- Photoinduced charge-separation using 10-methylacridinium ion loaded in zeolite Y as a photocatalyst with negligible back electron transfer across the zeolite-solution interface
-
Photoinduced electron transfer from Fe2+ loaded in zeolite Y to the singlet excited state of 10-methylacridinium ion in the zeolite occurs to give the acridinyl radical which reduces 7,7,8,8-tetracyanoquinodimethane in acetonitrile solution to yield the radical anion; the back electron transfer from the radical anion to Fe3+ across the zeolite-solution interface is shown to be negligibly slow.
- Fukuzumi, Shunichi,Urano, Tsutomu,Suenobu, Tomoyoshi
-
-
Read Online
- MECHANISM OF THE HYDRIDE TRANSFER REACTION OF LEUCO CRYSTAL VIOLET WITH CYANOMETHYLENE ACCEPTORS
-
In the hydride transfer reaction of Leuco Crystal Violet to form the Crystal Violet cation, the role of cyanomethylene acceptors was found to be essentially different from that of p-benzoquinones, both previously believed to act as ?-acceptors in the same manner.
- Nishimura, Norio,Zaman, Khan M.,Yamamoto, Shunzo
-
-
Read Online
- Ultrafast exciton decay in PbS quantum dots through simultaneous electron and hole recombination with a surface-localized ion pair
-
This paper describes the ultrafast decay of the band-edge exciton in PbS quantum dots (QDs) through simultaneous recombination of the excitonic hole and electron with the surface localized ion pair formed upon adsorption of tetracyanoquinodimethane (TCNQ). Each PbS QD (R = 1.8 nm) spontaneously reduces up to 17 TCNQ molecules upon adsorption of the TCNQ molecule to a sulfur on the QD surface. The photoluminescence of the PbS QDs is quenched in the presence of the reduced TCNQ species through ultrafast (≤15-ps) non-radiative decay of the exciton; the rate constant for the decay process increases approximately linearly with the number of adsorbed, reduced TCNQ molecules. Near-infrared and mid-infrared transient absorption show that this decay occurs through simultaneous transfer of the excitonic electron and hole, and is assigned to a four-carrier, concerted charge recombination mechanism based on the observations that (i) the PL of the QDs recovers when spontaneously reduced TCNQ1- desorbs from the QD surface upon addition of salt, and (ii) the PL of the QDs is preserved when another spontaneous oxidant, ferrocinium, which cannot participate in charge transfer in its reduced state, is substituted for TCNQ.
- Edme, Kedy,Bettis Homan, Stephanie,Nepomnyashchii, Alexander B.,Weiss, Emily A.
-
-
Read Online
- Microelectrochemical measurements of electron transfer rates at the interface between two immiscible electrolyte solutions: Potential dependence of the ferro/ferricyanide-7,7,8,8-tetracyanoquinodimethane (TCNQ)/TCNQ?- system
-
The reduction of 7,7,8,8-tetracyanoquinodimethane (TCNQ) in 1,2-dichloromethane (DCE) and nitrobenzene (NB), by aqueous ferrocyanide, and the back reaction were studied by scanning electrochemical microscopy. The effect of galvanic potential at the interface between two immiscible electrolyte solutions (ITIES) on electron transfer (ET) rates, with different electrolyte concentrations in the organic phase was evaluated. The ET rate constants for the forward and back reaction depended strongly on the interfacial potential drop, with an apparent ET coefficient close to 0.5. TCNQ?- was confined to DCE, but transferred from NB to water under certain experimental conditions, which could complicate kinetic analysis. The ET kinetics for the water/DCE system were analyzed further using Marcus theory. Close to zero driving force, the rate constants for the forward and back reaction were similar and in good agreement with predictions from Marcus theory with a sharp liquid/liquid interface. At equilibrium (when the forward and back ET rate constants were equal), the sharp boundary model for the ITIES predicted a bimolecular rate constant close to that measured experimentally.
