Hydrogen bonding and structure of silanediol dimers and tetramers

A new structure of tetrameric silanediols, which was not characterized experimentally before, was predicted by the B3LYP method. It is a cage-like (S4) structure with high complexation enthalpy (32 kcal/mol), in which all OH groups form hydrogen bonds. This type of tetramer may be proposed as a structural unit for the discotic liquid crystal phase of di-isobutylsilanediol. The conventional tetrameric structure which gives rise to experimentally observed chains in the silanediol crystals and five dimeric structures were also found as energy minima at the 2 H2Si(OH)2 and 4 H2Si(OH)2 potential energy surfaces.