Synthesis, electrochemical and spectroelectrochemical properties of novel phthalocyanine complexes of manganese, titanium and indium

Abstract

The new tetra peripheral 3,5-bis(trifluoromethyl)phenylethynyl substituted metallophthalocyanines (MPc) have been synthesized and their aggregative properties were investigated in different concentrations. Voltammetric and in situ spectroelectrochemical characterization of MPcs bearing metal centers with higher oxidation states In-III, Mn-III, and Ti-IV were performed in solution. While (InClPc)-Cl-III gave only Pc ring based reduction process, (MnClPc)-Cl-III and (TiOPc)-O-IV showed metal based reduction reactions in addition to Pc-based redox processes. The presence of redox active metal centers like (MnCl)-Cl-III and (TiO)-O-IV in the core of Pc ring increases the electrochemical activity of the complexes. The redox responses of the complexes confirmed the submitted structure of the complexes. During the electrochemical measurements, it was noticed that the presence of molecular oxygen in the electrolyte system considerably influenced the redox responses of the complexes due to the interaction of MPcs with O-2, which indicated the electrocatalytic and/or electrochemical sensing activities of the complexes for O-2 sensing. Electrocatalytic oxygen reduction and oxygen sensing measurements were performed in solution and in solid states as Langmuir-Blodgett multilayer thin films. While (InClPc)-Cl-III did not give any voltammetric signal for the interaction with molecular oxygen, square wave voltammetric (SWV) responses of (MnClPc)-Cl-III and (TiOPc)-O-IV show electrocatalytic activities of the complexes for oxygen reduction reactions (ORR). Moreover, interaction of O-2 with these complexes gave extraordinary anodic SWV signals in both of aprotic and protic solvents, which indicate possible usage of the complexes as molecular oxygen sensor. (C) 2014 Elsevier Ltd. All rights reserved.