An unprecedented Au₁₈ thiacrown directed by Au(I) ···Au(I) interactions and supported by tridentate phosphine (dpepp) and μ₃-sulfido ligands that highly resembles the 18-membered thiacrown ether [18]aneS₆ in appearance has been synthesized. The sulfides of the Au₃(μ₃-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 Au₁₈ macrocycle.