Search Results (5)

Pyrene (Pr) was used to improve the electrochemical and electrochromic properties of polythiophene copolymerized with 3,4-ethylenedioxythiophene (EDOT). The corresponding product, poly(3,4-ethylenedioxythiophene-co-Pyrene) (P(EDOT-co-Pr)), was successfully synthesized by electrochemical polymerization with different monomer concentrations in propylene carbonate solution containing 0.1 M lithium perchlorate (LiClO₄/PC (0.1 M)). The homopolymer and copolymer films were analyzed by Fourier transform infrared spectroscopy (FT-IR), color-coordinate and colorimetric methods, cyclic voltammetry (CV), spectroelectrochemistry (SEC), and UV–visible spectroscopy (UV-Vis). Homopolymer poly(3,4-ethylenedioxythiophene) (PEDOT) and the P(EDOT-co-Pr) copolymer were investigated, which included examining their colorimetric, electrochemical, and electrochromic characteristics. The color shifts resulting from redox reactions of the polymers were also observed. The copolymers with different monomer concentrations achieved multicolor shifts, such as light purple, dark blue, dark red, green, and earthy yellow. Moreover, P(EDOT-co-Pr) had a small optical bandgap (1.74–1.83 eV), excellent optical contrast (31.68–45.96%), and high coloring efficiency (350–507 cm² C⁻¹). In particular, P(EDOT1-co-Pr3) exhibited outstanding cycling stability, retaining 91% of its initial optical contrast after cycling for 10,000 s, and it is expected to be a promising candidate copolymer for electrochromic applications. Full article

The metallocenyl-containing β-diketonato rhodium(I) dicarbonyl complexes of [Rh(FcCOCHCOR)(CO)₂] where R = CF₃, 10; Fc = ferrocenyl = Fe^II(C₅H₅)(C₅H₄), 11; Rc = ruthenocenyl = Ru^II(C₅H₅)(C₅H₄), 12; and Oc = osmocenyl = Os^II(C₅H₅)(C₅H₄), 13 were synthesized. Complexes 10–13 were then subjected to an electrochemical study utilizing cyclic voltammetry (CV), square wave voltammetry (SWV), and linear sweep voltammetry (LSV) in the non-coordinating solvent/supporting electrolyte medium CH₂Cl₂/0.1 mol dm⁻³ [N(ⁿBu)₄][B(C₆F₅)₄]. The formal reduction potential for the electrochemical reversible Fc^0/+ couples in 10–13 was identified in the range 0.156 ≤ E^o′ ≤ 0.328 V while the electrochemically irreversible osmocenyl and ruthenocenyl oxidations were observed at peak anodic potentials of E_pa = 0.640 V and E_pa = 0.751 V, respectively. Resolution between the closely overlapping CV-determined Fc^0/+ and Rh^I/II couples was too poor for unambiguous measurement of the Rh^I/II redox potential, but square wave voltammetry allowed estimates of E^o′ (Rh^I/II) in the range 0.156 ≤ E^o′ ≤ 0.398 V. FT-IR spectroelectrochemistry confirmed the one-electron oxidation of Rh^I by the appearance of CO vibrational bands at stretching frequencies, which are associated with rhodium(II) and not rhodium(III). Cytotoxicity tests on 10 (IC₅₀ = 19.2 µM) showed it to be substantially less cytotoxic than the free β-diketone, FcCOCH₂COCF₃, and [Rh(FcCOCHCOCF₃)(cod)]. Full article

