Supramolecular Coordination Cages Based on N-Heterocyclic Carbene-Gold(I) Ligands and Their Precursors: Self-Assembly, Structural Transformation and Guest-Binding Properties.

The incorporation of functional groups into the cavity of discrete supramolecular coordination cages (SCCs) will bring unique functions and applications. Here, three dicarboxylate ligands (H 2 L1 Cl, H 2 L2 Cl and H 2 L3 Cl) containing N-heterocyclic carbene (NHC) precursors as linkers were introduced to construct SCCs by combining with two C 3 -symmertic (CpZr) 3 ( μ 3 -O)( μ 2 -OH) 3 clusters as three-connect vertices, resulted in a series of rugby-like V 2 E 3 (V = vertex, E = edge) type homoleptic cages ( SCC-1 , SCC-2 and SCC-3 ). However, V 4 E 6 -type tetrahedral cages ( SCC-4 and SCC-5 ), incorporating six Au-NHC moieties, were obtained when the corresponding NHC-gold(I) functionalized ligands (H 2 L1 Au , H 2 L2 Au ) were applied. For the first time, we present a trackable CpZr-involved cage to cage conversion to generate a heteroleptic V 2 E 3 cage ( SCC-6 ) from two homoleptic cages ( SCC-2 and SCC-5 ) with different geometries of V 2 E 3 and V 4 E 6 . The heteroleptic assembly SCC-6 can also be formed upon a subcomponent displacement strategy. The structural transformation and reassembly processes were detected and monitored by 1 H NMR spectroscopy and electrospray-ionization mass spectrometry. The formation of heteroleptic assembly was further supported by single crystal X-ray diffraction analysis. Moreover, homoleptic cage SCC-2 possesses a trigonal bipyramidal cationic cavity allowing the encapsulation of a series of sulfonate anionic guests.