New highly soluble phenoxy-substituted phthalocyanine and azaphthalocyanine derivatives: Synthesis, photochemical and photophysical studies and atypical aggregation behavior

A series of zinc phthalocyanines and corresponding aza-analogues azaphthalocyanines substituted with peripheral 2,6-diisopropylphenoxy substituents containing different functional groups (Br, OCH ₃, and OH) were synthesized and their photophysical properties were investigated. UV-vis and ¹H NMR analyses confirmed the non-aggregation behavior of the prepared complexes in most organic solvents. All investigated compounds showed good photophysical and photochemical properties in THF and DMF with Φ _F values in the range of 0.22-0.44 and Φ _Δ values ranging between 0.42 and 0.57. Hydroxylated compounds showed good solubility in polar solvents including ethanol, methanol, acetone and even in aqueous ethanol mixtures. Absorption spectra in aqueous ethanol indicated presence of only monomers even at very low ethanol content in water (0.5% of ethanol in water). Despite this, no fluorescence occurred from approximately 50% of ethanol in water suggesting presence of aggregates that do not differ from monomers in a shape of absorption spectra.