Subtle Influences of a Flexible Tecton on an R22(8) Carboxyl Dimer Synthon: From Molecular Threading to 2D → 3D Interpenetration

Abstract

The use of well-defined synthons and rigid tectons has allowed for great advancement in the reticular synthesis of hydrogen-bonded organic frameworks. However, the use and influence of flexible tectons on the well-reported R22 (8) carboxyl dimer synthon is a largely unexplored area. As part of our investigation, we report here the structures of ten polymorphs/pseudopolymorphs (1-10) of the flexible tecton 3-[2,5,5′-tris(2′-carboxyethyl)-1,1′-dioxo-1″λ6-thiolan-2″-yl]propanoic acid (L). L provided a rich variety of structures, which were described using three identified key structural motifs: a zigzag 1D chain, a dimer which may extend into a 1D chain, and a (4,4) net. Structure 3 consisted of a 1D chain, and structures 2, 5, 8, and 9 were 3D assemblies described using the dimer motif. Structures 4, 6, and 7 formed 1D chains of dimers as well as (4,4) nets, and these two motifs were stacked alternately in the overall structures. The structure of 1 formed a 1D zigzag chain which was threaded through a (4,4) net. The structure of 10 did not contain any of these motifs and instead consisted of a (6,6) net which was 4-fold interpenetrated. Solvent guest molecules were found to have no effect on the resulting structures. The carboxyl dimer synthon was present in 9 of the 10 reported structures. However, the flexibility of the tecton, while it gave rise to a diverse range of structures, resulted in limited control over the final assemblies.