Quenching of singlet oxygen (1Δg) by cobalt complexes with four nitrogen atoms in the equatorial plane

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Abstract

The quenching of singlet oxygen (1Δg) by cobalt(III)-bis-1,2-benzosemiquinone-diiminato complexes (general structure LCo(111)(BQDI)2ClO4) has been studied in different solvents by measuring the singlet oxygen phosphorescence decay in time-resolved experiments. The axial ligand (Ph3As, Ph3Sb, N-methyl-imidazole, pyrrolidine) has practically no influence on the quenching; however, the chlorinated benzosemiquinone-diiminato complex has a markedly lower quenching rate constant. The solvent effects can be fully explained by the difference in viscosity, which supports the assumption that the quenching is diffusion controlled. The reactive radius of the encounter pair has been estimated to be 0.3 nm, shorter than the radius of the complex itself, which points to the fact that singlet oxygen must approach the central cobalt atom at the (partially) open axial position. The significance of these results regarding the quenching of singlet oxygen by vitamin B12 derivatives is discussed.

Original languageEnglish
Pages (from-to)143-148
Number of pages6
JournalJournal of Photochemistry and Photobiology B: Biology
Volume58
Issue number2-3
DOIs
Publication statusPublished - Dec 1 2000

Keywords

  • Cobalt complexes
  • Diffusion controlled reaction
  • Quenching
  • Singlet oxygen

ASJC Scopus subject areas

  • Radiation
  • Radiological and Ultrasound Technology
  • Biophysics
  • Radiology Nuclear Medicine and imaging

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