Electrochemistry and spectroelectrochemistry of 5,10,15,20-tetrakis(1,3-benzodioxole) porphyrin and its manganese and iron complexes

2014 ◽  
Vol 18 (12) ◽  
pp. 1093-1100 ◽  
Author(s):  
Geani Maria Ucoski ◽  
Shirley Nakagaki ◽  
Fábio Souza Nunes
Keyword(s):  
Metal Ion ◽  
Supporting Electrolyte ◽  
Cation Radical ◽  
Soret Band ◽  
Iron Complexes ◽  
Structural Features ◽  
Cyclic Voltammograms ◽  
Free Base ◽  
Typical Experiment ◽  
Semi Empirical

Cyclic voltammetry and thin-layer spectroelectrochemical properties of the free base 5,10,15,20-tetrakis(1,3-benzodioxole)porphyrin ( H 2 P ), and its manganese and iron complexes ( MnP and FeP , respectively) were studied in dichloromethane with tetra-butyl ammonium hexafluorophosphate (TBAPF6) as supporting electrolyte. The free base undergoes two monoelectronic oxidations at +0.71 and +0.96 V vs.  Ag / Ag +, corresponding to the formations of the π-cation radical and dication. Two reductions were observed at -1.53 and -1.87 V corresponding to the formation of π-anion and dianion species. The cyclic voltammograms of the Mn III and Fe III complexes also showed a reversible process centered in the metal ion with E1/2 values at -0.61 and -0.59 V, respectively. In a typical experiment, in situ spectroelectrochemical response showed a decrease of the Soret band at 422 nm, a red shift of the Q-bands, and the new low intensity bands between 800–950 nm range. Structural features and spectroscopic assignments were proposed and discussed based on semi-empirical (molecular mechanics MMFF and ZINDO/S (Zerner method of intermediate neglect of differential overlap for spectroscopy) calculations.

Effect of fused indanedione (IND) groups and antipodal β-substituents on electrochemical properties of unsymmetrical metalloporphyrins

2020 ◽  
Vol 24 (10) ◽  
pp. 1155-1165
Author(s):  
W. Ryan Osterloh ◽  
Yuanyuan Fang ◽  
Nivedita Chaudhri ◽  
Lei Cong ◽  
Muniappan Sankar ◽  
...  
Keyword(s):  
Electrochemical Properties ◽  
Metal Ion ◽  
Anion Radical ◽  
Pyrrole Ring ◽  
Supporting Electrolyte ◽  
Central Metal ◽  
Tetrabutylammonium Perchlorate ◽  
Free Base ◽  
Reduction Potentials ◽  
Derivatives Of

The interacting effect of fused indanedione (IND) groups and antipodal Br [Formula: see text]-substituents on the electroreduction of free-base and transition metal tetraphenylporphyrins (TPPs) are elucidated through the use of cyclic voltammetry. A systematic study of the reduction potentials for mono- and di-fused derivatives of MTPP(IND)(R)2 and MTPP(IND)2(R)2 where R = Br or H and M = Cu[Formula: see text], Ni[Formula: see text], Zn[Formula: see text] or H2 is carried out in pyridine containing 0.1 M tetrabutylammonium perchlorate (TBAP) as supporting electrolyte and demonstrates how the overall electrochemical properties of these compounds can be tuned by systematic changes in the number of meso-[Formula: see text]fused IND groups on the molecule and the presence or absence of electron-withdrawing Br [Formula: see text]-substituents. Under these solution conditions, two reversible one-electron reductions are seen for H2TPP, while three reversible reductions are obtained for H2TPP(IND) or H2TPP(IND)Br2 and four for H2TPP(IND)2Br2. Multiple reductions also occur for the other investigated mono- and di-fused metalloporphyrins. Plots of measured [Formula: see text] values for the two ring-centered reductions of compounds in a given series vs. the number of fused IND groups are linear and with slopes varying in magnitude between 15 and 230 mV/IND depending upon the product of the electron transfer (anion radical or dianion), the specific central metal ion and the presence or absence of Br substituents on the pyrrole ring opposite the fused IND group(s). It is anticipated that the information from this study can be used for predicting the reduction potentials for yet to be synthesized compounds where a specific redox reactivity is desired.

