Optimal structure of acidic ionic liquids for synthesis of tetraphenylporphyrins

Abstract

The structure of the most optimal acidic ionic liquids for the tetraphenylporphyrin synthesis was investigated, focusing on the cationic structure of ionic liquids. The investigation in [[Formula: see text]im][CF3CO2] ([Formula: see text]=1-12) with different lengths of alkyl groups at the N(1) position of imidazolium showed that the highest yield of tetraphenylporphyrin (20%) was obtained when the alkyl chain length was C8, which indicated that [HC8im][CF3CO2] is the optimal ionic liquid for the tetraphenylporphyrin synthesis. In addition, we also investigated the influence of electron-withdrawing and electron-donating substituents at the C(2), C(4), and C(5) positions of the imidazolium cation of the acidic ionic liquids on the synthesis of tetraphenylporphyrins. The highest tetraphenylporphyrin yields were obtained in [HC8mim][CF3CO2], which suggested that the imidazolium cation with an octyl group at the N(1) position and a methyl group at the C(2) position was the optimal structure.