Thermo-Kinetic Investigation of Comparative Ligand Effect on Cysteine Iron Redox Reaction

Rizvi, Masood Ahmad; Teshima, Norio; Maqsood, Syed Raashid; Akhoon, Showket Ahmad; Peerzada, Ghulam Mustafa

doi:10.5562/cca2479

Cited by 7 publications

(4 citation statements)

References 16 publications

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“…The formal potential of transition metals redox couples can be modulated through the complexation with a suitable ligand. , Particularly, it has been reported that the redox potential of the Fe(III)/Fe(II) couple is shifted to more negative values upon complexation with ions such as citrate, chloride, oxalate, or ethylenediaminetetraacetic acid (EDTA). − Herein, we studied the effect of complexation of Fe(II) with citrate and chloride ions in the AuNPs synthesis. Thus, experiments in the presence of different citrate concentration (0.5, 0.75, and 1 mM) were performed at 40 °C for Au(III):Fe(II) molar ratio of 1:3 and for concentrations of PSS and Au(III) of 0.5 mg/mL and 0.5 mM, respectively.…”

Section: Resultsmentioning

confidence: 99%

Iron(II) as a Green Reducing Agent in Gold Nanoparticle Synthesis

Djafari

Fernández-Lodeiro

García‐Lojo

et al. 2019

ACS Sustainable Chem. Eng.

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Iron is the most abundant element by mass in the Earth. Despite being an inexpensive material used in a wide range of applications, its role as reducing agent for the synthesis of plasmonic nanoparticles has not been explored in detail. In the present work, we have studied the use of iron(II) sulfate as a green reductant for the synthesis of gold nanoparticles (AuNPs) in the absence or presence of different molecules. First, we demonstrate that iron(II), in the absence of any additive or capping agent, is able to reduce Au(III) to generate AuNPs. However, the reduction yield is not 100% and the obtained NPs are coated by an Fe(II)/Fe(III) oxo/hydroxo sulfate shell. Nevertheless, the presence of polystyrenesulfonate (PSS) in the reaction medium prevents the growth of this inorganic shell and leads to total Au salt reduction. Besides, PSS seems to play a role in the nucleation and growth steps since it induces the formation of raspberry-like AuNPs. Additionally, we have investigated the effect of modulating the formal redox potential of Fe(II), through its complexation with citrate, in the synthesis of AuNPs. Interestingly, we have found that the presence of citrate gives rise to uniform pseudospherical AuNPs with well-defined optical properties, indicating that citrate may alter the nucleation step. Finally, to explore the applicability of these green nanomaterials for SERS applications, the SERS performance of the obtained AuNPs has been analyzed using 4-nitrothiophenol (4-NTP) as model analyte.

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Section: Resultsmentioning

confidence: 99%

Iron(II) as a Green Reducing Agent in Gold Nanoparticle Synthesis

Djafari

Fernández-Lodeiro

García‐Lojo

et al. 2019

ACS Sustainable Chem. Eng.

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“…(3)] and makes Fe(III) cysteine redox reaction spontaneous. Potentiometric titration of Fe(III) with cysteine [20] displayed the potential jump at the equivalence point only in presence of the ligand and ca 50°C. Potential change in the vicinity of the inflection point was found to be proportional to stability of Fe(II) complex with the selected ligands (Fig.…”

Section: 3mentioning

confidence: 99%

Complexation modulated redox behavior of transition metal systems (review)

