Conformational investigations on three large dinuclear triple helicates by single crystal X-ray diffraction

Three new dinuclear triple helicates were synthesised using a ditopic semi-rigid pyridylylimine ligand L, separated by a diphenoxy-biphenol spacer providing considerable length to the backbone. L and the new large dinuclear triple helicate complexes [Fe2L3](BF4)4 (1), [Ni2L3](BF4)4 (2) and [Zn2L3](BF4)4 (3) have been characterised in solution and solid state. Single crystal X-ray diffraction was used to investigate overall complex ion shape as the coordination sphere was modulated by metal ion selection. Small differences in complex shape were seen to arise due to subtle distortions in coordination sphere environments. This study sheds light on how the length and twist of dinuclear triple helicates can be tuned by selection of coordinating metal ion.