Tetracyanoquinodimethane Anion Radical Research Articles

Tetraphenylethene Derivatives Bearing Alkylammonium Substituents: Synthesis, Chemical Properties, and Application as BSA, Telomere DNA, and Hydroxyl Radical Sensors.

Tetraphenylethene derivatives (TPEs) are used as luminescence probes for the detection of metal ions and biomolecules. These sensors function by monitoring the increase in the photoluminescence (PL) intensity of the TPEs resulting from aggregation-induced emission (AIE) upon interaction with the analytes. The AIE behavior of the sensors was investigated by measuring their PL. In this study, PL, PL lifetime, and confocal laser scanning microscopy measurements were carried out as part of our in-depth investigation of AIE behavior of TPEs for the detection of biomolecules and radical species. We used 1,1,2,2-tetrakis(4-((trimethylammonium)alkoxy)phenyl)tetraphenylethene tetrabromide (TPE-C(m)N+Me3Br-, m = 2, 4, and 6, where m denotes the number of methylene groups in the alkyl chain) and TPE-C(m)N+Me3TCNQ-• (TCNQ-• is the 7,7',8,8'-tetracyanoquinodimethane anion radical) as luminescent probes for the detection of bovine serum albumin (BSA), DNA, and the hydroxyl radical (•OH) generated from Fenton's reagent. The sensing performance of TPE-C(m)N+Me3Br- for BSA and DNA was found to depend on the length of the alkyl chains (m). UV-vis and PL measurements revealed that the responses of TPE-C(m)N+Me3Br- and TPE-C(4)N+TCNQ-• to Fenton's reagent depended on the solvent. The electrochemical properties of the TPE derivatives prepared in this study were additionally investigated via cyclic voltammetry.

Synthesis, properties and graft polymerization of ionic conjugated polymers with TCNQ anion radical

The reactions of N-(2,4-dinitrophenyl)pyridinium 7,7′,8,8′-tetracyanoquinodimethane anion radical (TCNQ−.), namely, salt(TCNQ−.), with piperazine and 2-methylpiperazines without catalyst addition resulted in the opening of pyridinium ring to yield ionic polymers with 5-piperazinium-2,4-dienylideneammonium (PDA) TCNQ−. and 2-methylpiperazinium-2,4-dienylideneammonium (MPDA) TCNQ−. units, respectively, namely polymer(R;TCNQ−.) (R = H, Me, (R)-(−)-Me, and (S)-(+)-Me). The polymerization of methyl methacrylate (MMA) and styrene (St) initiated by AIBN, followed by the treatment with polymer(R;TCNQ−.) afforded radical coupling between TCNQ−. and the terminal radical of growing PMMA and PSt, resulting in poly(PDA) and poly(MPDA) with the PMMA and PSt graft chains, i.e., polymer(R;TCNQ−;GC) (GC = graft chain; PMMA and PSt). The 1H NMR, UV–vis, and SEM data suggested that the structures of polymer(R;TCNQ−;GC) in solution depended on solvent polarity. The electrochemical, magnetic, optical, and thermal properties of the polymers were also investigated.

Synthesis, Physical Properties, Structural, and Electrochemical Characterization of Methimidazolium and Imidazolium-based Tetracyanoquinodimethane Anion Radical Salts

Two methimazolium and two imidazolium-based salts derived from combination with the tetracyanoquinodimethane (TCNQ) radical anion have been synthesized (1–4). The 1:1 (cation:anion) stoichiometry of the chemically synthesized materials is fully supported by steady-state voltammetric measurements at a microdisc electrode in acetonitrile. The methimazolium TCNQ salts (1 and 2), which contain an acidic proton on the cation, exhibit a protonation step coupled to the TCNQ1–/2– charge-transfer process. Solid–solid transformations at a TCNQ-modified electrode also lead to electrochemical synthesis of 1–4, but also indicate that other cation:anion stoichiometries are accessible. Atomic force microscopy for electrochemically synthesized samples exhibit rod-like morphology. Conductivity measurements on chemically and electrochemically prepared salts are in the semiconducting range. Scanning electrochemical microscopy approach curve data support the substantial conductivity of these solids. Extensive physicochemical characterization of these materials is in complete accordance with the X-ray crystal structure of 1-acetonitrile-3-methylimidazolium tetracyanoquinodimethane, [AMim+][TCNQ1–], 4.

