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. 2024 Nov 27;146(47):32311-32316.
doi: 10.1021/jacs.4c14509. Epub 2024 Nov 18.

Template and Solid-State-Assisted Assembly of an M9L6 Expanded Coordination Cage for Medium-Sized Molecule Encapsulation

Kenta Iizuka  1 , Hiroki Takezawa  1 , Makoto Fujita  1   2   3
Affiliations

Template and Solid-State-Assisted Assembly of an M9L6 Expanded Coordination Cage for Medium-Sized Molecule Encapsulation

Kenta Iizuka et al. J Am Chem Soc. .

Abstract

The M6L4 cage, self-assembling from six Pd(II) or Pt(II) 90-degree blocks and four triazine-cored triangular ligands, has an effective hydrophobic cavity of about 450 Å3 capable of encapsulating one or more small molecules. Here, from the same components, we successfully constructed an M9L6 cage with an internal volume expanded to 1540 Å3 via the self-assembly of an M8L6 precursor using pillar[5]arene as a template. This cage retains the high molecular recognition ability of the M6L4 cage while recognizing medium-sized guest molecules with molecular weights of up to ∼1600.

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Conflict of interest statement

The authors declare no competing financial interest.

Figures

Figure 1
Figure 1
Schematic representation of the concept: cavity expansion of M6L4 cage 1 into M9L6 cage 2.
Figure 2
Figure 2
(a) Synthetic scheme of M9L6 cage 2 through M8L6 cage 3 (see the text for the conditions). (b) Crystal structure of 3·4 (H atoms on the cage, counteranions, capping ligands on Pt atoms, and solvent molecules are omitted for clarity).
Figure 3
Figure 3
1H NMR spectrum (300 K, 600 MHz, D2O) of (a) inclusion complex 3·4, (b) empty 3, and (c) 2 (*, residual solvents). The host symmetry changes from C1 (in 3·4) to C2v (in 3) to D3h (in 2).
Figure 4
Figure 4
Crystal structures of inclusion complexes (a) 2·(6)6 (6: 1,3,5-trimethoxybenzene) and (b) 2·(7)3 (7: calix[4]arene). In (a) and (b), the side and top views of D3h symmetric host framework 2 are displayed, respectively. H atoms on the cage, counteranions, capping ligands on Pt atoms, and solvent molecules are omitted for clarity.
Figure 5
Figure 5
(a) Structures of target medium-sized molecules: rifampicin (8) and daptomycin (9). 1H NMR spectra (300 K, 600 MHz, D2O) of (b) 8 and mixtures of 2 with (c) 0.7 equiv of 8 (exclusively forming 2·8), (d) 1.2 equiv of 8 [a mixture of 2·8 and 2·(8)2], and (e) 2.0 equiv of 8 [exclusively forming 2·(8)2].
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