Bis(porphyrin)-anthraquinone triads: synthesis, spectroscopy, and photochemistry

J Phys Chem A. 2013 Apr 11;117(14):2944-51. doi: 10.1021/jp312134a. Epub 2013 Apr 3.

Abstract

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, (1)H 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 (kET) of these triads are found in the range 1.0 × 10(8) to 7.7 × 10(9) s(-1) and are found to be solvent dependent.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Anthraquinones / chemical synthesis
  • Anthraquinones / chemistry*
  • Anthraquinones / radiation effects
  • Electrochemistry
  • Magnetic Resonance Spectroscopy
  • Models, Molecular
  • Photochemistry*
  • Porphyrins / chemical synthesis
  • Porphyrins / chemistry*
  • Porphyrins / radiation effects
  • Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization

Substances

  • Anthraquinones
  • Porphyrins