -

X = Br

- -0 05

-0 1 3

-179 90

0 08

-0 10

0 24

0 0 6

-0 06

-179 95

17996

179 91

I79 94

0 01

-179 83

0 01

0 61

-179 41

179 27

I79 86

-179 85

0 07

-0 6 3

-137 54

42 41

-56 57

-166 03

I3 88 -

- X = I

- -0 05

0 04

-179 98

-0 16

-0 07

0 08

0 16

0 01

179 92

-17981

I79 86

-179 99

-0 17

-179 99

0 08

0 37

-179 80

179 69

-1 79 99

-179 89

0 03

-0 34

1 1 31

-168 87

109 20

-1 I9 74

60 30 -



Fig. 1. Labeling of the atoms for tolane (X = H) and halo-substituted derivatives (X = F, CI, Br, I).

obtained for benzene” and those reported in the crystal by X-ray d i f h ~ t i o n ~ ~ . Values detexminated by electron diffiaction’*23 1.400, 1.398 A or those by X-ray), 1.401 8, agree well with our calculations.

The 1.4053 and 1.4058 8, values obtained by AM1 for C( 1)-C(2) and C(13)-C(14) respectively, bonds adjacent to a triple bond and a phenyl ring, are in accordance only with the value 1.401 A reported by X-rag, but are fsr away from those by electron dif&action’.23 1.41 7,1.425 A or X-rayZ4 1.438, 1.439 4 and fiom those reported elsewhere24. The 1.200 A value obtained for the C=C triple bond length agrees with’.23 1.215, 1.207 8, andz4 1.198, 1.192 A and it is shorter than2 CND0/2, 1.216 A. The ring-C= single bond and the C=C bond are shorter than those of the phenylacetylene 1.448 and 1.208 A respectivelyZ5.

The internal rotation on the -C=C- bond in several halogen derivatives of tolane (x5c6-c =C-C,XJ has been determined by Molecular Mechanicsz6. Thus with X=F, the structure has a planar equilibrium conformation, while with X=Cl, Br the torsional potential function possesses a double minimum. Full optimizations in the barrier height of the potential function were performed with AM1 . Tables 3-3 only show the values obtained in tolane (X = H), the h d column.

The effect of the fluorine, chlorine, bromine and iodine substitution (X atom) on the ring structure and the triple bond were also studied in tolane (Fig. 1). In columns 5-8 of Tables 1-3 are shown the optimum


248 ALCOLEA PALAFOX

geometric parameters obtained. No appreciable variation of the character of the triple bond is observed with the X substitution.

Several interatomic distances of interest are also listed in Table 1. Thus it is noted that the phenyl rings of the tolane molecule are sufficiently separated fiom each other with a C(2)--C(14) distance of 4.011 8, by AM1 and 4.049 8, by X-ray’ for the steric interaction between them to be completely ruled out. Therefore the 7t-electron conjugation keeping two tolane rings in one plane may be opposed only by intermolecular interaction. When the atom X (see Fig. 1 ) are substituted by a halogen, the C(2)-C(14) distance has very small variation, less than 0.008 A. However, the rings are larger in the direction of the acetylene bridge. The C(2).-C(5) distance is maximum with fluorine, 2.828 A, and decrease with the decrement of the electronegativity of the substituent, until the value with iodme, 2.806 & whch is very close to that with hydrogen (tolane), 2.805 A. Consequently, C(5)--C(17) changes from 9.656 8, with X=fluorine to 9.621 A with X=iodme, or 9.616 A with X=hydrogen. Due to the trends in atomic sizes for the atoms represented in X, the X(8)-X(20) distance changes remarkably from 4.392 8, with X=hydrogen (minimum atomic radlus) to 3.545 A with X=iodine (maximum atomic radius).

In solution, the most probable tolane conformation has been reported as planar, as shown by electronic absorption spectra2’ and Raman spectra of solutions”, although some experimental results have been ascribed to the fraction of non-planar molecules present’. The electronic spectra of tolane in vapour phase in supersonic free jet has been published”.

VIBRATIONAL FREQUENCIES

Table 4 shows the bands computed by AM1 (the second column), their relative intensities (the third column), the reduced masses and force constant of each vibration (the fourth-fifth columns), the IR bands reported in solid and solution phases (the tenth-eleventh columns)’O, the Raman lines in the solid state (the twelfth column)’.” and the assignment established by AM1 (the thirteen column). The intensities were obtained by dividmg the computed value by the intensity of the strongest line (in


Tabl

e -

No. - I. 2.

3.

4.

5.

6.

7.

8-

10.

I I.

12.

13.

14.

15.

16.

17.

IS.

