Synthesis and photophysical properties of phthalocyanines having calixpyrrole units

Abstract

Zn²⁺ and Co²⁺ metallated phthalocyanines having four calixpyrrole units have been prepared from a calixpyrrole phthalonitrile using Zn²⁺ or Co²⁺ salts as templates of a phthalocyanine macrocycle. Host–guest complexes between the anions (Cl⁻, F⁻ and H₂PO₄⁻) and the calixpyrrole units are formed as evidenced by NMR, the shift in the reduction potential of the calixpyrrole units by cyclic voltammetry and by observation of two straight lines in the plot of the conductivity versus the amount of halide. While halides do not form complexes with Zn²⁺ or Co²⁺ ions of the phthalocyanine core in the ground state as evidenced by the lack of variation in the position of the Q-band in optical spectroscopy, upon 355 nm excitation, the apical metal–halide complex should be formed as a transient as evidenced by the comparison of the transient absorption spectra in the presence and absence of halides.