Catalysis of the decomposition of hydrogen peroxide by a complex of iron(III) with a synthetic macrocyclic ligand

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

“…This complex was synthesized according to the procedure of Melnyk et al [15] Compounds Fe(III)-2 and Fe(III)-3 were prepared similarly, but with addition of tetraethylammonium tetrafluoroborate instead of tetrafluoroboric acid after air oxidation. Unfortunately, attempts to prepare iron(III) complexes of ligands 4 were unsuccessful, although a number of different experimental conditions were tested.…”

“…[15] Rate constants were obtained from initial rates of oxygen production, determining the formation of oxygen from the pressure increase in a closed reaction system. Unfortunately, Melnyk et al [15] did not mention the total yield of oxygen formed under their conditions. The only information given is that oxygen production satisfies the stoichiometry implied by the catalase mechanism.…”

“…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.…”

“…[7Ϫ11] Less common are studies in which Fe III complexes are viewed as catalase mimics able to decompose hydrogen peroxide efficiently, and perhaps by a mechanism similar to that of the enzyme. [12Ϫ14] In 1979, Melnyk et al [15] introduced a nonheme tetraazamacrocyclic Fe III complex [Fe(III)-1], for which oxygen evolution was observed on interacting with hydrogen peroxide under acidic conditions. An account on previous studies of decomposition of hydrogen peroxide by iron(III) compounds is given in that publication.…”

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.…”