19. -

rcla

tivc

ntcn

rity

.

i

6 28

35 3 6 33 3 5 2 42

49 2 45 7 I I

75

IS 8

4. V

ibra

tiona

l fie

quen

cies

and

assig

nmen

t det

erm

ined

by A

M1

and

expe

rimen

tal ones

fiom

the

IR a

nd R

aman

spe

ctra

in to

lane

WM

J)

3.62

4.70

5.28

4.

39

4.94

4.21

6.42

2.

32

3.84

2.68

6.

95

3.19

7.

95

7.96

6.

77

1.91

2.

01

7.30

- -

Fmq.

(cm-' 1 12

53

55

137

I72

278

302

370

393

520

524

559

585

622

659

66 3

667

668 -

-

-

Fom

m

stan

t jyn

cyrA

) 0

0.0 I

0.01

0.

05

0.09

0. I9

0.35

0.

I9

0.35

0.43

1.

13

0.59

I .

60

1.81

1.

73

0.50

0.

53

I .92

-

- -

Jcsl

c fa

ctor

Ud

b

-

0.98

33

0.93

22

1.06

93

1.06

93

0.87

4 I

-

Sal

Cd

Mm

ey

(c

ni')

-

307

397

547

616

758

- -

@A

em

f -

2.2 I .o

0.6

- mb

initi

o al

cula

. ti

w' II

-

416

405

458

614

538

62 1

688

soec

tra'. an-'

solid

-

58 vs

81 s

157 v

w

280 s

285

m?

314

w?

385

w?

401 s

408 m

468 m

510 s

536 s

620

w

690 vs

66

8 w

IR so

lutio

n -

I56

vw

289

vw?

473

w

511 vs

45

5 sh?

539 vs

60

3 w

62

0 vw

69

0 vs

67

0 w

603

w

Ram

an

solid

32 w

4o

w

47 w

66

w

88 s

I07 v

s?

117w

I5

3 w

15

9 m

-

381

m?

403

w

539 s

622

w

691

vw

686 vw

Cha

ract

eriza

tion

r(rin

g)+

Win

g)

r'(M

g)+

r

ing)'

r(ri

ng)+

y(C

-C)

+ y(

CC

C)

16b

r-(r

ingy

y(

CC

C)

16a

I6b?

y(C

-C-C

-C)

+y(C

CC

. C-H

:

y(C

-C-C

-C)+

y(C

CC

) I6

b?

$(C

-C-C

-C)

+ $(

CC

C)'

y(C

.C)

+ y(

CC

C)'

4 a(

CC

C)

6a

8(C

CC

) 6b

Y(

CC

C) 4

y(

C-C

.-C-C

) + y(

CC

C)4

8(C

-C-C

-C)

+ 8(

CC

C)'

6b

a(C

=C) +

8(C

CC

) 6b

N

v)

(con

tinue

d)

P


Tabl

e 4.

(con

tinue

d)

-

20

21 22

23-

25.

26.

27.

28-

30-

32.

33.

34-

36.

37-

39.

40-

42-

44.

45-

47.

L

4 28

x9 3 21

48

28 3

20(8) 6

41

30(6) 12

II

20

28(19)

13(7)

14

3y

15)

56

78;

81 I

81;

88f

95 5

95 7

96C

988

I007

I073

1119

I I63

I171

I 198

I203

I227

1314

I363

1372

I503

622

I38

I37

125

I57

I57

65

0

I55

I76

436

I71

I20

142

110

241

I 08

I26

550

4 94

388

2.27

0.54

0.53

0.58

0.84

0.85

3.53

0.89

I .05

2.96

I .26

0.95

1.15

0.93

2.06

0.96

1.28

6.02

5.48

5. I6

I .(Mi93

1.1055

I 1055

1.0532

1.0227

1.0227

1.0178

1.0227

1.0222

1.0178

1.10

51

1.1051

1.1051

1.0373

1.2850

1.0373

0.9844

1.2850

1.04

5 I

10654

736

734

735

843

934

936

943

966

985

I053

1013

1053

1061

11

55

937

I183

1336

I060

1313

141

1

3.0

0.6

1.9

0. I

0.1

I .3

1.7

2.6

0.3

2.0

0.3

0.4

0. I I .7

756

770

999

994

999

1027

1077

I029

I I74

1326

I287

738 sh

757 vs

845 w

875 vw

918 s

998 m

965 vw

986

rn

I026 m

1071 s

1i5u

rn'

I179 w

1330 w

1281 rn

1312m

1435 w

756 vs

840 w

845 m

850 w

878 w

914 s

962 w

983 w

1001

w

1028 s

I070 s

I i5u

m?

1176w

1328 w

1280111'

1310rn

754 s

754 s

848 vw

914 vw

995

vs

974 w

983

rn

1025 w?