Rizvi

2015

Russ J Gen Chem

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Ligand effect is a favorable factor in modulation of redox potential of transition metal ion oxidation-reduction systems. Coordination promoted redox action of transition metals can be an efficient approach to design of new redox systems with specific applications. The current review is devoted to the complexation effect of selected ligands on the redox potential of iron, cobalt and copper redox couples and application of such systems in analytical estimations. Indirect estimation of non redox systems by a non redox reaction over a platinum electrode has been referred to as a pseudo indicator action. Application of coordination modulated redox potentials in the natural attenuation of toxic environmental contaminants is also presented.1 The text was submitted by the author in English.Complexation effect on redox potential. Redox systems with tailor made potentials are desired for applications in artificial photosynthetic reactions [1], fuel cell catalysts solar energy conversions [2], hydrogen production and bio-memitic chemistry [3]. Complexation with an appropriate ligand can modulate the redox potential of transition metals redox couples beyond the natural range [4,5]. The complexation effect on redox potential can be explained by specific stabilization of transition metal oxidation states in a redox couple. The complexation effect on redox potential can be rationalized using the thermochemical cycle (Scheme 1) [7,8]. The ligand effect is the promising phenomenon in the design and development of redox potentials with desired applications [6].According to Eq. (3) the ratio of formation constants β III /β II modulates the redox potential of a redox couple in complexes. With the proper adjustment of the ratio the redox potential can be tuned to any desired value. Thus the electrochemical behavior of transition metals ions is also modified by the complexation effect which leads to a different reduction potential in the complexed state compared to the free state [Eq. (3)]. The complexation effect on redox potentials helps to understand mechanisms of the natural redox processes [9],Scheme 1. Thermochemical cycle for complexation effect on redox potential. M 3+ aqua M 2+ aqua ΔG 1 e − ΔG 3 nL ΔG 2 nL M 3+ complex M 2+ complex ΔG 4 e − (3) E complex = E aqua − RT nF ln β III β II . ΔG 1 + ΔG 2 = ΔG 3 + ΔG 4 , ΔG 1 = −nFE aqua ; ΔG 2 = −RTln β II , ΔG 3 = −RTln β III ; ΔG 4 = −nFE complex , ΔG 4 = (ΔG 1 + ΔG 2 ) − ΔG 3 , −nFE complex = −nFE aqua + RT nF ln β III β II ,

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“…[9][10][11] These compounds can act as potential ligands with good binding interactions towards metal ions, [12][13] forming complexes that modify the redox behavior of metals [14] as reported for Fe II complexation by ligands. [3,4,[15][16][17] The impact of different organic ligands can be rationalized in terms of the complexation effect on the reduction potential of Fe III /Fe II redox couple, [14,18,19] Depending upon relative stabilization of the two oxidation states in transition metal redox couple, different ligands tune the formal redox potential of the Fe III -Fe II couple to a range of values. Modulating the redox potential of environmentally widespread Fe II ions by complexation with naturally occurring organic compounds can be interesting towards natural attenuation of contaminants under environmental conditions, [5][6][7][8] In continuation of our interest in using coordination compounds for synthetic and environmental applications, [20][21][22][23][24][25] this work presents the use of Fe II -complexes with prevalent compounds as ligands for waste water treatment under environmental conditions (aerobic, 20°C, pH 6-7).…”

Section: Introductionmentioning

confidence: 99%

Complexation Modulated Iron Redox Systems for Waste Water Treatment: A Natural Attenuation Model

et al. 2020

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Natural attenuation mimics nature's own cleansing mechanism and offers an effective solution for contaminant treatment under prevalent environmental conditions without generating secondary toxins. Despite obvious advantages, these processes are restricted by a narrow range of reduction potential available within natural water systems. Complexation reaction offers to modulate the redox potential range of transition metals allowing detoxification of persistent contaminants. Consequently, present work describes complexation modulated redox potential of iron systems with environmentally available ligands for degradation of contaminants (textile dyes, antibiotics and toxic metal ions) for a possible application in water treatment under natural attenuation concept. The observed spectrophotometric results are indicative of a significant ligand effect on degradation kinetics of studied contaminants by iron(II) complexes. The kinetic efficacies of iron(II) complexes for contaminant degradation were in the order: aqua

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Thermo-Kinetic Investigation of Comparative Ligand Effect on Cysteine Iron Redox Reaction

Cited by 7 publications

References 16 publications

Iron(II) as a Green Reducing Agent in Gold Nanoparticle Synthesis

Iron(II) as a Green Reducing Agent in Gold Nanoparticle Synthesis

Complexation modulated redox behavior of transition metal systems (review)

Complexation Modulated Iron Redox Systems for Waste Water Treatment: A Natural Attenuation Model

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