Two segregated columnar stack platinum-bis-dithiolene molecule solids showing spin-Peierls-type transition above room temperature

Abstract

Two new one-dimensional (1-D) compounds, [CH₃-BzPy][Pt(mnt)₂] (1) and [CH₃-BzPy-d₅][Pt(mnt)₂] (2) (CH₃-BzPy⁺ = 1-N-(4-CH₃-benzyl)pyridinium and the pyridine in CH₃-BzPy⁺ was replaced by pyridine-d₅ to give the CH₃-BzPy-d₅⁺; mnt²⁻ = maleonitriledithiolate), were synthesized and characterized. 1 and 2 show similar magnetic behavior in 1.8–400 K; they experience a spin-Peierls-type transition around 320 K and show a uniform antiferromagnetic S = 1/2 chain behavior in high temperature (HT) phase, a spin gap feature in low temperature (LT) phase. A symmetry breaking structural phase transition is associated with the spin-Peierls-type transition. Two isostructural compounds crystallize in space group P2(1)/c in HT phase, with a = 12.3066(8) Å, b = 27.0522(18) Å, c = 7.4248(4) Å, β = 104.204(6)° and V = 2396.3(3) ų for 1versus a = 12.3331(9) Å, b = 27.087(4) Å, c = 7.4501(9) Å, β = 104.149(13)° and V = 2413.3(6) ų for 2 at 353 K, while space group P in LT phase, with a = 7.3203(10) Å, b = 12.2816(16) Å, c = 26.904(4) Å, α = 88.500(4)°, β = 86.731(4)°, γ = 75.421(4)° and V = 2337.0(5) ų for 1versus a = 7.3308(8) Å, b = 12.2848(13) Å, c = 26.930(3) Å, α = 88.479(3)°, β = 86.652(4)°, γ = 75.563(3)° and V = 2344.5(4) ų for 2 at 296 K. DSC measurements revealed 1 and 2 showing almost the same T_C. This observation is distinction from the [Ni(mnt)₂]⁻-based spin-Peierls-type analogues [CH₃-BzPy][Ni(mnt)₂] and [CH₃-BzPy-d₅][Ni(mnt)₂] where the deuteration leads to T_C up shifting 2.3 K.