Chemically Modified Electrodes Based on 4-(azulen-1-yl)-2,6-bis ((e)-2-(thiophen-2-yl)vinyl) Pyrylium Perchlorate

The electrochemical behavior of 4-(azulen-1-yl)-2,6-bis((E)-2-(thiophen-2-yl)vinyl) pyrylium perchlorate (L) was studied by cyclic voltammetry, differential pulse voltammetry, and rotating disk electrode voltammetry. The electrochemical polymerization of L was studied. Modified electrodes covered by polyL films were obtained by successive scanning or by controlled potential electrolysis (CPE) at different charges and potentials. The new electrodes obtained by CPE were applied for sensing the following heavy metals ions: Cu(II), Pb(II), Cd(II), Hg(II). The best results have been registered for Pb(II) ion with a detection limit of 10-8 M.

Electroactive properties of a new azulene thioxo-imidazolidin-4-one ligand for modified electrodes

The electrochemical characterization of a new synthesized azulene compound (Z)-5-((5-iso­propyl-3,8-dimethylazulen-1-yl)methylene)-2-thioxoimidazolidin-4-one (L) using cyclic vol­tammetry, differential pulse voltammetry and rotating disk electrode is presented. Chemi­cally modified electrodes were obtained by successive scanning or by controlled potential electrolysis using different electrode potentials or charges. The new modified electrodes were tested in solutions containing different concentrations of the following heavy metals: cadmium, lead, mercury and copper. A good analytical response was obtained for Pb2+.

Clam-shaped cyclam-functionalized porphyrin for electrochemical reduction of carbon dioxide

A clam-shaped molecule comprising a Zn(II)-porphyrin and a Zn(II)-cyclam is synthesized and characterized. Its electrochemical behavior and catalytic activity for homogeneous electrochemical reduction of carbon dioxide (CO[Formula: see text] are investigated by cyclic voltammetry and compared with those of Zn(II)-meso-tetraphenylporphyrin and Zn(II)-cyclam. Under N2-saturated conditions, cyclic voltammetry of the featured complex has characteristics of its two constituents, but under CO2-saturated conditions, the target compound exhibits significant current enhancement. Iterative reduction under electrochemical conditions indicated the target compound has improved stability relative to Zn(II)-cyclam. Controlled potential electrolysis demonstrates that, without addition of water, methane (CH[Formula: see text] is the only detectable product with 1% Faradaic efficiency (FE). The formation of CH4 is not observed under the catalysis of the Zn(II)-porphyrin benchmark compound, indicating that the CO2-capturing function of the Zn(II)-cyclam unit contributes to the catalysis. Upon addition of 3% v/v water, the electrochemical reduction of CO2 in the presence of the target compound gives carbon monoxide (CO) with 28% FE. Dominance of CO formation under these conditions suggests enhancement of proton-coupled reduction. Integrated action of these Zn(II)-porphyrin and Zn(II)-cyclam units offers a notable example of a molecular catalytic system where the cyclam ring captures and brings CO2 into the proximity of the porphyrin catalysis center.

Ligand-Centered Electrochemical Processes Enable CO2 Reduction with a Nickel Bis(triazapentadienyl) Complex

We report the synthesis of Ni(TAPPy)₂ (TAPPy = 1,3,5-triazapentadienyl-2,4-bis(2-pyridyl)) and its reactivity with CO₂ under reducing conditions. Electrochemical reduction of Ni(TAPPy)₂under inert gas reveals that the complex accommodates up to two additional electrons, with DFT calculations indicating that electron density is delocalized almost exclusively onto the TAPPy ligand framework. The singly reduced product [K(crypt)][Ni(TAPPy)₂] (crypt = 2.2.2-cryptand) has been synthesized, and its EPR data is consistent with having ligand-based radical anion character. Controlled potential electrolysis experiments reveal that reduced Ni(TAPPy)₂ converts CO₂ to form CO; however, spectroscopic and computational data indicate that deactivation readily occurs to form Ni(L)(CO)<i>_n</i> compounds, CO₃^2-, and carboxylated (RCOO^-) ligand decomposition products. This study highlights that redox activity at the ligand can play an important role during the reduction of CO₂ using transition metal complexes.

Ligand-Centered Electrochemical Processes Enable CO2 Reduction with a Nickel Bis(triazapentadienyl) Complex

We report the synthesis of Ni(TAPPy)₂ (TAPPy = 1,3,5-triazapentadienyl-2,4-bis(2-pyridyl)) and its reactivity with CO₂ under reducing conditions. Electrochemical reduction of Ni(TAPPy)₂under inert gas reveals that the complex accommodates up to two additional electrons, with DFT calculations indicating that electron density is delocalized almost exclusively onto the TAPPy ligand framework. The singly reduced product [K(crypt)][Ni(TAPPy)₂] (crypt = 2.2.2-cryptand) has been synthesized, and its EPR data is consistent with having ligand-based radical anion character. Controlled potential electrolysis experiments reveal that reduced Ni(TAPPy)₂ converts CO₂ to form CO; however, spectroscopic and computational data indicate that deactivation readily occurs to form Ni(L)(CO)<i>_n</i> compounds, CO₃^2-, and carboxylated (RCOO^-) ligand decomposition products. This study highlights that redox activity at the ligand can play an important role during the reduction of CO₂ using transition metal complexes.

Electrochemical Characterization of Some Pyrrolo[1,2-c]Pyrimidine Derivatives

The electrochemical characterization of two pyrrolo[1,2-c]pyrimidine derivatives (I1 and I2) was realized by cyclic, differential pulse, and rotating disk electrode voltammetric methods. The character of redox processes was established by scanning on different domains and with different scan rates. The diffusion coefficients were determined. Modified electrodes have been obtained by cycling the potential or by controlled potential electrolysis at anodic potentials. The electrodes obtained with polyol1 and polyI2 films were characterized by cyclic voltammetry in ferrocene solution.

The Heavy Metals Sensing Based on 2,6-Bis(-2-(Thiophen-3-yl)Vinyl)-4-(4,6,8-Trimethylazulen-1-yl)Pyrylium Modified Electrodes

This paper focuses on electrochemical characterization of new azulene compound 2,6-bis((E)-2-(thiophen-3-yl)vinyl)-4-(4,6,8-trimethylazulen-1-yl)pyrylium (L) by cyclic voltammetry (CV), differential pulse voltammetry (DPV), rotating disk electrode voltammetry (RDE) on glassy carbon disk working electrodes. The character of redox processes was established by CV and RDE using increasing scan rates at different scan domains. PolyL modified electrodes have been prepared by scanning or controlled potential electrolysis (CPE). The complexing properties of L and polyL have been investigated towards detection of heavy metal ions by anodic stripping technique. The voltammetric curves present well defined peaks for Pb2+, Cd2+, Cu2+ and Hg2+, which can be used as analytical signals for their determination. The performances of the modified electrodes obtained at different potentials and charges have been evaluated. The best results have been obtained for Pb2+ and Cd2+ with the achievement of detection limits of 10-7 M.