3109-63-5Relevant academic research and scientific papers
Electrochemistry and ion-sensing properties of calix[4]arene derivatives
Chen, Shanshan,Webster, Richard D.,Talotta, Carmen,Troisi, Francesco,Gaeta, Carmine,Neri, Placido
, p. 7036 - 7043 (2010)
The cyclic voltammetric properties of several substituted calix[4]arenes were examined in acetonitrile and dichloromethane. The compounds that contained one phenolic group in the macrocyclic cavity were able to be electrochemically oxidised at positive potentials. In acetonitrile, cyclic voltammetry experiments indicated that the phenolic compounds were oxidised in a two-electron (one-proton) process over all measured scan rates (up to 50 V s-1), while in dichloromethane, the oxidation process occurred by one-electron at scan rates ≥5 V s-1, to most likely form the radical cations. In both solvents, longer timescale (minutes to hours) controlled potential coulometry experiments indicated that the oxidation process occurred by two-electrons per molecule, to form reactive diamagnetic cations that could not be reduced back to the starting materials under electrolysis conditions. The ion-sensing properties of the compounds were investigated in polymer membrane ion-selective electrodes and it was found that they responded reversibly in a Nernstian fashion to Groups 1 and 2 metals and had the highest selectivity to the cesium cation.
Competing hydrogen-bonding, decomposition, and reversible dimerization mechanisms during the one- and two-electron electrochemical reduction of retinal (Vitamin A)
Tan, Ying Shan,Yue, Yanni,Webster, Richard D.
, p. 9371 - 9379 (2013)
Retinal (R) can be sequentially voltammetrically reduced in CH 3CN in two one-electron processes to form first the anion radical (Ra?￠-) at -1.75 (?±0.04) V vs Fc/Fc+ (Fc = ferrocene) then the dianion (R2-) at -
METAL COMPLEXES WITH TETRAPYRROLE LIGANDS. 50. REDOX POTENTIALS OF SANDWICHLIKE METAL BIS(OCTAETHYLPORPHYRINATES) AND THEIR CORRELATION WITH RING-RING DISTANCES
Buchler, Johann W.,Scharbert, Bernd
, p. 4272 - 4276 (1988)
On the basis of prior work describing the synthesis and structure of sandwichlike metal bis(porphyrinates) M(OEP)2 (I:M=Y, La, ..., Lu, except Pm), the electron-transfer reactions of these double-deckers are presented.Apart from the CeIV complex Ce(OEP)2 (1c), all the other species contain MIII ions that are not affected in the redox reactions.The neutral MIII complexes 1 are porphyrin ?-radicals yielding the porphyrin ?-diradical cations + (2) upon reversible one-electron oxidation and the monoanions - (3) or the porphyrin ?-radical dianions 2- (4) upon reversible one- or two-electron reduction.Ce(OEP)2 (1c) is reversibly oxidized to the porphyrin ?-radical cation + (2c).The quasi-reversible reduction of (1c) gives the anion - (3c) with CeIII.For the neutral MIII complexes 1, the energies of the near-infrared absorption bands and the redox potentials for the processes 12 are correlated with the ionic radii rI. of the tervalent central ions MIII.A decrease of the ring oxidation potentials parallels a decrease of the ionic radii and, hence, the ring-ring distances in the double-deckers.
Electrochemical/chemical oxidation of bisphenol A in a four-electron/two- proton process in aprotic organic solvents
Chan, Ya Yun,Yue, Yanni,Li, Yongxin,Webster, Richard D.
, p. 287 - 294 (2013)
The electrochemical behavior of bisphenol A (BPA) was examined using cyclic voltammetry, bulk electrolysis and chemical oxidation in aprotic organic solvents. It was found that BPA undergoes a chemically irreversible voltammetric oxidation process to form compounds that cannot be electrochemically converted back to the starting materials on the voltammetric timescale. To overcome the effects of electrode fouling during controlled potential electrolysis experiments, NO+ was used as a one-electron chemical oxidant. A new product, hydroxylated bisdienone was isolated from the chemical oxidation of BPA with 4 mol equiv of NO+SbF6- in low water content CH3CN. The structure of the cation intermediate species was deduced and it was proposed that BPA is oxidized in a four-electron/two-proton process to form a relatively unstable dication which reacts quickly in the presence of water in acetonitrile (in a mechanism that is similar to phenols in general). However, as the water content of the solvent increased it was found that the chemical oxidation mechanism produced a nitration product in high yield. The findings from this study provide useful insights into the reactions that can occur during oxidative metabolism of BPA and highlight the possibility of the role of a bisdienone cation as a reactive metabolite in biological systems.
Phenylcyanamidoruthenium scorpionate complexes
Harb, Carmen,Kravtsov, Pavel,Choudhuri, Mohommad,Sirianni, Eric R.,Yap, Glenn P.A.,Lever,Crutchley, Robert J.
