Theoretical analysis of pressure induced spin crossover phenomenon in a di-nuclear Fe(II) molecular complex
Theoretical analysis of pressure induced spin crossover phenomenon in a di-nuclear Fe(II) molecular complex
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DOI：
10.1088/1361-648x/ab6044
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发表时间：
2020-04-17
影响因子：
2.7
通讯作者：
Dasgupta, Indra
中科院分区：
文献类型：
--
作者：
Chakraborty, Atasi;Chakraborty, Arup;Dasgupta, Indra
我们使用密度泛函理论和模型哈密顿方法研究了化学式为 [{Fe(bpp)(NCS)(2)}(2)('-bipy)]center dot 2MeOH（其中 bpp = -bis(pyrazol-3-yl)pyridine and '-bipy = '-bipyridine, 1）的 Fe 基双核分子配合物。我们的研究提供了对这些系统中实验观察到的压力驱动自旋交叉（SCO）现象的见解。随着压力的增加，Fe(II)阳离子的自旋态逐渐从高自旋态(S = 2)转变为低自旋(LS)态(S = 0)，并伴随着体积收缩。压力的逐渐增加会缩短 Fe-N 键长，并导致 FeN6 八面体的角度偏差，导致完全转变为 LS 态，而无需全局结构相变。我们对有效单点哈密顿量进行了精确对角化研究，证实了分子内相互作用对于 SCO 现象的重要性。我们研究了观察到的 SCO 现象的协同性。我们还研究了Co掺杂对Fe自旋态的影响，发现Fe的自旋态对掺杂原子的浓度有微妙的依赖性。过量的 Co 掺杂为 Fe 的中间自旋态的可能性铺平了道路，并且可以引起双稳态自旋跃迁过程。
We have studied a Fe-based di-nuclear molecular complex having the chemical formula [{Fe(bpp)(NCS)(2)}(2)('-bipy)]center dot 2MeOH (where bpp = -bis(pyrazol-3-yl) pyridine and '-bipy = '-bipyridine, 1) using density functional theory and model Hamiltonian approach. Our study provides insight to the pressure driven spin-crossover (SCO) phenomena observed experimentally in these systems. Upon increasing the pressure, the spin state of Fe(II) cation gradually changes from a high spin state (S =2) to a low spin (LS) state (S =0) accompanied by volume contraction. The gradual increase in pressure shrinks Fe-N bond length and also causes angular deviation of the FeN6 octahedron leading to full conversion to the LS state without global structural phase transition. We have carried out exact diagonalization study of an effective single site Hamiltonian and confirmed the importance of intramolecular interaction for SCO phenomena. We have investigated the cooperativity of the observed SCO phenomena. We have also studied the effect of Co doping on the spin state of Fe and find that the spin state of Fe has a subtle dependency on the concentration of dopant atoms. Excess Co doping pave the way towards the possibility of an intermediate spin state for Fe and can give rise to a bistable spin transition process.