Fast Screening for Antioxidant Properties of Flavonoids from Pterogyne nitens Using Electrochemical Methods

2012 ◽  
Vol 95 (3) ◽  
pp. 773-777 ◽  
Author(s):  
Leonardo Luiz Okumura ◽  
Luis Octávio Regasini Regasini ◽  
Daniara Cristina Fernandes ◽  
Dulce Helena Siqueira da Silva ◽  
Maria Valnice Boldrin Zanoni ◽  
...  
Keyword(s):  
Antioxidant Activities ◽  
Low Cost ◽  
Supporting Electrolyte ◽  
Antioxidant Properties ◽  
Reference Electrode ◽  
Structural Features ◽  
Quantitative Detection ◽  
Nonaqueous Media ◽  
Electrochemical Detector ◽  
Fast Screening

Abstract A fast, low-cost, convenient, and especially sensitive voltammetric screening approach for the study of the antioxidant properties of isoquercitrin and pedalitin from Pterogyne nitens is suggested in this work. These flavonoids were investigated for their redox properties using cyclic voltammetry in nonaqueous media using N,N-dimethylformamide and tetrabutylammonium tetrafluorborate as the supporting electrolyte, a glassy carbon working electrode, Ag|AgCl reference electrode, and Pt bare wire counter electrode. The comparative analysis of the activity of rutin has also been carried out. Moreover, combining HPLC with an electrochemical detector allowed qualitative and quantitative detection of micromolecules (e.g., isoquercitrin and pedalitin) that showed antioxidant activities. These results were then correlated to the inhibition of β-carotene bleaching determined by TLC autographic assay and to structural features of the flavonoids.

One-Pot Electrodeposition of NiS Nanoparticles as an Efficient Electrode for Nonenzymatic H2O2 and Glucose Sensors

NANO ◽  
2019 ◽  
Vol 14 (01) ◽  
pp. 1950010
Author(s):  
Zhiheng Huang ◽  
Chunchuan Gu ◽  
Jiajun Wen ◽  
Langlang Zhu ◽  
Mingzhen Zhang ◽  
...  
Keyword(s):  
Metal Ion ◽  
Electrochemical Impedance ◽  
Glucose Sensors ◽  
Cyclic Voltammograms ◽  
Impedance Spectra ◽  
Electrochemical Impedance Spectra ◽  
One Pot ◽  
X Ray ◽  
First Time ◽  
Nis Nanoparticles

In this paper, a new and one-pot electrodeposition method was expanded for the preparation of NiS nanoparticles-based electrochemical biosensor using metal-ion complexes as a precursor. Thioacetamide was used to control the production rate of NiS nanoparticles for the first time. The proposed electrochemical sensor was characterized by energy dispersive X-ray spectroscopy (EDX), field emission scanning electron microscope (FESEM), cyclic voltammograms (CV), and electrochemical impedance spectra (EIS). Experiment parameters were optimized. Under the optimized condition, the prepared NiS-based biosensor exhibited excellent electrocatalytic oxidation of H2O2 and glucose due to their small size. It provided fast and sensitive strategy for detecting H2O2 and glucose in the range of 1–5000 and 1–1000[Formula: see text][Formula: see text]M. The detection limit of 0.257 and 0.3[Formula: see text][Formula: see text]M was obtained for H2O2 and glucose. The mechanisms were also analyzed. The proposed biosensor exhibited excellent anti-interference and repeatability. Furthermore, it was applied in the actual sample analysis, such as human blood serum.

Cyclic Voltammetry of Iodine at the Organic Liquid/Aqueous Solution Interface

2007 ◽  
Vol 72 (7) ◽  
pp. 917-926 ◽  
Author(s):  
Shaoai Xie ◽  
Jinping Jia ◽  
Hong-Jin Chen
Keyword(s):  
Metal Ion ◽  
Composite Electrode ◽  
Polar Solvent ◽  
Electrochemical Reaction ◽  
Organic Liquid ◽  
Supporting Electrolyte ◽  
Cyclic Voltammetric ◽  
Solution Interface ◽  
Donor Solvent ◽  
Solvent Complex

The electrochemical behavior of iodine extracted with an organic solvent at the liquid/liquid interface was studied using a new composite electrode. The effects of various solvents and supporting electrolyte on the electrochemical reaction of iodine were analyzed by cyclic voltammetric curves. The formation of a polar solvent complex of iodine and a strong donor solvent in organic solution was comfirmed by UV-VIS spectra. A possible mechanism was suggested based on experiments. This method makes it possible to measure heavy metal ion in solution indirectly.

scholarly journals A trapped human PPM1A–phosphopeptide complex reveals structural features critical for regulation of PPM protein phosphatase activity