- Unwin,Zhang
-
-
Read Online
- Electron Transfer Reaction between Δ2,2'-Bi-1,3-dithiole (TTF) and 7,7,8,8-Tetracyanoquinodimethane (TCNQ). Electron Donating Property of TTF
-
The reaction between Δ2.2'-bi-1,3-dithiole (TTF) and 7,7,8,8-tetracyanoquinodimethane (TCNQ) in acetonitrile solution, TTF + TCNQ = TTF +. =TCNQ -., was analyzed spectrophotometrically.The thermodynamical data of chemical equilibrium were determined to be K=(2.8 +/- 0.1)*10-3 at 11 deg C, ΔH=-6.7 +/-1.3 kJ mol -1 and Σ=-72.8 +/- 17 JK-1mol-1.The reaction-rate study of the equilibrium in several solvents was also made by temperature-jump technique.The difference in the electron-donating properties between TTF and N,N,N',N'-tetramethyl-p-phenylenediamine (TMPD) is discussed by comparing the results with those of the reaction between TMPD and TCNQ.
- Yamagishi, Akihiko,Iida, Yoichi
-
-
Read Online
- Electrically conducting TCNQ Derivatives of Copper Sulphur/Nitrogen Chelates; Structure of a Novel Semiconducting Complex 2 which contains N-bonded TCNQ (pdto=1,8-di-2-pyridyl-3,6-dithiaoctane; TCNQ=7,7,8,8-tetracyanoquinodimethane)
-
Reaction in water of Cu(pdto)(ClO4)2 with Li(TCNQ)/TCNQ mixtures yields solid crystalline materials of formulae Cu(pdto)(TCNQ)x (x=2, 2.5, or 3) which display high electrical conductivities ; reaction of Cu(pdto)(ClO4) with Li(TCNQ) yields Cu(pdto)(TCNQ), a poor conductor which has been shown by X-ray crystallography to have a novel dimeric structure involving ?-? interaction between TCNQ units and which possesses Cu-TCNQ bonding.
- Humphrey, David G.,Fallon, Gary D.,Murray, Keith S.
-
-
Read Online
- Positive dendritic effects on the electron-donating potencies of poly(propylene imine) dendrimers
-
(Chemical Equation Presented) Two series of poly(propylene imine), PPI, dendrimers terminated with a redox-active donor, 4-dimethylaminobenzyl (4-DMAB), including their respective nondendronized model compounds, are reported. In these two series, a positive dendritic effect was observed for the formation of charge-transfer (CT) complexes between the dendrimers and 7,7,8,8- tetracyanoquinodimethane (TCNQ). However, the nondendronized compounds did not form CT complexes with TCNQ, even though their redox potentials are similar to those of the 4-DMAB units attached to the dendrimers.
- Ong, Winston,McCarley, Robin L.
-
-
Read Online
- Effect of comproportionation on voltammograms for two-electron reactions with an irreversible second electron transfer
-
Many organic and organometailic compounds are reduced or oxidized in two steps with the addition or removal of the second electron occurring with greater difficulty than the first In such EE reactions, a comproportionation reaction can occur in solution near the electrode by which the final product exchanges an electron with the reactant to form two molecules of the intermediate species. Normally, this comproportionation reaction has little or no effect in voltammetry. In this paper, a substantial effect of comproportionation is predicted for the case where the second electron-transfer reaction is irreversible. In steady-state voltammetry, the normally symmetric, sigmoid-shaped second wave is predicted to rise more sharply near its base than is observed in the absence of comproportionation and, in the limit of a very fast comproportionation reaction, an "onset potential" develops at which the current at the second wave increases abruptly from the limiting current of the first plateau. Experimental examples of these effects are presented for the reduction of tetracyanoquinodimethane in acetonitrile by steady-state microelectrode voltammetry, normal-pulse voltammetry, and cyclic voltammetry.
- Lehmann, Mark W.
