Characterization of supramolecular complexes by high resolution electrospray ionization mass spectrometry

High resolution mass spectrometry on time-of-flight (TOF) and ion trap (IT) mass spectrometers is used for the qualitative speciation of a heterodimetallic triple-stranded helicate [EuFe(L1)3](CIO4)5 and a toroidal complex [Ni3(L2)3](CIO4)6 (= circular single-stranded helicate) dissolved in acetonitrile. The resolution of about 5000 at peak width at half height using ion trap mass spectrometry (ITMS) and time-of-flight mass spectrometry (TOFMS) combined with electrospray ionization (ESI) is sufficient to resolve sextuply charged ions leading to a straightforward characterization of the complexes in solution. The ESI-MS response is influenced by the interface design, particularly for the heated capillary interface which requires optimized conditions for the study of non-covalent complexes.