O-Alkylation of Dihydroxo(tetraarylporphyrinato)phosphorus(V) and Antimony(V) Complexes with Alkyl Halides

The O-alkylation of dihydroxo(tetraarylporphyrinato)phosphorus(V) complexes with several kinds of alkyl bromide in MeCN in the presence of K2CO3 and 18-crown-6 ether produced dialkoxo(tetraarylporphyrinato)phosphorus(V) complexes in-moderate-good yields. Similar O-alkylation was applied to dihydroxo(tetraarylporphyrinato)antimony(V) complexes. The O-alkylation proceeded by the occurrence of an SN2 attack of the alkoxide anion of the complexes at the carbon substituted with halides

Fluorescence Responses on Ion Recognition with 2-(4-Dialkylaminophenyl)ethoxyantimony(V) Tetraphenylporphyrin

The effects of metal ions on the fluorescence spectra of 2-phenylethoxyhydroxyantimony(V) tetraphenylporphyrin hexa-fluorophosphate (1a–c) involving azacrown ether on axial ligands were investigated. Trivalent metal ions such as Al 3+, In3+, Ga3+, and Lu3+ which undergo the complexation with the azacrown ether remarkably enhanced the fluorescence quantum yields

Water-Solubilization of P(V) and Sb(V) Porphyrins and Their Photobiological Application

Porphyrins have been widely utilized as biochemical and biological functional chromophores which can operate under visible-light irradiation. Water-soluble porphyrins have been used as the drug for photodynamic therapy (PDT) and photodynamic inactivation (PDI). Although usual water-solubilization of porphyrins has been achieved by an introduction of an ionic group such as ammonium, pyridinium, sulfonate, phosphonium, or carboxyl to porphyrin ring, we proposed the preparation of water-soluble P and Sb porphyrins by modification of axial ligands. Alkyl (type A), ethylenedioxy (type E), pyridinium (type P), and glucosyl groups (type G) were introduced to axial ligands of Sb and P porphyrins to achieve water-solubilization of Sb porphyrin and P porphyrins. Here, we review their water-soluble P and Sb porphyrins from the standpoints of preparation, bioaffinity, and photosensitized inactivation

Effects of an Axial Ligand on the Reduction Potential, Proton Dissociation, and Fluorescence Quantum Yield of Hydroxo(porphyrinato)antimony(V) Complexes

The substituent effects on the reduction potentials (E1/2red), the proton dissociation constants of a hydroxo ligand (Ka), and the fluorescence quantum yields (Φ) in aryloxo(hydroxo)tetraarylporphyrinatoantimony(V) complexes were investigated. The E1/2red and Ka values were affected by substituents in the axial aryloxo ligand but, little affected by substituents in the porphyrin ring. Since E1/2red of tetraarylporphyrinatoantimony(V) complexes were higher than those of other metal-porphyrin complexes, it was suggested that the metal orbital greatly contributed to the LUMO level of the complex which can be related to the E1/2red and Ka values. Therefore, the substituent effects of the axial aryloxo ligand on the E1/2red and Ka values were attributed to the electron density of the antimony ion, which affected the LUMO level of the complexes. Moreover, the Φ of the porphyrin moiety depended on both the oxidation potential of the axial aryloxo ligands and the polarity of the solvent used. The fluorescences of the porphyrin moiety were quenched by the axial aryloxo ligands at rate constants of 108 - 1011 s-1

Neighboring Hetero-Atom Assistance of Sacrificial Amines to Hydrogen Evolution Using Pt-Loaded TiO2-Photocatalyst

Photocatalytic H2 evolution was examined using Pt-loaded TiO2-photocatalyst in the presence of amines as sacrificial agents. In the case of amines with all of the carbon attached to the hetero-atom such as 2-aminoethanol, 1,2-diamonoethane, 2-amino-1,3-propanediol, and 3-amino-1,2-propanediol, they were completely decomposed into CO2 and water to quantitatively evolve H2. On the other hand, the amines with both hetero-atoms and one methyl group at the β-positions (neighboring carbons) of amino group such as 2-amino-1-propanol and 1,2-diaminopropane were partially decomposed. Also, the photocatalytic H2 evolution using amines without the hetero-atoms at the β-positions such as ethylamine, propylamine, 1-butylamine, 1,3-diaminopropane, 2-propylamine, and 2-butylamine was inefficient. Thus, it was found that the neighboring hetero-atom strongly assisted the degradation of sacrificial amines. Moreover, rate constants for H2 evolution were compared among amines. In conclusion, the neighboring hetero-atom did not affect the rate constants but enhanced the yield of hydrogen evolution