Kinetic and photoredox behaviour of iron(III) complexes with Kojic acid

Bidentate kojic acid anions L- form Fe(III) chelates [FeL(H2O)(4)](2+), [FeL2(H2O)(2)](+), and [FeL3]. The rate of the chelates formation is proportional both to the concentration of hydrated Fe3+ and kojic acid HL. Using stopped-how technique the pH dependence of the rate of [FeL(H2O)(4)](2+) formation was followed. Being in dark, the chelates are redox-stable, the absorption of ultraviolet or visible radiation results in the photoreduction of Fe(III) to Fe(II). The overall quantum yields of Fe(II) formation for all individual chelates at the wavelengths of incident radiation lambda(irr) = 366 nm and 436 nm were determined. Using spin-trapping EPR, the radicals OH. were identified in irradiated aqueous solutions of FeL2+.