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Articles 1 - 11 of 11
Full-Text Articles in Physical Sciences and Mathematics
Voltammetry And Spectroelectrochemistry Of Tcnq In Acetonitrile/Rtil Mixtures, Abderrahman Atifi, Michael D. Ryan
Voltammetry And Spectroelectrochemistry Of Tcnq In Acetonitrile/Rtil Mixtures, Abderrahman Atifi, Michael D. Ryan
Chemistry Faculty Research and Publications
Understanding the solvation and ion-pairing interactions of anionic substrates in room-temperature ionic liquids (RTIL) is key for the electrochemical applications of these new classes of solvents. In this work, cyclic voltammetry and visible and infrared spectroelectrochemistry of tetracyanoquinodimethane (TCNQ) was examined in molecular (acetonitrile) and RTIL solvents, as well as mixtures of these solvents. The overall results were consistent with the formation of RTIL/acetonitrile nanodomains. The voltammetry indicated that the first electrogenerated product, TCNQ−, was not incorporated into the RTIL nanodomain, while the second electrogenerated product, TCNQ2−, was strongly attracted to the RTIL nanodomain. The visible …
Proton-Coupled Reduction Of An Iron Nitrosyl Porphyrin In The Protic Ionic Liquid Nanodomain, Abderrahman Atifi, Piotr J. Mak, Michael D. Ryan
Proton-Coupled Reduction Of An Iron Nitrosyl Porphyrin In The Protic Ionic Liquid Nanodomain, Abderrahman Atifi, Piotr J. Mak, Michael D. Ryan
Chemistry Faculty Research and Publications
The one-electron reduction of many molecules becomes much more favorable if combined with proton transfers or strong hydrogen bonding. Protic room temperature ionic liquids (RTILs), which can form nanodomains in solutions with molecular solvents (MS), can provide an efficient avenue for this process. In this work, we report on the voltammetry, UV/visible and resonance Raman spectroelectrochemistryof Fe(TPP)(NO) in the presence of aprotic/protic ammonium-based ionic liquids. While aprotic RTILs did shift the reduction to more positive potentials, similar shifts could be observed at much lower concentrations of diethylmethylammonium triflate (HAmOTf, a protic ionic liquid). Deconvolution of the rotating ring-disk electrode (RRDE) …
Altering The Coordination Of Iron Porphyrins By Ionic Liquid Nanodomains In Mixed Solvent Systems, Abderrahman Atifi, Michael D. Ryan
Altering The Coordination Of Iron Porphyrins By Ionic Liquid Nanodomains In Mixed Solvent Systems, Abderrahman Atifi, Michael D. Ryan
Chemistry Faculty Research and Publications
The solvent environment around iron porphyrin complexes was examined using mixed molecular/RTIL (room temperature ionic liquid) solutions. The formation of nanodomains in these solutions provides different solvation environments for substrates that could have significant impact on their chemical reactivity. Iron porphyrins (Fe(P)), whose properties are sensitive to solvent and ligation changes, were used to probe the molecular/RTIL environment. The addition of RTILs to molecular solvents shifted the redox potentials to more positive values. When there was no ligation change upon reduction, the shift in the E° values were correlated to the Gutmann acceptor number, as was observed for other …
Influence Of Rtil Nanodomains On The Voltammetry And Spectroelectrochemistry Of Fullerene C60 In Benzonitrile/Room Temperature Ionic Liquids Mixtures, Abderrahman Atifi, Michael D. Ryan
Influence Of Rtil Nanodomains On The Voltammetry And Spectroelectrochemistry Of Fullerene C60 In Benzonitrile/Room Temperature Ionic Liquids Mixtures, Abderrahman Atifi, Michael D. Ryan
Chemistry Faculty Research and Publications
The cyclic voltammetry of fullerene C60 was examined in mixed benzonitrile/RTIL solvents in order to probe the effect of nanodomains in the mixed RTIL/benzonitrile solutions and their effect upon the voltammetry. In probing the interactions of the fullerides (up to C603−) with RTILs, BMIm+ (1-butyl-3-methylimidazolium, mostly planar) and tetraalkylammonium (more spherical/flexible) salts were used. In order to investigate these shifts in more detail, the ΔE12° (=E°1–E°2) and ΔE23° (=E°2–E°3) values, which were independent of the reference potential, were used. At higher concentrations of …
Visible And Infrared Spectroelectrochemistry Of Zinc And Manganese Porphinones: Metal Vs. Porphyrin Reduction, Florentina Tutunea, Abderrahman Atifi, Michael D. Ryan
Visible And Infrared Spectroelectrochemistry Of Zinc And Manganese Porphinones: Metal Vs. Porphyrin Reduction, Florentina Tutunea, Abderrahman Atifi, Michael D. Ryan
Chemistry Faculty Research and Publications
The visible and infrared spectroelectrochemistry of zinc and manganese porphinones and porphinediones was carried out in THF solutions. The aim of this work was to use FTIR spectroelectrochemistry and DFT calculation to determine whether the reduction was centered predominantly on the metal or the macrocycle. For zinc(II), the first one-electron reduction must occur on the macrocyclic ring because the metal’s d-orbitals are filled (d10). The carbonyl bands on the macrocyclic ring were used to probe the electronic structure because they can be readily observed in the infrared spectra. The results of this study are complementary to previous spectroelectrochemical …
Spectroelectrochemical Elucidation Of The Kinetics Of Two Closely Spaced Electron Transfers, Robert L. Keesey, Michael D. Ryan
Spectroelectrochemical Elucidation Of The Kinetics Of Two Closely Spaced Electron Transfers, Robert L. Keesey, Michael D. Ryan
