Au^I⋅⋅⋅Au^I Interaction Assisted Host–Guest Interactions and Stimuli‐Responsive Self‐Assembly in Tetranuclear Alkynylgold(I) Calix[4]arene‐Based Isocyanide Complexes

Abstract

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 In . Drastic electronic absorption and emission changes were observed, which could be attributed to the formation of Au ⋅⋅⋅Au 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 H NMR 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.

Tripodal gold(i) polypyridyl complexes and their Cu+and Zn2+heterometallic derivatives. Effects on luminescence

“…Thus, the emission has being assigned to triplet metal-perturbed intraligand -*(C≡C) transitions or 3 MMLCT transitions according to literature. 10,18,21,[25][26][27][28][29] The large Stokes shift and the increased emission intensity upon deoxygenation of the samples support the phosphorescence assignment. In solid state significant emission could be recorded only for 1 and 2, with emission maxima that fits perfectly with the recorded for aggregated samples in solution (Figure S19).…”

Cation‐ and Solvent‐Induced Supramolecular Aggregation Studies of Crown Ether‐Containing Dinuclear Alkynylgold(I) Isocyanide Complexes

“…Upon increasing the water content in the solvent system of complex 8 , a drastic enhancement of the low‐energy emission band at about 640 nm occurs. Such a luminescence enhancement can be attributed to the emergence of a ligand‐to‐metal–metal charge transfer (LMMCT) emission . Since the complex is less soluble in water than in methanol, the solvation of the complexes would be reduced with increasing water content.…”

“…[13][14][15] Apart from metal cation-induced intramolecular assembly, supramolecular aggregation can also be induced by some noncovalent interactions such as hydrophobic-hydrophobic interactions, π-π stacking, and hydrogen-bonding interactions, and more recently, the utilization of metal-metal interactions. [16][17][18] Solvent-induced supramolecular assembly has also been demonstrated recently with platinum(II) [19][20][21][22] and gold(III), [23] as well as gold(I) cluster systems.…”

“…Such a luminescence enhancement can be attributed to the emergence of a ligand-to-metal-metal charge transfer (LMMCT) emission. [11][12][13][14][15] Since the complex is less soluble in water than in methanol, the solvation of the complexes would be reduced with increasing water content. The complex would undergo facile intermolecular aggregation that brings the gold atoms into close proximity.…”

“…Moreover, another approach for the design of alkali metal ion chemosensors involving a series of calixarene‐based bis(alkynyl)‐bridged Au I isocyanide complexes with crown ether pendants was reported with a similar strategy . Besides the alkali metal ions, the detection of di‐ and trivalent metal cations such as Mg 2+ , Al 3+ , and In 3+ by the utilization of the switching “on” and “off” of the Au ··· Au interactions has also been reported …”