One-dimensional molecular solid [I-BzPy-d₅][Pt(mnt)₂] (I-BzPy-d₅⁺ = 1-N-(4-iodobenzyl)pyridinium-d₅, mnt^2- = maleonitriledithiolate): Synthesis, crystal structure, magnetic property and variable-temperature infrared spectra

A new one-dimensional molecular solid, [I-BzPy-d₅][Pt(mnt) ₂] (mnt^2- = maleonitriledithiolate, I-BzPy-d ₅⁺ = 1-N-(4-iodobenzyl)pyridinium-d₅) was synthesized. [I-BzPy-d₅][Pt(mnt)₂] and its analog [I-BzPy][Pt(mnt)₂] are isostructural, crystallized in space group P-1 at ambient temperature. A hysteretic magnetic transition occurs at ca. 80 K with 5.6 K thermal hysteresis upon cooling. [I-BzPy-d₅][Pt(mnt) ₂] features an alternating S = 1/2 Heisenberg antiferromagnetic linear chain magnetic behavior with spin gap of 131 K in high-temperature phase, while 306 K in low-temperature phase. There is no significant isotope effect of both magnetism and phase transition by comparison of [I-BzPy-d ₅][Pt(mnt)₂] and [I-BzPy][Pt(mnt)₂]. The variable-temperature IR spectra in 10-293 K revealed the existence of pre-transition phenomenon up until 100 K and five intramolecular vibrational modes cooperating with the magnetic phase transition.