Structural Characterization of Organometallic Supramolecular Assemblies with Complex Shapes by Ion Mobility Spectrometry-Mass Spectrometry

Coordination-driven self-assembly is a technique that has been increasingly used to generate supramolecular materials for use in various nanotechnologies which require specifically designed cavities and shapes. Ion mobility spectrometry-mass spectrometry (IMS-MS) provides a method to characterize the shape of organometallic supramolecular assemblies that cannot be unambiguously characterized through traditional methods such as X-ray crystallography or NMR due to obstacles such as insolubility or symmetry between isomers. Here drift cell IMS-MS is used to obtain absolute cross sections of a number of 2- and 3-D supramolecular assemblies, some of which do not have X-ray structures available. Experimental cross sections are compared with modeled candidate structures to make a final conformation or structural assignment. The temperature dependence of the cross sections of rigid supramolecular assemblies was investigated by IMS-MS to evaluate the newly-developed projected superposition approximation (PSA) computational algorithm against the traditional projection approximation and trajectory methods.