Since the recognition of the multiple bond in [Re₂Cl₈]^2- by F. A. Cotton in 1960s, the chemistry of the dimetal- or multimetal-centered compounds has drawn increasing interest due to their structural diversity, rich physical properties and potential applications in catalysis, biological mimicry, magnetic coupling, electron transfer, functional materials, etc. Using a Au^I···Au^I bonding interaction-directed stepwise macrocyclization strategy, Yu and co-worker has developed a series of giant ring systems from Au₁₂ to Au₁₆ and Au₃₆ with novel luminescence properties in some cases（related work have been published in the important journals including J. Am. Chem. Soc.2005, 127, 17994-17995. Also see: Editors’ Choice by P. D. Szuromi, Science 2005, 310, 1745 Angew. Chem. 2008, 120(24), 4627-4630; Angew. Chem. Int.Ed. 2008, 47(24), 4551–4554 (VIP and Cover Picture). Based on previous work, we herein report a new class of gold(I)-containing metallo-organic cages {Au₈L₂} (L = tetrakis-dithiocarbamato-calix[4]arene, TDCC), 1–3, which are self-assembled from two deep-cavitand calix[4]arene-based dithiocarbamate ligands and eight Au(I) metal centers featuring a quadruple-stranded helicate structure. Interestingly, these functional supramolecular metallo-cages aggregate into two-dimensional sheet-like molecular arrays in the solid state, consisting of one-dimensional molecular wires with extended intra- and intermolecular Au^I···Au^I bonding interactions. The electronic absorption and emission spectra of complexes 1–3 confirm that the programmable self-assembly process occurs in a stepwise manner with the links built via aurophilic interactions. Photophysical investigations in the solution state revealed that the gold(I) molecular capsules could function as highly selective and sensitive phosphorescent sensors for silver ions and reversible light-convertible ion switches. These cages maybe used as a proof of concept metallo-supramolecular chemosensors and published in the Journal of the American Chemical Society, 2014, 136 (31), 10921–10929.

We design and synthsized a novel kind of tetra-dicarbodithiolatecalix[4]arene ligands L¹-L³ with different conformation via multi-step synthesis. By employing these function ligands reaction with linear assembling unit Au(THT) in solution, finally leading to the formation of a new class of two-dimensional gold (I)-containing molecular wires supramoleculars 1 and metallosupramolecular cage 2 {Au₈L₂}_n (n=1 or ∞; L=tetra-dicarbodithiolatecalix[4]arene, TDTC). These novel supramolecular capsules were depth self-assembled through inter- and intramoleculer Au^I…Au^I bonding based on 3-D flexible calix[4]arene-based supramolecular cages [Au₈L₂] consisting of octa-memberd Au(I) metal centers. Synchrotron radiation analysis of the complex 1-3 revealed the presence of cages with a pseudo C_4v symmetry. For these complexes, the crystallography indicated that the structure of gold (I) supramolecular cages as the building blocks was the quadruple-stranded helicate dimer. The 2-D Au^I…Au^I bonding molecular wire networks consisting of two types of chains [Au₈]_n (n=1, octa-atomic chains Au₈ and n=∞, infinite chains [Au₈]_n) were built from two neighboring supramolecular cages Au₈L₂ via aurophilic bonding and linked by bridging polydentate calix[4]arenes ligands. It's almost the same size with cage 1, the length from end to end is about 17.86Å (O11-O15), average distance between two four-membered Au^I…Au^I chains is 6.84 Å which become a slightly shorter than cage 1.The 2-D molecular wires containing aurophilic attraction exhibited green luminescence at 624 nm in the solid state and 550 nm in the CH₂Cl₂ at 298 K, respectively, which were assigned to the ³MC and ³LMCT or ³LMMCT between the Au(I) centers and organic cavitand ligands. Two types of one- dimensional continues metal-metal bonding chains Au₈ and [Au₈]_n with potential internal cavity possibly used as molecular container for appropriate guest molecules encapsulated within the spheroidal carceplex. Electronic absorption and emission studies of complexes 1–3 indicated the occurrence of a programmable self-assembly process in a concentration-dependent stepwise manner with the links built via aurophilic interactions. These novel gold(I) supramolecular cages exhibited green phosphorescence and have been shown to serve as highly selective and sensitive luminescent sensors toward Ag^I cation among various competitive transition metal ions.

Such supramolecular assemblies exhibit potential applications in host-guest chemistry, artificial enzyme, molecular recognition, and may serve as selective luminescent materials for sensors and OLEDs. This work was highly evaluated by international peers with the praise word of “highly origin concept”. At this time, we warmly thank professor Yam of HKU for their great work on the opt-electronic function determination and important discussion.