Structure, reactivity and tailoring of porous organic solids based on phenylacetylene silver coordination networks

This thesis studies the preparation of covalently crosslinked porous organic solids via phenylacetylene nitrile ligands and silver(I) ions coordination networks. A prototype of three-fold symmetric phenylacetylene nitrile ligand, 1,3,5-tris(4-ethynyl benzonitrile) (1) has been found to crystallize with silver(I) trifluoromethansulfonate to form a three dimensional channel structure. The extended channels found in this coordination network are of honeycomb type 15 A in diameter. Properties such as guest removal and exchange within this host crystal have been investigated. The honeycomb channels in the crystal structure are retained through both guest exchange and complete guest removal. The apohost (defined as a host without occluded guests) exhibits selectivity for new guests by absorbing aromatic molecules and not aliphatic molecules from the vapor phase. Repeated removal and reintroduction of benzyl alcohol guests is demonstrated to occur with the retention of crystallinity and without the macroscopic reformation of the crystallites. Investigations on molecular variants of the prototypic ligand 1 crystallized with silver(I) trifluoromethansulfonate have revealed a nearly invariant honeycomb porous structure type. Modifications involved both the attachment of pendant groups on the central aromatic ring of the parent molecule and the addition of elongated spacer unit between the central benzene ring and the peripheral nitrile groups. Single crystal refinements for five silver(I) salts of modified organic ligands as well as powder studies of 15 crystalline phases showed the consistent formation of the honeycomb channels, demonstrating that the parent porous architecture is stable both to functional modification as well as to size change. It was found in the case of a host with alcohol functionality that trifluoroacetic anhydride and silyl triflate both reacted with the host to form respectively an ester and a siloxane with retention of the porous structure type. In the case of a phenylacetylene nitrile molecule with three alcohol side chains, the introduction and subsequent reaction with di-t-butylsilyl bis(triflate) resulted in the formation of low polymers. This polymerized materials shows increased chemical robustness in contrast to the unpolymerized materials.