Metal-directed assembly of combinatorial libraries—principles and establishment of equilibrated libraries with oligopyridine ligands

Abstract

The cobalt(II) complexes [Co(bpy)₃][PF₆]₂, [Co(Me₂bpy)₃][PF₆]₂ (Me₂bpy = 4,4′-dimethyl-2,2′-bipyridine) and [Co(phen)₃][PF₆]₂ give paramagnetically shifted ¹H NMR spectra which may be fully assigned; the complexes are labile and ligand exchange is complete within mixing time in CD₃CN solutions to give libraries of heteroleptic complexes which have been fully characterised by one- and two-dimensional ¹H NMR spectroscopy. A library comprising mer and fac isomers of [CoL₃]²⁺ (L = 2,2′-bipyridine-5-carbaldehyde) can be amplified by specific reaction of the fac stereoisomer with a triamine to give a new hexadentate ligand, although other ligand exchange processes compete.