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An Imide Radical Anion which Assembles into -Stacks in Solution.

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Although we do not have unequivocal evidence, it is quite
reasonable to assume that the 1,2-aIkadienylidene carbenes
are involved as common key intermediates in the above reactions.16- They add to 1,3-dienes in both 1,2 and 1,4 manner
and selectively undergo 1,4 addition to an enforced cisoid
1,3-diene such as 5.
Experimental Procedure
3b/4b: A mixtureofnBu,NHSO,(2 mmo1)and aqueous 50% NaOH (100 mL)
was added to a benzene solution containing 1,l-dibromo-2,2-diphenylcyclopropane (1 a, 1 mmol) and an excess of 2-methyl-l,3-butadiene (Zb, 5 mmol).
The mixture was vigorously stirred at room temperature for 24 h. Flash column
chromatography on silica gel with hexane gave the 1,2-adduct 3 b and the
1.4-adduct 4 b in a 78:22 ratio in 37% yield.
Control experiment: A mixture of nBu,NHSO, (0.8 mmol) and an aqueous
50 % NaOH (25 mL) was added to a benzene solution containing 3 b (0.4 mmol)
and the resulting mixture was vigorously stirred at room temperature for 22 h.
Compound 3 b remained unchanged (270-MHz 'H NMR spectrum) and was
quantitatively recovered.
3b(oil): 'HNMR(270 MHz,CDCI,):b = 1.69(s,3H), 1.79(dd, I H , J = 6.0,
7.0 Hz), 1.95 (dd, 1 H, J =7.0, 8.7 Hz), 2.71 (dd, I H , J = 6.0, 8.7 Hz), 4.82 (s,
1 H), 4.92 (s, 1H), 7.18-7.40 (m, 1 OH). I3C NMR (67 MHz, CDCI,):
6 = 15.0, 19.2,28.8,83.1. 111.4, 112.2, 127.0, 126.9, 127.9, 128.3, 128.4, 128.4,
128.6, 137.7, 143.0, 189.2. IR: B[cm-'] = 3060, 2978, 1999, (C=C=C), 1638,
1599, 1493, 1473, 1444, 1031, 888, 768, 692.
4 b (oil): 'H NMR (270 MHz, CDCI,): 6 = 1.75 (s, 3H), 3.28 (s, 2H), 3.34 (s,
2H),5.36(s,1H),7.16-7.37(m,10H).13CNMR(67MHz,CDC1,):6=
16.5,
37.8, 41.5, 122.8. 126.9, 128.2, 128.4, 128.5, 128.6, 138.8, 143.0, 199.9. IR:
G[cm-'] = 3060, 3030, 2892, 1949 (C=C=C), 1659, 1601, 1493, 1454, 1444,
770, 696.
Received: January 24, 1991 [Z 4401 IE]
German version: Angew. Chem. 103 (1991) 1000
[I] Review articles on carbenes and carbene analogues: a) W. E. Keller: Phase
Transfer Reactions, Vol. 1 . 2 , Thieme, Stuttgart 1986 and 1987; b) M. Regitz
(Ed.): Houben- Weyl: Methoden der Organischen Chemie, Band E 196,
Thieme, Stuttgart 1989; c) P. J. Stang, Chem. Rev. 78 (1978) 383.
[2] a) P. D. Bartlett, A. S. Wingrove, R. Owyang, J. Am. Chem. SOC.90 (1968)
6067; b) A. G. Anastassiou, ;bid. 90 (1968) 1527; c) L. A. M. Turkenburg,
W. H. de Wolf, F. Bickelhaupt, Tetrahedron Lett. 23 (1982) 769; d) H. Mayr,
U. W Heigl, Angew. Chem. 97 (1985) 567; Angew. Chem. Int. Ed. Engl. 24
(1985) 579; e) L. W. Jenneskens, W
. H. de Wolf, F. Bickelhaupt, ibid. 97
(1985) 568 and 24 (1985) 585; f ) N. A. Le, M. Jones, Jr., E Bickelhaupt,
W H. de Wolf, J. Am. Chem. SOC.l l f (1989) 8491; g) J. B. Lambert, B. T.
Ziemnicka-Merchant, J Org. Chem. 55 (1990) 3460.
[3] T. Sasaki, S. Eguchi. T. Ogawa, J. Org. Chem. 39 (1974) 1927.
[4] T. B. Patrick, D. J. Schmidt, J Org. Chem. 42 (1977) 3354.
[5] H. Fujimoto, R. Hoffmann, J. Phys. Chem. 78 (1974) 1167.
[6] Recent review article on 1,2-alkadienylidene carbenes: P. J. Stang, in M.
Regitz (Eds.): Houben- Weyl: Methoden der Organischen Chemie, Band
E19b, Thieme, Stuttgart 1989, p. 136.
(71 L. Crombie, P. J. Griffiths, B. J. Walker, Chem. Commun. f969, 1206.
[8] K . Isagawa, Y. Kimura, Y. Tomita, K. Mizuno, Y. Otsuji, I989 Int. Symp.
Carbene-Type Reactive Intermediates, Kyoto, Japan (Abstract P-I 8).
