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First Proof of di- tri- and all-cis-Conformations in Sterically Hindered Trimethinecyanines (Carbocyanines) of the Indoline and Benzothiazole Series.

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CAS Registry numbers:
( t ) - 2 a , 77397-59-2; (?)-2b, 77172-23-7; (+)-3a, 83344-26-7; (5b), 75694-
01-8; ( f ) - 7 , 87393-66-6; (+)-9, 87393-67-7; (+)-lo, 87393-68-8; ( c ) - l l a ,
87393-69-9; l l b , 87393-70-2: (+)-12, 87393-71-3; (+)-13, 87393-72-4; (*)14, 87421-48-5; ally1 acetoacetate, I 118-84-9.
121 F. Arcamone, G. Cassinelli, F. Di Matteo, S. Forenza, M. C. Ripamonti,
G. Rivola, A. Vigevani, J. Clardy, T. McCabe, J. Am. Chem. SOC.102
(1980) 1462.
131 H. Sekizaki, M. Jung, J. M. McNamara, Y. Kishi, J. Am. Chem. Sor. 104
(1982) 7372.
151 F. Arcamone: Doxorubicin, Academic Press, New York 1981.
[S] A. S. Kende, S. D. Boettger, J. Org. Chem. 46 (1981) 2799.
[IS] K. Krohn, W. Baltus, Liebigs Ann. Chem. 1982, 1579.
1281 Note added in proof 2a has also been isolated as a natural product: G.
Cassinelli, G. Rivola, D. Ruggieri, F. Arcamone, A. Grein, F. Merli, C.
Spalla, A. M. Casazza, A. Di Marco, G. Pratesi, J. Anribiof. 35 (1982)
176.
First Proof of
di-, tri-, and ail-cis-Conformations in
Sterically Hindered Trimethinecyanines
(Carbocyanines) of the Indoline and Benzothiazole
Series**
To studv the steric effects. we selected the readilv accessible trimethinecyanines (carbocyanines) 1 and 2 for the
following reasons:
1) Molecular models of 1 and 2 indicate that if their methine chains (C2-ClO-Cl l -ClO'-C2') adopt the normal planar all-trans-conformation, marked steric interactions occur between the terminal groups E,E' and
bulky substituents X.
2) According to previously reported UV/VISL61,'H-NMR
spectroscopic[71,and X-ray crystallographic[s1findings,
these interactions are relieved by torsions about the
nonrigidized methine chains and by changing from the
all-trans- to the mono-cis-(EZEE and EEZE) conformations. Opposing substituent-induced shifts and changes
in intensity of the absorption bands of l a and 2a (see
Table 2+4) suggest that the steric effects of X lead, in
particular, to conversion of the all-trans-form into unknown conformations.
By Rudolf Allmann, Hans-Joachim Anis, Reinhard Benn,
Walter Grahn*, Stanislaw Olejnek, and Alicja Waikowska
We have undertaken a systematic investigation of the effects of structural variations on the charge distribution and
stereochemistry in cyanines and other cationic polymethines. These properties are of importance for the chemical
and physical properties of the dyes and for their applications in photographyL3'and laser technology. In addition,
cyanines are model compounds for the chromophore of
(bacterio)rh~dopsin[~~.
To determine these and to clarify the effects of substituents X on the light absorption of l a and 2a, we have
studied 1 and 2d by 'H-NMR spectroscopy between ca.
