Synthesis and electrochemical properties of purple manganese(III) and red titanium(IV) phthalocyanine complexes octa-substituted at non-peripheral positions with pentylthio groups

The synthesis and electrochemical characterisation of octapentylthiophthalocyaninato manganese(Ill) acetate (4) and octapentylthiophthalocyaninato titanium(IV) oxide (5) complexes are reported. The complexes have an unusual purple (4) and red (5) colouration since the Q-band is shifted to the near infra red region with Q-band maxima at 893 nm and 808 nm in dichloromethane for 4 and 5, respectively. The structures of the complexes were confirmed by elemental analysis and interpretation of their spectroscopic data, including 2D NMR. The cyclic voltammetry (CV) of the Mn complex (4) showed four quasi reversible couples. The reduction processes are attributed to (MnPC-2)-P-III/(MnPc-2)-Pc-II and (MnPc-2)-Pc-II/(MnPc-3)-Pc-II and the oxidation processes to (MnPc-2)-Pc-IV/(MnPc-2)-Pc-III and (MnPc-1)-Pc-IV/ (MnPc-2)-Pc-IV. The processes were confirmed by spectroelectrochemistry. A well-defined spectrum of the rare (MnPc-2)-Pc-IV species is reported. The CV of the Ti complex (5) showed two well-resolved reduction processes due to (TiPc-2)-Pc-IV/(TiPc-2)-Pc-III and (TiPc-2)-Pc-III/(TiPc-2)-Pc-II. However, oxidation processes of the complex revealed adsorption behaviour and resulted in decomposition on electrolysis using spectroelectrochemistry. (c) 2007 Elsevier Ltd. All rights reserved.