A new method for electrocrystallization of AgTCNQF4 and Ag2TCNQF4 (TCNQF4 = 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane) in acetonitrile

Semiconducting AgTCNQF₄ (TCNQF₄?=?2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane) has been electrocrystallized from an acetonitrile (0.1?M Bu₄NPF₆) solution containing TCNQF₄ and Ag(MeCN) ₄ ⁺ . Reduction of TCNQF₄ to the TCNQF ₄ ^1? anion, followed by reaction with Ag(MeCN) ₄ ⁺ forms crystalline AgTCNQF₄ on the electrode surface. Electrochemical synthesis is simplified by the reduction of TCNQF₄ prior to Ag(MeCN) ₄ ⁺ compared with the analogous reaction of the parent TCNQ to form AgTCNQ, where these two processes are coincident. Cyclic voltammetry and surface plasmon resonance studies reveal that the electrocrystallization process is slow on the voltammetric time scale (scan rate?=?20?mV?s^?1) for AgTCNQF₄, as it requires its solubility product to be exceeded. The solubility of AgTCNQF₄ is higher in the presence of 0.1?M Bu₄NPF₆ supporting electrolyte than in pure solvent. Cyclic voltammetry illustrates a dependence of the reduction peak potential of Ag(MeCN) ₄ ⁺ to metallic Ag on the electrode material with the ease of reduction following the order Au?<?Pt?<?GC?<?ITO. Ultraviolet-visible, Fourier transform infrared, and Raman spectra confirmed the formation of reduced TCNQF ₄ ^1? and optical microscopy showed needle-shaped morphology for the electrocrystallized AgTCNQF₄. AgTCNQF₄ also can be formed by solid?Csolid transformation at a TCNQF₄-modified electrode in contact with aqueous media containing Ag⁺ ions. Chemically and electrochemically synthesized AgTCNQF₄ are spectroscopically identical. Electrocrystallization of Ag₂TCNQF₄ was also investigated; however, this was found to be thermodynamically unstable and readily decomposed to form AgTCNQF₄ and metallic Ag, as does chemically synthesized Ag₂TCNQF₄.     

Structure and magnetic properties of tetraarylporphinatomagnesium(II) electron transfer salts of 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane,TCNQF4

The crystal structures of the 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane, TCNQF(4), electron transfer salts of meso-tetraphenylporphinatomagnesium(II), [MgTPP][TCNQF(4)].PhMe and [MgTPP][TCNQF(4)].3(1,2-C(6)H(4)Cl(2)), and meso-tetrakis(3,4,5-trimethoxyphenyl)porphinatomagnesium(II), [MgT(3,4,5-OMe)PP][TCNQF(4)].3(1,2-C(6)H(4)Cl(2)), provide the first structurally characterized examples of 1-D metal-radical chains involving [Mg(II)(porphyrin(*))](+). These salts possess [TCNQF(4)](*-) stabilized by trans-mu-coordination to Mg(II) and exhibit nu(CN) at 2199 and 2177, 2212 and 2187, and 2194 and 2172 cm(-1), respectively. The [TCNQF(4)](*-) species is planar and bridges two cations with MgN distances of 2.266(16), 2.221(2), and 2.276(3) A, respectively, which are shorter than the MnN 2.321(3) A distance observed for [MnT(3,4,5-OMe)PP][TCNQF(4)].3(1,2-C(6)H(4)Cl(2)). The room-temperature effective moments for [MgTPP][TCNQF(4)].xS (S = PhMe and 1,2-C(6)H(4)Cl(2)) and [MgTPP][C(4)(CN)(6)].PhMe are consistent with the calculated spin only value of 2.45 micro(B) with weak antiferromagnetic coupling (J(intra)/k(B) approximately -2.9 K; H = -2JSa.Sb) for these [TCNQF(4)](*-) salts and for this [C(4)(CN)(6)](*-) salt (J(intra)/k(B) approximately -0.8 K) on the basis of fits to several models. The coupling is significantly reduced with respect to that of the Mn analogues due to lack of spin on the metal site for [Mg(II)(por(*))](+). The antiferromagnetic coupling is enhanced for [MgT(3,4,5-OMe)PP][TCNQF(4)] with respect to [MgTPP][TCNQF(4)] as [TCNQF(4)](*-) gets closer to the [Mg(II)(por(*))](+) plane, which leads to greater interactions and coupling.     

