Comparison of aggregation properties and photodynamic activity of phthalocyanines and azaphthalocyanines

Phthalocyanines (Pc) and their aza-analogues azaphthalocyanines (AzaPc) (tetrapyrazinoporphyrazines) with eight n-octylsulfanyl or tert-butylsulfanyl peripheral substituents and different central metals (Mg, Zn, metal-free) were synthesized. Dimerization constants Kd and absorption spectra of pure monomeric and dimeric magnesium complexes in toluene were calculated using series of absorbances at different concentrations. The bulky tert-butylsulfanyl substituents were found to be much better inhibitors of aggregation than long alkyl chains. Also Pc are less aggregated in organic solvents then AzaPc, short explanation is given. Singlet oxygen production of Pc and AzaPc was compared using dye-sensitized photooxidation of 1,3-diphenylisobenzofuran in pyridine. Both Pc and AzaPc showed similar activity not dependent on type of peripheral substitution. Zinc complexes of both Pc and AzaPc exceeded the magnesium ones and metal-free dyes in singlet oxygen production approximately twice.