Synthesis and characterization of FeII complexes with a BPMEN type ligand bearing π‐accepting nitro groups.

In this paper, we describe the synthesis, characterization and stability studies of new FeII complexes prepared with ligand N,N'-dimethyl-N,N'-bis-(4-nitro-pyridin-2-ylmethyl)-ethane-1,2-diamine (L₄²NO₂). The properties of these complexes, probed by magnetic, spectroscopic and electrochemical techniques, are compared to those of the parent complexes prepared with the unsubstituted ligand N,N'-dimethyl-N,N'-bis-(pyridin-2-ylmethyl)-ethane-1,2-diamine (BPMEN or L₄²). The para-functionalization of the pyridine moieties with a π-accepting nitro group increases the ligand field strength and the Lewis acidity of the metal center at the same time, without altering the complex stability.