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

A series of Fe(II) complexes with (ClO4)(SeCN), (ClO4)(SCN), (Fe2OCl6)2−, and 2(BF4) counter-anions for complexes 1–4, derived from dmbpy (4,4′-dimethyl-2,2′-bipyridine), were prepared. The single-crystal studies and the Hirshfeld surfaces analysis revealed that the (Fe2OCl6)2− anion results more distortional octahedral geometry of the cation than other anions. In particular, the (ClO4)(SCN) and (Fe2OCl6)2− anions lead to complexes 2 and 3 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 4 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 1 was in high-spin (HS) state and complex 2 was in low-spin (LS) state.