Dicyanomethylene

Tetracyanoquinodimethane [1518-16-7] (5), 2,2 -(2,5-cyclohexadiene-l,4-diyhdene)bispropanedinitrile (TCNQ), is prepared by condensation of 1,4-cyclohexanedione with malononittile to give l,4-bis(dicyanomethylene)cyclohexane [1518-15-6] which is oxidized with bromine (31). 

These acids (51) are organic molecules that contain a plurality of cyano groups and are readily ionized to hydrogen ions and resonance-stabilized anions. Typical cyanocarbon acids are cyanoform, methanetricarbonitrile (5) 1,1,3,3-tetracyanopropene [32019-26-4] l-propene-l,l,3,3-tetracarbonitrile (52) 1,1,2,3,3-pentacyanopropene [45078-17-9], l-propene-l,l,2,3,3-pentacarbonitrile (51) l,l,2,6,7,7-hexacyano-l,3,5-heptatriene [69239-39-0] (53) 2-dicyanomethylene-l,l,3,3-tetracyanopropane [32019-27-5] (51) and l,3-cyclopentadiene-l,2,3,4,5-pentacarbonitrile [69239-40-3] (54,55). Many of these acids rival mineral acids in strength (56) and are usually isolable only as salts with metal or ammonium ions. The remarkable strength of these acids results from resonance stabilization in the anions that is not possible in the protonated forms. 

Quinolinium 2-dicyanomethylene-1,1,3,3-tetracyanopropanediide dimensions, 2, 110 Quinolinium iodide, 1-alkyl-Ladenburg rearrangement, 2, 300 Quinolinium iodide, 1-methyl-Ladenburg rearrangement, 2, 300, 335 Quinolinium iodide, [l-methyl-4-[3(5)-pyrazolyl]-blood sugar level and, 5, 291 Quinolinium perchlorate, 1-ethoxy-hydroxymethylation, 2, 300 Quinolinium perchlorate, 1-methyl-nitration, 2, 318 Quinolinium salts alkylation, 2, 293 Beyer synthesis, 2, 474 electrophilic substitution, 2, 317 free radical alkylation, 2, 45 nitration, 2, 188 reactions... 

Fluorescent small molecules are used as dopants in either electron- or hole-transporting binders. These emitters are selected for their high photoluminescent quantum efficiency and for the color of their emission. Typical examples include perylene and its derivatives 44], quinacridones [45, penlaphenylcyclopenlcne [46], dicyanomethylene pyrans [47, 48], and rubrene [3(3, 49]. The emissive dopant is chosen to have a lower excited state energy than the host, such that if an exciton forms on a host molecule it will spontaneously transfer to the dopant. Relatively small concentrations of dopant are used, typically in the order of 1%, in order to avoid concentration quenching of their luminescence. 

The basic principle of all diazotizations of aromatic amines with a hydroxy- or a sulfonamido group in the 4-position relative to the amino group involves a deprotonation of the OH or NH group, respectively, after diazotization of the amino group. There is also a case of a deprotonation of a CH group in the 4-position of an aniline derivative, namely in the diazotization of 4-aminophenylmalononitrile (2.41) which, by the sequence of steps shown in Scheme 2-23, yields 3-diazo-6-dicyanomethylene-1,4-cyclohexadienone (2.42), as found by Hartzler (1964). This product can also be represented by a zwitterionic carbanion-diazonium mesomeric structure. 

Quadratic hyperpolarisability DCJTB 4-(Dicyanomethylene)-2-tert-butyl-6 (l,l,7,7-tetrametbyljulolidyl-9-enyl)-4H-pyran Disperse red 1 HOMO-LUMO gap Electroluminescence Indium-tin-oxide Nonlinear optic... 

RUQPIC RUQPIC01 TOTSEA catena((/z2-Diiodo)-l,3,5-trithiacyclohexane) 1.3.5- Trithiacyclohexane (diiodine) Bis(tetra-n-butylammonium) bis(2-dicyanomethylene- 4.5- disulfanylcyclopent-4-ene- l,3-dionate)-palladium iodine... 

Fig. 1 Absorption and emission spectra of Cy3, CyS, Cy7, oxo-squaraine 13b (part 3 of this chapter) and dicyanomethylene squaraine 41j (part 4 of this chapter) in water (pH 7.4)...

Squaraine dyes 10b, 39a, 39b, 41a, 41c, 41d, and 41e were used to measure different proteins such as BSA, HSA, ovalbumin, avidin from hen egg white, lysozyme, and trypsin (Fig. 12) [58]. It is difficult to predict correlations between the dyes structures and the affinity or sensitivity of the dyes for different proteins. All squaraine probes exhibit considerable fluorescence increases in the presence of BSA. Dicyanomethylene-squaraine 41c is the brightest fluorescent probe and demonstrates the most pronounced intensity increase (up to 190 times) in presence of BSA. At the same time, the fluorescent response of the dyes 10b, 39a, 39b, 41a, 41c, 41d, and 41e in presence of other albumins (HSA and ovalbumin) is, in general, significantly lower (intensity increases up to 24 times). Dicyanomethylene-squaraine 41a and amino-squaraines 39a and 39b are the most sensitive probes for ovalbumin. Dyes 41d, 10b, and 41e containing an A-carboxyalky I -group demonstrate sufficient enhancement (up to 16 times) in the presence of avidin. Nevertheless, the presence of hydrolases like lysozyme or trypsin has only minor effects on the fluorescence intensity of squaraine dyes. 

