An unprecedented Au(18)thiacrown directed by Au(I)center dot center dot center dot Au(I) interactions and supported by tridentate phosphine (dpepp) and mu(3)-sulfido ligands that highly resembles the 18-membered thiacrown ether [18]aneS(6) in appearance has been synthesized. The sulfides of the Au-3(mu(3)-S) units in the central cavity point toward each other and are located on the same plane, allowing them to bind the soft Ag+ ion with immediate and pronounced spectroscopic changes. Reversible binding and spectroscopic changes can be readily achieved upon addition of CH3CN without disruption of the Au-18 macrocycle.