New designed naphthalimide-phthalocyanine pentads: Synthesis, photophysical and photochemical properties in DMSO and room temperature ionic liquids

[Display omitted] •First example of naphthalimide-phthalocyanine pentad was reported.•Zn(II) and Ga(III) were selected as central metal for high singlet oxygen generation.•Their absorption and fluorescence properties were investigated in DMSO and RTILs.•Singlet oxygen lifetime and quantum yields of the pendants were calculated. The synthesis and photoproperties of two novel multichromophoric compounds were unveiled. Their molecular design consisted of a phthalocyanine core bearing either Zn(II) or Ga(III) metal ions in the cavity and four naphthalimide chromophores in the periphery. Ground state absorption, fluorescence emission, fluorescence lifetime, fluorescence quantum yield and singlet oxygen generation properties of Zn(II) (1) and Ga(III) (2) pentads were investigated in DMSO and room temperature ionic liquids (RTILs) as well. 1 was aggregated in RTILs, however 2 exhibited monomeric and photostable behavior in 1-ethyl-3-methylimidazolium hexafluorophosphate. The singlet oxygen quantum yields were determined as 0.75 for 1 and 0.72 for 2 in DMSO, which were remarkably high compared to unsubstituted Zn(II) and Ga(III) phthalocyanines (0.67 and 0.41 in DMSO, respectively). In addition, their photostability were excellent; even they were more photostable than reference molecules. The observed attractive photophysical and photochemical properties of these novel pentads qualify them as promising photosensitizers for photodynamic therapy.