1074 sh

I034 vw

1159w

I142

s I156 rn

? I175 s

1181

w

1330 w

1334 w

10x6

w

1279111'

1311 m

b(C

CC

) 6a

y(C

-H) I

I or

I0b

y(C

-H) I

Oa

y(C

-H) I

I OT

IO

b

y(C

-H) 17b

y(C

-H) 17b

b(C

CC

) 12

y(C

-H) 17a

Y(C

-H) 5

b(

CC

C) 12

b(C

-H) 18a

b(C

-H) 18b

b(C

-H) 18a

b(C

-H) 9b

6(c

cc) 1

stro

ngly

coup

led w

ilt

b(C

-H) 9a I R

a

b(C

-H) 3

b(C

CC

) I s

trong

ly c

oupl

ed w

itt

v(C

=C) 14 I n

a

v(C

=C) 19a

;I;~&

c~up

lOd


48.

49.

50.

51.

52.

53.

54.

55.

56.

57-

59-

61-

63-

65-

-

-

I560

I563

I6

09

1712

I7

49

I752

17

77

I797

24

94

3183

31

84

3189

3 I92

32

0 I

=

33

71

17

100 27

21

14

88 8

34(1

9)

24(1

6)

6cy5

6)

R4(6

4)

74(2

8)

4.52

4.

55

4.89

8.

91

10.5

7 10

.62

10.7

4 10

.78

11.9

9 1.

08

1.08

1.

08

1.08

1.

09

6.48

6.

55

7.46

15

.39

19.0

6 19

.2 1

19.9

6 20

.52

43.9

5 6.

43

6.43

6.

47

6.49

6.

58

-

1462

14

66

1510

1582

15

84

1608

16

27

3056

30

53

3059

3062

30

69

-

,065

4 .0

654

,065

4

,105

1 ,1

051

1.10

51

1.10

51

1.2

1.5

1.2

1.1

0.8

1.6

1.7

0.5

1.0

0.9

0.6

0.2

1.04

15

I .042

9 1.

0429

1.04

27

I .043

3

-

I444

14

45

I490

I577

15

77

1606

16

16

2256

30

50

3059

3054

30

79

3086

- 14

44 vs

I492

s 15

00 s

I572

m

I600

s

3045

vw

3020

m

3031

m

3045

vw

3052

m

3080

s 30

63 s - 14

44 vs

1499

vs

1574

m

I600

s

3040

s 30

22 s

3082

s 30

62 s

- 14

40m

1481

s

I564 w

1583

sh

1589

vs?

2224

s 30

42 s

3015

w

3054

s 30

78 w

30

62 w

30

81 w

? - v(

C=C

) 1Yb

v(

C=C

) 19b

v(

C=C

) 19

a v(

-C-C

) + v

(C=C

) 19a

v(

C=C

) 8b

v(C

=C) 8b

v(C

=C) 8

a v(

C=C

) 8a

v(C

=C)

v(C

-X) 1

3 v(

C-H

) 7b

v(C

-H) 7

a

v (C

-H) 2

0a

v(C

-H) 2

0b

v(C

-H) 2

' Rel

ativ

e to

line

no

51.

'Cal

cula

ted

V~

,V

,~

~.

fro

m b

enze

ne m

olec

ule

[12]

. ' 1

oO.~v

,,-v,,,~

/v,,,

vq,

is th

e id

entif

ied

stron

ger b

and

ofth

e IR

spe

ctru

m in

the

solid

stat

e.

dAt 4

-3 IG

leve

l, fro

m re

f [9

]. "F

rom

ref

[8].

vs, v

ery

stro

ng; s

. stro

ng; m,

med

ium

; w, w

eak;

vw,

very

wea

k; sh

, sho

ulde

r; X

= su

bstit

uent

. 'w

eak

cont

ribut

ion

of th

is m

ode.

'N

omen

clat

ure

used

acc

ordi

ng

to re

f [ 1

01.


252 ALCOLEAPALAFOX

the present study, h e no. 5 1). In the svrth column appear the scale factors ( v , ~ , & ~ ) fiom benzenei2, used to correct the deficiency of the AM1 method. The results obtained are listed in the seventh column. The YO error determined in this way regarding the experimental data (IR, solid state) is collected in the eighth column.

When a monosubstituted benzene is considered, there are 24 ring vibrational modes in whch the substituent moves with negligible amplitude, and six more which are sensitive to the properties of the substituent . For these vibrations, in general, a good correlation between the reported and calculated fiequencies and intensities was observed. A graphical comparison of the spectra is presented in Fig. 2. For obvious reasons, the experimental fiequencies correspondmg to overtones and combination bands are not shown in Table 4.