-
-
Read Online
- Spectroscopic and thermal investigations on the charge transfer interaction between risperidone as a schizophrenia drug with some traditional π-acceptors: Part 2
-
The focus of present investigation was to assess the utility of non-expensive techniques in the evaluation of risperidone (Ris) in solid and solution states with different traditional π-acceptors and subsequent incorporation of the analytical determination into pharmaceutical formulation for a faster release of risperidone. Charge-transfer complexes (CTC) of risperidone with picric acid (PA), 2,3-dichloro-5,6-dicyano-p-benzoquinon (DDQ), tetracyanoquinodimethane (TCNQ), tetracyano ethylene (TCNE), tetrabromo-p-quinon (BL) and tetrachloro-p-quinon (CL) have been studied spectrophotometrically in absolute methanol at room temperature. The stoichiometries of the complexes were found to be 1:1 ratio by the photometric molar ratio between risperidone and the π-acceptors. The equilibrium constants, molar extinction coefficient (εCT) and spectroscopic-physical parameters (standard free energy (ΔGo), oscillator strength (f), transition dipole moment (μ), resonance energy (RN) and ionization potential (ID)) of the complexes were determined upon the modified Benesi-Hildebrand equation. Risperidone in pure form was applied in this study. The results indicate that the formation constants for the complexes depend on the nature of electron acceptors and donor, and also the spectral studies of the complexes were determined by (infrared, Raman, and 1H NMR) spectra and X-ray powder diffraction (XRD). The most stable mono-protonated form of Ris is characterized by the formation of +NH (pyrimidine ring) intramolecular hydrogen bonded. In the high-wavenumber spectral region ～3400 cm-1, the bands of the +NH stretching vibrations and of the pyrimidine nitrogen atom could be potentially useful to discriminate the investigated forms of Ris. The infrared spectra of both Ris complexes are confirming the participation of +NH pyrimidine ring in the donor-acceptor interaction.
- El-Habeeb, Abeer A.,Al-Saif, Foziah A.,Refat, Moamen S.
-
p. 464 - 477
(2013/04/23)
-
- Controlled nanoscale mechanical phenomena discovered with ultrafast electron microscopy
-
On again, off again: The reversible expansion and contraction of single crystals of [Cu(TCNQ)] induced by near-infrared laser pulses was studied with ultrafast electron microscopy (TCNQ = 7,7,8,8-tetracyanoquinodimethane). The crystal expands along the σ-
- Flannigan, David J.,Lobastov, Vladimir A.,Zewail, Ahmed H.
-
p. 9206 - 9210
(2008/12/22)
-
- Electrochemical studies of heterogeneous reduction of tetracyanoquinodimethane in poly(ethylene oxide) electrolytes using ac impedance and cyclic voltammetry at an ultramicroelectrode
-
Electrochemical studies of the TCNQ0/TCNQ- couple have been carried out using ac impedance spectroscopy and cyclic voltammetry at platinum ultramicroelectrodes (UME). Liquid poly(ethylene oxide) (PEO) CH3-O-(CH2-CH2-O4)-CH3 has been used as the solvent with different concentrations of the TCNQ0/TCNQ- couple and LiClO4 as the supporting electrolyte. On the basis of the ac impedance results at the UME it has been found that the double layer capacitance and standard heterogeneous rate constant are independent of the presence of electroactive species and supporting electrolyte concentrations, indicating that adsorption of electroactive species onto the electrode is not significant. The standard heterogeneous rate constant ks was found to be 0.109 ± 0.005 cm s-1. A similar value of k(s) = 0.094 cm s-1 was obtained for the second reduction step TCNQ-/TCNQ2-. Diffusion coefficients of both TCNQ and TCNQ- are equal, D = 1.0 x 10-6 cm2 s-1 for a 0.5 M LiClO4 solution. Higher diffusion coefficients are obtained in less concentrated supporting electrolyte. Comparison is made between these results and those reported previously for PEO-400 HO-(CH3CH2O)8-OH. The different end groups significantly influence the viscosity and hence k(s).
- Los,Zabinska,Kisza,Christie,Mount,Bruce
-
p. 5449 - 5454
(2007/10/03)
-
- In Situ Electrochemical EPR Studies of Charge Transfer across the Liquid/Liquid Interface
-
The in situ measurement of EPR spectra of radical ions generated at the polarized liquid/liquid interface is described in relation to the 7,7,8,8-tetracyanoquinodimethane (TCNQ), 2,3,5,6-tetrachloro-p-benzoquinone (TCBQ), and 2,3,5,6-tetrafluoro-p-benzoquinone (TFBQ) radical anions and the tetrathiafulvalene (TTF) radical cation. TCNQ and TTF were chosen as model compounds with which to quantify the performance of a novel liquid/ liquid electrochemical EPR cell. The anion radical of TCNQ and the cation radical of TTF in 1,2-dichloroethane (DCE) were produced at the water interface by electron transfer from/to the aqueous-phase ferricyanide/ferrocyanide redox couple by applying a potential difference between the two phases with a four-electrode potentiostat. The EPR signal intensity (at constant magnetic field) of the resultant organic radicals was monitored during potential step experiments which indicated that the EPR data could be modeled in terms of diffusional transport. TCBQ and TFBQ were chosen as compounds to model the electron transfer behavior of biologically important quinones at the oil/water interface. The EPR and voltammetric data obtained from TCBQ/TCBQ-· and TFBQ/ TFBQ-· indicated unambiguously that the two semiquinones are stable at the DCE/water interface and do not undergo immediate protonation.
