Hybrid Inorganic‐Organic Rotaxanes and Related Compounds

The extension of previous studies of heterometallic rings (HMRs) is described, including new synthetic chemistry and physics. These HMRs feature a ring of, typically, eight-metal centres with a central charge balancing cation. New HMRs and related molecules are described, varying the number of metals present. The eight-metal HMRs have been used as components of larger supramolecular assembly, most often by making the HMRs into [2]rotaxanes or pseudo-rotaxanes, where the thread of the rotaxane is terminated by a binding group such as pyridine. This allows the formation of [n]rotaxanes, where n = 3, 4, 5,7, 13 or 10¹⁴. Mass spectrometry and NMR studies of the HMRs have given greater understanding of the host-guest chemistry of these metal analogues of crown ethers. Physical studies have included 4D-inelastic neutron scattering and continuous wave and pulsed EPR spectroscopy to measure magnetic interactions between spin components of the supramolecular assemblies. The use of the HMRs as resists for high resolution lithography is also discussed.