Interaction of multiporphyrin systems with molecular oxygen in liquid solutions: Extra-ligation and screening effects

  • Sagun E
  • Zenkevich E
  • Knyukshto V
 et al. 
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Abstract

Steady-state and time-resolved studies indicate that for a sequence of porphyrin or chlorin chemical dimers Zncyclodimer → (ZnOEP)2Ph → (ZnOEP)2→ (ZnHTPP)2→ (ZnOEChl)2with relative lowering of excited S1- and T1states, the extra-ligation by pyridine (PYR) does not influence essentially on fluorescence parameters but leads to an increase of T1-states non-radiative decay (the most pronounced for dimers with higher lying T1-levels). For pyridinated dimers at 293 K T1-states quenching by molecular oxygen depends on the spacer flexibility and donor-acceptor interactions with PYR. In self-assembled triads and pentads energy and electron transfer (within a few ps) takes place from Zn-dimers to pyridyl substituted porphyrin extra-ligand, H2P, followed by the effective population of H2P T1-state. For these systems, bimolecular constants of H2P T1-states quenching by O2decrease by 1.4-1.8 times with respect to those found for individual monomeric porphyrins. This effect is explained by the screening action of a strongly quenched Zn-porphyrin dimer subunit limiting the access of oxygen molecule to the excited extra-ligand. © 2002 Elsevier Science B.V. All rights reserved.

Author-supplied keywords

  • Excited states quenching by molecular oxygen
  • Extra-ligation
  • Pentads
  • Porphyrin and chlorin dimers
  • Screening
  • Triads

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Authors

  • Eugenii I. Sagun

  • Valentin N. Knyukshto

  • Alexander M. Shulga

  • Dzmitry A. Starukhin

  • Christian Von Borczyskowski

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