Syntheses and structural characterization of iron(II) coordination polymers with flexible 1,4-bis(imidazol-1-ylmethyl)benzene ligand

•Flexible μ2-bix ligand can adopt various conformations.•SCN− anion form a 2D while the N3− ions form a 3D networks due to the presence of hydrogen bonds in the structure.•The polymers have been characterized by X-ray diffraction, elemental and thermal analyses and infrared spectroscopy.

Iron(II) coordination polymers {[Fe(bix)2(NCS)2]·H2O}n (1) and [Fe(bix)2(N3)2]n (2) were synthesized using the flexible bidentate N-donor 1,4-bis(imidazol-1-ylmethyl)benzene (bix) ligand together with the mono-anionic ligands such as NCS− and N3− ions. In both of these complexes the iron(II) ion is in a distorted octahedral arrangement. Polymers 1 and 2, exhibit 2D framework with the ABCDE… and ABAB… packing modes, respectively. By considering the non-classical C–H⋯N hydrogen bonds, complex 2 is a three-dimensional polymer. Due to the presence of seven different kinds of trans-gauche conformations of the flexible bix ligands in the asymmetric unit of 1, there are four crystallographically independent iron(II) ions. In contrast to 1, in complex 2, all the bix ligands have the same conformation (trans-gauche). So, there is only one kind of iron(II) ion in this structure. Moreover, an attempted synthesis of [Fe(bix)3](ClO4)2 lead to the formation of unexpected diprotonated ionic species [bixH2](ClO4)2 (3) which was identified by X-ray analysis and infrared spectroscopy. Polymers 1 and 2 have been characterized by infrared spectroscopy, elemental and thermal analyses and single-crystal X-ray diffraction.

Graphical abstractTwo Fe(II) coordination polymers with phenyl-imidazole based ligand, bix, were obtained with different structures. In each of these complexes, the metal centre is in a distorted octahedral geometry. {[Fe(bix)2(NCS)2]·H2O}n is a 2D polymer while [Fe(bix)2(N3)2]n forms a 3D network structure due to the presence of hydrogen bonds in this structure.Figure optionsDownload full-size imageDownload as PowerPoint slide