2018 ◽  
Vol 293 (21) ◽  
pp. 7993-8008 ◽  
Author(s):  
Subrata Debnath ◽  
Dalibor Kosek ◽  
Harichandra D. Tagad ◽  
Stewart R. Durell ◽  
Daniel H. Appella ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Metal Ions ◽  
Active Site ◽  
Metal Binding ◽  
Metal Ion ◽  
Catalytic Domain ◽  
Protein Phosphatases ◽  
Random Order ◽  
Structural Features

Metal-dependent protein phosphatases (PPM) are evolutionarily unrelated to other serine/threonine protein phosphatases and are characterized by their requirement for supplementation with millimolar concentrations of Mg2+ or Mn2+ ions for activity in vitro. The crystal structure of human PPM1A (also known as PP2Cα), the first PPM structure determined, displays two tightly bound Mn2+ ions in the active site and a small subdomain, termed the Flap, located adjacent to the active site. Some recent crystal structures of bacterial or plant PPM phosphatases have disclosed two tightly bound metal ions and an additional third metal ion in the active site. Here, the crystal structure of the catalytic domain of human PPM1A, PPM1Acat, complexed with a cyclic phosphopeptide, c(MpSIpYVA), a cyclized variant of the activation loop of p38 MAPK (a physiological substrate of PPM1A), revealed three metal ions in the active site. The PPM1Acat D146E–c(MpSIpYVA) complex confirmed the presence of the anticipated third metal ion in the active site of metazoan PPM phosphatases. Biophysical and computational methods suggested that complex formation results in a slightly more compact solution conformation through reduced conformational flexibility of the Flap subdomain. We also observed that the position of the substrate in the active site allows solvent access to the labile third metal-binding site. Enzyme kinetics of PPM1Acat toward a phosphopeptide substrate supported a random-order, bi-substrate mechanism, with substantial interaction between the bound substrate and the labile metal ion. This work illuminates the structural and thermodynamic basis of an innate mechanism regulating the activity of PPM phosphatases.

Self-assembly with fluorescence readout in a free base dipyrrin–polymer triggered by metal ion binding in aqueous solution

2019 ◽  
Vol 43 (24) ◽  
pp. 9711-9724 ◽  
Author(s):  
Rui Liu ◽  
Pothiappan Vairaprakash ◽  
Jonathan S. Lindsey
Keyword(s):  
Aqueous Solution ◽  
Self Assembly ◽  
Metal Ion ◽  
Zinc Ion ◽  
Ion Binding ◽  
Free Base ◽  
Metal Ion Binding

Profound morphological and fluorogenic changes ensue upon binding of a zinc ion by two polymers, each of which bears a single dipyrrin at one terminus, forming the bis(dipyrrinato)Zn(ii) complex.

Corrigenda - Complexes of binucleating ligands. III. Novel complexes of a macrocyclic binucleating ligand

1970 ◽  
Vol 23 (11) ◽  
pp. 2225 ◽  
Author(s):  
NH Pilkington ◽  
R Robson
Keyword(s):  
Schiff Base ◽  
Metal Ion ◽  
Organic Ligand ◽  
Structural Features ◽  
Crystallographic Analysis ◽  
Metal Salts ◽  
X Ray ◽  
Spectral Evidence ◽  
Binucleating Ligands

By reaction of 5-methylisophthalaldehyde with 1,3-diaminopropane in the presence of various metal salts the following complexes have been isolated: MCu2Cl2,6H2O, MCu2(ClO4)2,2H2O, MCu2(HSO4)2,H2O, MNi2Cl2,2H2O, MCo2Cl2,2CH3OH, MFezCl2,2CH3OH, MMn2Cl2,2H2O, MZn2Cl2,2H2O, (MH2)Ni(ClO4)2,2H2O where MH2 represents the macrocyclic tetrakis-Schiff base obtained by condensation of two molecules each of the diamine and dialdehyde components and M represents the derived dianion which behaves as a novel macrocyclic binucleating ligand. On the basis of magnetic and spectral evidence the complexes are assigned binuclear structures in which the cations are in an approximately square-pyramidal environment. These structural features have been confirmed in the case of MCu2Cl2,6H2O by an independently conducted X-ray crystallographic analysis. It is suggested that (MH2)Ni(ClO4)2,H2O is closely related to the others in that the nickel environment is square-pyramidal and that essentially the same organic ligand framework is present, with two protons rather than a metal ion occupying the second cavity of M.

