Soluble axially substituted phthalocyanines: Synthesis and nonlinear optical response

This review lays special stress on describing the synthesis of soluble axially substituted or bridged indium, gallium and titanium phthalocyanine complexes and their electronic absorption characteristics, photophysical and nonlinear optical properties. The enhanced solubility of the axially substituted or bridged phthalocyanine monomers and dimers, compared to the chloro analogues, shows that the usual tendency of phthalocyanines to form aggregates can be effectively suppressed by axial substitution. Axial substitution in phthalocyanine complexes has provoked relevant changes on the electronic structure of the molecule by altering the π-electronic distribution due to the dipole moment of the central metal-axial ligand bond. The nanosecond nonlinear absorption and the optical limiting of indium, gallium and titanium phthalocyanines seem to be dominated by a strong triplet state absorption in the optical region comprised between the Q- and B-bands in their UV/Vis absorption spectra.