A simple alternative method for preparing Sn(IV) porphyrins

Abstract

Sn(IV) porphyrins are highly desirable for various applications because of their stability, their preference for oxygen-donor ligands and because they possess properties which can be easily characterized using various spectroscopic techniques. The most established method for the preparation of the Sn(IV) porphyrins is refluxing the porphyrin with SnCl 2·2 H 2 O in pyridine as solvent. Although this method works efficiently, we found that the work-up results in a lot of unwanted materials and using large quantities of pyridine as solvent is not good under laboratory conditions. In this paper, we show that the Sn(IV) porphyrins can be prepared easily by treating porphyrin with SnCl 2·2 H 2 O in chloroform, dichloromethane and toluene as solvent containing 25–50% ethanol as co-solvent. The reaction works smoothly and involves simple work-up and straightforward chromatographic purification. The method works efficiently for meso and β-substituted porphyrins. The spectral and electrochemical properties of various Sn(IV) were studied and our studies showed that the properties are sensitive to the nature of substituent present at the meso-position.