The dicyanomethylene-squaraine dye 41e was found to be highly sensitive to trace protein-lipid interactions [109]. Lysozyme association with the lipid bilayer leads to a noticeable decrease in the fluorescence intensity of 41e. In a separate... 

The photostability of ring-substituted squaraines, especially dicyanomethylene-and f/no-squaraines is, in general, higher compared to oxo-squaraines and cyanines (Fig. 2). Increasing of the number of sulfo groups further improves the photostability of these dyes the photostability for hydrophilic dyes increases in the order 10b < 13b < Cy5 < 41h < 41i 41j < 41f < 41g [18]. Thio-squaraine dyes... 

The commercially available dicyanomethylene squaraine dye Seta-670-mono-NHS showed extremely low blinking effects and good photostability when used in single-molecule studies of multiple-fluorophore labeled antibodies [113]. Seta-670-mono-NHS and Seta-635-NH-mono-NHS were covalently labeled to antibodies and used in a surface-enhanced immunoassay [114]. From the fluorescence intensity and lifetime changes determined for a surface that had been coated with silver nanoparticles, both labeled compounds exhibited a 15- to 20-fold... 

Due to their displayed higher photostability, indolenine-based cyanines and squaraines are preferred for the design of fluorescent tracers. Dicyanomethylene- and thio-squaraines with substituted squaraine oxygens also show potential as highly photostable fluorescent probes. 

The discovery of high conductivity in some organic compounds has initiated a whole era of research. The first and most used acceptor molecule is 7,7,8,8-tetracyanoquinomethane. A selenophene analog has been prepared starting from 2,5-dibromoselenophene (118) as shown in Eq. (41).151 Data for the solution electrochemistry and ESR spectroscopy of 119 and other acceptors containing dicyanomethylene units have been determined.152 In an attempt to correlate oxidation potentials with LUMO energies no obvious... 

Dicyanomethylene compounds react with ethoxy cation 75 in the presence of DIPEA to form triafulvenes 95 87, 88. The same is true for 1,3-bis(dicyanomethylene)-indane and cyanomethylene dimedone, from which the sterically crowded vinylogous triafulvenes 96 and 97 were prepared88). 

The opposite is true for the o- and p-dicyanomethylene quinocyclopropenes 118-1257S. The only electron-transfer observed on polarography corresponds to a one-electron oxidation resulting in the radical cation 479. A qualitative explanation can be seen in the transformation of the quinocyclopropene into two Htickel-... 

Dicyano-substituted triafulvenes react with enamines to produce exclusively the cross-conjugated dicyanomethylene compounds 519, whose formation can be rationalized by a methylene bicyclo(2,l,0)pentane intermediate 51879 296 Since cyclanone enamines 520 and other cyclic enamines 522 react analogously, this C-C-insertion 237) of the triafulvene ring skeleton into the enamine C=C bond represents a versatile ring expansion mode (C + C3), which makes accessible a series of unsaturated medium-ring compounds (521/523) that are otherwise difficult to synthesize. 

A leading material reported as a red emitter is the fluorescent dye material typified by 4-(dicyanomethylene)-2-tert-butyl-6-(l,l,7,7-tetramethyljulolidyl-9-enyl)-4f/-pyran (DCJTB) [359]. This material is typically doped into an electron transporting host matrix such as Alq3 and delivers good chromaticity with CIE (0.646, 0.351) and a reasonable EL efficiency up to 4.4 cd/A and a power efficiency of 2.09 lm/W at 20 mA/cm2 and 6.8 V. The operational stability of the DCJTB-doped EL device has a projected half-life of over 33,800 h driven at an initial brightness of 100 cd/m2 (Scheme 3.95) [360]. 

T. Liu, C. Iou, S. Wen, and C.H. Chen, 4-(Dicyanomethylene)-2- -butyl-6-( 1,1,7,7-tetramethyl-julolidyl-9enyl)-4//-pyran doped red emitters in organic light-emitting devices, Thin Solid Films, 441 223-227 (2003). 

Ma et al. also studied PVK-based PPLEDs using rhenium complex in [28,51], They have prepared the PPLED in configuration ITO/PVK bpyRe (27) DCM (28)/Al (DCM is 4-(dicyanomethylene)-2-methyl-6-[p-(dimethylamino)styryl]-4//-pyran), where the bpyRe... 

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