A realistic model for heme-containing catalases and peroxidases: the X-ray structural characterisation of a non-porphyrin iron(III) macrocyclic complex, and the mechanism of its peroxidation of aromatic substrates

Reactions of Tetraazamacrocyclic FeIII Complexes with Hydrogen Peroxide − Putative Catalase Mimics?

“…[16,18] The preparation of ligand 3 was devised similarly, starting from pyridine-2,6-dicarbaldehyde; this was treated with the appropriate diamine in a copper template reaction to give the macrocycle. Diimine reduction by sodium borohydride and removal of copper(II) as sulfide provided 3 in 81% overall yield.…”

“…From the slope of the regression line, it is possible to calculate an average relative yield of O 2 of 0.4% for this range of hydrogen peroxide concentration. Thus, although oxygen is formed by the reaction between Fe(III)-1 and hydrogen peroxide at acidic pH, [15,16] this reaction is insignificant relative to the extent of hydrogen peroxide degradation.…”

“…An account on previous studies of decomposition of hydrogen peroxide by iron(III) compounds is given in that publication. The same group later [16] proposed that this catalytic activity proceeds through a high oxidation state Fe intermediate rather than through involvement of free hydroxyl radicals. The complex therefore had catalase-like and peroxidase-like activity attributed to it.…”

“…Recently, Busch's group also described a newly designed substituted triazacyclononaneϪFe II complex which decomposes hydrogen peroxide by a complex, multistep mechanism. [16,17] Our goal is the development of low molecular mass Fe III complexes that are soluble in water and decompose hydroScheme 1 gen peroxide to oxygen and water in high yield under physiological conditions (i.e. at pH ϭ 7.0Ϫ7.4) and at micromolar concentrations of both catalyst and hydrogen peroxide.…”

Studies of Pyridinyl‐Containing 14‐Membered Macrocyclic Copper(II) Complexes

“…The following compounds were prepared according to published procedures: pyridine-2,6-dicarbaldehyde, [27] 3,7,11,17-teraazabicyclo[11.3.1]heptadeca-1(17),13,15-triene (1), [6] {2,12-dimethyl-3,7,11,17-tetraazabicyclo[11.3.1]heptadeca-1(17),2,11,13,15-pentaene}nickel() perchlorate, [13] {2,12-dimethyl-3,7,11,17-tetraazabicyclo[11.3.1]heptadeca-1(17),13,15-triene}nickel() perchlorate, [13] (2R,12S)-2,12-dimethyl-3,7,11,17-tetraazabicyclo[11.3.1]-heptadeca-1(17),13,15-triene monohydrate (2), [28,29] N,N-bis(2-cyanoethyl)-2-methoxybenzylamine, N,N-bis(3-aminopropyl)-2-methoxybenzylamine, [1] 7-(2-methoxybenzyl)-3,7,11,17-tetraazabicyclo[11.3.1]heptadeca-1(17),13,15-triene (3), [1] 2,6-bis[(tosyloxy)methyl]pyridine, [30] dipropanolamine, [31] 4-oxa-1,7-heptanediol, [14] 4-oxaheptane-1,7-diyl ditosylate, [14] 3,7,11-trioxa-17-azabicyclo[11.3.1]heptadeca-1(17),13,15-triene (6). [14] Reduced adenine dinucleotide (β-NADH, disodium salt) and diethyleneaminotetraacetic acid (EDTA) were obtained from Sigma, while manganese() chloride dihydrate and 2-mercaptoethanol were supplied by Merck and 3,3Ј-oxydipropionitrile by Fluka.…”