Using a bottom-up strategy,small building blocks could form well-defined nanostructures or materials by supramolecular interactions.1 Inspired by the organic metallacages,2 we designed and constructed a rigid Y-type monomer 1 containing two terminal 4,4-bipyridine(BPY) salts units,a 120o V-type backbone and a tri(ethylene glycol)(TEG) soft chain.Interestingly,the self-assembly process between monomer 1 and cucurbit[8]uril(CB[8]) could be adjusted by the concentration of monomer.In highly diluted aqueous solution,stoichiometric addition of monomer 1 and CB[8] could form very small molecular necklaces(about 3 nm) that consist of six monomer 1 and six CB[8] macrocycles.