Synthesis and structural characterization of an iron(II) complex with biimidazole/amine tridentate ligands

The novel iron(ll) [FeL(2)]Cl1.3Br0.7 complex has been prepared, where L = bis[(1-methylimidazol-2-yl)methyl]amine. It crystallizes in the monoclinic system, space group P2(1)/c, with Z=4, a=9.328(4) Angstrom, b=9.174(4) Angstrom, c=19.389(9) Angstrom, and beta=97.90(3)degrees, The structure consists of mononuclear cations [FeL(2)](2+) separated by X(-) (Cl/Br) anions and DMF molecules of crystallization. The central iron is in a distorted octahedral environment provided by the two imidazoles and the amine nitrogen atoms of each ligand. Each halide ion is involved in six hydrogen bonds. The iron(ll) high-spin S=2 ground slate is confirmed by the Mossbauer, magnetic susceptibility, EPR and IH NMR data, The Mossbauer spectrum is characterized by the presence of two distinct doublets, assigned to the two components of [FeL(2)]Cl1.3Br0.7, namely 32% of [FeL(2)]Cl-2 and 68% of [FeL(2)]ClBr. This heterogeneity is explained by anion effects, through the hydrogen-bonding network, upon the electric field gradient at the ferrous site.