A rhenium tricarbonyl 4'-oxo-terpy trimer as a luminescent molecular vessel with a removable silver stopper.

Shining metal cups: A luminescent tube of triangular cross-section and stoppered by a silver ion (see picture: Re yellow, N blue, O red) is formed in two steps from commercial materials. The silver ion can be removed to give a tube, and both species are potential hosts for small ions and molecules; a change in luminescence is triggered by the encapsulation of silver.