Synthesis, crystal structure and magnetic characterization of two new ion-pair complexes containing bis(maleonitriledithiolate)nickelate anion and substituted benzylpyridinium cation

Two new ion-pair complexes, [FBrBzPyN(CH3)2]2[Ni(mnt)2] (1) and [FBrBzPyN(CH3)2][Ni(mnt)2] (2) (mnt2− = maleonitriledithiolate, [FBrBzPyN(CH3)2]+ = [1-(4′-fluoro-2′-bromobenzyl)-4-dimethylaminopyridinium]) have been prepared and characterized by elemental analyses, UV, IR, single crystal X-ray diffraction and magnetic susceptibility. The cations (D) and the anions (A) in 1 stack into a 1D alternating column (i.e., of type ⋯DDADDADD⋯) via short S⋯Br, N⋯F, C⋯N interactions, and C–H⋯Br hydrogen bonds. The cation–cation π⋯π stacking interactions within the columns give further rise to a 2D network structure. Compound 2 forms a 3D structure in which the Ni(III) ions stack into a uniform 1D zigzag magnetic chain through Ni⋯S, Ni⋯Ni, or π⋯π interactions with a Ni⋯Ni distance of 4.024 Å. Magnetic susceptibility measurements in the temperature range 2–300 K show that 1 is expected to be diamagnetic, and 2 exhibits an interesting spin-gap transition (Δ/kb = 460.6 K) around 155 K.