Concerning Table 4 it is noted that the computed frequencies are systematically higher than the experimental ones. Such an overestimation by AM1 is a general finding with semiempirical method^'^.^^. An analysis of the different modes is carried out in the following:

C=C modes: The triple bond stretching vibration was computed with weak intensity at 2494 cm-' and tentatively related to the very strong and polarized Raman band at 2224 cm-' in the solid state. By IR this mode has not been observed'. In acetylene this vibration appears at 1973 cm-I, while in methylacetylene (MA) it is at 2142 cm-], and in dunethylacetylene @MA) at 2240 cm-'. When the CH, group is replaced by the phenyl group the frequency is lowered by 24 cm", appearing in PA at 2 1 18 cm-', while the = C-C stretching fiequency is increased by - 260 mi', from 931 (MA) or 938 cm-' @MA) to 1192 cm-' (PA) (mode 13 of the ring). In tolane v( zC-C) is identified in the IR spectrum at ca. 1500 cm-' while the vibrations of mode 13, inter-ring stretching, appear at 3045 cm-' (scaled by AM1 at 3056 cm-' and by ab initio' at 3050 crn-') in dsagreement with the fiequency range established by Var~anyi '~, 1 100- 1300 cm-'. These features are due to the effect of conjugation, in correspondence with the difference observed by microwave measurements in the (=C-C) bond lengths, from 1.458 8, in MA to 1.448 A in PA' and 1.439 A in tolane4.

The C=C and C-Cs bending modes contribute to several vibrations because of extensive mixing of unlike symmetry coordinates. Thus below 700 cm" many of the frequencies computed by AM1



jt Y

E * I E 3

-c- 1

:: t- L L


254 ALCOLEAPALAFOX

correspond to ~(C-CEC-C) and y(C-C=C-C), several of which are illustrated in Fig. 2. In PA the linear 6(C-C=C) has been reported' at 152 cm-', while 6(C=C) and y(C=C) appeared at 516 and 352 cm-' respectively, values lower than in tolane, in which the latter mode is computed at 667, 520 and 393 cm-' and the former at 622 and 524 cm-'. All this is due to an increase in the conjugation effect by the new ring, reflected in the EC-C bond lengths: 1.467 A in dmethylacetylene (DMA), 1.448 A in PA and 1.438 A in tolane3'. In tolane-d,, these vibrations are lower ca. 20 cm-', Table 5 .

Ring modes: Referring to Table 4, the n o d modes of the ring are identified by numbers accordmg to Wilson's notation3', and appear with the experimental fiequencies in the spectral regions characteristic of mono-light substituted benzene^'^. Phase splitting in the experimental bands are not significant in the present compound, thus the fundamental bands appear both in IR and Raman spectra at about the same place8.'0.

In the present study, in the spectral region between 32 10 and 3000 cm-l , four normal modes of the ring were computed by AM 1, the radial vibrations: 2, 20b, 7a and 7b, and mode 13. The latter in mono-light benzene derivatives is characterized as stretching v(C-X). The strongvery strong intensity calculated for these modes, between the hghest determined by Ah41 , are in good agreement with the experimental frequencies8. Thus e.g., the IR bands at 3063, 3062 cm-', solid and solution phases respectively, and the Raman line at 3062 cm-' assigned as a C-H stretching, mode 2, were in agreement with the scaled frequency at 3069 mi' computed by AMl, the % error being very small, 0.2. Mode 20a was not characterized by AM1 . The IR band at 3052 cm-' and the Raman line at 3054 cm-' correspond to this mode.

In the 3000-1600 cm-' range, combinations of the highest ring modes and Fermi resonance have been reported for many experimental bands*, which are not shown in Table 4.

The relation and assignments by AM1 for most of the in-plane fundamentals in the 1600-1000 cm-' range are good. Modes 8a, 8b, 19a, 19b are typical C=C ring stretchings, while 1 8a, 3,9a and 18b are C-H in-plane bendings. No fiuther attention is paid to these vibrations due to the general agreement between scaled Ah41 and experimental fiequencies with very small error (%). An exception is made with the vibration



computed at 1503 cm-' (no. 47 in Table 4), mode 19a, because it appears strongly coupled with mode 18a. This kind of coupling has been studied by Schere?'.