Analysis of active chemical species generated by electrolysis using non-aqueous capillary electrophoresis. Detection of the anion radical and the divalent anion of tetracyanoquinodimethane.

We have investigated detection of the anion radical and the divalent anion of tetracyanoquinodimethane (TCNQ) by acetonitrile-CE under anaerobic conditions. With electrolysis at a potential of 0.0 V (vs. Ag/AgCl), an acetonitrile solution of TCNQ turned green, characteristic of the TCNQ anion radical (TCNQ-). Only one peak of the anionic compound was observed in CE of the electrolysis solution and it should be that of TCNQ-. Then, the electrolysis potential was shifted to -0.8 V expected to be sufficient potential for the further reduction of TCNQ-, and the solution turned almost colourless. In CE analysis of the latter solution, another anionic component possessing a larger electrophoretic mobility than that of TCNQ- was detected, and it was decomposed immediately under aerobic conditions. This product was strongly suggested to be the divalent anion of TCNQ, and the present method would contribute notably to detection of the unstable species.

Thermal Characteristics of the Langmuir−Blodgett Film Fabricated with Bipyridinium Bis-(Tetracyanoquinodimethane Anion Radical) Salts

The phase transition of the headgroup in a Langmuir−Blodgett film fabricated with bipyridinum bis-(tetracyanoquinodimethane anion radical) salts attached with long chain alkyl groups has been studied using electron spin resonance spectroscopy. The C18 double chain attached more efficiently to the dipyridinium stabilized the alkyl chain and headgroup structure than the C22 single chain. The stability of the film may be due to the size matching between headgroup and hydrocarbon. The headgroup melting temperature of the double chain compound was 367 K and that of the single chain compound was 347 K, which was identified by ESR spectroscopy. A pretransition between two gel states was found. The viscosity estimated with the rotational correlation time of electron spin resonance spectroscopy was 0.8 poise for the Langmuir−Blodgett films.

Cyclodextrin complexation of the tetracyanoquinodimethane anion radical: the chemical consequences of cavity size and alkyl derivatization

Optical spectroscopy shows that in aqueous solution the tetracyanoquinodimethane anion radical (TCNQ - ) exist in equilibrium with its π-π dimer (Boyd and Phillips). A study of the effect of various cyclodextrins on this equilibrium shows strilingly different results depending on cavity size and on alkyl derivatization. The equilibrium is unaffected by the presence of α-cyclodextrin. In contrast, γ-cyclodextrin complexes and stabilizes the π-π dimer

The combined effect of some peroxide initiators and tetracyanoquinodimethane anion-radicals on polymerization of methyl methacrylate in solution

The kinetics and mechanism of the reaction between the tetracyanoquinodimethane anion-radical and some organic peroxides, which brings about efficient initiation of free-radical polymerization of methyl methacrylate, has been investigated. It is shown that one-electron transfer takes place between the anion-radical and the peroxide molecule, when the latter is a sufficiently good acceptor. Subsequently the neutral tetracyanoquinodimethane formed, reacts with a benzoate anion, and also with a benzoate radical and a second tetracyanoquinodimethane anion-radical. The free-radicals that initiate polymerization are produced by reaction between these reaction products and peroxide molecules. The quantitative characteristics of the reactions were determined.

