Synthesis of a homochiral carboxylate-containing tetradentate ligand and its Co(III) complex

A new class of easily tunable, homochiral tetradentate ligand, (R,R)-[(N-benzyl-N-{2-[N-benzyl-N-(pyridine-2-yl)methyl]amino}cyclohexyl)amino]acetic acid (2), has been synthesized and characterized by NMR spectroscopy. The synthesis involves highly selective N-alkylation of the 1,2-diamine via an imidazolidine intermediate, giving up to 78% overall yield. The corresponding Co(III) complex of general composition [Co(2a)(NO2)2] has been synthesized and the major stereoisomer has been characterized by X-ray crystallography. Molecular calculation at PM3 level indicates that the major isomer is cis-β-Δ-syn isomer.