- Webster, Richard D.,Dryfe, Robert A. W.,Coles, Barry A.,Compton, Richard G.
-
p. 792 - 800
(2007/10/03)
-
- Spectroscopic studies of molecular interaction of 2-thiouracil and dithiouracil donors with 7,7,8,8-tetracyanoquinodimethane as an electron acceptor
-
The electronic absorption and electron spin resonance studies on the interaction of thiouracil and dithiouracil as donors with 7,7,8,8-tetracyanoquinodimethane (TCNQ) as an acceptor reveal that the absorption bands in these systems are not due to the charge transfer complex but are due to the formation of products (free radical in nature). The equilibrium constants, K, for the D-A systems as determined from the Benesi Hildebrand model follow the direct trend of pKH of the donors and K(dithiouracil) > · K(thiouracil).
- Randhawa,Sirdhana,Jassal,Sekhon
-
-
- Charge-Transfer Complexes of Benzo[b]thiophene with σ- And π-Electron Acceptors
-
The spectrophotometric properties of the charge-transfer (CT) complexes of benzo[6]thiophene with iodine at 24°C in different solvents such as cychlohexane, carbon tetrachloride, chloroform, dichloromethane, and 1,2-dichloroethane are studied. In addition the spectrophotometric and thermodynamic properties of the CT complexes of benzo[b]thiophene with tetracyanoethylene, chloranil, 2,3-dichloro-5,6-dicyano-p-benzoquinone and 7,7,8,8,-tetracyanoquinodimethane are studied. The results show that the equilibrium and the thermodynamic parameters and the wavelengths of the maximum absorption bands (λmax) of the complexes vary markedly with the solvent. The ionization potential and the donor sites of benzo[b]thiophene are also determined and discussed.
- Ayad, Mohamad M.
-
p. 2369 - 2373
(2007/10/03)
-
- HYDRIDE TRANSFER REACTIONS OF MICHLER'S HYDRIDE WITH DIFFERENT ?-ACCEPTORS
-
The hydride transfer reactions of 4,4'-bis(dimethylaminophenyl)methane (Michler's hydride) with p-benzoquinones were studied.The rate of formation of Michler's Hydrol Blue was followed spectrophotometrically.The second-order rate constants and the activation parameters were estimated.The formation of a charge-transfer complex was observed at low temperatures.Stable and unstable paramagnetic species formed during the reactions were assigned by ESR spectroscopy.The observed kinetic behaviour and the stoichiometry were in line with those previously obtained for the systems involving Leuco Crystal Violet, Leuco Malachite Green and Leuco Bindshedler's Green.Hence the reaction is considered to proceed according to the so-far accepted multi-step mechanism.However, when tetracyano-p-quinodimethane or tetracyanoethylene was used as a ?-acceptor, a comparatively stable radical ion pair was formed as a result of a one-electron transfer, followed by the gradual formation of Michler's Hydrol Blue.The kinetic behaviour and the stoichiometry of the reaction were examined, together with the enhanced kinetic effects of added triethylamine.A modified mechanism for these systems is proposed.The role of cyanomethylenes was found to be essentially different from that of p-benzoquinones, and therefore ?-acceptors are divided into two groups of cyanomethylenes and p-benzoquinones.
