Synthesis and Electrochemical and Photophysical Properties of Calixarene-Based Ruthenium(II) Complexes as Potential Multivalent Photoreagents

Abstract

The grafting of photoreactive and photooxidizing Ru^II(TAP) (TAP = 1,4,5,8-tetraazaphenanthrene) complexes on calix­[4 or 6]­arene molecular platforms is reported. Thus, either [Ru­(TAP)₂(phen)]²⁺ (phen = 1,10-phenanthroline) or [Ru­(TAP)₂(pytz)]²⁺ [pytz = 2-(1,2,3-triazol-4-yl)­pyridine] complexes are anchored to the calixarenes. The data in electrochemistry, combined with those in emission under steady state and pulsed illumination and the determination of the associated photophysical rate constants, indicate the presence of intramolecular luminescence quenching by the phenol moieties of calixarene. From transient absorption studies under pulsed laser irradiation, it is concluded that the quenching originates from a par proton-coupled electron transfer (PCET) process. Such an intramolecular quenching is absent when the phenol groups of the calixarene platform are derivatized by azido arms