A Ring of Rotaxanes: Studies of a Large Paramagnetic Assembly in Solution

NMR spectroscopy is the standard method for establishing chemical structure in solution but relies on the compound being diamagnetic. When a compound is paramagnetic, NMR resonances are broad-ened and structural information lost. Other methods such as diffuse light scattering can establish the size of a compound but gives little structural information. Here we report the synthesis and structural characterization of four [7]rotaxanes which form by coordinating hybrid inorganic-organic [2]rotaxanes to a central {Ni12} core. Small angle X-ray scattering supported by molecular dynamic simulations demonstrates that the large molecules are stable in solution and also provides structural information about the conformers present.