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

Four new mononuclear iron(III) complexes with the substituted-salicylaldimine ligands, [Fe(L1)(TCC)] (1), [Fe(L2)(TBC)] (2), [Fe(L3)(TBC)] (3) and [Fe(L4)(TCC)](CH3CN) (4) (HL1 = N′-(5-OH-salicylaldimine)-diethylenetriamine, HL2 = (N′-(5-Cl-salicylaldimine)-diethylenetriamine, HL3 N′-(5-Br-salicyl-aldimine)-dipropylenetriamine, HL4 = (N′-3,5-Br-salicylaldimine)-dipropylenetriamine, H2TCC = tetrachlorocatechol, and H2TBC = 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 N3O3 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(L1)Cl2], [Fe(L2)Cl2], [Fe(L3)(Cl2)], and [Fe(L4)Cl2] 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.