Temperature-Dependent Solvent Disruption of Guanidinium-1,5-Naphthalenedisulfonate Networks Yields a One-Dimensional Pore Structure

Abstract

Crystallization of mixtures of the host compounds 1,5-naphthalenedisulfonate and guanidinium results in a new three-component network structure in the presence of linear fatty acid esters. The formation of this new topology is temperature-dependent and arises from the disruption of the basic guanidinium-sulfonate sheet structure through the incorporation of the solvent 2-methoxyethanol within the host network. Examination of the hightemperature crystal phase, the fatty acid ester-free 2-methoxyethanol solvate, reveals that the GS sheet topography of this network is directed by the hydrogen-bond interactions of the solvent and host. In the fatty acid ester inclusion compound, which crystallizes at lower temperatures, the host-guest interaction is much more explicit, with each 2-methoxyethanol molecule participating in three hydrogen bonds, becoming the third component of the host structure. The result of this new assembly is the creation of hydrophobically lined pores with an available cross-section area of 4.1 × 4.7 Å 2 within which the linear fatty acid ester guests are contained. Hydrophobic interactions and tight host-guest packing provide an explanation for formation of the entropically unfavorable three-component host network.

Separation of polyunsaturated fatty acids by selective inclusion in guanidinium‐1,5‐naphthalenedisulfonate‐2‐methoxyethanol host networks

“…Hydrogen-bonding motif of three-component G-NDS-2-methoxyethanol inclusion compound. (a) the GS-2-methoxyethanol tape (b) view of GS-2-methoxyethanol tube perpendicular to the plane of the page, showing back-to-back connectivity of two GS-2-methoxyethanol tapes through 2-methoxyethanol alcohol proton-S oxygen hydrogen bonding, (c) network connectivity resulting from NDS linkage through successive GS-2-methoxyethanol tubes, and (d) resulting pore structure with the disordered fatty acid ester guest removed (for further details, see Voogt and Blanch, 2005).…”

“…Previous work has demonstrated the ability to include long, linear guests such as triglyme and fatty acid methyl esters within G-NDS hydrogen-bonded networks (Russell et al, 1997;Voogt and Blanch, 2005). Here this network is applied to the separation of 18:0 and 18:3 methyl esters.…”

“…Inclusion of methanol is commensurate, G 2 NDSÁ2(methanol), and the solvate molecules are stabilized by two moderate-strength hydrogen bonds that form between each methanol guest molecule and a host G (Voogt and Blanch, 2005). This host-guest interaction with methanol drives solvate formation, thus preventing significant inclusion of the fatty acid guest, which is only minimally able to form hydrogen bonds with the host.…”

“…The sheet is shown in (a), formed by the interconnection of adjacent hydrogen bonded ribbons. The pores, or channels (with guests removed) that result from the interconnection of adjacent sheets through the NDS pillar are illustrated in (b) for the crystal structure of the inclusion of 2-methoxyethanol (for further details, see Voogt and Blanch, 2005). Carbon, oxygen, nitrogen, sulfur, and hydrogen atoms are shown in gray, red, blue, yellow, and white, respectively.…”

“…We recently reported modification of the inclusion network structure through incorporation of a third component within the host network, the solvent 2-methoxyethanol (Voogt and Blanch, 2005), and this new architecture is presented in Figure 3. While the connectivity of this network maintains the hydrogen-bonded ribbon motif, these ribbons no longer interconnect to form the two-dimensional hydrogen-bonded sheet.…”