Bis(quinolyl)pyridine and Bis(isoquinolyl)pyridine Ligands for Carbon-Rich Molecular Clefts

Abstract

This thesis describes the synthesis of a 2,6-bis(quinolyl)pyridine ligand that can form a large molecular cleft upon metal coordination. The walls of the cleft are defined by the 42 carbon PAH hexa-peri-hexabenzocoronene (HBC) that is able to bind aromatic guests through complementary supramolecular interactions. The cleft ligand is synthesised in 11 steps from commercial starting materials and the structure is confirmed by NMR, mass spectrometric and infrared spectroscopic measurements. Significant challenges were encountered in the synthesis of some precursors and the various methods attempted are outlined. In particular, efficient routes for the preparation of the bifunctional heterocycles 7-bromo-2-iodoquinoline and 7-bromo-2-acetylquinoline were developed. Complexation studies of the cleft ligand with Pd(II), Ag(I) and Ru(II) metal centres have been undertaken and complexes identified primarily by mass spectrometry measurements; the moderate solubility of the products hindered purification and complete characterisation. A second HBC-based ligand with a larger bis(isoquinolyl)pyridine binding cleft is proposed and preliminary steps towards its synthesis are also described.