Electrochemical studies of dimeric rhodium(III) porphyrins containing a dibasic nitrogen-heterocyclic bridging ligand

1988 ◽  
Vol 27 (13) ◽  
pp. 2320-2325 ◽  
Author(s):  
Y. H. Liu ◽  
J. E. Anderson ◽  
K. M. Kadish
Keyword(s):  
Electrochemical Studies ◽  
Bridging Ligand ◽  
Dimeric Rhodium ◽  
Nitrogen Heterocyclic

Modulation of Internuclear Communication in Multinuclear Ruthenium(II) Polypyridyl Complexes

2003 ◽  
Vol 68 (8) ◽  
pp. 1467-1487 ◽  
Author(s):  
Wesley R. Browne ◽  
Frances Weldon ◽  
Adrian Guckian ◽  
Johannes G. Vos
Keyword(s):  
Ground State ◽  
Weak Interactions ◽  
Electrochemical Studies ◽  
Protonation State ◽  
Ruthenium Polypyridyl ◽  
Bridging Ligands ◽  
Polypyridyl Complexes ◽  
Bridging Ligand ◽  
Dinuclear Ruthenium ◽  
Ruthenium Polypyridyl Complexes

The syntheses and characterisation of a series of mononuclear and dinuclear ruthenium polypyridyl complexes based on the bridging ligands 1,3-bis-[5-(2-pyridyl)-1H-1,2,4-triazol-3-yl]benzene, 1,4-bis-[5-(2-pyridyl)-1H-1,2,4-triazol-3-yl]benzene, 2,5-bis-[5-(2-pyridyl)-1H-1,2,4-triazol-3-yl]thiophene, 2,5-bis-[5-pyrazinyl-1H-1,2,4-triazol-3-yl]thiophene are reported. Electrochemical studies indicate that in these systems, the ground state interaction is critically dependent on the nature of the bridging ligand and its protonation state, with strong and weak interactions being observed for thiophene- and phenylene-bridged complexes, respectively.

A Pyridinic Fe-N4 Macrocycle Effectively Models the Active Sites in Fe/N-Doped Carbon Electrocatalysts

2020 ◽  
Author(s):  
Travis Marshall-Roth ◽  
Nicole J. Libretto ◽  
Alexandra T. Wrobel ◽  
Kevin Anderton ◽  
Nathan D. Ricke ◽  
...  
Keyword(s):  
Oxygen Reduction ◽  
Active Sites ◽  
Catalytic Properties ◽  
Reduction Reaction ◽  
Iron Phthalocyanine ◽  
Electrochemical Studies ◽  
Onset Potential ◽  
Nitrogen Doped Carbon ◽  
Iron Active Sites

Iron- and nitrogen-doped carbon (Fe-N-C) materials are leading candidates to replace platinum in fuel cells, but their active site structures are poorly understood. A leading postulate is that iron active sites in this class of materials exist in an Fe-N<sub>4</sub> pyridinic ligation environment. Yet, molecular Fe-based catalysts for the oxygen reduction reaction (ORR) generally feature pyrrolic coordination and pyridinic Fe-N<sub>4</sub> catalysts are, to the best of our knowledge, non-existent. We report the synthesis and characterization of a molecular pyridinic hexaazacyclophane macrocycle, (phen<sub>2</sub>N<sub>2</sub>)Fe, and compare its spectroscopic, electrochemical, and catalytic properties for oxygen reduction to a prototypical Fe-N-C material, as well as iron phthalocyanine, (Pc)Fe, and iron octaethylporphyrin, (OEP)Fe, prototypical pyrrolic iron macrocycles. N 1s XPS signatures for coordinated N atoms in (phen<sub>2</sub>N<sub>2</sub>)Fe are positively shifted relative to (Pc)Fe and (OEP)Fe, and overlay with those of Fe-N-C. Likewise, spectroscopic XAS signatures of (phen<sub>2</sub>N<sub>2</sub>)Fe are distinct from those of both (Pc)Fe and (OEP)Fe, and are remarkably similar to those of Fe-N-C with compressed Fe–N bond lengths of 1.97 Å in (phen<sub>2</sub>N<sub>2</sub>)Fe that are close to the average 1.94 Å length in Fe-N-C. Electrochemical studies establish that both (Pc)Fe and (phen<sub>2</sub>N<sub>2</sub>)Fe have relatively high Fe(III/II) potentials at ~0.6 V, ~300 mV positive of (OEP)Fe. The ORR onset potential is found to directly correlate with the Fe(III/II) potential leading to a ~300 mV positive shift in the onset of ORR for (Pc)Fe and (phen<sub>2</sub>N<sub>2</sub>)Fe relative to (OEP)Fe. Consequently, the ORR onset for (phen<sub>2</sub>N<sub>2</sub>)Fe and (Pc)Fe is within 150 mV of Fe-N-C. Unlike (OEP)Fe and (Pc)Fe, (phen<sub>2</sub>N<sub>2</sub>)Fe displays excellent selectivity for 4-electron ORR with <4% maximum H<sub>2</sub>O<sub>2</sub> production, comparable to Fe-N-C materials. The aggregate spectroscopic and electrochemical data establish (phen<sub>2</sub>N<sub>2</sub>)Fe as a pyridinic iron macrocycle that effectively models Fe-N-C active sites, thereby providing a rich molecular platform for understanding this important class of catalytic materials.<p><b></b></p>

