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Co-crystal engineering is a promising method to create new classes of advanced materials. Co-crystal structure prediction is more challenging when one or more of the lattice constituents (tectons) are flexible molecules. This study reports four co-crystals that were prepared by mixing HAuCl 4 or HAuBr 4 with C 3 -symmetric tectons based on a 1,3,5-(methylacetamide)benzene scaffold. X-ray analysis of the co-crystals revealed the presence of three dominant supramolecular interactions; (a) hydrogen bonding between tecton amide NH residues and the AuX 4 − anion, (b) electrostatic stacking of the Au center against the tecton's π-electrons, (c) very short hydrogen bonds within a proton-bridged-carbonyls motif. Within all four co-crystals, the sterically-geared tecton was trapped in a high energy molecular conformation, which increased the number of favorable intermolecular interactions in the lattice. We infer from the results that the likelihood of high energy molecular conformations within a co-crystal increases if there are multiple dominant intermolecular interactions. Application of this generalizable rule should lead to improved crystal structure prediction.
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Supramolecular Paradigm for Capture and Co‐Precipitation of Gold(III) Coordination Complexes
Abstract A new supramolecular paradigm is presented for reliable capture and co‐precipitation of haloauric acids (HAuX4) from organic solvents or water. Two classes of acyclic organic compounds act as complementary receptors (tectons) by forming two sets of directional non‐covalent interactions, (a) hydrogen bonding between amide (or amidinium) NH residues and the electronegative X ligands on the AuX4−, and (b) electrostatic stacking of the electron deficient Au center against the face of an aromatic surface. X‐ray diffraction analysis of four co‐crystal structures reveals the additional common feature of proton bridged carbonyls as a new and predictable supramolecular design element that creates one‐dimensional polymers linked by very short hydrogen bonds (CO⋅⋅⋅OC distance <2.5 Å). Two other co‐crystal structures show that the amidinium‐π⋅⋅⋅XAu interaction will reliably engage AuX4−with high directionality. These acyclic compounds are very attractive as co‐precipitation agents within new “green” gold recovery processes. They also have high potential as tectons for controlled self‐assembly or co‐crystal engineering of haloaurate composites. More generally, the supramolecular paradigm will facilitate the design of next‐generation receptors or tectons with high affinity for precious metal square planar coordination complexes for use in advanced materials, nanotechnology, or medicine.
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- Award ID(s):
- 1708240
- PAR ID:
- 10236610
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- Chemistry – A European Journal
- Volume:
- 27
- Issue:
- 2
- ISSN:
- 0947-6539
- Format(s):
- Medium: X Size: p. 751-757
- Size(s):
- p. 751-757
- Sponsoring Org:
- National Science Foundation
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