One-dimensional molecular solid [I-BzPy-d5][Pt(mnt)2] (I-BzPy-d5+ = 1-N-(4-iodobenzyl)pyridinium-d5, mnt2− = maleonitriledithiolate): Synthesis, crystal structure, magnetic property and variable-temperature infrared spectra

• A new one-dimensional molecular solid was achieved.
• This molecular solid shows a hysteretic magnetic transition occurs at ca. 80 K upon cooling with 5.6 K thermal hysteresis.
• Intramolecular vibrational modes cooperate with the magnetic phase transition.
• There exists pre-transition phenomenon up until 100 K in this molecular solid.

A new one-dimensional molecular solid, [I-BzPy-d5][Pt(mnt)2] (mnt2− = maleonitriledithiolate, I-BzPy-d5+ = 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-d5][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.

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