Functional model for catecholase-like activity: Synthesis, structure, spectra, and catalytic activity of iron(III) complexes with substituted-salicylaldimine ligands

Abstract

Four new mononuclear iron(III) complexes with the substituted-salicylaldimine ligands, [Fe(L 1)(TCC)] ( 1), [Fe(L 2)(TBC)] ( 2), [Fe(L 3)(TBC)] ( 3) and [Fe(L 4)(TCC)](CH 3CN) ( 4) (HL 1 = N′-(5-OH-salicylaldimine)-diethylenetriamine, HL 2 = (N′-(5-Cl-salicylaldimine)-diethylenetriamine, HL 3 N′-(5-Br-salicyl-aldimine)-dipropylenetriamine, HL 4 = (N′-3,5-Br-salicylaldimine)-dipropylenetriamine, H 2TCC = tetrachlorocatechol, and H 2TBC = tetrabromocatechol), were prepared and characterized by XRD, EPR, and Mössbauer spectroscopy. The coordination sphere of the Fe(III) in complexes 1– 4 is a distorted octahedral with N 3O 3 donors set which constructed by the Schiff-base ligands and the catecholate substrates of TBC or TCC. The in situ prepared Fe(III) complexes [Fe(L 1)Cl 2], [Fe(L 2)Cl 2], [Fe(L 3)(Cl 2)], and [Fe(L 4)Cl 2] in absence of TBC or TCC show a high catecholase-like activity for the oxidation of 3,5-DTBC to the corresponding quinone 3,5-DTBQ.