, p. 1621 - 1630 (2013)
Nine [Ru(Tp)(dppe)L] complexes, where Tp is hydrotris(pyrazol-1-yl)borate, dppe is ethylenebis(diphenylphosphine), and L is (4-nitrophenyl)cyanamide (NO2pcyd-), (2-chlorophenyl)cyanamide (2-Clpcyd -), (3-chlorophenyl)cyanamide (3-Clpcyd-), (2,4-dichlorophenyl)cyanamide (2,4-Cl2pcyd-), (2,3-dichlorophenyl)cyanamide (2,3-Cl2pcyd-), (2,5-dichlorophenyl)cyanamide (2,5-Cl2pcyd-), (2,4,5-trichlorophenyl)cyanamide (2,4,5-Cl3pcyd-), (2,3,5,6-tetrachlorophenyl)cyanamide (2,3,5,6-Cl4pcyd-), and (pentachlorophenyl)cyanamide (Cl5pcyd-), and the dinuclear complex [{Ru(Tp)(dppe)}2(μ-adpc)], where adpc 2- is azo-4,4-diphenylcyanamide, have been prepared and characterized. The crystal structures of [Ru(Tp)(dppe)(Cl5pcyd)] and [{Ru(Tp)(dppe)}2(μ-adpc)] reveal the RuII ion to occupy a pseudooctahedral coordination sphere in which the cyanamide ligand coordinates to RuII by its terminal nitrogen atom. For both complexes, the cyanamide ligands are planar, indicating significant π mixing between the cyanamide and phenyl moieties as well as the azo group in the case of adpc2-. The optical spectra of the nominally ruthenium(III) species [Ru(Tp)(dppe)L]+ were obtained through spectroelectrochemistry measurements and showed an intense near-IR absorption band. Time-dependent density functional theory calculations of these species revealed that oxidation of the ruthenium(II) species led to species where partial oxidation of the cyanamide ligand had occurred, indicative of noninnocent character for these ligands. The spin densities reveal that while the 3-Clpycd species has substantial RuII(3-Clpycd0) character, the Cl5pycd species is a much more localized ruthenium(III) complex of the Cl5pycd monoanion. Some bond order and charge distribution data are derived for these ruthenium(III) species. The near-IR band is assigned as a quite complex mixture of d-d, 4dπ to L(NCN) MLCT, and L(NCN) to Ru 4d LMCT with even a scorpionate ligand component. Spectroelectrochemistry was also performed on [{Ru(Tp)(dppe)} 2(μ-adpc)] to generate the mixed-valence state. The intense intervalence transition that is observed in the near-IR is very similar to that previously reported for [{Ru(trpy)(bpy)}2(μ-adpc)]2+, where trpy is 2,2′:6′,2″-terpyridine and bpy is 2,2′-bipyridine, and by analogy identifies [{Ru(Tp)(dppe)} 2(μ-adpc)]+ as a delocalized mixed-valence complex.
PGSE NMR diffusion overhauser studies on [Ru(Cp*)(η6- arene)][PF6], plus a variety of transition-metal, inorganic, and organic salts: An overview of ion pairing in dichloromethane
Moreno, Aitor,Pregosin, Paul S.,Veiros, Luis F.,Albinati, Alberto,Rizzato, Silvia
, p. 5617 - 5629 (2008)
PGSE diffusion, 1F, 1H HOESY and 13CNMR studies for a series of [Ru(Cp*)(η6-arene)][PF6] (1) salts are presented. The solid-state structure of [Ru(Cp*) (η6-fluorobenzene)][PF6] (1c) is reported. The extent of the ion pairing and the relative positions of the ions are shown to depend on the arene. For the solvent dichloromethane, new and literature PGSE data for PF6- salts of transition-metal, inorganic, and organic salts are compared. Taken together, these new results show that the charge distribution and the ability of the anion to approach the positively charged positions (steric effects due to molecular shape) are the determining factors in deciding the amount of ion pairing. DFT calculations of the charges in four salts of type 1, as well as in a variety of other salts, using a natural population analysis (NPA), support this view. This represents the first attempt, using experimental data, to understand, correlate, and partially explain the various degrees of ion pairing in a widely different collection of salts.
Thermal stability of quaternary ammonium hexafluorophosphates and halides
Zhuravlev,Nikol'skii,Voronchikhina
, p. 824 - 830 (2013)
Thermal decomposition of hexafluorophosphates of short-chain tetraalkylammonium salts of the general formula R3R'NPF6, where R3 = R' = CH3, C2H5, C 4H9; R3 = C2H5, R' = CH2C6H6 or CH2CH=CH2, was studied by thermal gravimetric analysis. Measurements were performed in air in the temperature interval 20-500°N. The thermal stability of halides with the same cations in the same temperature interval was studied for comparison. The effect of cation on the thermal stability of the halides and hexafluorophosphates was examined. The mechanism of thermal decomposition of quaternary ammonium hexafluorophosphates was suggested.
