Porous molecular crystals are of great interest as materials because of their potential for structural modularity, solution processibility, and expansive long-range order. However, the development and proliferation of porous molecular crystals have been limited by the typical unpredictability of non-covalent assembly of molecular building blocks (tectons). Significant advancements have been made using hydrogen bonding (H-bonding) interactions to template crystal porosity, but the competition with other non-covalent interactions frequently guides H-bonding tectons into close packing structures. One avenue to improving control over porous molecular crystal structure is to investigate whether alternate non-covalent interactions can afford more predictable intermolecular connectivity. Herein is the first demonstration that chalcogen bonding interactions can mediate the nucleation and growth of porous molecular crystal structures. The studied triptycene tris(selenadiazole) (Trip3Sez, Figure 1A) molecular tecton was inspired by the self-association of chalcogenadiazoles through pairs of highly directional chalcogen bonds, which resembles the symmetry of common H-bonding motifs found in porous molecular crystals. Crystallization studies revealed that chloroaromatic solvents can be used to selectively mute π-based close packing interactions, enabling extensive selenadiazole self-association via extended [Se–N]<sub>2n</sub> chalcogen bonding ribbon motifs (Figure 1B), which template porosity in Trip3Sez lattices (Figure 1C). The Trip3Sez crystallization results indicate that highly directional chalcogen bonding affords orthogonality to competing close-packing interactions, which can be leveraged for predictable control over the assembly of porous molecular crystals.

Assembly of porous molecular crystals through chalcogen bonding interactions

ACS Spring Meeting 2021

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