A tetranuclear organorhenium(i) complex of the 2,3,5,6-tetrafluoro-7,7,8,8-tetracyano-p-quinodimethane radical anion, TCNQF4 (-)

The radical complex {(mu(4)-TCNQF4)[Re(CO)(3)(bpy)](4)}(PF(6))(3), as prepared and isolated from the reaction between TCNQF4 and [Re(CO)(3)(bpy)(MeOH)](PF(6)), was studied electrochemically and by IR vibrational spectroscopy, UV-Vis-NIR absorption spectroscopy, and by EPR at 9.5, 190 and 285 GHz. The isotropic g factor of 2.0058, the detectable g anisotropy, and the (185,187)Re EPR hyperfine coupling of 0.95 mT for four equivalent metal nuclei support predominant, but not exclusive, spin localisation at the bridging ligand. Nitrile and metal carbonyl stretching frequencies as well as the typically structured near infrared absorption band lend further support to (TCNQF4 (-))(Re(I))(4) as the most appropriate oxidation state formulation. In comparison to the non-radical complex {(mu(4)-TCNQ)[Re(CO)(3)(bpy)](4)}(PF(6))(4) an X-ray structure analysis of {(mu(4)-TCNQF4)[Re(CO)(3)(bpy)](4)}(PF(6))(3) shows a marginally more twisted (ReNCCCNRe)(C(6)X(4))(ReNCCCNRe) configuration and a different up/down arrangement of the [Re(CO)(3)(bpy)](+) groups. This first isolation, electrochemical, structural and spectroscopic characterisation of a discrete tetranuclear radical complex of a TCNQ-type ligand suggests a link between the stability of such materials and the rather small structural changes on ligand-based electron transfer.     

Ion-radical salt of 2-tert-butyltetrathiatetracene with 7,7,8,8-tetracyanoquinodimethane (2∶1)

Conclusions We synthesized 2-tert-butyltetrathiatetracene and its 2:1 complex with 7,7,8,8-tetra-cyanoquinodimethane, which has an ion-radical nature.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 3, pp. 696–697, March, 1977.The authors express their gratitude to L. I. Buravov for measuring the electrical conductivity.     

Synthesis and reactions of 2-hydroxy-4-oxo-4-(2,3,5,6-tetrafluoro-4-methoxyphenyl)-but-2-enoic acid methyl ester

2-Hydroxy-4-oxo-4-(2,3,5,6-tetrafluoro-4-methoxyphenyl)-but-2-enoic acid methyl ester (1) was synthesized by the reaction of pentafluoroacetophenone with dimethyl oxalate in the presence of sodium methylate. Subsequently, reactions of compound 1 with aniline, o-phenylenediamine, and o-aminophenol were investigated. In addition, the thermal cyclization of ester 1 was studied and led to the formation of 5,6,8-trifluoro-7-methoxy-4-oxo-4H-chromene-2-carboxylic acid methyl ester (6) due to nucleophilic substitution of the 3-fluoro group. Hydrolysis of compound 1 and subsequent cyclization by treatment with SOCl₂ gave 5-(2,3,5,6-tetrafluoro-4-methoxyphenyl)-furan-2,3-dione (3). Thermal decarbonylation of compound 3 under mild conditions resulted in the formation of 3-(2,3,5,6-tetrafluoro-4-methoxyphenyl)-propene-1,3-dione (4) which dimerized to pyranone 5.     

Reactions of hexamethyldilead with 7,7,8,8-tetracyanoquinodimethane (TCNQ) and tetracyanoethylene (TCNE)

Hexamethyldilead reacts with TCNQ to give Pb(TCNQ)₂ and tetramethyllead and with TCNE to give Pb(TCNE).     

Synthesis and characterization of poly(2,3,5,6-tetrafluoro-1,4-phenylenevinylene)

Poly(2,3,5,6-tetrafluoro-1,4-phenylenevinylene) (PTFPV) was prepared for the first time by the Stille cross-coupling reaction and the resulting material was characterized through MALDI-TOF mass spectrometry, employing a novel sample preparation protocol suitable for insoluble compounds; preliminary optical and electrooptical measurements were performed.     

High pressure Raman studies of 7,7,8,8-tetracyanoquinodimethane (TCNQ) and CuTCNQ

The high-pressure Raman studies of 7,7,8,8-tetracyanoquinodimethane (TCNQ) single crystals and polycrystalline CuTCNQ are presented in this paper. TCNQ shows a phase transition at 22 kbar, a pressure higher than reported earlier. CuTCNQ undergoes a first order phase transition at 30 kbar, which is characterized by the abrupt disappearance of all the Raman bands.     