Copper(II) Porphyrin as Biomimetic Catalyst for Oxidation of Trimethylphenol

2016 ◽  
Vol 846 ◽  
pp. 706-711 ◽  
Author(s):  
Nurliana Roslan ◽  
Salasiah Endud ◽  
Zainab Ramli ◽  
Hendrik Oktendy Lintang
Keyword(s):  
Soret Band ◽  
Acid Group ◽  
Proton Nuclear Magnetic Resonance ◽  
Free Base ◽  
H Nmr ◽  
Functional Models ◽  
Vis Spectroscopy ◽  
Cytochrome P 450 ◽  
Potential Use

Synthetic metalloporphyrins have long been recognized either as functional models or mimics of the cytochrome P-450 enzymes and they are versatile compounds with potential use in drug delivery, catalysis and electronics. In the present study, the metalloporphyrin, (meso-tetra-(p-sulfonatophenyl)-porphyrinato)copper, CuTSPP was synthesized in the reaction between free-base porphyrin, meso-tetra (p-sulfonatophenyl)porphyrin, H2TSPP and copper(II) acetate monohydrate. The materials were characterized using Fourier Transform Infrared Spectroscopy (FTIR), Ultraviolet-Visible (UV-Vis) Spectroscopy, Proton Nuclear Magnetic Resonance (1H NMR) Spectroscopyand Mass Spectrometry (MS) analysis. The FTIR spectra of both free-base porphyrin and CuTSPP showed the appearance of three pronounced bands indicating the presence of the salt form (R-SO3Na) of the sulfonic acid group. Characterization of CuTSPP by UV-Vis spectroscopy confirmed that the insertion of copper into the free-base porphyrin was successful by the appearance of the Soret band and Q bands. The catalytic activity of CuTSPP was tested in the oxidation of 2,3,6-trimethylphenol (TMP) at 60 °C using hydrogen peroxide (H2O2) as oxidant. The reaction parameters including the reaction temperature and time have been optimized. The only product obtained by means of TMP oxidation with H2O2 using CuTSSP is 2,3,5-trimethylbenzoquinone (TMBQ), an important precursor for the industrial production of Vitamin E.

Solvent and acidity effects on the UV-visible spectra and protonation-deprotonation of free-base octaethylcorrole

2008 ◽  
Vol 12 (01) ◽  
pp. 1-10 ◽  
Author(s):  
Zhongping Ou ◽  
Hongxia Sun ◽  
Weihua Zhu ◽  
Zulin Da ◽  
Karl M. Kadish
Keyword(s):  
Equilibrium Constants ◽  
Visible Spectrum ◽  
Soret Band ◽  
Free Base ◽  
Tetrabutylammonium Hydroxide ◽  
Experimental Conditions ◽  
Visible Spectra ◽  
Meso Position ◽  
Uv Visible ◽  
Strong Acids

The UV-visible spectrum of free-base octaethylcorrole, (OECor) H 3, was recorded in thirteen different nonaqueous solvents as well as in a mixed acetonitrile/acid solvent containing one of seven different acids. Spectra were also measured in seven different solutions of neat concentrated acid and in CH 3 CN containing piperidine or tetrabutylammonium hydroxide as an added base. The overall data was analyzed as a function of solvent acidity or basicity parameters and the number of protons on the central nitrogens of the macrocycle, the predominant form of the corrole in these solutions being respresented as (OECor)H 3, [ (OECor)H 4]+, [ (OECor)H 2]− or [ (OECor)H ]2− where OECor = trianion of octaethylcorrole. The mono-protonated corrole, [ (OECor)H 4]+, is formed in concentrated acetic acid or in CH 3 CN containing 0.10 M trifluoroacetic acid, H 2 SO 4, HCl , H 3 PO 4 or HClO 4. The mono-deprotonated corrole, [ (OECor)H 2]−, is generated in piperidine while doubly deprotonated [ (OECor)H ]2− exists in solutions of tetrabutylammonium hydroxide. An addition of protons to the macrocycle of [ (OECor)H 4]+ also occurs in the presence of concentrated strong acids and this results in a loss of the characteristic Soret band of the corrole leading presumably to [ (OECor)H 5]2+ where the second proton has been added to a meso-position of the macrocycle. The UV-visible spectral changes upon formation of [ (OECor)H 4]+, [ (OECor)H 2]− or [ (OECor)H ]2− in CH 3 CN were monitored during a titration with the relevent acid or base and equilibrium constants for protonation or deprotonation of (OECor)H 3 were determined using standard equations. The measured logK values are compared to protonation and deprotonation constants obtained for two related corroles and two related porphyrins under the same experimental conditions.

Sign in / Sign up

Export Citation Format

Share Document