Stereoselective coordination chemistry of the tetradentate chelating ligand (2R,3R)-bis(2,2′-dipyridyl-5-methoxyl)butane

Abstract

The enantiomerically pure ligand L^3RR (2R,3R)-bis(2,2′-dipyridyl-5-methoxyl)butane has been synthesised by linking two 2,2′-bipyridine units with (2R,3R)-butandiol. The reaction of L^3RR with Zn(II) afforded a mononuclear species and the ¹H NMR spectroscopy points to a C₁ symmetry, expected for a distorted trigonal bipyramidal coordination environment. These observations were confirmed by MM2 calculations and electrospray mass spectrometry. The reaction of L^3RR with iron(II) indicated the formation of a dinuclear species by mass spectrometry. Solution state CD spectroscopy indicates that both complexes adopt a Λ-configuration, implying a single stranded dinuclear iron(II) complex is present rather than the anticipated triple helical architecture.