Synthesis, characterization, electrochemistry and spectroelectrochemistry of new non-peripherally substituted lutetium bis phthalocyanines

Abstract

The synthesis, characterization, spectral, and electrochemical properties of bis-(phthalocyanine)lutetium (III) (LuPc2) bearing halogenated (F (F-LuPc2), Cl (Cl-LuPc2) and Br (Br-LuPc2)) phenoxy groups were reported for the first time. To explore the possible application of the LuPc2 complexes, their detailed redox mechanisms were determined by voltammetric and spectroelectrochemical characterizations. One of the Pc rings exhibits radical characteristics as a result of the sandwich structures of the complexes, which led to the typical one electron reduction process between 0.20 and 0.40 V and the typical one electron oxidation process between 0.60 and 0.80 V. In addition to the characteristic [Pc.- Lu3+Pc2- ]/[Pc2- Lu3+Pc2- ]1- reduction and [Pc.- Lu3+Pc2- ]/ [Pc.- Lu3+Pc.- ]1+ oxidation couple of the complexes, further two-electron reduction and oxidation processes were also observed due to the simultaneous electron transfer reactions of each Pc ring at very close potentials. Moreover, at more negative potentials sequential one electron reduction waves for each Pc ring were also observed. While the Cl-LuPc2 reduced at less positive potential and more negative potential, changing Br with Cl and F alters the ease of the electron transfer reactions of the complexes. In situ spectroelectrochemical results supported these voltammetric assignments. Moreover, distinct color changes of LuPc2 in the solution observed with in situ spectroelectrochemical measurements indicated their functionality as electrochromic materials.