Hydrogen-Bond-Assisted Symmetry Breaking in a Network of Chiral Metal-Organic Assemblies.
Journal of the American Chemical Society
American Chemical Society (ACS)
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Rizzuto, F., Pröhm, P., Plajer, A., Greenfield, J., & Nitschke, J. (2019). Hydrogen-Bond-Assisted Symmetry Breaking in a Network of Chiral Metal-Organic Assemblies.. Journal of the American Chemical Society, 141 (4), 1707-1715. https://doi.org/10.1021/jacs.8b12323
Herein we elucidate the interplay of chiral, chelate, solvent and hydrogen-bonding information in the self-assem- bly of a series of new three-dimensional metal-organic architectures. Enantiopure ligands, each containing H-bond donors and acceptors, form different structures depending on the ratio in which they are combined: enantiopure components form M4L4 assemblies, whereas racemic mixtures form M3L3 stacks. Chiral amplification within M3L3 enantiomers was observed when a 2:1 ratio of R and S subcomponent enantiomers was employed. Simply switching the solvent (from MeCN to MeOH) or chelating unit (from bidentate to tridentate) increased the diversity of structures that can be generated from these building blocks, leading to the selective formation of novel M2L2 and M3L2 assemblies. The addition of achiral ligand building blocks resulted in the formation of further structures: When an achiral subcomponent was combined with its R- and S- chiral conge- ners, a three-layer heteroleptic architecture was generated, with the achiral unit sitting at the top of the stack. When combined with the S enantiomer only, however, the achiral unit assembled in the center of the structure, thus demonstrating the selec- tive placement of achiral units within chiral systems. Further sorting experiments revealed that combining R and S stereo- centers within a single ligand led to diastereoselective product generation. These results show how geometric complementa- rity between different ligands impacts upon the degree of hydrogen bonding within the assembly, stabilizing specific low- symmetry architectures from among many possible structural outcomes.
EPSRC (via University of Manchester) (EP/P027067/1)
European Commission Horizon 2020 (H2020) ERC (695009)
External DOI: https://doi.org/10.1021/jacs.8b12323
This record's URL: https://www.repository.cam.ac.uk/handle/1810/288723