确定 σ 和 π 合的 conformational 景观 使用 para-Phenylene 和"Aviram-Ratner"桥梁
Daniel E Stasiw1, Jinyuan Zhang1, Guangbin Wang1
1†Department of Chemistry, North Carolina State University, Raleigh, North Carolina 27695-8204, United States.
Journal of the American Chemical Society
|July 9, 2015
概括
我们量化了分子结构如何影响捐赠者-桥梁-接受器系统中的电子合. 在桥上放置甲基组揭示了对磁交换的显著sigma和pi轨道贡献,这对分子电子学至关重要.
科学领域:
- 分子磁力学分子磁力学
- 超分子化学 超分子化学
- 计算化学的计算化学
背景情况:
- 对于设计分子电子设备而言,了解捐赠者 - 桥梁 - 接受器 (D-B-A) 系统中的电子合至关重要.
- 桥形状对磁交换合器 (J) 和电子合器 (H(DA)) 的影响是复杂的.
- 区分Sigma (σ) 和pi (π) 轨道对这些合的贡献仍然是一个关键的挑战.
研究的目的:
- 在D-B-A双根中实验确定电子合矩阵元件 (H(DA)) 的扭矩依赖.
- 阐明 σ 和 π 系统在各种桥梁 (烯,甲基替代烯,双循环[2.2.2] ) 中对磁性和电子交换的贡献.
- 为了将桥梁形状与磁性和电子合的数量相关联.
主要方法:
- 合成和表征具有定义桥梁结构的D-B-A双基 (金属半基供体,基氧化物接受体).
- 测量磁敏度以确定磁交换合常量 (J).
- 使用CASSCF (完全活性空间自相一致场) 计算进行计算分析.
- 使用3D"Ramachandran类型"图表可视化扭曲依赖.
主要成果:
- 根据桥梁形状,观察到磁交换 (J ≈ 1-175 cm-1) 和电子合 (H(DA) ≈ 450-6000 cm-1) 的显著变化.
- 在基桥上的甲基替代允许分离构造上依赖的 (π) 和独立的 (σ) 贡献.
- CASSCF的计算准确地重现了实验观察到的磁交换合的趋势.
结论:
- 该研究通过实验量化了分子构成对D-B-A系统中电子和磁交换合器的显著影响.
- 通过战略分子设计和分析,可以明确区分 σ 和 π 轨道对这些合的贡献.
- 这些发现为合理设计具有可调节电子和磁性特性的分子材料提供了基础.
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