7,7,8,8 Tetracyanoquinodimethan

Other miscellaneous applications of malononitdle are the synthesis of 7,7,8,8-tetracyanoquinodimethane (46) which is a powerful electron acceptor in the formation of charge-transfer complexes which are of interest because of their conductivity of electricity (96), as well as of 2-chloroben2yhdene malononitnle [2698-41-1] (45) also known as CS-gas, which is a safe lachrymatory chemical used for self-defense devices (97). 

Photoirradiation of 7,7,8,8-tetracyanoquinodimethane (TCNQ) in toluene afforded 1,6-addition product (pseudoexcitation band in Scheme 32) [145], The 1,6-addition thermally occurs with a stronger donor, p-methoxytoluene (transfer band in Scheme 32) [146]. 

Another type of dimer is that which consists of two radical molecules stacked on each other in a n-n interaction. Such dimers have been observed e.g., with 9-ethylphenazyl radical, tetramethyl-p-phenylenediamine cation radical (167), 7,7,8,8-tetracyanoquinodimethane radical anion (168), methylviologen cation radical (169), and l-alkyl-4-carbomethoxypyridinyl radicals (170). Attempts have been reported (170, 171) to interpret the electronic spectra of dimers of this kind by MO calculations. 

Other oxidants such as TCNQ (7,7, 8,8 -tetracyanoquinodimethane) can be used to oxidize a pentafluorophenylgold(I) complex, as takes place in the case of Q2[Au2(p,-dmit)(C6F5)2], which in the presence of TCNQ evolves in the oxidation of one gold atom giving a gold(III) [108] complex according to Equation 3.20... 

El-Brashy [51] reported the determination of primaquine and other antimalarials via charge-transfer complexes. Powdered sample of primaquine phosphate was dissolved in water and the solution was adjusted to an alkaline pH with 6 M ammonia and extracted with chloroform. The extract was dried with anhydrous sodium sulfate, filtered, and evaporated to dryness under nitrogen and the residue was dissolved in acetonitrile. Portions of the solution were mixed with 0.2% 7,7,8,8-tetracyanoquinodimethane, diluted with acetonitrile, and set aside for 10 min before the absorbance was measured at 845 nm versus a reagent blank. The calibration graphs were linear from 0.4 to 3 pg/mL and recovery was 98%. 

Cyanocarbon syntheses by the E. I. Dupont de Nemours Co. (1950-1964), which yielded several interesting electrical semiconductors based on the electron acceptor 7,7,8,8-tetracyanoquinodimethan (TCNQ). 

The electron acceptor 7,7,8,8-tetracyanoquinodimethane (TCNQ, 145) is capable of abstracting one electron from a donor molecule, yielding deeply colored solutions of a... 

Fe(abptrz)2(tcnq)2] is an iron(II) complex of the triazole 4-amino-3,5-bis(pyridin-2-yl)-1,2,4-triazole (abptrz) and the 7,7, 8,8 -tetracyanoquinodimethane (tcnq) radical anion whose structure, (132), Mossbauer and IR spectra, and magnetic behavior (thermally induced (280 K) spin crossover -S = 2 -S = 0) have been established. " ... 

Through reduction or oxidation of the molecule by a dopant molecule. Atoms or molecules with high electron affinity, such as iodine, antimony pentafluoride (SbCls), or 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F4-TCNQ), may oxidize a typical organic semiconductor such as poly(p-phenylene) derivatives, leaving them positively charged. Reduction, i.e., addition of an electron, may be obtained by doping with alkali metals. 

Matsushima T, Adachi C (2008) Enhancing hole transports and generating hole traps by doping organic hole-transport layers with p-type molecules of 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane. Thin Solid Films 517 874... 

Zambounis JS, Mizuguchi J, Rihs G, Chauvet O, Zuppiroli L (1994) Optical and electrical properties of evaporated 2,5-bis-methylthio-7,7, 8,8 -tetracyanoquinodimethane. J Appl Phys 76 1824-1829... 

Harada, S. and Schelly, Z. A. (1982). Reversed micelle of dodecylpyridinium iodide in benzene. Pressure-jump relaxation kinetic and equilibrium study of the solubilization of 7,7,8,8-tetracyanoquinodimethane. J. Phys. Chem., 86, 2098-102. 

The aim of the study was to create high-sensitive point-contact type gas sensors based on derivatives of 7,7,8,8-tetracyanoquinodimethane (TCNQ) and to test them in analysis of exhaled air for diagnosis and monitoring of human organism state. 

The infinite-dilution half-wave potential of 7,7,8,8-tetracyanoquinodimethane (TCNQ)... 

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). 

Much work has been undertaken to modify electrode surfaces with films which are themselves conducting. The most promising approaches involve organic charge transfer and radical ion polymers. Coordination chemistry has, to date, played little part in this work (a good recent review is available),67 but one example relating to ferrocene chemistry can be quoted. In this example a well known electron acceptor, 7,7, 8,8 -tetracyanoquinodimethane (TCNQ 27), is modified and incorporated into polymer (28) in which the iron(II) of the ferrocene unit is the electron donor. The electrical conductivity of such a film will depend on partial electron transfer between ion and TCNQ centres as well as on the stacking of the polymer chains. The chemistry of other materials, based on coordination compounds, which have enhanced electrical conductivity is covered in Chapter 61. 

True CT complexes are formed between unsaturated electron acceptors, among which the derivatives with cyano and nitro groups predominate. The most common strong electron acceptors are 1,2,4,5-tetracyanobenzene, 7,7,8,8-tetracyanoquinodimethane (1), tetracyano-p-benzoquinone (2), tetracyanoethylene (TCNE) (3) and many electron-donor... 

Tetracyanoquinodimethane (1) and tetracyanoethylene (3) are able to form CT complexes with crown ethers which are electron-donor molecules25. A recent study has recorded the spectral properties and stability constants of 89 tetracyanoethylene CT complexes with donors26. The main interaction in these complexes is an electron transfer (ji -> it ) between the HOMO of the donor and the LUMO of the acceptor. 

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]. 

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