The effect of the number of carbohydrate moieties on the azaphthalocyanine properties

Abstract

A series of azaphthalocyanines (AzaPc) bearing one, two, four or eight isopropylidene-protected galactosyl units was prepared by azide–alkyne click reaction or by classical Pc template cyclotetramerization of the corresponding dicyanopyrazine and AzaPc properties important for photodynamic therapy were compared. All compounds absorbed at long wavelengths (above 650 nm) and belonged to strong singlet oxygen producers (Φ_Δ = 0.58–0.64) retaining significant fluorescence emission (Φ_F = 0.026–0.23). The only exception was the compound with four isopropyliden-protected galactosyl units where partial aggregation was observed. Removal of protecting groups increased the polar character of all AzaPc. However, only AzaPc bearing eight galactoses was found to be water-soluble (105 mg mL⁻¹) but noticeably aggregated in water as well as in organic solvents (DMF, DMSO). Amphiphilic AzaPc bearing one deprotected galactose was incorporated into the lipidic bilayer of liposomes in a nonaggregated form. Liposomes may therefore be a suitable delivery system for this amphiphilic photosensitizer.