Spectral Studies of Ferrous Deuteroporphyrin in Organic Solvents

Abstract

THE studies of iron II porphyrins are of interest with regard to the properties of haemoproteins. Iron remains in the ferrous state in oxymyoglobin and oxyhaemoglobin, but is either in a ferrous or a ferric state in cytochromes. Two difficulties are inherent to these studies; haems oxidize quickly in air, and it is difficult to find convenient reducing agents, especially in organic media. Reduction is easy in water, which unfortunately causes aggregation^1–3 to obscure the specific properties of haems. Whitten et al. prepare haem by incorporating ferrous iron into porphyrins in deaerated solutions, and have reported the haem spectra in mixture of acetic acid and various solvents⁴. Unfortunately, this method precludes studies of coordinating properties of iron, which would be best carried out in non-aqueous solvents. Deuterohaemin dimethyl ester can be readily reduced in heterogeneous phases; aqueous sodium dithionite and a non-miscible organic solvent in which a haem is easily solubilized⁵. In tetrachloromethane and chloroform, five-coordinate chloromethyl compounds are postulated, and may result from a cyclic mechanism involving radical species⁵.