Tetracyanido(difluorido)phosphates M+[PF2(CN)4]-
Bresien, Jonas,Ellinger, Stefan,Harloff, J?rg,Schulz, Axel,Sievert, Katharina,Stoffers, Alrik,T?schler, Christoph,Villinger, Alexander,Zur T?schler, Cornelia
, p. 4474 - 4477 (2015)
The systematic study of the reaction of M[PF6] salts and Me3SiCN led to a synthetic method for the synthesis and isolation of a series of salts containing the unprecedented [PF2(CN)4]- ion in good yields. The reaction temperature, pressure, and stoichiometry were optimized. The crystal structures of M[PF2(CN)4] (M=[nBu4N]+, Ag+, K+, Li+, H5O2+) were determined. X-ray crystallography showed the exclusive formation of the cis isomer in accord with 31P and 19F solution NMR spectroscopy data. Starting with the K[PF2(CN)4] the room temperature ionic liquid EMIm[PF2(CN)4] was prepared exhibiting a rather low viscosity.
Lewis Acidity Scale of Diaryliodonium Ions toward Oxygen, Nitrogen, and Halogen Lewis Bases
Legault, Claude Y.,Mayer, Robert J.,Mayr, Herbert,Ofial, Armin R.
supporting information, (2020/03/13)
Equilibrium constants for the associations of 17 diaryliodonium salts Ar2I+X- with 11 different Lewis bases (halide ions, carboxylates, p-nitrophenolate, amines, and tris(p-anisyl)phosphine) have been investigated by titrations followed by photometric or conductometric methods as well as by isothermal titration calorimetry (ITC) in acetonitrile at 20 °C. The resulting set of equilibrium constants KI covers 6 orders of magnitude and can be expressed by the linear free-energy relationship lg KI = sI LAI + LBI, which characterizes iodonium ions by the Lewis acidity parameter LAI, as well as the iodonium-specific affinities of Lewis bases by the Lewis basicity parameter LBI and the susceptibility sI. Least squares minimization with the definition LAI = 0 for Ph2I+ and sI = 1.00 for the benzoate ion provides Lewis acidities LAI for 17 iodonium ions and Lewis basicities LBI and sI for 10 Lewis bases. The lack of a general correlation between the Lewis basicities LBI (with respect to Ar2I+) and LB (with respect to Ar2CH+) indicates that different factors control the thermodynamics of Lewis adduct formation for iodonium ions and carbenium ions. Analysis of temperature-dependent equilibrium measurements as well as ITC experiments reveal a large entropic contribution to the observed Gibbs reaction energies for the Lewis adduct formations from iodonium ions and Lewis bases originating from solvation effects. The kinetics of the benzoate transfer from the bis(4-dimethylamino)-substituted benzhydryl benzoate Ar2CH-OBz to the phenyl(perfluorophenyl)iodonium ion was found to follow a first-order rate law. The first-order rate constant kobs was not affected by the concentration of Ph(C6F5)I+ indicating that the benzoate release from Ar2CH-OBz proceeds via an unassisted SN1-type mechanism followed by interception of the released benzoate ions by Ph(C6F5)I+ ions.
Gold(I) Complexes Nuclearity in Constrained Ferrocenyl Diphosphines: Dramatic Effect in Gold-Catalyzed Enyne Cycloisomerization
Nguyen, Tuan-Anh,Roger, Julien,Nasrallah, Houssein,Rampazzi, Vincent,Fournier, Sophie,Cattey, Hélène,Sosa Carrizo, E. Daiann,Fleurat-Lessard, Paul,Devillers, Charles H.,Pirio, Nadine,Lucas, Dominique,Hierso, Jean-Cyrille
supporting information, p. 2879 - 2885 (2020/08/13)
Di-tert-butylated-bis(phosphino)ferrocene ligands bearing phosphino substituents R (R=phenyl, cyclohexyl, iso-propyl, mesityl, or furyl) allow tuning the selective formation of Au(I) halide complexes. Thus, dinuclear linear two-coordinate, but also rare mononuclear trigonal three-coordinate and tetrahedral four-coordinate complexes were formed upon tuning of the conditions. Both Au(I) chloride and rarer Au(I) iodide complexes were synthesized, and their X-ray diffraction analysis are reported. The significance of the control of structure and nuclearity in Au(I) complexes is further illustrated herein by its strong effect on the efficiency and selectivity of gold-catalysed cycloisomerization. Cationic linear digold(I) bis(dicyclohexylphosphino) ferrocenes outperform other catalysts in the demanding regioselective cycloisomerization of enyne sulphonamides into cyclohexadienes. Conversely, tetrahedral and trigonal cationic monogold(I) complexes were found incompetent for enyne cycloaddition. We used the two-coordinate linear electron-rich Au(I) complex 2 b (R=Cy) to extend the scope of selective intramolecular cycloaddition of different 1,6-enyne sulfonylamines with high activity and excellent selectivity to the endo cyclohexadiene products.
