Ion Mobility Mass Spectrometry Uncovers Guest‐Induced Distortions in a Supramolecular Organometallic Metallosquare

The encapsulation of the tetracationic palladium metallosquare with four pyrene‐bis‐imidazolylidene ligands [1]4+ with a series of organic molecules was studied by Electrospray ionization Travelling Wave Ion‐Mobility Mass Spectrometry (ESI TWIM‐MS). The method allowed to determine the Collision Cross Sections (CCSs), which were used to assess the size changes experienced by the host upon encapsulation of the guest molecules. When fullerenes were used as guests, the host is expanded ΔCCS 13 Å2 and 23 Å2, for C60 or C70, respectively. The metallorectangle [1]4+ was also used for the encapsulation of a series of polycyclic aromatic hydrocarbons (PAHs) and naphthalenetetracarboxylic diimide (NTCDI), to form complexes of formula [(NTCDI)2(PAH)@1]4+. For these host:guest adducts, the ESI IM‐MS studies revealed that [1]4+ is expanded by 47–49 Å2.. The energy‐minimized structures of [1]4+, [C60@1]4+, [C70@1]4+, [(NTCDI)2(corannulene)@1]4+ in the gas phase were obtained by DFT calculations.Introduction We present an ion‐mobility mass spectrometry (IM‐MS) study on the encapsulation characteristics of a shape‐adaptable organometallic metallocage, and demonstrate that IM‐MS in combination with DFT calculations constitutes a reliable approach to quantify distortions experienced by the host upon guest encapsulation.