Synthesis of multi-imidazolium salt ligands containing calixarene fragments and their N-heterocyclic carbene Ag(I) macrocyclic complexes

Two unsymmetrical bis-imidazolium ligands, two symmetric tetra-imidazolium ligands and their dinuclear NHC-Ag macrocyclic complexes have been prepared and characterized. The X-ray diffraction analysis showed that the molecule 5a adopts a twisted macrocyclic structure, in which the two Ccarbene-Ag-Ccarbene axials are crossed and the two p-t-butylphenoxyl groups are in a staggered conformation.