Hydrogen-Bonding 3D Networks by Polyhedral Organosilanols: Selective Inclusion of Hydrocarbons in Open Frameworks

Abstract

Tetrahedral organosilanols E[C6H4Si(i-Pr)2OH]4 (E = C, 2a; E = Si, 2b) as well as octahedral organosilanols Si8O12(CH═CHC6H4SiR2OH)8 (R = i-Pr, 5a; R = Ph, 5b) have been derived from tetraphenylmethane and -silane (1a,b) and octavinyloctasilsesquioxane (3) designed for self-assembly of 3D hydrogen-bonding networks possessing large porosity. X-ray analyses following crystallization of 2a,b from THF/benzene and either hexane or heptane revealed adamantane-type networks with hydrogen bonds between the silanols of four separate molecules and selective inclusion of hexane or heptane, respectively. Upon changing the mixed solvent to THF/benzene/cyclohexane, X-ray analysis of 2a showed an inclusion compound of composition 2a·1.5benzene. TOPOS analyses of 2a·1.5benzene demonstrated a non-adamantane-type framework with sra network topology. Crystallization of 5a,b from acetone/benzene followed by X-ray analyses confirmed the production of the inclusion compounds 5a·18benzene and 5b·23benzene. The open frameworks of 5a·18benzene and 5b·23benzene are constructed with zeolitic or fluorite cages, and ast or flu network topology results, based on the TOPOS program. The packing of benzene molecules in 5a·18benzene and 5b·23benzene was found to be similar to that of crystals of pure benzene in edge-to-face arrangements. Thus, hydrogen-bonding networks of polyhedral organosilanols have shown selective inclusion of hydrocarbons into large cavities with adjustable porosity and without interpenetration of one network into another.