Hydroxy‐Substituted Oligosilane Dendrimers: Controlling the Electronic Properties through Hydrogen Bonding

cis,cis-1,3,5-Trihydroxynonamethylcyclohexasilane: A Cyclopolysilane with Unusual Properties

“…The geometry around the silicon atoms of 2 is approximately tetrahedral, with Si−Si−Si bond angles close to the respective angles found in the similar cyclohexasilanol 1 or 1,3- and 1,4-(HO) 2 Si 6 Me 10 . In the crystal packing two molecules are bridged by six intermolecular hydrogen bonds, forming “barrel-type” dimers just as were observed for the isostructural six-membered rings [RSi(OH)O] 3 and [RSi(OH)NH] 3 (R = (Me 3 Si) 2 CH) or by hydroxy-substituted oligosilane dendrimers MeSi[SiOHMeSiMe(SiMe 3 ) 2 ] 3 recently reported in the literature. , It was possible to locate the three hydroxyl protons in the difference Fourier map. Each of them turned out to be disordered over two positions.…”

Oligosilanylsilatranes

“…This conformation is of some importance, as it is known to facilitate the delocalization of σ-bonding electrons . In addition to conformational properties, also electronic factors such as substituent electronegativity − and hypercoordination , can influence the optical absorption properties. We therefore were interested in introducing silyl substituents into oligosilanes, which have a weakened Si–Si bond.…”

An Approach to Dendritic Oligosilanes: Controlling the Conformation through Ring Formation

“…This results in a statistical distribution of highly flexible conformers, each contributing differently to the extent of σ-conjugation along the Si−Si backbone. Controlling the silicon backbone conformation in these branched architectures would be highly desirable, because it would allow the assignment of distinct absorption bands as being associated with the existence of different conformers, as we have shown very recently for structurally similar hydroxy-functionalized oligosilane dendrimers . Several approaches have been introduced to control the silicon backbone conformation of linear oligosilanes such as inclusion into cyclodextrins, conformational logging by hydrogen bond interactions, and incorporation of pentacoordinate silicon atoms or of cyclic and bicyclic structures .…”

“…Controlling the silicon backbone conformation in these branched architectures would be highly desirable, because it would allow the assignment of distinct absorption bands as being associated with the existence of different conformers, as we have shown very recently for structurally similar hydroxy-functionalized oligosilane dendrimers . Several approaches have been introduced to control the silicon backbone conformation of linear oligosilanes such as inclusion into cyclodextrins, conformational logging by hydrogen bond interactions, and incorporation of pentacoordinate silicon atoms or of cyclic and bicyclic structures . In particular, the last approach, introduced by Michl and by Tamao, proved to be the most successful, as demonstrated for various all-anti conformers of different chain lengths that could be obtained by incorporating tethering groups (CH 2 ) n ( n = 1−4).…”