The strong band at 1 142 cm", among the strongest bands in the Raman spectrum, and assigned to the symmetrical C,-C stretching, is not computed drectly by AM1 , but can be included in the normal mode 1 (vibration no. 39 in Table 4). Although the Raman line at 702 cm-' is assigned to the ring breath (mode l), the vibrational mode of thls band is heavily mixed, and it is not concentrated on one mode but is distributed over several ring modes. Thus it is scaled at 937 and 1060 cm-', out of the range predicted by Varsanyi14 (1100-1300 cm-') due to the strong coupling with mode 18a. The asymmetric C,-C stretching, reported by IR"'' in the solid state at 1312 cm", is associated with mode 14, computed by AM1 and scaled at 13 13 cm-I. In PA this mode has been identifiedl4." at 1331 cm-'. The scaled AM1 value at 1336 cm" of mode 3, C-H bending, is in agreement with the IR bands at 1330,1328 cm-I, solid and solution phases respectively, and the Raman lines at 1330,1334 cm-' .

Below lo00 mi' appear the C-H (modes 5 , l Oa, 17a, 17b and 1 1) and C-X (mode lob) out-of-plane vibrations. The IR fiequencies of modes 5 and 17% 986 and 965 cm-' respectively, are very close to those ofPAI4, 986 and 97 1 cm-' and those of benzene, 990 and 967 cm'' respechvely. Thus the scale factors used in tolane and tolaned,, for these modes, reproduce the IR fiequencies perfectly by AM1 , the error being only 1 cm".

The IR band a! 840 cm-' and the Raman line at 848 cm-' have been assigned' as out-of-plane ring vibrations y(CCC), but in our study they corresponded to the y(C-H) mode 10% the scaled AM1 fiequency being at 843 cm-'.

With strong intensity appear the normal mode 11, scaled by Ah41 at 735 cm-' and related to the sharp very strong IR band at 757 cm-'. In PA this mode has been registered in IR at 756 cm-' with very strong inten~ity'~.

The assignments published in the region below 400 cm-' have been often uncertain because of experimental acuities, both in the Raman and IR spectra. The IR fiequency reported at 285 cm-' has been interpreted" as an asymmetric vibration of the tolane skeleton whose totally symmetric mode has been identiiied at 260 cm-' in the fluorescence


256

Table 5. Characteristic frequencies of tolane-d,, - No -

1 2 3 4 5 6 7 8-

10 11 12 13 14 I5 16

17 I8 19 20 21 22-

24

25.

27- 29

3 0. 32 33. 35 36 37. 39 -

10 50 54

128 162 256 291 312

356 444 487 507 528 544 571

606 63 5 648 658 665 692

74 1

815

830 835

848 863 864 873 889 891 944

6 27 34 3 6

38 3

3 ( 5 )

2 36 2

48 85 6

41

7 9 7

72 8 4

4

21(57:

5 36

18 (26: 1 1

9(24: 32

4 12(38:

1

- scale

factor Used -

0.9130

1.1008

1.0725

1.0725

1.0515 1.0515 1.0545

1.0725

1.0572

1.0623 1.0393

1.0393 1.0393 1.0058 1.0058 1.0058 1.0820 1.0206

860 872 857 955

- - caled iq. an.') =

342

480

532

592

626 632 656

69 1

77 I

78 1 803

81C 83C 855 868 884 823 92:

847 w 878 w 9 0 9 ~ 7 824m 925 m 958 m

- - % TOP

- -

5 ;

1 ; 3 .

01

2 ( 1 1

0 1 :

2 ( 31 O ( 01

0

:: 0 ' 2 . 1 ' 1 2 ' 0

3 . a -

- - Ab

laiuo -2lG' - -

263 376 345 35(

ALCOLEA PALAFOX

Characterization

;(ring). +

r '(ring)' r '(ring)+ rIring)* y(C-C) + y(CCC) 16b r ' ( c c c y y(CCC) 16a

y(C-CeC-C)+y(CCC) 160 y(C-C-C-C)+y(CCC) 160

6(C-C=C-C) +6(CCC)* y(C-D) 11 y(C-C) + y(C-D) 1 1

y(C-C) + y(CCC)* 4

6(CCC) 6a

6(C-C=C-C) + 6(CCC) 6t 6(CCC) 6b 6(C.C) + 6(CCC) 6b y(C-X) lob y(C-X) 10b y(C-D) 10a

b(CCC) 6a

y(C-D) 17b

y(C-D) 17a a(C-D) 18a

b(C-D) 18b 6(C-D) 18a

6(C-D) 9a 6(C-D) 9a Y(C-D) 5 6(CCC) 12

6(C-D) 9b


DIPHENYLACETILENES

Table 5. (continued)

1.1 0

3.2 1.6 0.9

1.0 0.6

0 2.3

0.3 0.8 0

0.5

0.1 1.6

0.2 0.1 1.7

257

1036 1036111 957 1036m? 662 915? 846 1003

1284 1277111 1367 1325 1340111 1326 1322s 1430 1382111

1414vs? 1570vs?

