Radical scavenging and catalytic activity of metal-phenolic complexes.
A series of metal-ligand complexes were prepared by the reaction of various metal ions, namely, Cu(II), Mn(II), or Fe(II) with phenolic derivatives of [catechol, chlorogenic acid (CGA), n-propyl gallate (nPG), 3-hydroxy anthranilic acid, resveratrol, and rutin] and characterized by UV-vis spectroscopy. The metal/ligand complexing ratio and complexation constants have been determined. The complexes were probed for their reactivity toward various free radicals (e aq-, CO2*-, and O2*-). Pulse radiolysis studies showed that the one-electron reduction of metal/phenol complexes by CO2*- radicals was metal-centered, and this was confirmed by the formation of an initial adduct with CO2*- radicals. Rate constants for the scavenging of superoxide anions with metal complexes ranged between 10(7)-10(9) dm3 mol(-1) s(-1) and those for the reaction of e aq- with the metal complexes were in the range of (1-5) x 10(9) dm3 mol(-1) s(-1), depending on the pH of the solution. Cyclic and differential pulse voltammetric studies showed that the reduction potential of the complexes are found to range between -0.022 to 0.45 V vs normal hydrogen electrode.
Mahal
Harbir S
HS
Radiation and Photochemistry Division, Analytical Chemistry Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400085, India.
Kapoor
Sudhir
S
Satpati
Ashis K
AK
Mukherjee
Tulsi
T
D002384:Catalysis; D003300:Copper / Q000737:chemistry; D004566:Electrodes; D016166:Free Radical Scavengers / Q000138:chemical synthesis / Q000737:chemistry*; D006859:Hydrogen / Q000737:chemistry; D007501:Iron / Q000737:chemistry; D008024:Ligands; D008345:Manganese / Q000737:chemistry; D019216:Metals, Heavy / Q000737:chemistry*; D009942:Organometallic Compounds / Q000138:chemical synthesis / Q000737:chemistry*; D010084:Oxidation-Reduction; D010636:Phenols / Q000737:chemistry*; D012680:Sensitivity and Specificity; D013056:Spectrophotometry, Ultraviolet / Q000379:methods
D016166:Free Radical Scavengers; D008024:Ligands; D019216:Metals, Heavy; D009942:Organometallic Compounds; D010636:Phenols; D008345:Manganese; D003300:Copper; D006859:Hydrogen; D007501:Iron