New stable germenes

Organogermanium Analogues of Alkenes, Alkynes, 1,3-Dienes, Allenes, and Vinylidenes

In this review, the latest achievements in the field of multiply bonded organogermanium derivatives, mostly reported within the last two decades, are presented. The isolable Ge-containing analogues of alkenes, alkynes, 1,3-dienes, allenes, and vinylidenes are discussed, and for each class of unsaturated organogermanium compounds, the most representative examples are given. The synthetic approaches toward homonuclear multiply bonded combinations solely consisting of germanium atoms, and their heteronuclear variants containing germanium and other group 14 elements, both acyclic and cyclic, are discussed. The peculiar structural features and nonclassical bonding nature of the abovementioned compounds are discussed based on their spectroscopic and structural characteristics, in particular their crystallographic parameters (double bond length, trans-bending at the doubly bonded centers, and twisting about the double bond). The prospects for the practical use of the title compounds in synthetic and catalytic fields are also briefly discussed.

Inorganic-Cored Photoactive Assemblies: Synthesis, Structure, and Photochemical Investigations on Stannoxane-Supported Multifluorene Compounds

Organostannoxanes were used as inert supports for the preparation of multichromophore assemblies. The synthesis involves a single-step procedure and allows the preparation of compounds in which the number of chromophore units can be varied from one to six. Thus, the reactions of LCOOH (1-fluorenecarboxylic acid) or L'COOH (9-fluorenecarboxylic acid) with various organostannoxane precursors afforded the fluorenyl derivatives [Ph(3)SnO(2)CL] (1), [Ph(3)SnO(2)CL'] (2), [{nBu(3)SnO(2)CL''}(n)] (3), [{nBu(3)SnO(2)CL'}(n)] (4), [{tBu(2)Sn(OH)O(2)CL}(2)] (5), [{tBu(2)Sn(OH)O(2)CL'}(2)] (6), [{[nBu(2)SnO(2)CL](2)O}(2)] (7) [{[nBu(2)SnO(2)CL'](2)O}(2)] (8), [{nBuSn(O)O(2)CL}(6)] (9), and [{nBuSn(O)O(2)CL'}(6)] (10). Interestingly, the formation of 3 is accompanied by an unusual oxo-transfer reaction. The ligand L is oxidized at the 9-position. Compounds 1, 3, 5, 7, and 8 were characterized by X-ray crystallography. The solid-state structures of these compounds reveal rich supramolecular structures owing to multiple intermolecular interactions between the various supramolecular synthons present in these molecules. The optical behavior of 1-10 is primarily dictated by the fluorenyl periphery. These compounds display strong blue fluorescent emission in solution and blue-green fluorescent emission in the solid state. Fluorescence lifetimes of all of these compounds are on the nanosecond timescale, and this suggests that the emission originates from the singlet excited state to the ground state. Intermolecular interactions in the solid state lead to considerable broadening of the emission bands.