AuI•••AuI Interaction Assisted Host-Guest Interactions and Stimuli-Responsive Self-Assembly in Tetranuclear Alkynylgold(I) Calix[4]arene-Based Isocyanide Complexes

Multi-stimuli-responsive tetranuclear gold(I) complexes were prepared based on a tetra(alkynyl)calix[4]arene framework, with incorporation of a series of isocyanide ligands of tunable hydrophilicity. This class of complex was found to exhibit high sensitivity towards group IIIA metal ions especially In3+. Drastic electronic absorption and emission changes were observed, which could be attributed to the formation of (AuAuI)-Au-I interactions during the binding event. Solvent-induced self-aggregation was also observed upon changing the solvent environment to a more polar medium, with the formation of nanoaggregates and the turning-on of the aurophilic interactions, leading to interesting luminescence and morphological changes. The aggregation process was monitored by UV/Vis absorption, emission and (HNMR)-H-1 spectroscopy and dynamic light scattering (DLS) studies, and the morphological changes were studied by electron microscopy. This new class of complex has shown high sensitivity towards external stimuli and demonstrated the feasibility of employing the on-off switching of aurophilicity as an effective design strategy for the construction of functional supramolecular systems.