- 100 and 35°C. We interpret the temperature-dependent
spectra of the methyl, ethyl, and phenyl derivatives l b , l c ,
Table 2 + 4 (Extract). Longest wavelength absorption maxima and conformations of the trimethines 1 and 2 in methanol
2, Z=Z'=S, R = R = E t [a]
Benzothiazole Series
1, Z=Z'=CMe2, R = R ' = M e
Indoline Series
X
a,,,
6.10-4
[nm]
[L.mol-'-cm-']
(13.1)
P
H
544
b
Me
551.5
(6.74)
c
Et
553.5
(5.29)
d
t-Bu
529
(2.16)
e
Ph
570.5
(5.78)
Conformation
in solution
a,,,
lnml
E . lo-"
[L.mol-'.cm-']
Conformation
in solution
all-truns(EEEE)
planar
tri&(ZEZZ
and ZZEZ) twisted
cation cf. 3 and 3'
tri-cis(ZEZZ
and ZZEZ) twisted
cation cf. 3 and 3'
all-cis(ZZZ2)
helical
cation cf. 4
and 4 '
tri-cis(ZEZZ
and ZZEZ) twisted
cation cf. 3
and 3'
556.5
(14.2)
all-truns(EEEE) planar [7]
542
(13.3)
mixture of mono-cis(EE2E) and EZEE,
twisted; prevalent isomer) and all-(runs [7]
547.5
(13.1)
mixture of mono-cis(EEZE) and EZEE,
twisted; prevalent isomer) and all-!runs [7]
593
560
(2.10)
(19.7)
di-cis(EZZQ helical
cation cf. 5 and 5 '
mixture of all-truns(preva1ent isomer)
and mono-cis(EE2E and EZEE, twisted) 171
[a] To facilitate comparison, we assign a higher priority to nitrogen than to sulfur
[*I
[**I
876
Priv.-Doz. Dr. W. Grahn, H.-J. Anis
Institut fur Organische Chemie der Technischen Universitat
Schleinitzstrasse, D-3300 Braunschweig (Germany)
Prof. Dr. R. Allmann, Dr. S. Olejnek, A. Waikowska
Fachbereich Geowissenschaften der Universitat Marburg (Germany)
Dr. R. Benn
Max-Planck-Institut fur Kohlenforschung,
Mulheim a. d. Ruhr (Germany)
Conformational Analysis of Polymethines, Part 1. This work was supported by the Deutsche Forschungsgemeinschaft and by the Fonds der
Chemischen Industrie. We thank Dr. T. Debuerdemueker. Universitat
Ulm, for the MULTAN calculations on the structures of Ib and Id.
0 Verlug Chemie GmbH, 6940 Weinheim, I983
and l e as arising from isomerization between the degenerate conformers tri-cis(2EZZ) 3 and tri-cis'(Z2EZ) 3',
which in l b is frozen at -98°C (AGZ =38.5 kJ/mol). In
contrast, in the tert-butyl compound Id the process, which
is interpreted as isomerization between the degenerate
conformers all-cis 4 and all-cis' 4', is frozen at ca. 0°C
(EA=48.43+1.09 kl/mol,ASC= -11.5-+1 J K-lrnol-').
The previously ~nobserved~'~
temperature dependence of
the 'HSNMR spectrum Of the terf-butyl
2d with
benzothiazole groups can be explained by isomerization
0570-0833/83/1111-0876 $ 02.50/0
Angew. Chem. Int. Ed. Engl. 22 (1983) No. I I
Wavelength absorption band and transformation of the alltrans- into the all-cis-form and not-as previously suggestedL7]-into the mono-cis-form.
Received: February 22, 1982;
revised: September 6, 1983 (2990 IE]
German version: Angew. Chem. 95 (1983) 900
The complete version of this manuscript appears in:
Angew. Chem. Suppl. 1983. 1147-1175
tri-cis 3
ZEZZ
X= Me, Et, Ph
all-cis 4
zzzz
di-cis
5
CAS Registry numbers:
la, 87450-54-2; lb, 87450-58-6; lc, 87450-56-4: Id, 87450-60-0; le, 8745062-2; 2, 87461-57-2.
t r i - c i s 3’
ZZEZ
[3] a) D. M. Stunner, D. W. Heseltine: “Sensitizing and Desensitizing
Dyes” in T. H. James: The Theory of the Photographic Process, 4th edit.,
Macmillan, New York 1977, p. 194ff; b) L. G. S. Brooker, F. L. White,
D. W. Heseltine, G. H. Keyes, S. G. Dent Jr., E. J. van Lare, J . Phot. Sci.
I (1953) 173; Chem. Absfr. 48 (1954) 38234.
[5] a) F. Derguini, C. G. Caldwell, M. G. Motto, V. Balogh-Nair, K. Nakanishi, J. Am. Chem. SOC.I05 (1983) 646; b) T. Kakitani, H. Kakitani, B.
Honig, K. Nakanishi, ;bid. 105 (1983) 648.
[6] J. Fabian, H. Hartmann: Light Absorprion of Organic Colorants, Springer, Berlin 1980, p. 183f.
