Electrochemical synthesis and electrochromic application of a novel polymer based on carbazole

The compound containing carbazole and thiophene, named as B1 was synthesized with 4-(9H-carbazol-9-yl) phenol and 3,4-dibromo thiophene. Additionally, the electrochemical polymer of B1 was synthesized and coated onto an ITO-glass surface via electrochemical oxidative polymerization. The electrochemical synthesis of the polymer was performed both in 0.05 M LiClO₄ supporting electrolyte in AN/BF₃EtE (1:1, v/v) and an AN/LiClO₄ solvent/electrolyte solution. The compounds were characterized by FT-IR and NMR techniques. The spectroelectrochemical and electrochromic properties of this polymer were also investigated for two electrolyte solution systems. The switching ability of this polymer was measured as the percent transmittance (%T) at its point of maximum contrast. According to the electrochromic measurements, the synthesized polymer had a blue color when it was oxidized, and also when it was reduced, it had a transparent color. Additionally, redox stability measurements indicates that the polymer had a high stability and it could be used to produce new polymeric electrochromic devices and also, it was a good candidate for electrochromic devices (ECDs) applications.     

Electrochemical characterization of alternate conducting carbazole-bisthiophene units

An electrochemical and theoretical character of alternate copolymer of carbazole and bithiophene units was investigated. Polymerization is processed as two steps bielectronic oxidation of molecule. With monoelectronic oxidation is connected stable radical cation with spin located mainly on carbazole. The electrochemical properties of polymer are dependent on thickness of film deposited on electrode. In case of the thin layers one it is observed characteristic redox couple of carbazole oxidation to radical cation. Analysis of polymer behavior and results of spectrochemical measurements indicate on mixed type of electroconductivity.Molecular structures, HOMO-LUMO gaps and nature of highest occupied and lowest unoccupied molecular orbitals were also studied in presented work for oligomers ranging from monomer to octamer. The studies applied density functional theory (DFT).     

Synthesis, characterization, electrochemistry and spectroelectrochemistry of novel soluble porphyrazines bearing unsaturated functional groups

Metalloporphyrazines with a 2-methyl-2-pentenyl group fused to each pyrrole unit were synthesized starting with the corresponding unsaturated dicarbonitrile derivative. The new compounds were characterized by elemental analysis together with FTIR, ¹H-NMR, and UV-Vis spectroscopy and via voltammetric and spectrochemical methods. Electrochemical and spectroelectrochemical measurements demonstrate that while metal-free and magnesium porphyrazines gave common porphyrazine (Pz) ring-based electron-transfer reactions, incorporating redox active metal center, Co^II, into the porphyrazine core extended the redox activity of the ring system with reversible metal-based reduction and oxidation couples of the metal center in addition to the common Pz ring-based electron transfer processes. The unsaturated functional groups of the porphyrazines did not alter the common electrochemical behavior of the complexes. An in situ electrocolorimetric method, based on the 1931 CIE (Commission Internationale de l’Eclairage) system of colorimetry, was applied to investigate the color of the electro-generated anionic and cationic forms of the complexes for possible electrochromatic applications.     

Electrochemical synthesis and characterization of mixed molybdenum-rhenium oxides

The electrodeposition of Mo_xRe_1−xO_y films (0.6 ≤ x ≤ 1) on indium-tin oxide (ITO) coated glass substrates from acidic peroxo-polymolybdo-perrhenate solutions is described. Trends in film growth were established as a function of potential from +0.4 V to −0.7 V vs Ag/AgCl by analyzing the composition and stoichiometry of the deposit using inductively coupled plasma mass spectrometry (ICPMS) and X-ray photoelectron spectroscopy (XPS). These experiments show that the concentration of rhenium increases linearly with the deposition potential and that the deposits are mixed-valent containing up to five different metal oxidation states (i.e., Mo^IV, Mo^V, Mo^VI, Re⁰, Re^IV). Electroanalytical techniques were used to explore the deposition mechanism, including chronocoulometry, cyclic voltammetry, spectroelectrochemistry, and electrochemical quartz crystal nanogravimetry (EQCN). At potentials positive to −0.26 V, perrhenate (Re^VIIO₄⁻) behaves as a redox mediator to accelerate the deposition of a mixed-valent molybdenum oxide, but at more negative potentials mixed molybdenum-rhenium oxides are produced.     

Spectroelectrochemistry at the liquid|liquid interface: Parallel beam UV-vis absorption

We present two novel UV-vis absorption spectroelectrochemical cells for the study of electrochemical processes at polarized liquid|liquid interfaces based on the parallel incidence of the light beam with respect to the interface. The first one is a crude design (Cell 1) based on an existing cylindrical cell for liquid|liquid electrochemistry. The second design (Cell 2) is superior and based on the assembly of the four-electrode set-up inside a rectangular quartz spectrophotometric cuvette. In both cases it is demonstrated that absorption spectroelectrochemistry in parallel beam configuration can be a sensitive probe of processes such as ion transfer at the polarized liquid|liquid interface, if the contribution from the bulk of the sampled phase is removed. In particular, the electrochemical and spectroscopic performance of both cell designs was evaluated using the well-known transfer of Ru(bpy)₃²⁺ across the water|1,2-DCE interface as a model reaction.     

