Chloranil, complex

Fig. 1 Charge-transfer absorption spectra of enol silyl ethers complexes with re-acceptors. (a) Spectral changes accompanying the incremental additions of cyclohexanone enol silyl ether [2] to chloranil in dichloromethane. Inset Benesi-Hildebrand plot, (b) Charge-transfer absorption spectra of chloranil complexes showing the red shift in the absorption maxima with decreasing IP of the enol silyl ethers, (c) Comparative charge-transfer spectra of EDA complexes of a-tetralone enol silyl ether [6] showing the red shift in the absorption maxima with increasing EAs of the acceptors tetracyanoben-zene (TCNB), 2,6-dichlorobenzoquinone (DCBQ), chloranil (CA), and tetracyanoqui-nodimethane (TCNQ). Reproduced with permission from Ref. 37.

Tetrachlorohydroquinone (45) is closely related to chloranil and might be expected to show overcrowding effects similar to those found in chloranil by Ueda. The crystal structure of tetrachlorohydroquinone has been investigated by Sakurai (1962) using nuclear quadrupole resonance and X-ray diffraction techniques. The crystal makes use of the molecular centre of symmetry and the asymmetric unit consists of half a molecule. The analysis shows that the C—O bond deviates by 0-9° from the aromatic plane and that the two adjacent C—Cl bonds are also bent out of the benzene plane, in the same direction, through 0-8°. (This is reminiscent of Harding and Wallwork s findings for chloranil in the hexamethylbenzene-chloranil complex.) Sakurai... 

However, it should be noted that studies of the effects of high pressures (several hundred kilobars) on the p-phenylenediamine-chloranil complex have established a complicated reaction sequence involving initial formation of the cation radical-anion radical pair, leading ultimately to tetrachlorohydroquinone and polyazo-phenylene (Sakata et al., 1974). 

Figures 3.22. Plausible structures of (a) EM/o-chloranil and (b) DP-PPY/o-chloranil complexes. (Reprinted with permission from ref 105, Am, Inst. Phys.)...

Complexing of DEAE with BI3 resulted in an increase of BE of the Ni electrons of DEAE from 399 eV to approximately 402 eV. With charge transfer complexes, formed with ortho- or para-chloranils, the BE of Ni electrons shifted to 401.4 eV (Fig. 15) and the Cl2p electrons had BE values of 197 for the Cl ion and 200.4 for the organic chlorine. These complexes were paramagnetic, as illustrated by the EPR spectrum for the DEAE-o-chloranil complex shown in Figure 16. The singlet of g-value of 2.0059, indicates... 

For complexes of donors with low ionization potential or acceptors of high electron affinity (or both) the charge-transfer band may be found in the near infrared. For example, the p-phenylenediamine-chloranil complex shows a new absorption at 942 m in acetonitrile. In polar solvents the complex of )S-carotene and iodine shows a new absorption at 1000 m/z. This complex is a 1 2 complex, characterized as [(C4oH56)I ]l3". The charge-transfer absorption is attributed to the moiety (C4oH56-+I" ) in which the I is acting as a very powerful electron acceptor . A band at 900 mju has been assigned to a donor-acceptor complex of riboflavin and dihydroflavin . 

Pyrrole has been also oxidized by means of halobenzoquinones [32,33]. The electrical conductivity of the polypyrrole-chloranil complex is about 2 to 10 S cm while for the PPy-pfluoranil and PPy-[a-bromanil complexes it is in the range of 10 to 10 S cm . Synthesis and doping of polypyrrole has been performed by 2,3-dichloro-5,6-dicyano-/ -benzoqui-none (DDQ) and tetrachloro-o-benzoquinone from bulk polymerization [34]. The polypyrrole complexes so produced are semiconducting and granular, with electrical conductivities of the order of 10 to 10 S cm . ... 

Kuboyama, A. (1964) Molecular complexes and their spectra. XVII. The iodine and the chloranil complexes with thianthrene analogs. J. Am. Chem. Soc.,i6, 164-167. 

Fig. 9. I.ll. spectra in CH-bending and CH-stretching regions of hexamethyl-benzene and its chloranil complex. (By the kind permission of Pergamon Press, Oxford, England.)...

At attempt was made (101) to test the isolated vibration hypothesis [Sec. Ill A, 1(b)] with this system, by comparing the vibrational frequencies in the CH stretching and bending region of hexa-methylbenzene and its stable chloranil complex. Equation (III-10) requires a net downward shift of 100 cm. , shared among the three CH stretching and three CH bending modes. It can be seen... 

Synergistic preconcentration of Mo -chloranilate complex by electrolysis and chemisorption... 

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