- Zaman, Khan. M.,Nishimura, Norio,Yamamoto, Shunzo,Sueishi, Yoshimi
-
p. 309 - 315
(2007/10/02)
-
- (Pyridinylmethylidene)dithioles: Synthesis, Structure, and Reactivity
-
Spectral characteristics, an X-ray crystal structure, and molecular orbital calculations indicate that (pyridinylmethylidene)dithioles 3, prepared from butadiynyl precursors 4 and hydrogen sulfide in basic methanol, are analogous in their bonding to the parent 1-aza-6,6λ4-dithiapentalenes 1 which, according to ab initio studies at Hartree-Fock level, is best represented as an (iminomethylidene)dithiole.An interaction between the sulfur and the nitrogen atoms is evident from the significant polarization of the S-S bond in those isomers where the nitrogen is proximal to the dithiole moiety.A comparison of the calculated structures of 1 and 3 with experimental data, as well as preliminary calculations on the related system trithiapentalene 2, suggest that ab initio methods using a single determinant are inadequate to describe these hypervalent sulfur systems.For example, an asymmetric structure is calculated to be the minimum energy from for 2 in contradiction to experimental results.Electrophilic substitutions, ring rearrangement, and reaction with electron acceptors are described for 3.
- Potts, Kevin T.,Nye, Susan A.,Smith, Kennith A.
-
p. 3895 - 3901
(2007/10/02)
-
- Outer-Sphere Electron-Transfer Oxidation of 10,10'-Dimethyl-9,9',10,10'-tetrahydro-9,9-biacridine
-
10,10'-Dimethyl-9,9',10,10'-tetrahydro-9,9'-biacridine acts as a unique two-electron donor in the electron-transfer oxidation with various organic oxidants.The rate-determining step is electron transfer from (AcrH)2 to oxidants, followed by facile cleavage of the C(9)-C bond of (AcrH)2.+ to yield the acridinyl radical (AcrH.) and 10-methylacridinium ion (AcrH+).The second electron transfer from AcrH. to oxidants is much faster than the initial electron transfer from (AcrH)2 to oxidants.On the other hand, the corresponding monomer, 10-methyl-9,10-dihydroacridine (AcrH2), acts as a normal hydride (two electrons and proton) donor in the reactions with oxidants.Rates of electron-transfer reactions from (AcrH)2 to various inorganic and organic one-electron oxidants depend solely on the one-electron-reduction potentials of the oxidants irrespective of the size of the oxidants, indicating that (AcrH)2 acts as a novel two-electron outer-sphere electron-transfer reagent.The one-electron-oxidation potential of (AcrH)2 (vs SCE) has been evaluated as 0.62 V, which is less positive than that of the corresponding monomer (0.80 V).
- Fukuzumi, Shunichi,Tokuda, Yoshihiro
-
p. 8409 - 8413
(2007/10/02)
-
- 7. Tetrazinodiheteroarene: 'Charge -Transfer'-Komplexbildung mit Akzeptorverbindungen
-
The formation of charge-transfer complexes and radical-ion pairs of donor compounds 1-6 with acceptor compounds 7-12 has been investigated by means of VIS/NIR-spectrospcopic methods.The equilibrium constants KCT (up to 1100M-1) for the donor/acceptor couple dipyridotetrazine (2)/ethylenetetracarbonitrile (11) and spectra of the CT complexes have been determined in 1,2-dichloroethane solution at 25 deg C.Results are discussed in relation to known CT-complex properties and to voltammetric redox-potentials E1/2.
- Hellrung, Bruno,Balli, Heinz
-
-
- Formation Reactions of Phosphorus Ylide-Tetracyanoquinodimethane Complexes
-
The complexation reactions of tetracyanoquinodimethane (TCNQ) with phosphorus ylides have been studied.The binding energy is related to the electron density on the ylide atom as controlled by substituents.The degree of charge-transfer in the complex is also controlled by the substituents.The rate of formation of ylide-TCNQ complexes is slow enough to be measured, and a correlation between the reaction rate and the basicity of the ylide atoms was also established.
- Tsuchiya, Shinji,Mitomo, Shun-ichi,Kise, Hideo,Seno, Manabu
-
p. 245 - 248
(2007/10/02)
-
- PREPARATION OF 7,7,8,8-TETRACYANOQUINODIMETHANE AND ITS DERIVATIVES
-
The reaction of terephthaloyl chloride with cyanotrimethylsilane in the presence of pyridine gave 1,4-bis(dicyanotrimethylsiloxymethyl)benzene, which was treated with POCl3-pyridine to afford tetracyanoquinodimethane (TCNQ) along with its dichloride.Similarly, 2,5-dimethyl-TCNQ and 2-bromo-TCNQ were prepared from the corresponding tetraphthaloyl chlorides.