1538 1538w 1538 1 5 5 6 ~ 1570 1570-

1578 m 1584 1590111 2260 2 2 3 5 ~ 7 2250 2258w? 2272: 2275 s 22811 2289vs 22911 2255 I

10231 7(25) 10571 7 1141 1312 1354 1436 1500 1504 1564

1696 1739 1741 1770

1794 2335 2337

40- 42. 43. 44. 45- 47. 48. 49. 50.

51. 52. 53. 54.

55. 56. 58-

60- 62- 64- 66.

51 4

20(42) 68 36 81 18

100 25 16 14

85 7(17)

lS(10)

3.9764 1 .mo6 1.2878 12878 1.0507 1.1313 1.1305 1.1305 1.1313

1.1277 1.1277 1.1277

1.1277 1.0277 1.0232 1.0288 1.0288 1.0321

-

- 1048 1036 886

1019 1289 1269 1327 1330 1382

1542 1544 157C

1591 227; 2284 2271 228t 229:

-

b(C-D) 3 B(CCC) 12 B(CCC) 1 b(CCC) 1

v(C=C) 14 v(C=C) 19s v(C=C) 1% v(Clc) 19b v(C=C) 19s

v(=CC) + v(C=C) 19a v(C=C) 8b v(C=C) 8b v(C=C) 8a + v(=C-C)

v(C=C) 8s + v(=C-C) v(C-D) 7b v(C-X) 13 v (C-D) 20a v(C-D) 20b v(C-D) 2 v(C=C)

'IR intensityrelated to line no. 51. lOO.(v,-v,,,I/v,, v,+ is the identified stronger band of the IR spectrum in the solid state. the solid state, from rd [ 101. v$ vay strong; s, strong; m, mediwn; w, weak; VW, very weak; sh, shoulder, X = substituent.

'At C31G level, fkom rcf.[9].

*weak contribution ofthis mode. 'Nomenclature used according to ref. [13]

spectrum3'. By AM1 a band with medium intensity at 278 cm-' was wmputed and associated with mode 16b, and their motions described in Fig. 3. In general, the vibrations computed by AM1 in this region corresponded to out-of-plane modes of the C-GC-C moiety or of the totally tolane skeleton (Fig. 3). In Fig. 4 is compared the predicted AM1 fiequencies with the experimental.

Similar conclusions carried out with the spectrum of tolane may also be dtawn fiom the analysis of the spectra of tolaned,,, Table 5 . The theoretical spectra computed by AM1 is plotted in Fig. 5 , which can be compared with the experimental IR and Raman spectraG".


258 ALCOLEA PALAFOX

54 0-'

r (ring) 57 cm-' ring)

*=a- 394 ao-'

y(CCC) 16b 520 cm-'

y(CCC) 16b

559 em-' y ( -CK-C)

585 Cm"

6(CCC) 6a

667 0-' y(C-CrC-C) + YfCCC) 4

Fig. 3. Several characteristic vibrations observed by AM1 in tolane with the fiequency in which they were computed.



t z 10 m W

O€- I II

>

+ Z - 20 W E

30 4 d

40

n

T T-p 270

IR L r' U."

W 0.9 V = 1.0 2 8 1.1 Y, m 1.2 a

1.3 4 I I I I I I I

400 300 200 100

Wavenumber (crn-')

Fig. 4. (a) AM1 theoretical spectrum. (b) Far inbred spectra*. 'With scaled frequencies .

OTHER MOLECULAR PROPERTIES

In Table 6 are shown several thermodynamic parameters by AM1 on tolane and halo-substituted derivatives, while in Table 7 are listed the values of the charge and atomic electron density. AM1 method gives a reasonably good description of the stereo-geometry and ground-state properties compared with MINDO/3 and and overall electron di~tribution~~, related to that reported' by CNDO/2. In a previous optimization by CND0/2 of the triple-bond distance the charge on the -C. atoms has been calculated, -0.063 e in acetylene and -0.052 e in


260 ALCOLEA PALAFOX

.I

P====-


DIPHENY LACETILENES 26 1

Tabk6. Scvaalthamodynarmc ‘ paramctm computed by AM 1 in tolam and haltxubstituted derivatives.

Parameter X = H planar 5 17.69

546.29

954.70

-

Parameter

Entropy (J/mol K): Total Translational RotatiaOal V i b r a t i d

q ,lanar

2.83 0.25 0.23

452.04 173.38 133.63 145.03 -

tolane’. These close values are due to the fact that the character of the triple bond is not appreciably disturbed by the presence of one or two phenyl rings’. In our AM1 study the halo-substitution did not change this character and the net atomic charges and atomic electron density on the carbons of the acetylene bridge remained almost invariable. In tolane (X=H), the acetylene moiety withdraws electrons of the neighbour carbons. Thus in the carbons the lowest net atomic charge (in absolute value) and atomic electron density corresponded to C(2) and C( 14) while the highest corresponded to the carbons in metu position, C(4), C(6) and C(16), C(18). In the haloderivatives, the charge on C(2), C( 14) was also positive and increased fiom clorine to iodine. No other carbon atom had


Tabl

e 7.