Donor-acceptor (D-A) type conjugated polymers are of high interest in the field of electrochromism. In this study, three novel conjugated copolymers (PBPE–1, PBPE-2 and PBPE-3) based on quinoxalino[2′,3′:9,10]phenanthro[4,5-abc]phenazine (A) as the acceptor unit and 4,8-bis((2-octyldodecyl)oxy)benzo[1,2-b:4,5-b′]dithiophene (D1) and 3,3-didecyl-3,4-dihydro-2H-thieno[3,4-b][1,4]dioxepine (ProDOT-decyl₂, D2) as the donor units with different donor-to-acceptor ratios were successfully synthesized through Stille coupling polymerization. The polymers were then characterized by cyclic voltammetry (CV), fourier transform infrared (FT-IR) spectoscopy, X-ray photoelectron spectroscopy (XPS), spectroelectrochemistry, thermogravimetry (TG), electrochromic switching and colorimetry. Optical band gap values were calculated as 1.99 eV, 2.02 eV and 2.03 eV, respectively. The three copolymers have good solubility, distinct redox peaks, wide absorption spectra, good thermal stabilities, bright color changes and significant electrochromic switching properties. Compared to the other two copolymers, the PBPE-3 film exhibited high coloration efficiency values of 513 cm²·C⁻¹ at 504 nm and 475 cm²·C⁻¹ at 1500 nm. The films have the advantage of exhibiting cathodic and anodic coloration. Full article

Most non-metalized Salen-type ligands form passivation thin films on electrode surfaces upon electrochemical oxidation. In contrast, the H₂(3-MeOSalen) forms electroactive polymer films similarly to the corresponding nickel complex. There are no details of electrochemistry, doping mechanism and charge transfer pathways in the polymers of pristine Salen-type ligands. We studied a previously uncharacterized electrochemically active polymer of a Salen-type ligand H₂(3-MeOSalen) by a combination of cyclic voltammetry, in situ ultraviolet–visible (UV–VIS) spectroelectrochemistry, in situ electrochemical quartz crystal microbalance and Fourier Transform infrared spectroscopy (FTIR) spectroscopy. By directly comparing it with the polymer of a Salen-type nickel complex poly-Ni(3-MeOSalen) we elucidate the effect of the central metal atom on the structure and charge transport properties of the electrochemically doped polymer films. We have shown that the mechanism of charge transfer in the polymeric ligand poly-H₂(3-MeOSalen) are markedly different from the corresponding polymeric nickel complex. Due to deviation from planarity of N₂O₂ sphere for the ligand H₂(3-MeOSalen), the main pathway of electron transfer in the polymer film poly-H₂(3-MeOSalen) is between π-stacked structures (the π-electronic systems of phenyl rings are packed face-to-face) and C-C bonded phenyl rings. The main way of electron transfer in the polymer film poly-Ni(3-MeOSalen) is along the polymer chain, while redox processes are ligand-based. Full article

[FeFe]-hydrogenases efficiently catalyzes hydrogen conversion at a unique [4Fe–4S]-[FeFe] cofactor, the so-called H-cluster. The catalytic reaction occurs at the diiron site, while the [4Fe–4S] cluster functions as a redox shuttle. In the oxidized resting state (Hox), the iron ions of the diiron site bind one cyanide (CN⁻) and carbon monoxide (CO) ligand each and a third carbonyl can be found in the Fe–Fe bridging position (µCO). In the presence of exogenous CO, A fourth CO ligand binds at the diiron site to form the oxidized, CO-inhibited H-cluster (Hox-CO). We investigated the reduced, CO-inhibited H-cluster (Hred´-CO) in this work. The stretching vibrations of the diatomic ligands were monitored by attenuated total reflection Fourier-transform infrared spectroscopy (ATR FTIR). Density functional theory (DFT) at the TPSSh/TZVP level was employed to analyze the cofactor geometry, as well as the redox and protonation state of the H-cluster. Selective ¹³CO isotope editing, spectro-electrochemistry, and correlation analysis of IR data identified a one-electron reduced, protonated [4Fe–4S] cluster and an apical CN⁻ ligand at the diiron site in Hred´-CO. The reduced, CO-inhibited H-cluster forms independently of the sequence of CO binding and cofactor reduction, which implies that the ligand rearrangement at the diiron site upon CO inhibition is independent of the redox and protonation state of the [4Fe–4S] cluster. The relation of coordination dynamics to cofactor redox and protonation changes in hydrogen conversion catalysis and inhibition is discussed. Full article