Far IR and Raman spectroscopy of [Fe–(PM-BiA)2 (NCS)2] and [Fe –(PM-PEA)2 (NCS)2] are performed to record the vibration modes of these complexes and their evolutions during spin state transition. THz spectroscopy is used to measure the far IR absorption of these compounds down to 20 cm-1. Using density functional theory calculations we are able to retrieve and to visualize these vibrations in both high spin and low spin states. In both compounds, Raman spectra recorded in the 800 cm-1 2250 cm-1 wavenumber range are well accounted for by our computations. For far IR vibration modes, most of the experimental absorption peaks above 100 cm-1 are well reproduced. However, below 100 cm-1 , marked differences are recorded. For [Fe–(PM-BiA)2 (NCS)2] we demonstrate that the interactions with surrounding molecules impacts non-negligibly the computed far IR spectra and can partly correct for this difference.

中文翻译：

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自旋态转变对 [Fe-(PM-BiA)2 (NCS)2] 和 [Fe -(PM-PEA)2 (NCS)2] 自旋交叉化合物振动的影响：实验和理论远红外和拉曼研究。

[Fe–(PM-BiA)2 (NCS)2] 和 [Fe –(PM-PEA)2 (NCS)2] 的远红外和拉曼光谱用于记录这些配合物的振动模式及其在自旋过程中的演变状态转换。太赫兹光谱用于测量这些化合物低至 20 cm-1 的远红外吸收。使用密度泛函理论计算，我们能够在高自旋和低自旋状态下检索和可视化这些振动。在这两种化合物中，我们的计算很好地解释了在 800 cm-1 2250 cm-1 波数范围内记录的拉曼光谱。对于远红外振动模式，大多数 100 cm-1 以上的实验吸收峰都得到了很好的再现。但是，低于 100 cm-1 时，会记录到显着差异。