Val

ues o

f the

char

ge an

d at

omic

elec

tron

den

sity i

n to

lane

and

seve

ral h

alo-

subs

titut

ed by

AM

l. D

ue

to th

e sy

mm

etry

of t

he m

olec

ule,

onl

y th

e val

ues o

f ring

I are

show

n =

No.

c1 c2

c3

c4

c5

C6

c7

X8

H9

HI0

XI I

A

12 =

Net

atom

ic ch

arge

s X=A

4.1059

3.9718

4.1054

4. I333

4.1209

4. I335

4.1077

0.8618

0.8659

0.8669

0.8617

0.8659

-

= A

tom

ic ele

ctro

n de

nsity

X

=F

4.0801

4.0392

3.8593

4. I873

4.0715

4. I874

3.8606

7.0873

0.8435

0.8537

7.0870

0.8434

-

- X

=C

I

4.0797

3.9560

4.0342

4.1311

4.1042

4.1307

4.0358

6.9894

0.8477

0.8545

6.9900

0.8471

-

- X

=B

r

4.0787

3.9151

4.1461

4.0988

4.1215

4.0990

4.1483

6.9224

0.8473

0.8540

6.9219

0.8473

-

- X

=I

4.0835

3.9028

4.2435

4.0875

4.1283

4.0875

4.2466

6.8334

0.8497

0.8556

6.8324

0.8495

-

-



positive chatge in the molecule. An exception was noted with X=F, where C(3), C(7) had the positive charge, which was due to the strong electronegativity of fluorine which withdraws electrons on the adjacent carbon.

Concerning the dipole moment, there are no data in the bibliography on tolane, but it has been reported in bis(3'- fluoropheny1)acetylene by CNDO and INDO methods in their different conformations as a function of the dihedral angle', and in PA by microwave stark effect5, 0.656 pD.

The enthalpies of formation of compouuds containing carbon, hydrogen, oxygen and nitrogen by AM1 have been reported to be in agreement with MNDO and the experimental dataM, the mean absolute errors being 6.64 (MNDO) and 5.88 kcal mot' (AM1).

SUMMARY

The geometric parameters computed by the AM1 semiempirical method in phenylacetylene agreed well with the crystallographic results. An exception was observed in the ring-C= single binding to the acetylenic carbon of the molecule.

A good reproduction of the experimental frequencies was obtained with AM1 . The % enur obtained using scale factors, was very small, less than 3.5%. In the assignments, most of the relevant vibrational ikquencies were m accordance with those reported in their IR and Raman spectra. The vii t ions were recognized as characteristic of a monosubstituted benzene and could be interpreted on the basis of two phenyl groups weakly interacting through the acetylenic bridge.

Concerning the intensity of the vibrations it was noted that, in general, the modes not detected in the spectra were those having the lowest computed intensities.

The assignment of tolane, sumnand . m Table 3, was sigdicantly supported by the parallel assignment of tolane-d,,.

ACKNOWLEDGEMENTS

Gmitude is wqmsed to prof. J.E. Boggs for his hospitality and provision of all the facilities of his department. This research was supported in part by grants 6om


264 ALCOLEA PALAFOX

the Robert A. Welch Foundation, the Texas Advanced Technology Program, and Cray Research, Inc. The computations made use of the Cray Computers of the University of Texas Center for high performance computing.

REFERENCES

1. A.V. Abnrmeakov, A. Almenningen, E.M. CyVin, S. J. Cyvin, T. Jonvik, L.S. Ktdnn, C. Romming and L.V. Vilkov, Acta Chem. Scandinavica, A 42,674 (1988).

2. A. Mavridis and I. Moustakali-Mavridis, Acta Crystallogr., B 33,3612 (1977).

3. V.D. Samarskaya, R.M. Myasnikova and A.I. Kitaigorodskii, Kristullogrcrfiya, 13,6 16 ( 1968).

4. A.A. Espiritu and J.G. White, Z. Krist., 147, 177 (1978).

5. S.J. Gym, B.N. Cyvin and J. Bmvoll, Kgl. Norske ndenskab. Selskabs SknBer (Pm. Royal Norwegian Soc. of Sciences and Letters), 5 (1982).