A convenient preparation of 2,3,5,6-tetrafluoro-4-iodo-benzaldehyde and its application in porphyrin synthesis

An efficient synthesis of 2,3,5,6-tetrafluoro-4-iodo-benzaldehyde (1) is presented. This new compound was readily obtained via iodination at low temperature of the lithio derivative of 2-(2,3,5,6-tetrafluoro-phenyl)-[1,3]dioxolane (4). The crystal structure of 1 consists of linear polymeric chains, with non-covalent O?I bonding as the directing interaction, responsible for the observed assembly. Aldehyde 1 is further employed in the synthesis of 5,10,15,20-tetrakis(pentafluorophenyl)porphyrin (6), a potential precursor of supramolecular assemblies.     

A re-examination of the use of 7,7,8,8-tetracyanoquinodimethane (TCNQ) in determining the critical micelle concentrations

Summary A detailed re-examination of the use of TCNQ in ] determining the critical micelle concentration (c. m. c.'s) of aqueous and reversed micelles was carried out. The mechanism of the interaction of TCNQ with ionic and non-ionic detergents was investigated in order to delineate the origin of the production of the dye anion-radical. In several cases, the formation of the latter species can be eliminated, or kept to a minimum, if highly purified detergents and solvents were used. Under these conditions, the neutral TCNQ visible absorption band should be used in the c.m.c. determination. The origin of the formation of the TCNQ anion-radical has been traced to the presence of difficulty removable impurities in the anionic and/or non-ionic surfactants, and to the reaction of the dye with the counter-ion of the positive micelles.     

A novel reaction of 7,7,8,8-tetracyanoquinodimethane (TCNQ): charge-transfer chromophores by [2 + 2] cycloaddition with alkynes

A series of donor-acceptor molecules, featuring intense low-energy intramolecular charge-transfer bands, was prepared by regioselective [2 + 2] cycloaddition between 7,7,8,8-tetracyanoquinodimethane (TCNQ) and N,N-dialkylanilino-substituted (DAA-substituted) alkynes, followed by ring opening of the initially formed cyclobutenes.     

Characteristic of the Ag(bipy) 2 2+ /Ag(bipy) 2 + and Ag(phen) 2 2+ /Ag(phen) 2 + systems in acetonitrile

The values of standard potentials of redox systems formed by the complexes of Ag(II) and Ag(I) with 2,2-bipyridine and 1,10-phenanthroline in acetonitrile have been determined. The properties of the above systems in water and acetonitrile are compared. The possibility of application of these systems for the construction of electrodes with a constant potential in different solvents is discussed.

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Charakteristik der Systeme Ag(bipy) ₂ ²⁺ /Ag(bipy) ₂ ⁺ und Ag(phen) ₂ ²⁺ /Ag(phen) ₂ ⁺ in Acetonitril

Zusammenfassung Die Standardpotentialwerte der Redoxsysteme, die durch Komplexbildung von Ag(II)- und Ag(I)-Ionen mit 2,2-Bipyridin und 1,10-Phenantrolin gebildet werden, wurden in Acetonitril bestimmt. Die Eigenschaften dieser Redoxsysteme in Wasser und Acetonitril wurden verglichen.Es wurde weiterhin die Möglichkeit der Anwendung dieser Systeme zur Konstruktion einer Elektrode mit unveränderbarem Potential in verschiedenen Lösungsmitteln diskutiert.

     

Structural studies in main group chemistry : XIX. Organotin(IV) derivatives of tetracyanoethylene, 7,7,8,8-tetracyanoquinodimethane and 2,3,5,6-tetrachlorobenzoquinone. The isolation of stable organotin-substituted radicals

