Metal–organic rotaxane frameworks; MORFs

Linear exodentate pyridinium ligands such as 1,2-bis(4,4'-bipyridinium)ethane or its bis N-oxide derivative can be used as axles for the formation of [2]pseudorotaxanes utilising 24-membered crown ethers such as dibenzo-24-crown-8 ether (DB24C8) as the wheel. These [2]pseudorotaxanes can be used to construct coordination networks using transition or lanthanide metal ions as the connecting nodes. 1-, 2- and 3D metal-organic rotaxane frameworks (MORFs) are possible. The resulting materials contain mechanically interlocked units and may be the forerunners of unique solids which contain machine-like components in an ordered array.