Synthesis, crystal structure and magnetic properties of A[Ni(mnt)2] complexes [A=1-(4-nitrobenzyl)quinolinium or 1-benzylpyridinium; mnt2- = maleonitriledithiolate]

Two new ion-pair complexes A[Ni(mnt)(2)], [A = 1-(4-nitrobenzyl)quinolinium (1), and 1-benzylpyridinium (2)] have been prepared and characterized. The crystal structure of (1) has been determined by X-ray diffraction analysis. In the solid state, anions and cations of (1) form completely segregated stacking columns, with the Ni . . . Ni distances alternating between 3.890(4) and 4.965(5) Angstrom in the [Ni(mnt)(2)](-) stacking column. The variable temperature magnetic susceptibilities of (1) and (2) have been measured over the 77-300 K range and the results reveal that (1) is diamagnetic and that (2) shows a weak antiferromagnetic spin exchange interaction between the metal ions. The e.p.r. spectra of (1) and (2) in MeCN at room temperature were similar, the g-values being almost identical.