The reaction of organotin chlorides with the lithium salt of 7,7,8,8-tetracyanoquinodimethane (TCNQ) or hexaalkylditins with TCNQ yield stable organotin-substituted free radicals of the types R₃SnTCNQ^. (R = Me, n-Pr, n-Bu) and Me₂Sn(TCNQ^.)₂. The reaction of hexaphenylditin with TCNQ yields a (σ → π) charge transfer complex of stoichiometry (Ph₃SnSnPh₃)·TCNQ, whilst [Me₂SnCl(terpyridyl)⁺](TCNQ^-·) was isolated from the reaction of [Me₂SnCl(terpyridlyl)⁺][Me₂SnCl₃^-] and LiTCNQ. The oxidation of hexaalkylditins by tetracyanoethylene (TCNE) yields stable free radicals of the type R₃SnTCNE·, but treatment with 2,3,5,6-tetrachlorobenzoquinone yields either R₃SnOC₆Cl₄O·-p (R = Me) or R₃SnOC₆Cl₄OSnR₃-p (R = n-Bu, Ph). Tin-119 Mössbauer spectroscopy shows that the derivatives R₃SnTCNQ· and R₃TCNE· have trigonally-bipyramidally coordinated tin with planar [SnC₃] skeletons and bridging [TCNQ·] and [TCNE·] groups forming infinite one-dimensional chain structures. Me₃SnOC₆Cl₄O·-p was inferred to possess a similar structure but with oxy bridges forming chains with a Sn---O---Sn---O backbone. Me₂Sn(TCNQ·)₂ has a structure intermediate between tetrahedral and octahedral with a non-linear MeSnMe unit and anisobidentate chelation by two TCNQ groups. The TCNQ derivatives were of two types: (i) “green” or “brown”, indicative of delocalisation of the Ione electron over the cyanoquinone ligand, and (ii) a “blue” form in which spin-pairing of the Ione electron between adjacent organic groups takes place. Me₃SnTCNQ· may exist in both forms depending upon the mode of preparation.     

Isolation of p-tricyanovinylphenyldicyanomethide ion via a [2+2] cycloaddition of 7,7,8,8-tetracyanoquinodimethane (TCNQ) molecules

In the presence of CoCl₂·6H₂O and dppm (bis(diphenylphosphino) methane), the reaction of TCNQ (7,7,8,8-tetracyanoquinodimethane) molecules by [2+2] cycloaddition forms a p-tricyanovinylphenyldicyanomethide ion (PCQ⁻), which has been obtained as one anion unit in one new compound [Co(dppmdo)₃][PCQ⁻]₂·H₂O 1 (dppmdo = bis(diphylphospine oxide) methane). Its structure was determined by X-ray crystallography: 1 crystallizes in with a = 14.174(3) Å, b = 19.553(4) Å, c = 19.776(4) Å, α = 112.72(3)°, β = 95.43(3)°, γ = 110.79(3)°, and Z = 2. It was characterized by IR spectra, UV–Vis spectra, and cyclic voltammogram. Magnetic properties indicate that no magnetic coupling between PCQ⁻ and [Co(dppmdo)₃]²⁺ unit.     

(n‐Nitrophenyl)acetonitrile,with n = 2, 3 and 4

The molecular structures of the three title nitro‐substituted phenyl­aceto­nitriles, C₈H₆N₂O₂, at 123 K show that the mol­ecules are linked together very differently. In the 2‐ and 4‐nitro compounds, there are both O?H and N_cyano?H interactions, whereas the crystal lattice of the 3‐nitro compound is essentially built up by O?H interactions. The O atoms seem to prefer the aromatic H atoms, while the cyano N atoms prefer the methyl­ene H atoms. The phenyl–nitro torsion angles are ?19.83 (13), ?5.69 (12) and ?2.88 (12)°, while the phenyl–cyano­methyl torsion angles are ?62.27 (12), ?147.99 (9) and ?16.75 (14)° in the 2‐, 3‐ and 4‐NO₂‐substituted compounds, respectively.     

Constructing highly conducting metal-metal bonded solids by electrocrystallization of [Pt(II)2(RCS2)4] (RCS2(-) = dithiocarboxylato, R = methyl or ethyl)

Partially oxidized one-dimensional (1D) Pt-Pt chain compounds [Pt2(MeCS2)4]4ClO4.5PhCN (1) and [Pt2(EtCS2)4]5(ClO4)2 (2) were synthesized by electrocrystallization of diplatinum(II,II) complexes from different solvents. 1 and 2 consist of 1D Pt-Pt chains of stacked Pt-Pt dimers with short interdimer S...S contacts. Depending on the number of ClO4- per dimer and their positions, 1 forms a regular stack of Pt-Pt dimers, whereas 2 forms pentamer of dimers in the 1D chain. 1 exhibits high electrical conductivity (4.2-8.0 S cm-1) at 300 K and metallic behavior above 125 K. 2 is a semiconductor. 1 exhibits almost temperature independent magnetic susceptibility (ca. 1.1 x 10-4 emu mol-1) which is attributed to Pauli paramagnetism, whereas the spin degree of freedom in 2 has been lost. Although the basic structures are closely related, they exhibited different solid-state properties that depend on the valence state of the platinum atoms and the periodicity within the 1D chain.