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Effects of the Peripheral Substituents, Central Metal, and Solvent on the Photochemical and Photophysical Properties of 5,15-Diazaporphyrins.

Satoshi OmomoRyosuke FukudaTomoaki MiuraTatsuya MurakamiTadaaki IkomaYoshihiro Matano
Published in: ChemPlusChem (2019)
Metal complexes of 3,7,13,17-tetrakis(di(4-carboxyphenyl)amino)-5,15-diazaporphyrin (MDAP-COOH; M=Pd, Cu) and their ethyl ester precursors (MDAP-COOEt; M=Pd, Cu) have been synthesized for use as near-infrared (NIR)-light-responsive photosensitizers. Under irradiation with visible or NIR light, PdDAP-COOEt in toluene generated singlet oxygen (1 O2 ) with an excellent quantum yield (ΦΔ =0.99), whereas CuDAP-COOEt exhibited a lower efficiency (ΦΔ =0.21). The water-soluble PdII complex PdDAP-COOH also behaved as a photosensitizer (ΦΔ =0.20) in a micellar solution. The photophysical properties of these dyes were measured by transient absorption techniques. It was found that the efficiency of the energy transfer from the triplet state of MDAP-COOR (R=Et, H) to the ground state of dioxygen was highly dependent on the peripheral substituents, the central metal, and the solvent. Furthermore, the phototoxicity of PdDAP-COOH toward HeLa cells under irradiation of NIR light (720 nm) was evaluated. As expected, PdDAP-COOH exhibited good photodynamic activity, and control experiments confirmed that 1 O2 was generated as the active oxygen species.
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