Variable Pore Size, Variable Chemical Functionality, and an Example of Reactivity within Porous Phenylacetylene Silver Salts

Abstract

Investigations on molecular variants of the 3-fold symmetric 1,3,5-tris(4-ethynylbenzonitrile)benzene crystallized with silver triflate revealed a nearly invariant pseudohexagonal porous structure type. Modifications involved the attachment of pendant groups to the central aromatic ring of the parent molecule. Pendant groups include the vinyl group, stilbene, the chiral group myrtanol, and groups with different chemical functionalities such as alcohols, ethers, and esters. Modifications also included the addition of elongated spacer units between the central benzene ring and the peripheral nitrile groups. In these molecules the acetylene bridges of 1,3,5-tris(4-ethynylbenzonitrile)benzene were replaced with diacetylene, ethynylbenzene, and diethynylbenzene type units. Single-crystal refinements for pentoxy-2,4,6-tris(4-ethynylbenzonitrile)benzene·AgOTf and 1,3,5-tris(4-(4-ethynylbenzonitrile)phenyl)benzene·AgOTf as well as powder data on 12 crystalline phases showed the consistent formation of pseudohexagonal channels, demonstrating that the parent porous architecture is stable both to functional modification of the interior of the channel as well as to enlargement of the pores. Pentoxy-2,4,6-tris(4-ethynylbenzonitrile)benzene·AgOTf refined in the monoclinic space group Am. 1,3,5-Tris(4-(4-ethynylbenzonitrile)phenyl)benzene·AgOTf was found to be triclinic with space group P1̄. These crystals have pseudohexagonal channels respectively 15 and 25 Å in diameter. Cell constants based on powder data are compatible with channel diameters ranging from 10 to 30 Å. The latter channel diameters are among the largest known for organic porous solids. The introduction of the chiral myrtanol unit led to the preparation of a chiral porous solid. The thermal and chemical stabilities of these phases were investigated. The pseudohexagonal structure proved stable to complete solvent loss from the channel. It was found in the case of a host with alcohol functionality that an acid anhydride guest, trifluoroacetic anhydride, reacted with the host to form an ester with retention of the porous structure type.

Surface-Template Assembly of Two-Dimensional Metal−Organic Coordination Networks

“…In particular, coordination complexes are interesting not only for the structural aspects but also for their intriguing functional properties, which one may exploit in the fields of catalysis, magnetism, and optical applications. [8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27] The promise of these construction strategies for creating functional materials has already been demonstrated for different applications, such as second harmonic generation, 15,16 gas storage, including sizeselective sorption and molecular recognition, [17][18][19][20] and catalysis, [21][22][23][24] as well as applications to magnetic materials. 8,[25][26][27] The coordination interaction has also been employed to construct supramolecular architectures at surfaces, offering the possibility to design low-dimensional organic-inorganic hybrid materials.…”

Persistent Honeycomb Structures in Porous and Other Two-Component Solids

“…[12,15] We have found that phenylacetylene molecules with three capping nitrile groups radially pointing out from the core of the molecule engender in the coordinating silver ions a similar trigonal planar geometry. Examples of such nitriles are given in Figure 2.…”

“…To wit, we can introduce guests into the hexagonal columnar pores which will react with the channel walls and ultimately strengthen these walls. For example, we recently reported [12] that acid anhydrides can react in an alcohol derivatized hexagonal porous channel to form esters without loss of crystallinity, as evidenced by X-ray powder data. In this work we prepared a phenylacetylene nitrile whose alcohol groups dangle into the honeycomb pores.…”

“…Illustrative examples, taken from solved singlecrystal X-ray data, are given in Figure 3. [12,16] Figure 3c is for the organic molecule shown in Figure 2 with seven aromatic rings and three acetylene bridges while Figure 3d is for the molecule shown in Figure 2d with four aromatic rings, three acetylene bridges and six ethylene oxide side chains.…”

“…For example, the use of chiral organic molecules leads to chiral pores. [12] Alternatively, the hydrophilicity of the pore wall can be controlled by covalently attaching appropriate organic side chains, from aromatic ring systems to polyethers. While such organic porous solids would never have the thermal stability of their inorganic counterparts, they could nevertheless function effectively as stereoselective and chemical function selective agents.…”