Département de chimie moléculaire

Keggin and Dawson-type polyoxometalates (POMs) decorated by organometallic [cyclometalated ruthenium(II) polypyridine complex] or org. (pyrene) chromophores were prepd. by postfunctionalization of hybrid disilylated POM platforms. The connection is made in a very efficient and modular way via Sonogashira coupling reactions, which provide a rigid linkage between the POM and the photoactive centers. Electronic properties have been inferred from electrochem. and photophys. studies and reflect poor electronic interactions between both partners. The presence of the POM leads to luminescence quenching of the chromophores, which was attributed to an intramol. electron transfer from the chromophore to the POM. The rate of this process is much faster in the POM-pyrene than in the POM-Ru system. It depends on the driving force dictated by the redox potentials of both partners but also in the case of the POM-Ru system on the presence of the metallacycle, which acts as a mol. dielecs. and delays the intramol. electron transfer. In the POM-Ru system, a comparative study of the luminescence quenching showed that the electron transfer is still more important in the covalently bonded hybrids than in systems where the POM and the ruthenium complexes are assembled via electrostatic interactions. [on SciFinder(R)]