Facile synthesis, photophysical and electrochemical redox properties of octa- and tetracarboxamidophenylporphyrins and the first example of amido-imidol tautomerism in porphyrins

We synthesized 5,10,15,20-tetrakis(4′-carboxamidophenyl)porphyrin (1) and 5,10,15,20-tetrakis(3′,5′-dicarboxamidophenyl)porphyrin (2) in excellent yields. 1 and 2 exhibited temperature dependent amido-imidol tautomerism in DMSO-d6.184