Effect of quaternary ammonium salts on spectral properties of zinc octacarboxyphthalocyanine

The paper presents results of the research on the influence of quaternary ammonium salts on UV–vis absorption and emission spectra of zinc octacarboxyphthalocyanine (ZnPcOC). Quaternary ammonium salts which show biological activity play a crucial role. In ZnPcOC solutions with a proper concentration of tetrabutylammonium salts (TBAX), a strong bathochromic shift band (λmax = 760 nm – “R” band) showing red fluorescence appears in time. The presence of tetrabutylammonium salt causes pH increase and, consequently, a gradual dissociation of carboxyl groups in ZnPcOC molecule. It seems that –COO— anions present in the ZnPcOC complex can interact with tetraalkylammonium cations, causing a decrease in symmetry in ZnPcOC complex. As a result, the “R”- band appears in the UV–vis spectrum of ZnPcOC. •The influence of quaternary ammonium salts on spectral properties of zinc octacarboxyphthalocyanine was studied.•In UV–vis absorption spectra of ZnPcOC(aq) occur a strong bathochromic shift band, called the “R” band.•The R band is stable over time and shows red fluorescence.