Tetraquinoxalinoporphyrazine-π-extended NIR-absorbing photosensitizer with improved photostability

A novel ionogenic water-soluble zinc complex with n-extended ligand - tetraquinoxalinoporphyrazine bearing eight benzoate groups - ZnQPz(COONa)8 was synthesized by template condensation of a new building block, dipentyl 4,4'-(6,7-dicyanoquinoxalin-2,3-diyl)dibenzoate followed by alkaline hydrolysis of ester groups. The photophysical properties of the complex were studied and a significant bathochromic shift of the Q-band by 100 nm was observed as compared to conventional phthalocyanine complexes. However, in contrast to other NIR-absorbing n-extended derivatives with similar optical properties, ZnQPz(COONa)8 showed a high degree of photostability - its photobleaching rate in DMSO was about 3 times lower than that of the zinc tetra-15-crown-5-naphthalocyanate Zn[(15C5)4Nc]. The improved photostability together with the ability to generate singlet oxygen (CYRILLIC CAPITAL LETTER EF Delta = 0.65 in aqueous DMSO) and absorb light in the near infrared region makes quinoxaline-porphyrazine a good candidate for use in photodynamic therapy.

Automated summary

A novel ionogenic water-soluble zinc complex, ZnQPz(COONa)8, was synthesized by template condensation and alkaline hydrolysis. It exhibited a significant bathochromic shift and higher photostability compared to similar NIR-absorbing derivatives, making it a promising candidate for photodynamic therapy.