- Yamaguchi, Shunro,Hanafusa, Terukiyo
-
p. 689 - 690
(2007/10/02)
-
- Kinetics of the Reaction of Alkylamines with 7,7,8,8-Tetracyanoquinodimethane (TCNQ) in Organic Solvents
-
The following sequence of substitution reactions was studied spectrophotometrically in organic solvents: where R = butyl, octyl, dodecyl, and hexadecyl.The production of 7-(alkylamino)-7,7,8-tricyanoquinodimethanes proceeds via the formation of the anion radical of TCNQ (TCNQ anion radical) whose rate of appearance was found to be a function of the chain length of R, reaching a maximum for octylamine.The formation of TCNQ anion radical was sensitive to the solvent polarity and electron-donor power and was associated with a small enthalpy and a highly negative entropy of activation.Above a certain the rate of disappearance of TCNQ anion radical was independent of the amine concentration, and the reaction had a much higher enthalpy and entropy of activation.The occurrence of tautomerism precluded an investigation of the conversion of 7-(octylamino)-7,8,8-tricyanoquinodimethane into 7,7-bis(octylamino)-8,8-dicyanoquinodimethane.A study of the reaction of octylamine with 7-morpholino-7,8,8-tricyanoquinodimethane (which does not exist in tautomeric forms) showed that the second substitution step proceeds with the same mechanism as the first one.The only difference between the two compounds (TCNQ and its monosubstituted morpholino derivative) is one of reactivity.
- Seoud, Omar A. El,Ribeiro, Francisco P.,Martins, Abilio,Brotero, Paula P.
-
p. 5099 - 5102
(2007/10/02)
-
- STUDIES OF THE CHARGE-TRANSPHER COMPLEXES OF AZOXY COMPOUNDS WITH ?-ACCEPTORS
-
Charge-transfer complexes of aryl azoxy compounds with some ?-acceptors in dichloromethane were studied spectrophotometrically at 25 deg C in the visible region.The spectroscopic data indicate that the complexes are not strong in nature and the Ph-N=-->O group is resposible for the complexation with ?-acceptors.Comparison with nitrones has been made.The 1H NMR and IR spectra of some solid complexes differ in important respects from those of either component taken separately.The effect of temperature on the stability of the complexes is discussed.Job's method shows that the stoicheiometric ratio of the complexes is 1:1.
- El-Din, Ahmed Moukhtar Nour
-
p. 401 - 404
(2007/10/02)
-
- Photochemical Oxidation of a Tetracyanoquinodimethane Radical-ion Salt
-
The kinetics and mechanism of the one-electron oxidation of the electronically excited tetracyanoquinodimethane radical-anion (TCNQ.-Na+) by weak electron acceptors (C2HBr5 and CCl4) in solutions have been investigated spectrophotometrically.It is shown that, when the radical-anion TCNQ-. is photoexcited by light corresponding to the absorption bands (in the region of 422 and 700 nm), the electron-donating capacity of the radical-ion is enhanced and this entails the one-electron oxidation of TCNQ.-Na+, which does not occur under dark conditions.The quantum yields of the one-electron photochemical oxidation reactions of TCNQ.- have been determined.It has been established that the photochemical oxidation of TCNQ-. by pentabromoethane proceeds via a bimolecular mechanism.
- Ganyuk, L. N.,Guba, N. F.,Pokhodenko, V. D.
-
p. 1232 - 1235
(2007/10/02)
-
- REACTION OF DIAZONIUM SALTS WITH THE TETRACYANOQUINODIMETHANE ANION-RADICAL
-
Diazonium salts react with the tetracyanoquinodimethane anion-radical with the release of nitrogen and the formation of 1,2-bis-1,1,2,2-tetracyanoethane, where R = H, Me OMe, Cl, CN, NO2, NMe2.During the pyrolysis of these compounds and subsequent irradiation of the reaction mass with UV light 7-(4-R-phenyl)-7,8,8-tricyanoquinodimethanes (R = H, Me, Cl, OMe, NMe2) were obtained with small yields.
- Bespalov, B. P.
-
p. 736 - 740
(2007/10/02)
-