6. A. Liberles and B. Matlosz, J. OR. Chem., 36,2710 (1971).

7. S. Saeb, J. AlmlbC J.E. B o g s and J.G. Stark, J. Mol. Struct., 200, 361 (1989).

8. G. Baranovic, L. Colombo and D. Skare, J. Mol. Strucr., 147, 275 (1986).

9. A. Shimojima and H. Takahashi,. J. Phys Chem., 97,9103 (1993).

10. C. Pecile and B. Lunelli, Can. J. Chem., 47,235 (1969).

1 1. B. Kellerer, H.H. Hacker and J. Brandmuller, Indian J. PUM Appl. Phys., 9,903 (1971).

12. M. Alcolea Palafox, paper in preparation.

13. M. Alcolea Palafox, J. Mol. Stmcr., 236, 161 (1991).



14.

15.

16.

17.

18.

19.

20.

21.

22.

23.

24.

25.

G. Varsanyi, Assignments for vibmtional spectra of seven hundred benzene derivatives, vol. 1, Ed. Adam Hilger, London 1974.

J.C. Evans and R.A. Nyquist, S’ctivchim. Acta, 16,918 (1960).

D. Lh-Vien, N.B. Colthup, W.G. Fateley and J.G. Grasselli, The Handbook ofInjwrvd andRaman Chamcteristic Frequencies of Organic Molecules, H.B. Jovanovich (Ed.), Academic Press, Inc., pp. 95, San Diego (California) 199 1.

M.J.S. Dewarand J.J.P. Stewart, Q.C.RE. Bull., 6, 506 (1986).

D.A. Liotard, E.F. Healy, J.M. Ruiz and M.J.S. Dewar, AMPAC MAM/AL. Version 2.1. A general molecular orbital package, Ed. R.D. Dennington, II & E.F. Healy, Univ. of Texas at Austin (1989). QCPE program no. 506.

M.J. Frisch, G.W. Truclcs, M. Head-Gordon, P.M.W. Gill, M.W. Wong, J.B. Fcmxmm, B.G. Johnson, H.B. Schlegel, M.A. Robb, E.S. Replogle, R Gomperts, J.L. Andres, K. Raghavacw J.S. Binkley, C. Gonzalez, R.L. Martin, D.J. Fox, D.J. Defiees, J. Bakery J.J.P. Stewart, and J.A. Pople, GAUSSUN 92, Gaussian Inc., Pittsburgh PA, 1992.

D.M. Storch, DRAW molecule drawing pivgram, Dewar group, University of Texas at Austh, USA (1984).

(a) RD. Stephens and C.E. Castro, J. Org. Chem., 28,3313 (1963). (b) C.E. Castro, E.J. Gaughan and D.C. Oweley, J Org. Chem., 31,4071 (19w.

E.G. Cox, D.W.J. Cruiclcshauk and J.A.S. Smith, Pivc. R SOC. London., Ser A, 247, 1 (1958).

M.E. Nipan, PhD Thesis, Department of Chemistry, Moscow State University, Moscow 1982.

H. hgartinger, Chem. Ber., 106,751 (1973).

AP. Cox, 1.C. Ewart and W.M. Stigllani, J Chem. SOC. Faraday Trans., 2,71,504 (1974).


266 ALCOLEA PALAFOX

26. R Stolevik and P. Bakken, J. Mol. Struct., 239,205 (1990).

27. H. Suzula., K. Kayano, T. Shida and A. Kira, Bull. Chem. SOC. Jpn., 55, 3690 (1982).

28. K. Okuyama, T. Hasegawa, M. It0 and N. Mikami, J. P@s. Chem., 88, 1711 (1984).

29. B. Lunelli, G. Orlandi, F. Zerbetto and M.G. Giorgiui, J. Mol. Struct. (Theochem.), 60,307 (1989).

30. G. Baranovic, L. Colombo, K. Furic, J.R. Durig, J.F. Sullivan and J . Mdc, J. Mol. Strucf., 144, 53 (1986).

31. E.B. Wilson, Phys. Rev., 45,706 (1934).

32. J.R. Scherer, Spectmchim. Acra, 19,601 (1963).

33. G.V. Gobov, Opt. Spectry. USSR, 15, 194 (1963).

34. (a) M.J.S. Dewar, E.G. Zoebisch, E.F. Healy and J.J.P. Stewart, J. Am. Chem. SOC., 107, 3902 (1985). (b) M.J.S. Dewar and K.M. Dieter, J . Am. Chem. SOC., 108,8075 (1986).

35. A.L. McClellan, Tables of experimental dipole moments, Rahara Enterprises, pp. 401, El Cerrito, California 1989.

Received: August 3, 1995 Accepted: September 22, 1995


Vibrational spectra and structure of diphenylacetilenes

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