A strongly hydrogen-bonded one-dimensional high-spin dinuclear Fe( <scp>ii</scp> ) complex

In this study, we report the synthesis and detailed characterization of a novel chain compound, composed of hydrogen-bonded dinuclear complexes, in which two Fe(II) ions are bridged by a 2,2'-biimidazolate (bim^2-) dianion. The crystal structure of [(tpma)Fe(μ-bim)Fe(Hbim)₂] (1), where tpma = tris(2-pyridylmethyl)amine, exhibits a 1D zigzag chain architecture, formed through double hydrogen bonds between terminal 1<i>H</i>-2,2'-biimidazolate monoanions (Hbim^-), with an N⋯H distance of 1.72 Å. Magnetic susceptibility measurements reveal weak antiferromagnetic coupling between the Fe(II) centers with the exchange constant <i>J</i> = -1.4 cm^-1, mediated by the bridging ligand. The directional hydrogen bonding network, combined with π-π and H-π intermolecular interactions, suggests potential for proton dynamics that could lead to ferroelectric behavior. This complex represents the first example of a bim^2- ligand bridging two iron ions and the first dimeric complex containing both bim^2- and Hbim^- ligands, which form strong one-dimensional hydrogen bonds. Investigation of ferroelectric behavior and potential interplay between functional properties are ongoing.