Investigations into the Coordination Chemistry of 1,3-Bis(2′-benzimidazolylimino)isoindoline

The N,N,N-tridentate ligand, 1,3-bis(2 '-benzimidazolylimino)isoindoline (1) is derived from the reaction of diiminoisoindoline (DII) with 2-aminobenzimidazole and readily binds metal ions. We synthesized several metal complexes of 1 including iron (2), nickel (3), cobalt (4), copper (5) and zinc (6) and were able to structurally characterize all of them as well as free base 1 via single crystal X-ray diffraction methods. Only compounds with a 1:1 metal: ligand stoichiometry were observed, possibly due to the steric bulk of the benzimidazole ligand arms. Ligand 1 binds more tightly than the similar BPI ligand, exhibiting more uniform M-N bond lengths. All compounds exhibit hydrogen bonding via the external N-H group of the benzimidazolyl units, including many cases of extensive hydrogen bond network formation in the solid state.