Synthesis, electrochemical and photophysical properties of phthalocyaninato oxotitanium(iv) complexes tetra-substituted at the α and β positions with arylthio groups

Abstract

The synthesis, electrochemical and photophysical properties of the following tetra-substituted thiol oxotitanium phthalocyanines are reported for the first time: 1,(4)-(tetraphenylthiophthalocyaninato)titanium(IV)oxide (5a); 1,(4)-(tetrabenzylthiophthalocyaninato)titanium(IV)oxide (5b); 2,(3)-(tetraphenylthiophthalocyaninato)titanium(IV)oxide (6a) and 2,(3)-(benzylthiophthalocyaninato)titanium(IV)oxide (6b). Cyclic voltammograms of all four complexes are similar, with three reversible reduction couples each involving a one electron transfer process. The first two reductions were confirmed by spectroelectrochemistry to be metal-based reductions due to Ti^IVPc⁻²/Ti^IIIPc⁻² and Ti^IIIPc⁻²/Ti^IIPc⁻² redox processes, while the last reduction was confirmed to be a ring-based reduction due to Ti^IIPc⁻²/Ti^IIPc⁻³. Low fluorescence quantum yields (0.05–0.14), relatively long triplet lifetimes (150–210 µs) and triplet yields (0.31 to 0.82) were observed.