The novel multidentate ligand 2,3,5,6-tetrakis(benzimidazole-2-yl)pyrazine is synthesized from pyrazine-2,3,5,6-tetracarboxylic acid and characterized with means of NMR, IR, UV-Vis-NIR, TGA, elementary analysis and XRPD. The tridentate ligand with two coordination sites forms deeply coloured complexes with Fe(ClO4)2 and Fe(BF4)2, respectively. Based on former work within the research group with the substance class of bis(benzimidazol-2-yl)pyridines the major aim of this work is the synthesis of a bridging ligand to form polynuclear iron(II) compounds of a similar spin transition behaviour as it has been observed in the series of the mononuclear [Fe(4-X-bzimpy)3] compounds. The complexes, which have been synthesized for the first time witin the scope of this work, are of equimolar composition, i.e. the ratio of iron(II) to ligand is 1:1, and it is assumed that a one-dimensional network is formed in which units consisting of one ligand-molecule and one coordinated iron are linked to each other. For characterization of the novel complex compounds IR, TGA and XRPD measurements have been conducted. XRPD powder patterns show that predominantly amorphous powders have formed.
Furthermore, the powders have been investigated with temperature dependent UV-Vis-NIR spectroscopy and SQUID magnetometry in a range within 123 K and 373 K and within 4.2 K and 300 K, respectively.