Fusion of two homoleptic truncated tetrahedra into a heteroleptic truncated octahedron

Abstract

The exploration of novel structures and structural transformation of supramolecular assemblies is of vital importance for their functions and applications. Herein, based on coordination-driven self-assembly, we prepare a neutral truncated tetrahedron and a heteroleptic truncated octahedron, whose structures are unambiguously confirmed by X-ray diffraction analysis. More importantly, the truncated tetrahedron is quantitatively transformed into the truncated octahedron through its fusion with another cationic truncated tetrahedron, as evidenced by fluorescence, mass and NMR spectroscopy. This study not only deepens our understanding of the process of supramolecular fusion but also opens up possibilities for the subsequent preparation of advanced supramolecular assemblies with complex structures and integrated functions.

Fig. 1. Representations of (a) cell fusion and (b) cage fusion.

Fig. 2. Illustration of the self-assembly of metallacages 4a–4c.

Fig. 3. Partial ³¹P{¹H} NMR spectra (243 MHz, CD₃CN, 295 K) of (a) 4a, (b) 4b and (c) 4c. Partial ¹H-NMR (600 MHz, 295 K) of (d) 1 (CD₃OD), (e) 4a (CD₃CN), (f) 2 (CDCl₃), (g) 4b (CD₃CN), and (h) 4c (CD₃CN). The peak for CHCl₃ is marked with an asterisk. ESI-TOF-MS spectra of metallacages (i) 4b and (j) 4c.

Fig. 4. (a)–(c) Crystal structures of metallacages 4a, 4b (ref. 45) and 4c. Hydrogen atoms, counterions, and solvent molecules are omitted for clarity.

Fig. 5. (a) Fluorescence spectra of ligand 1 in CH₃CN/H₂O (ν : ν = 9 : 1), ligand 2 and metallacages 4a–4c in CH₃CN. (b) Time-dependent fluorescence spectra of an equimolar mixture of 4a and 4b in CH₃CN. λ_ex = 265 nm and c = 10.0 μM.

Fig. 6. (a) Time-dependent ESI-TOF-MS spectra of the mixture of 4a and 4b (c = 500.0 μM). Partial ¹H (600 MHz) and ³¹P{¹H} NMR (243 MHz) spectra of (b) 4b, and 4b with (c) 0.2, (d) 0.4, (e) 0.6, (f) 0.8 and (g) 1.0 equivalents of 4a (CD₃CN at 295 K).