Pillarplex rim-iodination and investigations of a controlled threading towards PEG polyrotaxanes

Macrocyclic N-heterocyclic carbene (NHC) complexes are increasingly utilized in supramolecular assemblies to create cavities through non-covalent interactions. This thesis focuses on a metal-organic subclass of these supramolecular hosts, specifically pillarplexes of the form M8L2(X)4 (where M = Ag, Au; X=OTf, PF6; OAc), which are octanuclear NHC complexes forming metallocavitand structures. While pillarplexes exhibit intrinsic properties, such as the ability to host linear molecules and luminescence, functionalization is essential to expand their structural and functional capabilities for advanced biological and industrial applications. The first objective of this thesis was to introduce iodine functionality at the pyrazole backbone of the calix[4]imidazolium[2]pyrazolate ligand (H6L(X)4) and synthesize rim-iodinated pillarplexes, thus opening advanced possibilities for further functionalization and structural expansion. Iodination was accomplished by adapting the established bromination method, using N-iodosuccinimide as a mild and selective iodine source widely employed in iodination reactions. The resulting ligand precursor H6LI(PF6)4 was then used to coordinate silver(I) and gold(I), with the main goal of obtaining rim-iodinated metallocavitands. Characterization of the functionalized ligand and pillarplexes was performed using NMR spectroscopy, mass spectrometry, elemental analysis, and single crystal X-ray diffraction. The second part of the thesis focused on studying polyrotaxane formation using pristine pillarplex. Polypseudorotaxanes were first explored, utilizing pristine pillarplex as the cavitand and NH2-terminated PEG as the axle. Various host-guest molar ratios, solvents, and temperatures were tested. Subsequently, polyrotaxane and rotaxane synthesis was investigated using a literature-known stoppering reaction. However, no evidence of polyrotaxane formation was observed using the employed synthetic strategy.