Madoka Yasuike

REINVESTIGATION OF SYNTHETIC METHODS FOR ZINC MESO-TETRAPHENYLTETRABENZOPORPHYRIN

Abstract The reaction of 3-benzylidenephthalimidine (3-BPI) with zinc acetate for the preparation of the meso- tetraphenyltetrabenzoporphyrin zinc complex (ZnP4TBP) is reinvestigated. From the structural analyses of the reaction product with ultraviolet-visible absorption spectra, field desorption mass spectra (FDMS) and 1H NMR spectra, it is shown that this reaction procedure gives a complicated mixture of ZnTBP derivatives with meso-phenyl substituent(s) the number of which is from one to four. The product obtained by the reaction of isoindole with benzaldehyde in the presence of zinc acetate is also discussed.

Formation of tetrabenzoporphine skeleton by the reactions of phthalimide with zinc carbonates

Abstract The high temperature reactions of phthalimide potassium salt (PIK) with various zinc carbonates were carried out. The reaction of PIK with zinc acetate yielded tetrabenzoporphinato zinc (ZnTBP). Tetratert-butyltetrabenzoporphinato zinc (ZntBu 4 TBP), whose four tert-butyl substituents were positioned on the TBP periphery, was also prepared in a similar way using the 4-tert-butylphthalimide potassium salt (4-tBuPIK). These results were explained on the basis of the function of zinc acetate as the meso -methine carbon source of the TBP structure. The use of zinc phenylacetate instead of zinc acetate in the reaction of PIK led to the production of meso -phenyl substituted ZnTBPs, although they were different in the number of meso -phenyl substituent(s). The attempt to introduce alkyl residues at the meso -position(s) by the reaction of PIK in the presence of zinc alkylacetate having a long alkyl chain was not successful, except for the substitution of the methyl group using zinc propionate.

Singlet oxygen generation by tetrabenzoporphyrins as photosensitizer

Abstract The efficiency of the photosensitized generation of singlet oxygen ( 1 O 2 ) with meso -phenyl substituted tetrabenzoporphyrin metallo complexes as sensitizer was determined from the limiting quantum yield of the (+)-limonene photooxygenation and compared with that of hematoporphyrin (HP), which has been known to serve as an effective sensitizer, using a HeNe laser light (633 mm). Among the diamagnetic (Mg, Zn, and Cd) complexes treated here, the Zn complexes were most efficient for the (+)-limonene photooxygenation with the limiting quantum yields of Φ(−A)=0.4. This result was comparable to that of HP. The direct observation of the intensity of 1 O 2 emission by the laser flash photolysis technique supported these results.

Optical and redox properties of meso-diphenyltetrabenzoporphyrins

Abstract The meso -diphenyltetrabenzoporphyrin zinc complex ( 1b , ZnP 2 TBP) having two phenyl substituents at the neighboring meso -positions was isolated by the careful purification of the reaction product of 3-benzylidenephthalimidine (3-BPI) with zinc acetate. The treatment of 1b with trifluoroacetic acid led to the successful demetalation-of 1b to its metal free compound ( 1 e, H 2 P 2 TBP). Hence, the other divalent metallic complexes such as magnesium ( 1a ), cadmium ( 1c ) and palladium ( 1d ) were readily prepared by metal insertion into 1e with the appropriate metal sources. The well-defined structural elucidation of these meso -diphenyltetrabenzoporphyrins (P 2 TBP) has enabled us to determine their electrochemical and optical properties. Among the metallo P 2 TBPs discussed here, the Mg complex possesses both the lowest oxidation and reduction potentials whilst the Pd complex has the highest oxidation and reduction potentials. This result was explained on the basis of the induction effect on the porphyrin ring current by the central metal ion. The absorption maxima of these metallo P 2 TBPs were also affected by the central metal ions. Since these TBPs reasonably fluoresce at room temperature and phosphoresce at 77 K as in the case of the corresponding metallotetraphenylporphyrins (TPP), their excited state energies were measurable. Their fluorescence quantum yields (φ f ) and lifetimes (τ f ) obeyed the heavy atom effect by the central metal ions. Finally, we also discussed their redox properties in the excited stares.

Triplet state electron transfer pathway for tetrabenzoporphyrin-diphenyliodonium salt photoinitiator system

Abstract A triplet state electron transfer mechanism for the photoreaction between meso -diphenyl-tetrabenzoporphyrin (P 2 TBP) metallo complexes, e.g. magnesium (1a, MgP 2 TBP), zinc (1b, ZnP 2 TBP) and cadmium (1c, CdP 2 TBP), and diphenyliodonium (DPI) salt was confirmed by the detection of the cation radicals of P 2 TBP using nanosecond laser flash photolysis equipment, as expected from the estimation of the free energy changes (ΔG T ). Rate constants ( T k q ) of the triplet state quenching of metallo P 2 TBP complexes by DPI, determined from the slopes of Stern-Volmer plots, approximately obeyed a diffusion-controlled limit in accordance with fully exothermic ΔG T values. Since the fluorescence of the magnesium and zinc complexes was quenched by DPI at high concentrations (above 10 −3 M), as previously reported, both excited states were deactivated by the onium salt, depending on its concentration. However, it was presumed that a triplet state electron transfer pathway was preferred for the cadmium complex because of its short fluorescence lifetime.

Oxidative fluorescence quenching of meso-diphenyltetrabenzoporphyrins with onium salts

Abstract The fluorescence quenching of either meso -diphenyltetrabenzoporphyrin zinc or magnesium complexes, ZnP 2 TBP and MgP 2 TBP. respectively, by onium salts has been studied in acetonitrile. The dependence of the fluorescence quenching rate constants, k q , on the free energy change, δ G , indicates that the photosensitization between these substances primarily takes place based on the photoinduced electron transfer from the singlet excited TBP molecule to the quencher.

The ′onium butyltriphenylborates as noveldonor–acceptor initiators for free radicalphotopolymerization

Novel donor-acceptor initiators, ′onium butyltriphenylborates, containing both an ′onium cation (electron-accepting radical generator) and a butyltriphenylborate anion (electron-donating radical generator) within the same molecule, are synthesized and investigated for the photopolymerization of an acrylic monomer mixture.