Porous siloxane linked phenylacetylene nitrile silver salts from solid state dimerization and low polymerization

Three 3-fold symmetric rigid backbone phenylacetylene nitrile molecules have been prepared to which one to six hydroxy side chains have been attached. These molecules were cocrystallized with silver(I) trifluoromethanesulfonate (triflate) to form microcrystalline porous solids. X-ray powder data show that all three crystal structures are isotypic to the crystal structures found in previous single crystal studies on related systems. Structural models based on these earlier single crystal structures have theoretical powder patterns in reasonable agreement with the experimentally observed patterns. These crystalline materials were allowed to react with silyl triflates. ¹H NMR and X-ray powder studies show that the silyl triflate groups react with the alcohol terminated side chains to form siloxane linkages with retention of the initial crystal structure. In the case of 1,3,5-tris(4-((4-cyanophenyl)ethynyl)-2-((4-hydroxybutoxy)methyl) phenylethynyl)benzene, a phenylacetylene nitrile molecule with three alcohol side chains, the introduction of di-tert-butylsilyl bis(trifluoromethanesulfonate) resulted in the formation of low polymers with average weight molecular weight of 7 x 10⁴. This polymerized material shows increased chemical robustness in contrast to the unpolymerized material. It is stable in a variety of solvents, including overnight exposure to boiling water. Exchange experiments with toluene show that this final material is still porous.