A Systematic Study of Electrochemical and Spectral Properties for the Electronic Interactions in Porphyrin-Triphenylamine Conjugates

[[abstract]]A series of mono-, di-, tri-, and tetra-triphenylamine (TPA)-substituted porphyrinatozinc complexes have been synthesized to investigate their spectral and electrochemical properties. The varied shapes of absorption spectra of porphyrintriphenylamine (Por-TPA) conjugates in comparison with tetramesitylporphyrinatozinc (ZnTMP) indicate that there are strong interactions between porphyrin and TPA moieties. In general, the electron-donating capability of a substituent on TPA and the number of TPA derivatives that bond with porphyrin would cause Soret band broadening and intensification of the Q(0,0) band. Due to the antenna effect of these conjugates, the fluorescence quantum yields were enhanced when more TPA moieties were linked. Cyclic voltammetry and spectroelectrochemical methods revealed the redox properties of Por-TPA conjugates. Axial ligation of porphyrinatozinc with N-methylimidazole was useful in differentiating the oxidation site of Por-TPA conjugates. The first one-electron oxidations of these conjugates are at the porphyrin ring. The charge-transfer bands present in the near-IR region in the absorption spectra of Por-TPA radical cations are evidence of an electronic interaction between porphyrin and TPA. The electron-donating strength of the TPA group and the symmetry of the Por-TPA conjugate affect the intensity of the charge-transfer band.[[note]]SC