Cyclic Voltammetry Measurements (cyclic + voltammetry_measurement)

Distribution by Scientific Domains

Selected Abstracts

Air-Stable n-Type Organic Field-Effect Transistors Based on Carbonyl-Bridged Bithiazole Derivatives

Yutaka Ie
Abstract An electronegative conjugated compound composed of a newly designed carbonyl-bridged bithiazole unit and trifluoroacetyl terminal groups is synthesized as a candidate for air-stable n-type organic field-effect transistor (OFET) materials. Cyclic voltammetry measurements reveal that carbonyl-bridging contributes both to lowering the lowest unoccupied molecular orbital energy level and to stabilizing the anionic species. X-ray crystallographic analysis of the compound shows a planar molecular geometry and a dense molecular packing, which is advantageous to electron transport. Through these appropriate electrochemical properties and structures for n-type semiconductor materials, OFET devices based on this compound show electron mobilities as high as 0.06,cm2 V,1 s,1 with on/off ratios of 106 and threshold voltages of 20,V under vacuum conditions. Furthermore, these devices show the same order of electron mobility under ambient conditions. [source]

Ring-Borylated 15-Electron and 17-Electron ansa -Chromocene Complexes, their Physical Properties and Molecular Structures

Abstract A detailed study of the thermal decomposition of the zwitterionic, ring-borylated ansa -chromocene hydrido carbonyl complex [Cr(CO)H{Me4C2(C5H4)[C5H3B(C6F5)3]}] (2) is described. This complex is formed in the reaction between [Cr(CO){Me4C2(C5H4)2}] (1) and B(C6F5)3 in toluene at ,78,C. Above ,25,C, 2 decomposes to a 50:50 mixture of the low-spin, 17,e CrIII complexes [Cr(CO){Me4C2(C5H4)[C5H3B(C6F5)3]}] (3,b) and [Cr(CO){Me4C2(C5H4)2}][HB(C6F5)3] (4). Carbon monoxide elimination from 3,b generates high-spin, 15,e [Cr{Me4C2(C5H4)[C5H3B(C6F5)3]}] (3,a), which coordinates two other electron-donating ligands, such as xylyl isocyanide, PMe3, and PPh2Me to form the low-spin, 17,e electron complexes 3,c, 3,d, and 3,e, respectively. High-spin, 15,e [Cr{Me4C2(C5H4)2}][HB(C6F5)3] (5) is generated by heating 3,b in toluene at 100,C and periodically removing the evolved CO. Efforts to isolate more than a few X-ray quality crystals of 5 were thwarted by its tendency to form an insoluble precipitate (6) with the same molecular formula. Heating the solution of 5 at 120,C results in its partial conversion (ca. 28,%) to 3,a, thereby allowing the formation of 3,a in yields as high as 74,% from the reaction between 1 and B(C6F5)3. The X-ray crystal structures of 3,b,e and 5 are described. Cyclic voltammetry measurements on 3,a,e reveal a dramatic reduction in the redox potentials of the complexes relative to their non-borylated analogues. DFT calculations show that this is due primarily to electrostatic stabilization of the oxidized species by the negatively charged borylate group. EPR and 19F,NMR spectroscopy allow 3,a to be distinguished from its Lewis base adducts 3,b,e and reveal the relative affinities of different Lewis bases for the chromium. [source]

Dynamical Complexity in Electrochemical Oxidations of Thiocyanate

Abstract Kinetics and mechanism of the electrochemical oxidation of thiocyanate on a Pt electrode were investigated by using various electrochemical methods, in which both current and potential oscillations have been observed. Cyclic voltammetry measurements illustrate that the oxidation process consists of two steps. In addition to the oscillatory behavior, the system also exhibits bistability, in which the oxidation could be switched between a high and a low current density states with a temporal potential perturbation. The presence of inert ions with stronger absorption also induces transitions from oscillatory to steady reactions in the thiocyanate system. [source]

Synthesis and Electrochemical Study of an Original Copper(II)-Capped Salen,Cyclodextrin Complex

Elise Deunf
Abstract A new metallocapped cyclodextrin (CD) was synthesized by the regioselective debenzylation, induced by diisobutylaluminium hydride (DIBAL-H), of perbenzylated cyclodextrins. This reaction allowed for the efficient preparation of an unprecedented CD,salen type copper(II) complex. The electrochemical behavior of both the bound and unbound CD,salen compounds was investigated by cyclic voltammetry. Notably, it was shown that the presence of tert -butyl groups at the ortho - and para -positions of the salen aromatic rings stabilized the copper(II) phenoxyl radical species that was generated upon the one-electron oxidation of the starting compound. Importantly, this stabilization remained effective when the salen-type ligand was covalently attached to the CD. This allowed for investigations of the reactivity of the copper(II) phenoxyl radical complex towards a primary alcohol to be performed by cyclic voltammetry. This reaction can be considered as mimicking the behavior of galactose oxidase. However, under these conditions, no reactivity was observed in the presence of benzyl alcohol. This may be due to distortion, either of the initially square planar salen ligand after its grafting to the CD primary face, and/or of the CD itself. On the other hand, the electrochemical reduction of the un-grafted copper(II) salen-type ligand led to a transient anionic species that exhibited significant stability on the time-scale of the slow cyclic voltammetry measurement in the absence of the CD, but was unstable in the presence of the CD. In the latter case, it was demonstrated that the anionic species was protonated by the CD. Importantly, this protonation was not fast enough to prevent catalytic activation of iodomethane by the electro-generated copper(I)-capped salen CD complex. [source]

Synthesis and characterization of imine-coupled polyphenols containing carbazole units

smet Kaya
Abstract Imine coupled phenolic monomers containing carbazole unit were synthesized in four steps. The monomers were polymerized via oxidative polycondensation by air as oxidant in an aqueous alkaline medium at 50C. The structures of compounds were confirmed by ultraviolet,visible (UV,vis), Fourier transform infrared, and 1H- and 13C-NMR techniques. The conductivity measurements of these polymers were made by the four-point probe technique and iodine was used as doping agent. The highest occupied molecular orbital, the lowest unoccupied molecular orbital, and electrochemical and optical band gap values were calculated by the results of the UV,vis and the cyclic voltammetry measurement, respectively. The number-average molecular weight, weight-average molecular weight, and polydispersity index values were determined by the size exclusion chromatography technique. Also, thermal behavior of these polymers was determined by thermogravimetric/differential thermal analysis measurements in a N2 atmosphere between 20 and 1000C. 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009 [source]

Electrostatic Assembly of a Redox Catalysis System for Detection of Glutamate

Abstract Interfacial assemblies capable of determining glutamate by redox catalysis are prepared by electrostatic assembly of alternating layers of ferrocene poly(allylamine) polymer and glutamate oxidase on a gold electrode. Deposition of the polymer was confirmed in cyclic voltammetry measurements by the presence of a surface wave corresponding to the oxidation of the ferrocene group. In the presence of glutamate in the adjacent electrolyte solution, the current increases and approaches a pseudosteady state, consistent with redox catalysis. Electrodes modified with glutamate oxidase had a linear response to glutamate up to 0.0045,M with sensitivity of 20,,A/cm2 and a limit of detection of 31.4,,M glutamate. An apparent Michaelis,Menten constant of 0.40(0.13),mM for the confined glutamate oxidase was determined for this assembly. When used in flow-injection experiments, glucose oxidase modified electrodes responded to transient zones of glucose; however, the detection limits of the assemblies to the flowing stream were substantially higher than found for measurements on static solutions. [source]