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 Delta CCS 13 angstrom(2) and 23 angstrom(2), for C-60 or C-70, 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 angstrom(2).. The energy-minimized structures of [1](4+), [C-60@1](4+), [C-70@1](4+), [(NTCDI)(2)(corannulene)@1](4+) in the gas phase were obtained by DFT calculations.Introduction

Automated summary

The study investigated the encapsulation of tetracationic palladium metallosquare with four pyrene-bis-imidazolylidene ligands using ESI TWIM-MS and determined Collision Cross Sections (CCS). The host exhibited expansion when fullerenes or polycyclic aromatic hydrocarbons were encapsulated, with expansions ranging from 13 to 49 angstrom(2). DFT calculations were used to obtain energy-minimized structures of the complexes in the gas phase.