Counter-anions-tuned crystal structure and intermolecular interactions of a series of iron (II) complexes derived from 4,4′-dimethyl-2,2′-bipyridine

<p>A series of Fe(II) complexes with (ClO<sub>4</sub>)<sup>−</sup>(SeCN)<sup>−</sup>, (ClO<sub>4</sub>)<sup>−</sup>(SCN)<sup>−</sup>, (Fe<sub>2</sub>OCl<sub>6</sub>)<sup>2−</sup>, and 2(BF<sub>4</sub>)<sup>−</sup> counter-anions for complexes <b>1–4</b>, derived from dmbpy (4,4′-dimethyl-2,2′-bipyridine), were prepared. The single-crystal studies and the Hirshfeld surfaces analysis revealed that the (Fe<sub>2</sub>OCl<sub>6</sub>)<sup>2−</sup> anion results more distortional octahedral geometry of the cation than other anions. In particular, the (ClO<sub>4</sub>)<sup>−</sup>(SCN)<sup>−</sup> and (Fe<sub>2</sub>OCl<sub>6</sub>)<sup>2−</sup> anions lead to complexes <b>2</b> and <b>3</b> stabilized via C-H···π interactions and π···π interactions, which were not found in the other two complexes. However, the double-chain structure of complex <b>4</b> was formed by C-H···F and C-H···C hydrogen bonds interactions. Due to the influence of different anions, magnetic susceptibility measurements showed that complex <b>1</b> was in high-spin (HS) state and complex <b>2</b> was in low-spin (LS) state.</p>