A Synthetic Approach of New Trans-Substituted Hydroxylporphyrins

The synthesis of new trans A2B2-substituted porphyrins bearing oxygenic substituent (methoxy, acetoxy, hydroxy) at the periphery of the ring are described. All of the synthesized products were characterized by 1H-N.M.R., 13C-N.M.R., and H.R.M.S. Electrochemical studies revealed two one-electron oxidations and two reductions. In addition, the X-ray structure of one methoxy-derivative was determined

“Spider”-Shaped Porphyrins with Conjugated Pyridyl Anchoring Groups as Efficient Sensitizers for Dye-Sensitized Solar Cells

Two novel “spider-shaped” porphyrins, <i>meso</i>-tetraaryl-substituted <b>1PV-Por</b> and zinc-metalated <b>1PV-Zn-Por</b>, bearing four oligo­(<i>p</i>-phenylenevinylene) (oPPV) pyridyl groups with long dodecyloxy chains on the phenyl groups, have been synthesized. The presence of four pyridyl groups in both porphyrins, which allow them to act as anchoring groups upon coordination to various Lewis acid sites, the conjugated oPPV bridges, which offer the possibility of electronic communication between the porphyrin core and the pyridyl groups, and the dodecyloxy groups, which offer the advantage of high solubility in a variety of organic solvents of different polarities and could prevent porphyrin aggregation, renders porphyrins <b>1PV-Por</b> and <b>1PV-Zn-Por</b> very promising sensitizers for dye-sensitized solar cells (DSSCs). Photophysical measurements, together with electrochemistry experiments and density functional theory calculations, suggest that both porphyrins have frontier molecular orbital energy levels that favor electron injection and dye regeneration in DSSCs. Solar cells sensitized by <b>1PV-Por</b> and <b>1PV-Zn-Por</b> were fabricated, and it was found that they show power conversion efficiencies (PCEs) of 3.28 and 5.12%, respectively. Photovoltaic measurements (<i>J</i>–<i>V</i> curves) together with incident photon-to-electron conversion efficiency spectra of the two cells reveal that the higher PCE value of the DSSC based on <b>1PV-Zn-Por</b> is ascribed to higher short-circuit current (<i>J</i>_sc), open-circuit voltage (<i>V</i>_oc), and dye loading values. Emission spectra and electrochemistry experiments suggest a greater driving force for injection of the photogenerated electrons into the TiO₂ conduction band for <b>1PV-Zn-Por</b> rather than its free-base analogue. Furthermore, electrochemical impedance spectroscopy measurements prove that the utilization of <b>1PV-Zn-Por</b> as a sensitizer offers a high charge recombination resistance and, therefore, leads to a longer electron lifetime