DENDRIMERS OF NANOMETER-SIZE BASED ON METAL-COMPLEXES - LUMINESCENT AND REDOX-ACTIVE POLYNUCLEAR METAL-COMPLEXES CONTAINING UP TO 22 METAL CENTERS

Treelike (dendritic) structures made of Ru-II-polypyridine complexes have been prepared by the ''complexes-as-metals and complexes-as-ligands'' synthetic strategy. The key building blocks are Ru-II complexes of the 2,3-bis(2-pyridyl)pyrazine (2,3-dpp) bridging ligand, where one of the two chelating sites can be protected by methylation. Dendrimers containing four, ten, and twenty-two metal ions have been obtained. These dendrimers exhibit strong absorption in the UV/Vis spectral region, a moderately strong red luminescence, and a great number of metal-based oxidation and ligand-based reduction processes. The nature of the terminal ligands determines in which subunits of the supramolecular array the HOMO and LUMO orbitals and the luminescent excited state are localized. The reported synthetic strategy is efficient, characterized by a full, step-by-step control of the growth process, and can be easily extended to building blocks containing other metals and/or ligands.