Effect of amino acid fragments in tetraphenylporphin derivatives on the Ph-dominance interval of dication porphyrin

Abstract

The effect of amino acid fragments in tetraphenylporphin derivatives on the pH range of porphyrin dominance as a dication was studied. For this purpose, the protonation processes of unsymmetrically substituted derivatives of 5,10,15,20-tetraphenylporphyrin: 5-(4′-aminophenyl)-10,15,20-triphenylporphine, 5-(4′-tyrosinylamidophenyl)-10,15,20-triphenylporphine and 5-(4′-glycinacylaminophenyl)-10,15,20-triphenylporphine were analyzed in acetonitrile. It was found that in acidic acetonitrile solutions the pH range of dominance of the doubly protonated form depends on the nature of the substituent in the para -position on the periphery of the phenyl fragment of the porphyrin ring: electron-donating substituents expand the pH range of dominance of the porphyrin in the dication form, while electron-withdrawing substituents decrease it. The calculation of the energies of the molecular orbitals of the studied compounds by the DFT method with the B3LYP/cc-pVDZ set showed good agreement between the experimental results and the calculations.