Photo-excitation energy transfer between a titanium(IV)-porphyrin complex and oxygen molecule

Takatoshi Matsumoto, Kiyoko Takamura

Research output: Contribution to journalArticlepeer-review

6 Citations (Scopus)

Abstract

The Ti-TPyP reagent, i.e. an acidic aqueous solution of oxo[5,10,15,20-tetra(4-pyridyl)-porphyrinato]titanium(iv) complex, denoted as TiO(tpyp), was developed as a highly sensitive and specific reagent for detecting hydrogen peroxide. In our previous paper, the photosensitizing effect of the TiO(tpyp) complex on the detection of hydrogen peroxide using this reagent was explored based on the experimental findings. In the present paper, computational analysis was carried out for the molecular level elucidation of the energy transfer mechanism between the photo-excited TiO(tpyp) complex and triplet oxygen to form singlet oxygen under aqueous acidic conditions. The protonated form of the TiO(tpyp) complex, i.e. [TiO(tpypH4)] 4+ complex, was found to be the entity responsible for the energy transfer to triplet oxygen. The interaction sites between the [TiO(tpypH 4)]4+ complex with triplet oxygen were then discussed based on their molecular orbital characteristics and the potential energy changes accompanying the approach of triplet oxygen molecule Σ3O2 to the [TiO(tpypH4)]4+ complex. The obtained results show that the C-N portion of the porphyrin ring plays a predominant role in the energy transfer from the photo-excited porphyrin to Σ3O2. Σ3O2 is then converted to Δ1O2 through Σ1O 2. The Δ1O2 molecule reaches its stable state at the distance of 3.21 Å from the C-N portion of the porphyrin ring with its stabilization energy of 0.99 kcal mol-1. The stabilization energy for the Δ1O2 molecule thus formed is small, implying no stable bond formation between the Δ1O2 molecule and the [TiO(tpypH4)]4+ complex and that it moves away from the C-N portion immediately after the energy transfer from the photo-excited porphyrin.

Original languageEnglish
Pages (from-to)4289-4294
Number of pages6
JournalAnalytical Methods
Volume4
Issue number12
DOIs
Publication statusPublished - 2012 Dec 1

ASJC Scopus subject areas

  • Analytical Chemistry
  • Chemical Engineering(all)
  • Engineering(all)

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