Resonance Raman spectroelectrochemistry. 2. Scattering spectroscopy accompanying excitation of the lowest 2B1u excited state of the tetracyanoquinodimethane anion radical

Resonance Raman spectroelectrochemistry. 2. Scattering spectroscopy accompanying excitation of the lowest 2B1u excited state of the tetracyanoquinodimethane anion radical

Resonance Raman spectroelectrochemistry. 3. Tunable dye laser excitation spectroscopy of the lowest 2B1u excited state of the tetracyanoquinodimethane anion radical

Resonance Raman spectroelectrochemistry. 3. Tunable dye laser excitation spectroscopy of the lowest 2B1u excited state of the tetracyanoquinodimethane anion radical

Rates of electron-transfer reactions between tetracyanoquinodimethane anion radical and substituted p-benzoquinones in acetonitrile

Rates of electron-transfer reactions between tetracyanoquinodimethane anion radical and substituted p-benzoquinones in acetonitrile

Solvent Effect on the Dimerization of Tetracyanoquinodimethane Anion Radical

Abstract The thermodynamic quantities of the dimerization of tetracyanoquinodimethane (TCNQ) anion radical in water–ethanol mixtures were determined. The free energy of dimerization −ΔG showed a monotone decrease with an increase in ethanol content, whereas the enthalpy and the entropy of dimerization, −ΔH and −ΔS, showed a maximum. This unusual behavior is explained by proposing a solvation model in which the water molecules are attracted more strongly around the TCNQ− dimer than are the ethanol molecules. The entropy was found to play an important role in the dimerization.

The Reflection Spectra of Complex Salts of the Tetracyanoquinodimethane Anion Radical

Abstract Reflection measurements of the pressed pellets of two 2 : 3 complex salts and six 1 : 2 complex salts of the tetracyanoquinodimethane (TCNQ) anion radical were carried out over the 5000–43000 cm−1 range by the use of Avery’s method. The polarized normal-incidence reflection was measured for the Ph3PCH3(TCNQ)2single crystal. The observed results were examined on the basis of the composite-system method. For 2 : 3 salts, the transition energy and the oscillator strength are interpreted by the use of the N-A-A model (N: TCNQo and A-A: TCNQ anion dimer); it is concluded that the interaction between the two components, N and A-A, is weak. In the solid-state spectra of 1 : 2 salts, the assignments were made by the use of the polarization results of the normal-incidence reflection of the Ph3PCH3(TCNQ)2 crystal. Besides the four transitions corresponding to those of 2 : 3 salts, two new CT bands with weak intensities were observed and assigned. Except for quinolinium(TCNQ)2, a spectral change correlative to the electrical conductivity was found in the 1 : 2 salts and discussed in relation to the extent of the delocalization of the negative charge of (TCNQ)2−. The spectrum of quinolinium(TCNQ)2 exhibits a remarkable intensity decrease compared with those of the other 1 : 2 salts.

The Reflection Spectra of Simple Salts of the Tetracyanoquinodimethane Anion Radical

Abstract The reflection measurements were carried out for fourteen simple salts of the tetracyanoquinodimethane (TCNQ) anion radical over the range from 5000 to 42000 cm−1 by Avery’s method. The solid-state spectra show three bands (CT, YI, and YII) and exhibit distinct differences depending on the cation species. According to the differences in the transition energy (σi) and the oscillator strength (fi), the fourteen salts were classified into three groups (A, B, and C). The solid-state spectra of Group A resemble that of the dimer in an aqueous solution. Group B is characterized by the red shift of the CT band and the intensity increase in the YII band. The spectra of Group C exhibit a vibrational structure in the YI band which is similar to the monomer spectrum in an aqueous solution. Moreover, the large dispersion of the refractive index and the intensity increase in the bands of local excitation were observed for Group C. The electronic structures of these groups were studied by the use of the composite-system method. By taking account of the crystal structure of RbTCNQ-I, belonging to Group A, the stabilization energy (J*) of the ground state was calculated from σCT and fCT. The J* values for ten salts in Group A correspond well to the singlet-triplet separation in the ground state observed by ESR measurements.