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. 2020 Feb 14;11(1):880.
doi: 10.1038/s41467-020-14703-4.

Self-assembled conjoined-cages

Sagarika Samantray  1 , Shobhana Krishnaswamy  1 , Dillip K Chand  2
Affiliations

Self-assembled conjoined-cages

Sagarika Samantray et al. Nat Commun. .

Abstract

A self-assembled coordination cage usually possesses one well-defined three-dimensional (3D) cavity whereas infinite number of 3D-cavities are crafted in a designer metal-organic framework. Construction of a discrete coordination cage possessing multiple number of 3D-cavities is a challenging task. Here we report the peripheral decoration of a trinuclear [Pd3L6] core with one, two and three units of a [Pd2L4] entity for the preparation of multi-3D-cavity conjoined-cages of [Pd4(La)2(Lb)4], [Pd5(Lb)4(Lc)2] and [Pd6(Lc)6] formulations, respectively. Formation of the tetranuclear and pentanuclear complexes is attributed to the favorable integrative self-sorting of the participating components. Cage-fusion reactions and ligand-displacement-induced cage-to-cage transformation reactions are carried out using appropriately chosen ligand components and cages prepared in this work. The smaller [Pd2L4] cavity selectively binds one unit of NO3-, F-, Cl- or Br- while the larger [Pd3L6] cavity accommodates up to four DMSO molecules. Designing aspects of our conjoined-cages possess enough potential to inspire construction of exotic molecular architectures.

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Conflict of interest statement

The authors declare no competing interests.

Figures

Fig. 1
Fig. 1. Cartoon representation of the design approaches for making of self-assembled multi-3D-cavity cages.
a linearly conjoined homoleptic cages, and b linearly/laterally conjoined targeted homo- and heteroleptic cages (this work).
Fig. 2
Fig. 2. Structure of the ligands.
The ligands L1–L6.
Fig. 3
Fig. 3. Synthetic scheme for the complexes 2a−2d, 3a−6a, and 4e/4f.
Self-assembled coordination cages featuring one or more 3D-cavity constructed by complexation of Pd(NO3)2 with appropriate ligand(s) to afford a/b/c/d/e homoleptic complexes; f/g heteroleptic complexes via integrative self-sorting; k mixture of homoleptic complexes via narcissistic self-sorting. Cage-fusion reactions to yield h/i heteroleptic complexes (however, no fusion in the case of j).
Fig. 4
Fig. 4. Characterization of the complexes 2a−6a and 4e/4f.
Partial 1H NMR spectra (400 MHz, DMSO-d6, 300 K) of a cage 2a (diastereomeric mixture), b cage 3a (trinuclear), c mixture of 4e and 4f (tri- and hexanuclear), d cage 4a (tetranuclear), e cage 5a (pentanuclear), and f cage 6a (hexanuclear).
Fig. 5
Fig. 5. Crystal structures showing the cationic portions.
a Cage 2c (binuclear), b cage 3a (trinuclear), c cage 4acI (tetranuclear), d cage 5c (pentanuclear), and e cage 6c (hexanuclear) (encapsulated guests, counter-anions, solvents, and hydrogen atoms are excluded for clarity. ORTEP diagram for complexes and suitable crystal structures showing encapsulated guests are available in the Supplementary Figs. 134–143).
Fig. 6
Fig. 6. Ligand-displacement-induced cage-to-cage transformations.
Initial-cage/ligand-input/final-cage/displaced-ligand a system 3a/L5/4a/L3; b system 3a/L6/6a/L3; c system 4a/L6/6a/L3&L5; d system 5a/L6/6a/L5; e system 4e/L3/4a/L5; f system 4e/L6/6a/L5; g system 3a/L5&L6/5a/L3 (stoichiometry are provided in the figure. The complex 4e coexists with 4f).
See this image and copyright information in PMC

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