Solvent effect on the aggregation of amphiphilic phthalocyanines substituted by polyethyleneoxide

Metal-free and copper(II) tetra-β-polyethyleneoxide-substituted phthalocyanine derivatives, TDEO6-MPc, where polyethylene oxide derivative is hexaethyleneglycolmonododecylether (DEO6), were synthesized. Those compounds are soluble in both lipophilic and hydrophilic solvents. By taking advantage of this amphiphilic property, solvent effect on the aggregation of the phthalocyanine was studied by means of UV-vis absorption and fluorescence spectroscopies. Dimerization constants of TDEO6-MPc in non-coordinating solvents were determined by the concentration dependence of absorption spectra. Aggregation is suppressed by the increase in the ET(30) value (acceptor property) of solvents in non-coordinating solvents, whereas it is promoted by the increase in Donor Number (donor property) of solvent in coordinating solvents.