Quinone recognition by amide hydrogen bonding in porphyrin systems

Abstract

5,15-cis-Bis(2-trifluoroacetamidophenyl)porphyrin 2c and its pentafluorobenzamidophenyl analogue 2e have significant recognising ability for p-benzoquinone 3a, which is explained by the large negative enthalpy change of the 2c–3a complex and by the small entropy change of the 2e–3a complex, respectively. Porphyrin 2e recognises electron-rich p-benzoquinone more effectively than electron-deficient p-benzoquinone, which is ascribed to the enthalpy change of the complexation induced by the hydrogen bonding of amide protons of 2e with oxygen atoms of the substituted p-benzoquinone.