Crystal structures, magnetic and dielectric features of two new isostructural one-dimensional platinum-bis-dithiolene molecular solids

Two new one-dimensional (1-D) molecular solids, [CH2 = CH-BzPy][Pt(mnt)2] (1) and [CH2 = CH-BzPy-d5][Pt(mnt)2] (2) where CH2 = CH-BzPy-d5+ = 1-N-(4-vinylbenzyl) pyridinium-d5 and mnt2− = maleonitriledithiolate, were synthesized and characterized. A structural phase transition undergoes with TC ≈ 335 K in the crystals of 1 and 2, which were confirmed by variable-temperature magnetic susceptibility and DSC measurements. Crystals of 1 and 2 are isostructural in both high- and low-temperature phases. Besides the strong similarity in crystal structures, they show quite analogous magnetic and dielectric features. Above TC, the magnetic behavior is failed to follow the S = ½ Heisenberg linear chain model; below TC, a spin gap is opened for 1 and 2. The thermally-assisted dielectric relaxation occurs above ca. 280 K for 1 and 2, and this relaxation process is related to the dipole motion of the disordered CH2CH groups in the cation under an ac electrical field.