Inhibition Effects of Some Organic Compounds on Zinc Corrosion in 3.5% NaCl

2008 ◽  
Vol 59 (5) ◽  
Author(s):  
Viorel Branzoi ◽  
Alina Pruna ◽  
Florina Branzoi
Keyword(s):  
Organic Compounds ◽  
Electrochemical Impedance ◽  
Corrosion Process ◽  
Diffusion Control ◽  
Cathodic Reaction ◽  
Zinc Electrode ◽  
Electrochemical Studies ◽  
Nacl Solution ◽  
Sodium Dodecylsulphate ◽  
Zinc Corrosion

The inhibition of zinc corrosion in 3.5% NaCl solution by some organic compounds (sodium dodecylsulphate (SDS), sodium dodecylbenzosulphonate (SDBS) and sodium 1,4-bis(2-etylhexyl) sulphosuccinate (AOT)) was investigated. The inhibition efficiencies were determined by polarization measurements of the zinc electrode in the solution. Electrochemical impedance spectroscopy (EIS) was also used for electrochemical studies of zinc electrode in this medium. The results showed that the used surfactants inhibit the cathodic reaction of hydrogen evolution and at low anodic overvoltage the corrosion process is under activation control, while at high anodic overvoltage the process is under diffusion control.

QCM and Electrochemical Studies of Li Intercalation in V6O13

1990 ◽  
Author(s):  
Heai-Ku Park ◽  
Kathryn Podolske ◽  
Zafar Munshi ◽  
W. H. Smyrl ◽  
B. B. Owens
Keyword(s):  
Electrochemical Studies

Naphthoquinone-based hydrazone hybrids: synthesis and potent activity against cancer cell lines

2020 ◽  
Vol 16 ◽  
Author(s):  
Délis Galvão Guimarães ◽  
Arlan de Assis Gonsalves ◽  
Larissa Araújo Rolim ◽  
Edigênia Cavalcante Araújo ◽  
Victória Laysna dos Anjos Santos ◽  
...  
Keyword(s):  
Anticancer Activity ◽  
Cell Lines ◽  
Cancer Cell ◽  
Biological Activities ◽  
Supporting Electrolyte ◽  
Cancer Cell Lines ◽  
Molecular Structures ◽  
Cytotoxic Activities ◽  
Electrochemical Studies ◽  
Ic50 Values

Background: Natural naphthoquinones have shown diversified biological activities including antibacterial, antifungal, antimalarial, and cytotoxic activities. However, they are also compounds with acute cytotoxicity, immunotoxicity, carcinogenesis, and cardio- and hepatotoxicity, then the modification at their redox center is an interesting strategy to overcome such harmful activity. Objective: In this study, four novel semisynthetic hydrazones, derived from the isomers α- and β-lapachones (α and β, respectively) and coupled with the drugs hydralazine (HDZ) and isoniazid (ACIL), were prepared, evaluated by electrochemical methods and assayed for anticancer activity. Method: The semisynthetic hydrazones were obtained and had their molecular structures established by NMR, IR, and MS. Anticancer activity was evaluated by cell viability determined by reduction of 3-(4,5-dimethyl-2-thiazol)-2,5-diphenyl-2H-tetrazolium bromide (MTT). The electrochemical studies, mainly cyclic voltammetry, were performed, in aprotic and protic media. Result: The study showed that the compounds 2, 3, and 4 were active against at least one of the cancer cell lines evaluated, being compounds 3 and 4 the most cytotoxic. Toward HL-60 cells, compound 3 was 20x more active than β-lapachone, and 3x more cytotoxic than doxorubicin. Furthermore, 3 showed an SI value of 39.62 for HL-60 cells. Compound 4 was active against all cancer cells tested, with IC50 values in the range 2.90–12.40 μM. Electrochemical studies revealed a profile typical of self-protonation and reductive cleavage, dependent on the supporting electrolyte. Conclusion: These results therefore indicate that compounds 3 and 4 are strong candidates as prototypes of new antineoplastic drugs.

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