Tetracyanoquinodimethane reactions

Esr spectroscopy has also been used to study pure solvent dynamics in electron self-exchange reactions (Grampp et al., 1990a Grampp and Jaenicke, 1984a,b). When the systems are not linked by a spacer (i.e. TCNQ- /TCNQ (TCNQ = tetracyanoquinodimethane), the homogeneous bimolecular rate constants /chom are given by (10), with fcA the association constant and kET... 

The presence of a cyano group seems to be important[649]. The reaction has been successfully applied to halides of pyridine, quinoline, isoquinoline, and oxazoles[650]. An interesting application is the synthesis of tetracyanoquinodimethane (789) by the reaction of /7-diiodobenzene with malononitrile[651]. 

The Menschutkin reaction has been used to prepare poly(viologens) (115) directly (Scheme 31). These polymers were found to be quite useful as polyelectrolyte redox-polymers and for the preparation of conductive polymers when complexed with the 7,7, 8,8 -tetracyanoquinodimethane (TCNQ) radical anion (71MI11100). 

Mediators such as 7,7,8,8-tetracyanoquinodimethane (TCNQ) [166], hexacyanoferrate(III) [168] and CoPC [169], which have been applied to a carbon paste or ink, are reduced by the reaction with thiocholine and then reoxidised at the carbon electrode (Fig. 23.6). A second type of mediator has involved the addition of Prussian blue (ferric hex-anocyanoferrate) into an AChE and choline oxidase (ChO) bienzyme biosensor. Prussian blue mediates the reduction of hydrogen peroxide produced by the conversion of choline to betaine by ChO [170]. 

Moreover, the current-potential curves are affected by the disproportionation reaction therefore, other variables (the rate constant for the disproportionation reaction) must be taken into account. Since experimental results for many interesting systems show clear evidence of slow kinetics, ad hoc simulation procedures have typically been used for the analysis of the resulting current-potential curves [31, 38, 41, 48]. As an example, in reference [38], it is reported that a clear compropor-tionation influence is observed for an EE mechanism with normal ordering of potentials and an irreversible second charge transfer step. In this case, the second wave is clearly asymmetric, showing a sharp rise near its base. This result was observed experimentally for the reduction of 7,7,8,8-tetracyanoquinodimethane in acetonitrile at platinum electrodes (see Fig. 3.20). In order to fit the experimental results, a comproportionation rate constant comp = 108 M-1 s-1 should be introduced. 

Although arylation or alkenylation of active methylene compounds can be carried out using a Cu catalyst, the reaction is sluggish. However, the arylation of malononitrile (390) or cyanoacetate proceeds smoothly in the presence of a base and Pd catalysts [189], Tetracyanoquinodimethane (392) is prepared by the coupling of / -diiodoben-zene with malononitrile (390) to give 391, followed by oxidation [190], Presence of the cyano group seems to be essential for intermolecular reactions. However, the intramolecular arylation of malonates, / -keto esters and /i-diketones proceeds smoothly [191]. The bromoxazole 393 reacts with phenylsulphonylacetonitrile (394)... 

Tetracyanoquinodimethane (TCNQ) and many of its derivatives are easily reduced to anions of the type TCNQ-, which form salts with various cations. With many cations, e.g., tetrathiafulvalene cations (TTF+), and N-methyl phenazinium cations (NMP+), the TCNQ- anions form electronically conducting salts (- molecular metals, -> charge-transfer complexes) that can be used as electrodes, especially because of their electrocatalytic properties (- biosensors, -> electrocatalysis, -> molecular metals) [i,ii]. TCNQ undergoes insertion electrochemical reactions (-> insertion electrochemistry) leading to TCNQ salts [iii, iv]. Polymers... 

L. H. Yu, Y. F. Ming, and M. G. Fan, Studies on photoinduced electron transfer reaction between pyrryl-substituted fulgide and tetracyanoquinodimethane, Chin. Sci. Bull., 38(21), 1775-1778... 

Suzuki et al. reported the photochemical reaction of CT crystals, in which cycloaddition reaction of bis(l,2,5-thiadiazolo)tetracyanoquinodimethane 10 (electron acceptor) and 2-divinylstylene 11 (electron donor) is efficiently induced (Scheme 6) [14]. The structural feature of the CT crystal is the asymmetric nature of the inclusion lattice because of the adoption of a chiral space group, P2. The [2 + 2] photoadduct was formed via the single crystal-to-single crystal transformation, and the optically active product with 95% ee was obtained. 

Metal-vapour-deposition methods have begun to provide new low-valent complexes of uncommon stoichiometry. The preparation of gram quantities of paramagnetic (ji = 2.02 BM) [Co(bipy)2] has been reported and its reactions with Br2, tetracyanoethylene and tetracyanoquinodimethane studied.283 Electrochemically it behaves identically to [Co(bipy)3]2+ (equation 47).283... 

An unusual anion exchange takes place in the reaction between 2,6-diphenylthiopyrylium (18) iodide and tetracyanoquinodimethane (TCNQ) in acetonitrile. The iodide ion undergoes oxidation to iodine, leaving as counter-ion of 18 the radical anion of TCNQ (77TH1). Salts of this type have been also prepared by metathesis (69JCP377). 

Kihara et al. [188] have introduced a series of redox reactions suitable for studying the electron transfer (8). These systems involved ferrocene or tetrathiafulvalene as electron donor or tetracyanoquinodimethane as electron acceptor in the organic solvent phase, and Fe(CN), Ce, Fe ", or Cr207 as electron acceptor, or Fe(CN)6 or hydroquinone as electron donor, in the aqueous phase. Since all these systems showed reversible behavior under the conditions of current-scan polarogra-phy, no kinetic- data have been reported. 

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