Design of metal-organic assemblies via shape complementarity and conformational constraints in dual curvature ligands

08 June 2022, Version 3
This content is a preprint and has not undergone peer review at the time of posting.

Abstract

While common in biological systems, building blocks with low symmetry and flexibility pose numerous problems for synthetic self-assembly such as the formation of isomers of assemblies that are usually difficult to distinguish and purify. We herein report a design and synthesis strategy relying on shape complementarity and conformational constraints in dual curvature ligands that effectively promotes high selectivity during self-assembly and self-sorting of metal-organic assemblies. Three aromatic amide-based ligands (L1-L3) with a central 1,8-diazatriptycene core were designed and used for self-assembly with Pd2+. While hundreds of stereoisomers based on the conformational flexibility around the amides and the unsymmetrical non-planar structure of the core are possible upon coordination with the metal, the constraints designed into the ligands direct the self-assembly towards only a single Pd2L4 cage (L1) or Pd4L8 double-walled metallomacrocycle (L2) structure, even in mixtures of the ligands. We further demonstrate that this structural approach and the modularity of the ligand synthesis affords ready access to the first deep endohedral functionalized double-walled Pd4L8 cavitands (L3). These results highlight the potential of this new design strategy and open the door to selectively functionalized cavity-based architectures for numerous applications.

Keywords

Coordination cages
Palladium
Supramolecular Catalysis
Selective Self-Assembly
Endohedral Functionalization

Supplementary materials

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Description
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Supporting Information
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Complete experimental procedures, additional spectra figures, and tables of NMR, ESI-TOF-MS, CIF and crystal data.
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Pd4(L3)8
Description
Cif file for Pd4L38
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Pd2(L1)4
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cif file for Pd2(L1)4
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Pd4(L2)8
Description
cif file for Pd4(L2)8
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