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Three ring-shaped AEE-active silole-containing compounds were synthesized by mild condensation reactions. Cyclotrisiloxane compound 1 displays high solid-state quantum yield (Φfl = 0.86) with the fluorescence maximum at 512 nm. This high fluorescence efficiency results mainly from decreased vibrational pathways to fluorescence decay due to the intramolecular C-H⋯π interactions. [ABSTRACT FROM AUTHOR]

Abstract: Spirogermabifluorene (C24H16Ge, 1) and the anionic products of its reduction with alkali metals were prepared and investigated by single-crystal X-ray diffraction. A monoanionic intermediate product of the reduction, formed upon the cleavage of a Ge–C bond and proton abstraction from the solvent, was isolated in the form of the cesium salt, [Cs+(diglyme)(C12H8GeC12H9 −)] (2). Structural investigation of 2 revealed the presence of a tricoordinated germanium center and complexation of the cesium cation by two aromatic moieties. The reduction of 1 with an excess of alkali metals leads to the cleavage of the second Ge–C bond with subsequent elimination of biphenyl to give the C12H8Ge2− dianion which was crystallized as the sodium adduct, [{Na+(THF)}2(C12H8Ge2−)] (3). The structural elucidation for complex 3 shows η3- and η5-coordinations of the sodium ions to the π-system of dianions. The resulting Na⋯C and Na⋯Ge contacts along with the Na⋯OTHF interactions lead to the formation of the zigzag polymeric chains in the crystal lattice of 3. [Copyright &y& Elsevier]