Two new ruthenium(II) polypyridyl dimers containing the large planar aromatic bridging ligands 9,11,20,22-tetraazatetrapyrido[3,2-a:2'3'-c:3' ',2''-l:2''',3'''-n]pentacene (tatpp) and 9,11,20,22-tetraazatetrapyrido[3,2-a:2'3'-c:3'',2' '-l:2''',3'''-n]pentacene-10,21-quinone (tatpq) have been synthesized and characterized by (1)H and (13)C NMR, MALDI mass spectrometry, and elemental analyses. The electronic properties (UV-vis, redox, photophysical) of these dimers are analyzed in the context of orbital calculations (PM3 level) on the bridging ligands. A localized orbital model is proposed in which low-lying acceptor orbitals on the center portion of the ligands effectively quench the Ru(II)-based MLCT emission via a mechanism that can be viewed as intramolecular electron transfer to specific subunits of the bridges.
Metallodendrimere mit zehn chiralen Ru‐Zentren wurden stereospezifisch hergestellt (siehe Bild; •=chirales Ru(diimin)3‐Zentrum). Diese Moleküle sind konformativ starr und weisen wohldefinierte Topologien auf: Einige Diastereomere haben Strukturen mit makroskopischer Chiralität, andere sind scheibenförmig. Dieser Unterschied in der Global‐ oder Tertiärstruktur kommt in unterschiedlichen Eigenschaften im kolloidalen Zustand zum Ausdruck, wie durch Messungen der elektrischen Doppelbrechung gezeigt wurde.
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