Synthesis of a tricationic subphthalocyanine with potential use in photoinactivation of bacteria

A novel chloro[2,9,16(2,9,17)-trikis-4-(N-methylpyridyloxy)]subphthalocyaninnato boron(III) iodide (SubOPc³⁺) has been synthesized by boron trichloride-induced cyclotrimerization of 4-(4-pyridyloxy)phthalonitrile in 1-chloronaphthalene. This approach produced a regioisomers mixture of chloro[2,9,16(2,9,17)-trikis-4-(pyridyloxy)]subphthalocyaninnato boron(III) (SubOPc) with 19% yield. Exhaustive methylation of SubOPc with methyl iodide yielded 92% of tricationic SubOPc³⁺. The spectroscopic and photodynamic properties of the SubOPc³⁺ were compared with its homologous non-charged SubOPc and with subphthalocyanine (SubPc). The cationic SubOPc³⁺ is essentially aggregated in solution of different solvents and it is partially dissolved as monomer in N,N-dimethylformamide (DMF)/water (10% v/v)/HCl (1.2 mM). The singlet molecular oxygen, O₂(¹Δ_g), production was evaluated using 9,10-dimethylanthracene (DMA). The photodynamic effect was strongly dependent of the medium, diminishing where the sensitizer is aggregated but it increases in an appropriated surrounding microenvironment. The studies show that SubOPc³⁺ can be an interesting agent with potential applications in photodynamic inactivation of bacteria.