Synthesis and characterization of three geometric isomers of rutheniumII(2,2′-bipyridyl)(salicylaldehyde)2

A new synthesis of RuII(bpy)(sal)2 (1) (bpy=2,2′-bipyridyl, sal=salicylaldehyde) has been developed and the separation and characterization of all three geometric isomers have been completed. The isomers are denoted 1a (phenolic oxygens trans), 1b, (aldehyde oxygens trans), and 1c (aldehyde oxygen trans to phenolic oxygen). All three isomers have been characterized by 1H NMR, high resolution FAB-MS, UV–Vis, and cyclic voltammetry. Additionally, 1a has been characterized by solid-state UV–Vis and a single-crystal X-ray structural study. The solid-state packing of the RuII(bpy)(sal)2 molecules in the structure of 1a displays intermolecular π–π interactions between bpy ligands of adjacent molecules. The bpy interactions form infinite π-stacks with alternating short stacking distances of 3.437 and 3.402 Å.