Difunctionalized N-Confused Porphyrins: Synthesis, fluorescence, and electrochemical studies

Seven di-substituted N-confused porphyrins (NCPs) 9-15 bearing two aryl functional groups (cis-A2B2 type) were synthesized in 4-7% yields via [3+1] approach. The corresponding five 5,10-diaryl-substituted symmetrical tripyrranes 1-5 were prepared and condensed with 2,4-bis(hydroxypentaflurophenyl)pyrrole 6. Two outer N-methyl type A2B2 NCPs 14 and 15 were also prepared via a similar approach using a new key precursor 8. All the porphyrins 9-15 were characterized by high-resolution mass spectrometry, NMR, infrared spectroscopy, UV-visible spectroscopy, fluorescence spectroscopy, and cyclic voltammetry. Fluorescence studies of 9-15 showed blue-shifted emission maxima and lower Stokes shifts values when compared with N-confused tetraphenylporphyrin (NCTPP). Electrochemical studies indicated easier oxidation of N-methyl NCPs 14 and 15 when compared with remaining NCPs 9-13.