Bis(porphyrin)–Anthraquinone Triads: Synthesis, Spectroscopy, and Photochemistry

Molecular triads based on bis­(porphyrin)–anthraquinone having azomethine bridge at the pyrrole-β position have been designed and synthesized. Both free-base AQ-(H₂)₂ and zinc AQ-(Zn)₂ triads are characterized by elemental analysis, MALDI-MS, ¹H NMR, UV–visible, and fluorescence spectroscopy (steady-state and time-resolved) as well as electrochemical method. The absorption spectra of both Soret and Q-bands of the triads are red-shifted by 12–20 nm with respect to their monomer units. The study supported by theoretical calculations manifests that there exists a negligible electronic communication in the ground state between the donor porphyrin and acceptor anthraquinone of these triads. However, interestingly, both the triads exhibit significant fluorescence emission quenching (51–92%) of the porphyrin emission compared to their monomeric units. The emission quenching is attributed to the excited-state intramolecular photoinduced electron transfer from porphyrins to anthraquinone. The electron-transfer rates (<i>k</i>_ET) of these triads are found in the range 1.0 × 10⁸ to 7.7 × 10⁹ s^–1 and are found to be solvent dependent

Ethynyl thiophene-appended unsymmetrical zinc porphyrin sensitizers for dye-sensitized solar cells

Four unsymmetrical porphyrins of A2B donor–π–acceptor type have been designed, synthesized, characterized and their photovoltaic properties explored. Polycyclic aromatic hydrocarbons (PAH), such as pyrene or fluorene, act as a donor, the porphyrin is the π-spacer, appended with an ethynyl thiophene linker, and either cyanoacrylic acid or malonic acid acts as the acceptor. All of the compounds were characterized by 1H NMR and mass spectrometry. UV-Vis absorption spectra and B or Soret (λex at 440 nm for the four sensitizers reported) band-excited fluorescence emission spectra were also obtained. The electrochemical properties suggest that the first oxidation is ring-centred, which is supported by in situ spectro-electrochemical and DFT computational studies. The synthesized porphyrins were applied in dye-sensitized solar cells (DSSCs). A conversion efficiency of up to 3.14%was realized for PYR–Por–MA under our experimental conditions

Ethynyl thiophene-appended unsymmetrical zinc porphyrin sensitizers for dye-sensitized solar cells

Four unsymmetrical porphyrins of A2B donor–π–acceptor type have been designed, synthesized, characterized and their photovoltaic properties explored. Polycyclic aromatic hydrocarbons (PAH), such as pyrene or fluorene, act as a donor, the porphyrin is the π-spacer, appended with an ethynyl thiophene linker, and either cyanoacrylic acid or malonic acid acts as the acceptor. All of the compounds were characterized by 1H NMR and mass spectrometry. UV-Vis absorption spectra and B or Soret (λex at 440 nm for the four sensitizers reported) band-excited fluorescence emission spectra were also obtained. The electrochemical properties suggest that the first oxidation is ring-centred, which is supported by in situ spectro-electrochemical and DFT computational studies. The synthesized porphyrins were applied in dye-sensitized solar cells (DSSCs). A conversion efficiency of up to 3.14%was realized for PYR–Por–MA under our experimental conditions