Chemistry Faculty Research and Publications
The use of spectroelectrochemistry to facilitate the analysis of an EE mechanism was reported in this work. Using a set of spectra as a function of potential, the spectra of all three oxidation states were determined using evolving window factor analysis. From these spectra, the concentration of each species in solution was determined for each potential. Using these data, the current was calculated. Unlike the direct measurement of current, the current due to each redox process was determined, allowing one to analyze each redox process separate from the other. With the use of the Butler–Volmer equation, the redox potential and …
Visible And Infrared Spectroelectrochemistry Of Cobalt Porphinones And Porphinediones, Florentina Tutunea, Michael D. Ryan
Visible And Infrared Spectroelectrochemistry Of Cobalt Porphinones And Porphinediones, Florentina Tutunea, Michael D. Ryan
Chemistry Faculty Research and Publications
The visible and infrared spectroelectrochemistry of the redox chemistry of CoII–porphinone complexes were examined and compared with similar studies of the respective iron complexes. Cobalt(II) porphinone complexes undergo a one-electron reduction and two one-electron oxidations within the potential region that was studied in this work. The one electron spectroelectrochemical reduction of CoII(P) (P = octaethylporphyrin (OEP), octaethylporphinone (OEPone), and octaethylporphinedione (OEPdione)) were studied using visible spectroscopy, and their cobalt(I) complexes were characterized. The same reduction was examined by FTIR spectroscopy for P = OEPone and OEPdione. The infrared spectra showed downshifts of the νCO band …
The Voltammetric Study Of The Reduction Of Tetraalkylammonium Perchlorate By Fe(Tpp)2-, Chathra Shirani De Silva, Michael D. Ryan
The Voltammetric Study Of The Reduction Of Tetraalkylammonium Perchlorate By Fe(Tpp)2-, Chathra Shirani De Silva, Michael D. Ryan
Chemistry Faculty Research and Publications
Tetraalkylammonium ions react with Fe(TPP)2− to form Fe(TPP)(R)− and trialkylamine. The tetrabutylammonium cation was verified to be the source of the alkyl group in the product, Fe(TPP)(R)−, by using (1H5C2)3(2H5C2)N− as the cation and 2H NMR. The reaction of Fe(TPP)2− with Bu4N− was monitored by cyclic voltammetry and thin layer spectroelectrochemistry. The activation parameters were measured, and were most consistent with an electron transfer (ET) mechanism. The rate of the reaction of tetramethyl and tetraethylammonium ions with Fe(TPP) …
Use Of Factor Analysis In Multi‐Electron Spectroelectrochemistry, Michael D. Ryan, Robert L. Keesey
Use Of Factor Analysis In Multi‐Electron Spectroelectrochemistry, Michael D. Ryan, Robert L. Keesey
Chemistry Faculty Research and Publications
Spectroelectrochemistry and voltammetry contain both unique and complementary information. For multielectron transfers, information on each electron exchange is only directly accessible in the voltammetric data if the potentials are well separated so that two distinct waves can be observed. If the E°’s are close together, the voltammetric data will contain the sum of the two exchanges which can only be deconvoluted by modeling the system and solving the appropriate equations. On the other hand, the spectroscopic data contains direct information on each electron exchange even when the E°’s are close together. Unfortunately, this information cannot be readily extracted if the …
Electrochemistry And Spectroscopy Of Sulfate And Thiosulfate Complexes Of Iron Porphyrins, Philip Walter Crawford, Michael D. Ryan
Electrochemistry And Spectroscopy Of Sulfate And Thiosulfate Complexes Of Iron Porphyrins, Philip Walter Crawford, Michael D. Ryan
Chemistry Faculty Research and Publications
The electrochemical and spectroscopic properties of the complex formed by the addition of thiosulfate to ferric porphyrins were examined. The NMR spectrum of the thiosulfate–ferric porphyrin complex was consistent with a high-spin ferric complex, while the EPR spectrum at liquid nitrogen temperatures indicated that the complex under these conditions was low-spin. Such behavior has been previously observed for other ferric porphyrin complexes. The visible spectra were characterized by a shift in the Soret band to higher energies, with smaller changes in the longer wavelength region. The complex was reasonably stable in DMF, but slowly reduced over several hours to Fe …
Electrochemistry And Spectroelectrochemistry Of Iron Porphyrins In The Presence Of Nitrite, Zhongcheng Wei, Michael D. Ryan
Electrochemistry And Spectroelectrochemistry Of Iron Porphyrins In The Presence Of Nitrite, Zhongcheng Wei, Michael D. Ryan
Chemistry Faculty Research and Publications
The reaction of nitrite with ferric and ferrous porphyrins was examined using visible, infrared and NMR spectroscopy. Solutions of either ferric or ferrous porphyrin were stable in the presence of nitrite, with only complexation reactions being observed. Under voltammetric conditions, though, a rapid reaction between nitrite and iron porphyrins was observed to form the nitrosyl complex, Fe(p)(NO), where P = porphyrin. The products of the reduction of ferric porphyrins in the presence of nitrite were confirmed by visible spectroelectrochemistry to be Fe(P)(NO) and [Fe(P)]2O. Visible, NMR and infrared spectroscopy were used to rule out the formation of Fe(P)(NO) by the …