Pressure effect on spin-Peierls-like transition in quasi-1D spin systems [RBzPy][Ni(mnt)2]

Two quasi-1D molecular magnets, [RBzPy][Ni(mnt)2] (RBzPy+ = 1-(4′-nitrobenzyl)pyridinium (1) and 1-(4′-brominobenzyl)pyridinium (2); mnt2− = maleonitriledithiolate), are isostructural and possess a spin-Peierls-like transition at Tc ≈ 184 K for 1 and ≈112 K for 2 at ambient pressure. The magnetic susceptibility measurements under different applied pressures disclosed two compounds exhibiting similar magnetic behaviors. For each compound, the spin transition shifts to higher temperature with pressure and the paramagnetism in high-temperature phase is suppressed. These trends seem to be explicable by the shortened distances induced by the pressure between magnetic [Ni(mnt)2]− anions and thus leading to enhancements of antiferromagnetic interactions.