Synthesis And Properties Of Organometallic Cages Bearing Imidazo [1,5-?] Pyridine-based N-Heterocyclic Carbene Ligands

In recent years,the design and synthesis of poly-NHC?N-heterocyclic carbenes,NHC?ligands and the preparation of metallosupramolecular assemblies from such ligands have become a burgeoning area of research.The prevalence of a fixed,nearly linear C_NHC-M-C_NHC?M=Ag^I,Au^I?coordination mode causes the two NHC precursors assembled together by metal ions in a"face-to-face"fashion.Among the linear NHC-M-NHC complexes,imidazolium and benzimidazolium are the most common NHC donors.However the metal-carbene bond length is fixed to approximately 2.0?,which greatly limits the cavity size of metal-carbene assemblies and brings great challenges for its subsequent applications.The thesis has designed and synthesised a series of new poly-NHC precursors by the replacement of conventional imidazol-2-ylidene NHC moieties with imidazo[1,5-a]pyridine scaffold.Two types of novel metal-carbene assemblies are successfully constructed through the metal-controlled self-assembly reactions.The specific content is as follows:In the first part,we demonstrated a facile synthetic strategy for the preparation of tris-imidazo[1,5-a]pyridine-based NHC ligand precursors,which were used to access cage-like trinuclear silver?I?and gold?I?hexacarbene complexes by a metal-controlled self-assembly approach.The new hexacarbene assemblies feature a large cavity that can easily accommodate a molecule of dimethyl sulfoxide as molecular guest.This is the first study of a unique“host–guest”system containing an organometallic cylinder-like cage derived exclusively from poly-NHC ligands.The second part reported on the use of 2,4,6-triphenyl-1,3,5-triazine-bridged imidazo[1,5-a]pyridinium salts to assemble interlocked hexanuclear silver?I?dodecacarbene complexes and their transmetalation to hexanuclear gold?I?dodecacarbene complexes.The?···?interaction between ligands is the main driving force for the formation of interlocking structures.The structure of the organometallic cage was confirmed by NMR spectroscopy,mass spectrometry and X-ray crystallography.This is the first study of the interlocked organometallic cages derived to date exclusively from poly-NHC ligands and the first transmetallation of interlocked molecular species,which provides simple and useful methods for preparing various interlocked organometallic complexes.