[9] M. S. Baird, Top. Curr. Chem. 144 (1988) 137.
An Imide Radical Anion which Assembles into
n-Stacks in Solution**
By Jean-Frangois Penneau and Larry L. Miller*
Partially oxidized or reduced n-stacks are the most common structural elements in conducting organic charge transfer salts of the broad class typified by tetracyanoquinodimethane/tetrathiafulvalene (TCNQ/TTF).['] We have ob['I Prof. L. Miller, Dr. J.-F. Penneau
Department of Chemistry, University of Minnesota
Minneapolis, MN 55455 (USA)
[**I This work was supported by the Office of Naval Research and the National Science Foundation. We thank B. Stallman for the synthesis of 1.
986
0 VCH Verlagsgesehchaft mbH,
W-6940 Weinheim, 1991
served unusual spectral effects which lead to the conclusion
that the radical anion 1'@assembles into similar n-stacks in
solution. In particular the NIR, and ESR of l.Oin aqueous
NaCl are extremely similar to the spectra of the conducting
solid complex salt of l'@and provide a spectral signature for
n-stacks. Although n-dimers of radical anions are well
known,[21we know of no examples of radical ion n-stacks in
solution.[31Such entities are interesting as models for conducting solids and the solutions have potential utility as
infrared dyes.[s]
la@,
formed by electrochemical reduction in DMF,L6]
shows absorption in the visible spectral region, with the most
intense band at 1 = 473 nm (E = 31 000), and a 13-line ESR
spectrum well simulated by aH(4H)= 1.90 G, aN(2N)=
0.95 G. The spectra were essentially identical to those of
similar naphthalene diimide radical anions[61and aHconformed to expectations based on a Huckel MO calculation
and solution of the McConnell equation. It is concluded that
the monomeric radical anion is present.
In aqueous media it was convenient to generate the radical
anion by reduction of 1 with one equivalent of sodium
dithionite. In the absence of oxygen the solutions were stable
for weeks. In water or in 80% H,0/20% DMF the optical
spectrum of 1.O was quite different from the spectrum in
neat DMF. There was a new NIR band at 1140nm
(E = 3900) and the VIS band was shifted to 453 nm. This
observation is consistent with the literature on radical ion
dimers in aqueous media.[21Such dimers, e.g. (TCNQ'@), ,
give NIR bands due to charge transfer between the n-electron systems in the stacks, and a Davidov blue shift of the
VIS absorption. Since the room-temperature spectrum in
water follows Beers law over the range 0.02-2 mM, we conclude that essentially all the radical anions are dimerized
under these conditions. Raising the temperature to 90°C
caused the spectrum of l'@in aqueous DMF to revert to that
of the monomer in DMF. The ESR spectrum underwent
corresponding changes. In water or aqueous DMF a weak,
25-line spectrum (aH= 1.93, aN= 1.08 G ) was observed at
room temperature. Raising the temperature of the aqueous
DMF solution to 100°C did not change the shape, but by
using a nitroxyl standard it was shown that the spin concentration increased from 7 % to 94 % of the lSeconcentration.
The weak signal at room temperature is consistent with literature reports which indicate that radical ion n-dimers have
diamagnetic ground states.l2]
In aqueous NaCl solutions there was an unexpected evolution of the NIR absorption. As the concentration of lSeor
NaCl was increased the absorption moved to much longer
wavelengths. This is illustrated in Figure 1 for 0.43-4.3 mM
I*@in 0.5 M NaCI. As a further example, the spectrum of l'@
(4.8 mM) in 5 M NaCl had a maximum at 1740 nm and extended far into the IR region. Such very long-wavelength
absorptions are characteristic of charge transfer along the
delocalized n-stacks of solid, conducting, charge transfer
salts.['* The ESR spectrum underwent an unexpected
change as well. In dilute solutions the weak, 25-line spectrum
was observed, but in concentrated solutions the signal was
asymmetric (Fig. 2).
0570-0833191jO808-09868 3.50+ ,2510
Angew. Chem. Int. Ed. Engl. 30 (1991) No. 8
anion. This increases the water solubility and gives a propensity for ion aggregation.L41
Received: March 13. 1991 [Z 4493 IE]
German version: Angew. Chem. 103 (1991) 1002
c x 10‘
1
-I
I
I
800
1300
h [nml
-
1800
Fig. 1. NIR spectra of l’e in 0.5 M aqueous NaCl solution. Concentration of
a) 0.43 mM. b) 2.1 mM. C) 4.3 mM.
When a solution of 1.O in water was slowly evaporated
under vacuum a shiny black film resulted. The ESR spectrum of the film was anisotropic and the line shape depended
on the orientation of the film in the magnetic field (Fig. 2).
[l] J. R. Ferraro, I. M. Williams: Introduction to Synthetic Ekcrrical Conductors, Academic Press, New York, 1987.
[2] R. H. Boyd, W. D. Phillips, J Chem. Phys. 43 (1965) 2927; Z . G. Soos, S. R.
