The first hexagonal octadecanuclear Ag macrocycle [Ag18(TTTMB)12](NO3)18·30H2O has been hydrothermally synthesized. The outside and inner diameters of the unprecedented architecture are about 27.72(13) Å and 15.37(7) Å, respectively. This complex displays a huge increase in the intensity and lifetime of phosphorescence with decreasing temperature.
