Molecular Dyads and Triads Based on Phenothiazine and π-extended Tetrathiafulvalene Donors, Ruthenium(II) Bisterpyridine Complexes and Polyoxometalates

Molecular dyads were prepared by the functionalization of organic electron donor units, i.e., a phenothiazine (PTZ) moiety and a π-extended tetrathiafulvalene (exTTF) moiety with Ru(II) bisterpyridine complexes. In addition, the complexes were equipped with a terminal alkyne group, which was used for the coupling with a Keggin-type polyoxometalate (POM). In this regard, molecular triads were prepared whereby the central Ru(II) complex should act as photosensitizer and the POM as electron acceptor. Certain spectral changes were observed upon attachment of the donors and the POM framework to the Ru(II) complexes. In particular, the emission of the Ru(II) complex became reduced significantly with increasing donor strength, which suggested an intramolecular electron transfer via reductive emission quenching. The introduction of the POM framework revealed no further quenching of the emission and is tentatively ascribed to minor influence of the electron acceptor on the excited states of the Ru(II) complex.

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