电子控制四坐标双酸铁复合体中的旋转交叉特性
Francesca Milocco1, Folkert de Vries1, Imke M A Bartels1
1Stratingh Institute for Chemistry, University of Groningen, Nijenborgh 4, 9747 AG Groningen, The Netherlands.
Journal of the American Chemical Society
|November 16, 2020
概括
研究人员开发了具有可调节的旋转交叉行为的铁酸复合体. 这些化合物通过在低旋转和高旋转状态之间切换来显示材料科学和催化应用的潜力.
科学领域:
- 协调化学
- 材料科学
- 旋转交叉现象
背景情况:
- 在d块金属复合体中的旋转状态转换对于结构,反应性和信息存储和金属酶催化等应用至关重要.
- 旋转交叉化合物通常局限于八面体环境中的协调和金属中心;低协调的旋转交叉复合物很少见.
- 通过固态和电子效应调整连接体场强度 (ΔO) 是设计自旋交叉材料的关键策略.
研究的目的:
- 合成和表征四坐标, (伪) 四面体铁 (II) 复合物,其中包括酸联体.
- 通过电子替代效应在溶液中研究热诱导的旋转交叉过渡 (S=0到S=2).
- 探索固态包装对旋转交叉行为的影响.
主要方法:
- 一系列六个铁II复合物的合成,具有不同的酸连接体.
- 基于溶液的旋转交叉研究,包括温度依赖的测量 (T1/2).
- 通过X射线结晶学进行固态结构分析.
- 密度函数理论 (DFT) 计算以了解旋转交叉热力学和电子效应.
主要成果:
- 所有六种合成的铁 (II) 复合物都表现出在室温 (300368 K) 以上的过渡温度 (T1/2) 的旋转交叉.
- 射线结晶学显示,大多数复合物在固体状态下具有低旋转,但包装效应会导致严格的高旋转或逐渐的旋转交叉行为.
- DFT计算证实了低旋转状态的稳定,这是由于formzanate连接体的π-接受器特性,产生了"反转"连接体场和显著的金属连接体共价性.
结论:
- 在低坐标铁 (II) 复合体的溶液中,formzanate配体上的电子替代剂有效调节自旋交叉热力学.
- 固态包装效应可以显著影响观察到的旋转状态和交叉行为,有时会超过内在的电子偏好.
- 这项研究强调了酸对设计具有可调节性质的新型自旋交叉材料的潜力,替代剂的放置 (C-Ar与N-Ar) 对金属-酸结合有不同的影响.
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