Electrochemistry, spectroelectrochemistry and electrochemical polymerization of titanylphthalocyanines

Detailed electrochemical characterization of tetrakis(2-dimethylaminoethylsulfanyl phthalocyaninato) oxotitanium(IV) and octakis(2-dimethylaminoethylsulfanyl phthalocyaninato) oxotitanium(IV) derivatives has been carried out by the cyclic voltammetry, differential pulse voltammetry, controlled potential chronocoulometry and spectroelectrochemical measurements. Cyclic and differential pulse voltammograms of both complexes are similar, with two metal-based and one ligand-based reduction couples having diffusion controlled reversible one-electron transfer character. Both complexes are polymerized on the working electrode electrochemically during the positive potential sweeps. Spectroelectrochemical measurements confirm the metal and ligand-based assignments of the redox couples.     

Cyclic voltammograms obtained from the optical signals: Study of the successive electro-oxidations of rutin

This paper describes a novel method of obtaining cyclic voltammograms (CVs) from optical signals. The obtained CVs correspond to the various specific species involved in the electrode process, which give more detailed information on the system under investigation than the common CV. For this purpose cyclic voltabsorptometry was used to investigate the successive oxidation processes of rutin on a graphite-wax electrode by using a long optical-path thin-layer electrochemical cell. The dynamic UV spectra of rutin showed the information on the structures of the oxidation products at different potentials. Cyclic voltabsorptiograms (CVAs) were measured in three potential ranges at the characteristic absorption wavelengths of rutin, 346, 254 and 296 nm, respectively. The CVs of three species in solution (rutin and its two products) were obtained from the derivative cyclic voltabsorptiograms (DCVAs). Based on this the redox mechanisms of rutin in different CV peaks were discussed.     

Synthesis and characterization of poly(N-(2-(thiophen-3-yl)methylcarbonyloxyethyl)maleimide) and its spectroelectrochemical properties

A new monomer; N-(2-(thiophen-3-yl)methylcarbonyloxyethyl) maleimide (NMT) was synthesized. The chemical structure of the monomer was characterized by Nuclear Magnetic Resonance (¹H-NMR) and Fourier Transform Infrared (FTIR) Spectroscopy. Electrochemical polymerization of NMT was performed in acetonitrile (AN)/borontrifloride ethylether (BFEE) solvent mixture (1:1, v/v) where tetrabutylammonium tetrafluoroborate (TBAFB) was utilized as the supporting electrolyte. The resulting conducting polymer was characterized by Fourier Transform Infrared (FTIR) Spectroscopy, thermal analyses and Scanning Electron Microscopy (SEM). Electrical conductivity was measured by the four-probe technique. The spectroelectrochemical behavior and switching ability of P(NMT) film were investigated by UV–Vis spectrophotometry. P(NMT) revealed color changes between yellow and blue in the reduced and oxidized states respectively.     

Optical and electrochemical characteristics of sol–gel deposited iron oxide films

Homogenous, crack free iron oxide films are prepared by the sol–gel spin coating technique from a solution of iron iso-propoxide and isopropanol. The films were characterized by X-ray diffractometry (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), UV-visible (UV–Vis) spectroscopy and cyclic voltammetry (CV). XRD of the films showed that they had an amorphous structure. The optical constants refractive index (n) and extinction coefficient (k) were measured by scanning spectrometer in the wavelength range of 390–990 nm. The n and k values were found n =2.3±0.01 and k =0.2±0.002 at 650 nm. The electrochemical behavior investigated in 0.5 M LiClO₄ propylene carbonate (PC) electrolyte-CV examinations showed good rechargeability of the Li⁺/e⁻ insertion extraction process beyond 300 cycles. Spectroelectrochemistry showed that these films exhibit weak cathodic coloration in the spectral range of 350–800 nm.     

The anodic dissolution of zinc and zinc alloys in alkaline solution. I. Oxide formation on electrogalvanized steel

The polarization behaviour of zinc in alkaline solution has been investigated using atomic emission spectroelectrochemistry. By independently measuring the oxidation rate of zinc (electrical current) and the rate of Zn²⁺ dissolution (partial elemental current) it is possible to calculate the amount of insoluble zinc cations produced at any instant. Assuming the insoluble cations are present as a zinc oxide film, the growth of this film as a function of potential and time was determined. On the basis of kinetic evidence, it was found that at least three forms of zinc based oxide/hydroxide films form during polarization experiments. Type I oxide formation occurs when the metal/electrolyte interface becomes locally saturated with Zn²⁺ ions. Type II oxide forms on the metal surface underneath the film of Type I oxide but has little inhibiting effect on zinc dissolution. Type III oxide is produced in much smaller quantity and results in a transition to the passive state. This may be due to a potential induced transition of Type II → Type III oxide.