Bondeson in J. S . Miller (Ed.): Extended Linear Chain Compounds, Plenum
Press, New York 1983.193-257; S . Nakayama, K. Suzuki, Bull Chem. Soc
Jpn. 46 (1973) 3694; M. de Sorgo, B. Wasserman, M. Szwarc, J Phys. Chem.
76 (1972) 3468; N. Sakai, I. Shirotani, S . Minomura, Bull. Chern. Sac. Jpn.
44 (1971) 675.
[3] This phenomenon is somewhat analogous to the aggregation of certain dyes
[4], which form stacks and give excitonic bands. Because the dyes are closed
shell molecules the bonding between molecules in the stack, the electronic
structure of the stack, and the nature of the optical transition are somewhat
different. There appear to be no examples of dye aggregates that absorb at
such long wavelengths. There are no long-wavelength bands in aqueous
NaCl solutions of neutral 1.
[4] D. G. Duff, C. H. Giles in F. Franks (Eds.): Water; A Comprehensive Treatise, Val. 4, Plenum Press, New York, 1975, Chap. 3.
[5] J. Fabian, R. Zahradnik, Angew. Chem. I01 (1989) 693; Angew. Chem. Inr.
Ed. Engl. 28 (1989) 677.
[6] T. M. Dietz, B. J. Stallman, W. S. V. Kwan, J. F. Penneau, L. L. Miller,
Chem. Commun. 1990, 367.
[7] J. B. Torrance, B. A. Scott, B. Welber, F. B. Kaufman, P. E. Seiden, Phys.
Rev. B19 (1979) 730.
[8] J. E. Wertz, J. R. Bolton: Eleclron Spin Resonance, Chapman and Hall, New
York, 1986, Chap. 7, 8.
191 G. Heywang, L. Born, H. G. Fitzky, T. Hassel, J. Hocker, H.-K. Muller, B.
Pittel, S. Roth, Angew. Chem. fOf (1989) 462; Angew. Chem. I n l . Ed. Engl.
28 (1989) 483.
Enantiomer Separation on Immobilized ChirasilMetal and Chirasil-Dex by Gas Chromatography
and Supercritical Fluid Chromatography **
By Volker Schurig,* Dieter Schmalzing,
and Michael Schleimer
Dedicated to Professor Michael Hanack
Fig. 2. ESR spectra of l’e. a) 8 mM in 0.5 M aqueous NaCl at 280 K. b) Thin
with thin dimension perpendicular to magnetic field; ( 11) with one long
film, (I)
dimension parallel to magnetic field at 300K. Scale bar corresponds to
0.6 Gauss.
These spectra suggest that the asymmetric solution spectrum
results from unoriented, slowly tumbling aggregated radicals, that are similar to the oriented radicals immobilized in
the film.t81A KBr pellet of the film, like the NaCl solutions
of
showed an NIR absorption extending into the IR.
The 4-probe conductivity of a pure pressed pellet was
0.1 S cmThus, it has been demonstrated that l-@
assembles into an
aggregate in aqueous NaCl which has similar optical and
magnetic resonance properties as the conducting solid.
These spectral qualities are characteristic of radical anion
stacks. Indeed, an X-ray crystal structure of a conducting
naphthalene dianhydride salt has shown x-stacks of radical
anions.[g1Whether the stacks in solution are composed of
Oare doped with another redox state is not known.
only l mor
It does seem important, however, that laeis actually a tri-
’.
Angew. Chem. I n l . Ed. Engl. 30 (1991) No. 8
0 VCH
The development of surface-bonded stationary phases by
cross-linking and/or chemical binding (“immobilization”)
represented a breakthrough in high-resolution capillary
chromatography.[’’ The resulting merits are stable films, low
bleeding of the stationary phase, high washout stability, and
hence use in splitless and on-column sampling. To achieve
universal physico-, chemo-, and enantioselective stationary
phases based on chemically modified chiral polysiloxanes,
e.g. Chirasil-Val,[’I Chira~il-Metal[~I
and Chira~il-Dex,~~.
an immobilization on the glass surface is desirable.
We describe here the immobilization of enantioselective
metal chelate and cyclodextrin phases. Chiral polysiloxanes
can be immobilized thermally or radically.L6- The nickel@)
Chirasil-Metal 1 prepared by us according to Scheme 1 and
the octanyl Chirasil-Dex 2c obtained according to Scheme 2
can be immobilized thermally on the fused silica surface with
The thermal immobilization
binding rates of up to 75 %.I1’
does not lead to any decomposition and/or epimerization,
[*] Prof. Dr. V. Schurig, Dipl.-Chem. D. Schmalzing
DipL-Chem. M. Schleimer
Institut fur Organische Chemie der Universitat
Auf der Morgenstelle 18. W-7400 Tubingen (FRG)
[**I This work was supported by the Deutsche Forschungsgemeinschaft, the
Fonds der Chemischen Industrie und Chrompack International, Middelburg (The Netherlands) (supply of fused-silica capillary columns). We
thank G. J. Nicholson, U . Miihleck and Professor E. Boyer, Tubingen, for
valuable discussions.
Verlagsgesellschaft mbH, W-6940 Weinheim, 1991
OS70-0833/91/0808-0987 $3.50+ .25/0
987
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