171 P. M. Henrichs, S. Gross, J . Am. Chem. Sac. 98 (1976) 7169.
181 a) S. Dahne, S. Kulpe: “Structural principles of unsaturated organic
compounds. With special reference to X-ray analyses of coloured substances”, Abh. Akad. Wiss. DDR, Abt. Math., Nafunviss.. Tech. 8 N
(1977) 1; Chem. Abstr. 88 (1978) 189321m; b) K. Nakatsu, H. Yoshioka,
S. Nishigaki: “X-Ray Crystallographic Studies on Photographic Dyes”,
Kwansei Gakuin University Annual Studies 29 (1980) 213.
[ 171 R. Allmann, D. Kucharczyk, Z . Kristallogr., Kristallgeom., Kristallphys.,
Knstallchem. 162 (1983) 6.
all- cis’ 4’
A Boron-Carbon Double Bond**
di- cis‘ 5‘
EZZE
between the degenerate conformers di-cis(EZZE) 5 and dicis’-(EZZE) 5‘, which is frozen at -96°C.
The ’H-NMR spectroscopic findings were corroborated
by X-ray structure analyses of l b , Id, and 2d. In the crystal, the cations of the cyanines adopt the same conformations as in solution. The pronounced twisting of the methine chain in l d , for example, forces the N atoms separated by 298 pm to lie almost on top of each other (cf. 4
and 4’).
In principle, the cations in 1 and 2 can assume ten conformations which form five classes: all-trans, mono-, di-,
tri-, and all-cis (cf. 3-5). Now, one example of each of
these is known. A sixth conformation, the unsymmetrical
di-cis(ZZEE and EEZZ)-form, was observed in the crystalline 10,lO‘-dimethyltrimethinecyanine of the indoline series‘17’.
The steric demands of the substituents X and the groups
E,E’ determine the respective conformation and the position of equilibrium between the conformers (Table 2 4).
In accord with inspection of molecular models, the steric
interactions between X and E,E’ in the all-trans-form adopted by la and 2a thus cause the changes in conformation. The different effects of the alkyl and phenyl groups X
on the light absorption of l a and 2a (Table 2+4) arise
from these conformational changes which, because of the
different steric demands of the groups E and E‘, produce
different effects in the two dye series. This becomes particularly noticeable with the tert-butyl group: in the indoline
series 1 this leads to the hypsochromic shift of the longest
wavelength absorption band and to a change in conformation from all-trans to all-cis; in contrast, in the benzothiazole series 2 it leads to a bathochromic shift of the longest
+
Angew. Chem. Int. Ed. Engl. 22 (1983) No. 11
By Hartmut Klusik and Armin Berndt*
2,4-Diboramethylenecyclopropane porirane-2-ylideneborane(2)l 3 is the first compound containing a B=C
double bond. It is formed on reaction of 1,l-bis(tert-butylchloroboryl)-2,2-bis(trimethylsilyl)ethene 11’’ with W
Na alloy in boiling pentane (yield 60%).
CMe,
1
Me,Si
\
/
F=C,
Me,Si’
Me,Si
I
CMe,
l
-
BlCMe3
I
B.CMe3
2
1
CMe,
Me,Si\
Me&,
C-C=B-CMe,
Me,Si
Me,Si
C-C=B-CMe,
\ /
/
3
B
CMe,
The structure of 3 follows from ‘H-, I3C- and ”B-NMR
spectral2’. Signals for the two C-atoms of the C2B2skeleton
appear below -40°C at 6 = 115.2 and 25.0 in the region
for sp2 and sp3 C-atoms; both signals show line-broadening characteristic of a C-atom bound to boron. Hence the
structure of a 2,3-diboramethylenecyclopropane‘3‘for 2
can be ruled out. Below - 11“C the B atoms give rise to
[*I Prof. Dr. A. Berndt, H. Klusik
[**I
Fachbereich Chemie der UniversitBt
Hans-Meenvein-Strasse, D-3550 Marburg (Germany)
This work was supported by the Fonds der Chemischen Industrie. We
thank Dr. P. H. M. Budzelaar and Dr. S.M . van der Kerk. Utrecht, for
the first hints on the structure of the compound 3, and Prof. K. Dehnicke, Marburg, and Prof. P. u. R . Schleyer, Erlangen, for valuable discussions.
0 Verlag Chemie GmbH. 6940 Weinheim, 1983
0570-0833/83/1111-0877 $02.50/0
877
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conformational, series, proof, carbocyanine, first, tri, sterically, indolines, hindered, benzothiazoles, cis, trimethinecyanines
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