Singlet oxygen generation of subphthalocyanine-fused dimer and trimer

Abstract

Subphthalocyanine (SubPc) macrocycles are known as an interesting class of nonplanar aromatic dyes. Despite documented high fluorescence and singlet oxygen quantum yields, the properties of SubPcs in photodynamic therapy (PDT) are underestimated, because their absorption bands do not reach a significant wavelength range. With this in mind, we combined a SubPc ring and a SubPc ring by introducing a common benzene ring and obtained a SubPc dimer (2) and trimer (3) with the Q-band at the near-IR region, owing to the expansion of the [Formula: see text] electron conjugated system. In this study, we reported 1O2 generation abilities of 2 and 3based on the applied absolute singlet oxygen quantum yields ([Formula: see text]absolute). Subsequent research revealed that 2 and 3 showed the potential to generate 1O2 to not only in toluene but also in DMSO. Although the photocytotoxicity of 2 and 3 were investigated upon photo-irradiation with a low light dose of approximately 1.5 J/cm2, 2 and 3 showed almost negligible toxic properties toward HEp2 cells.

Recent advances in subphthalocyanines and related subporphyrinoids

“…Very few other peripheral substituents such as halogens, thioether, and phenoxy groups have been incorporated into fused SubPc dimers, all of them with lower yields. 187,[267][268][269][270] The synthetic methods, summarized in Table 2, are very similar, only differing in the excess of phthalonitrile acting as peripheral unit employed, and the addition or not of o-DCB as reaction co-solvent. Most probably, either the lack of stability and/or solubility of the intermediates or final products might be the reason for the remarkable different yields, which are also summarized in Table 2.…”

“…Peripheral functionalization with aryl and vinylene moieties has been achieved by modification of preformed SubPzs through Pd catalyzed, CuTC mediated cross-coupling reactions of hexasulfanylated SubPzs with a variety of arylboronic 512,518 or vinylboronic 512 acids, respectively (Scheme 20). This strategy has allowed to introduce functional groups of different nature attached to the SubPz periphery through arylene (255)(256)(257)(258)(259)(260)(261)(262)(263)(264)(265)(266)(267) or vinylene (268)(269)(270) linkers. The resulting extended p-systems showed strong electronic communication between the macrocycles and the terminal functional groups, this serving to modulate in depth the electronic character of the macrocycles.…”