Magnetic properties of RBzPy[Ni(α-tpdt)2] (R = H, Br, F):: effects of cis-transdisorder

Three new salts RBzPy(+)[Ni(alpha-tpdt)(2)](-) (alpha-tpdt = 2,3-thiophenedithiolate, BzPy = benzylpyridine, R = H, Br, F) were prepared and structurally and magnetically characterized. A common structural feature of these compounds is the arrangement of the anions with thiophenic sulfur atoms connecting to a coordinating sulfur atom of a neighbouring anion, placed almost perpendicular to each other. The cations are positioned with the pyridine rings inserted between thiophenic rings of anions, maximizing pi - pi interactions. Depending on the cation substitution structural differences and variable degrees of cis - trans disorder in the anions are observed, which affect the magnetic properties. HBzPy[Ni(alpha-tpdt)(2)] displays dominant ferromagnetic interactions and cluster glass behaviour at low temperatures, BrBzPy[Ni(alpha-tpdt)(2)] shows dominant antiferromagnetic interactions with a magnetic anomaly at similar to 6 K and FBzPy[Ni(alpha-tpdt)(2)] magnetic behavior is dominated by weak ferromagnetic interactions but without magnetic ordering down to 1.5 K.