title: Effect of anion ligation on electron transfer of double-linked zinc porphyrin-fullerene dyad.
abstract: The interaction between metalloporphyrins and their axial ligands plays an important role in the electron transfer (ET) processes in which the excited porphyrin participates. An efficient photoinduced ET reaction of a double-linked zinc(II) porphyrin-fullerene dyad was demonstrated in ionic environment. The chloride ion of tetrabutylammonium chloride (TBACl) electrolyte solution ligates the zinc porphyrin moiety in the dyad which results in a red shift of the absorption bands and lowers the energy of the charge-separated state by about 0.26 eV as compared to the nonligated dyad. Excitation of the porphyrin chromophore results in ET from porphyrin to fullerene in a moderately polar solvent, anisole. In nonionic and nonligating ionic environments, the ET reaction occurs through an intermediate state, an intramolecular exciplex, which has emission in the near-infrared region of the spectrum. This emission is not observed directly for the dyad in TBACl/anisole solution, but evidence of the exciplex intermediate was seen in the time-resolved measurements. The lower energy of the charge-separated state in the ligated environment explains the different ET reaction rates determined in the spectroscopic studies: the charge recombination process of the ligated dyad is about 5 times faster than that of the nonligated one.
authors: Department of Chemistry and Bioengineering, Tampere University of Technology, Tampere, Finland. ali.al-subi@tut.fi
authors: Ali H
authors: AH
authors: Al-Subi
authors: Marja
authors: M
authors: Niemi
authors: Nikolai V
authors: NV
authors: Tkachenko
authors: Helge
authors: H
authors: Lemmetyinen
mesh_terms: D000838:Anions / Q000737:chemistry; D004563:Electrochemistry; D004579:Electron Transport; D037741:Fullerenes / Q000737:chemistry*; D008665:Metalloporphyrins / Q000737:chemistry*; D008958:Models, Molecular; D015394:Molecular Structure
chemical_list: D000838:Anions; D037741:Fullerenes; D008665:Metalloporphyrins; C017802:zinc hematoporphyrin