Unusual magnetic transition around 210 K in a new 1D molecular solid based on image ion

A new ion-pair complex, [CNBzPyNH2][Ni(mnt)2] (1), where [CNBzPyNH2]+ = 1-(4′-cyanobenzyl)-4-aminopyridinium and mnt2− = maleonitriledithiolate, forms a completely segregated uniform stacking column with the Ni⋯Ni distance 3.863 Å and shows a peculiar magnetic transition from paramagnetism in the high-temperature (HT) phase to spin gap in low-temperature (LT) phase around 210 K. The DSC analysis reveals that the phase transition is first order.