Photoreduction of iron protoporphyrin IX chloride in non‐ionic triton X‐100 micelle studied by electronic absorption and resonance Raman spectroscopy

Abstract

Resonance Raman and electronic absorption studies of iron protoporphyrin IX chloride (hemin) in non-ionic Triton X-100 micelle in the absence and presence of hindered imidazole (2-methylimidazole and 1,2-dimethylimidazole) and unhindered imidazole under various experimental conditions are reported. Hemin undergoes photoreduction at the metal center, both in the absence and presence of hindered imidazole, in anaerobic, alkaline and neutral pH conditions on photoexcitation by laser radiation at 441.6 and 457.9 nm. It is inferred from this study that only the monomer hemin encapsulated within the micelle under the alkaline pH conditions is photoreducible. The photoreduction of hemin in this micelle occurs from an electron transfer as a result of dissociation of coordinated hydroxyl ion to the iron atom in the photoexcited state, which may also involve the OH ! Fe charge transfer transition around 360 nm.

A Supramolecular‐Hydrogel‐Encapsulated Hemin as an Artificial Enzyme to Mimic Peroxidase

“…The Soret bands of the hemin inside the hydrogel (at 400 nm, the bands are similar to hemin in aqueous micelle solutions and artificial proteins [19,20] ) agree with the spectra of hemin chloride in dimethyl sulfoxide and methanol, [21] suggesting monomeric hemin chloride. As reported, [19,20] the weak absorbance band at 585 nm should be ascribed to chargetransfer transition. The weak shoulder at 365 nm in the spectra of Gel II indicates the presence of a small amount of monomeric haematin.…”

A Supramolecular‐Hydrogel‐Encapsulated Hemin as an Artificial Enzyme to Mimic Peroxidase

“…The Soret bands of the hemin inside the hydrogel (at 400 nm, the bands are similar to hemin in aqueous micelle solutions and artificial proteins19, 20) agree with the spectra of hemin chloride in dimethyl sulfoxide and methanol,21 suggesting monomeric hemin chloride. As reported,19, 20 the weak absorbance band at 585 nm should be ascribed to charge‐transfer transition. The weak shoulder at 365 nm in the spectra of Gel II indicates the presence of a small amount of monomeric haematin.…”

Enantioselective Activity of Hemin in Supramolecular Gels Formed by Co‐Assembly with a Chiral Gelator

“…The Soret band of the hemin in gels (420 nm) appears obvious redshift which suggests hemin molecule mainly exist as monomers . As reported, the weak absorbance shoulder at 365 nm is the presence of a small quantity of monomeric haematin . The spectral features implied that the imidazole of LHC18 and DHC18 formed a coordination with the iron .…”