多自由基特性的仿生稠环材料分子理论设计及自旋耦合调控与动态特性理论研究

The function-directed molecular design and functional modification of the low-dimension and low-size polycyclic graphene-like patches continues to be a hot topic in the novel carbon-based materials field. Thermal vibrations of a molecule, the inherent property of a molecule, can lead to fluctuations of its structure, and thus assign them richful dynamics spintronic properties. Besides, various biological molecular fragments like porphyrin present some special properties distinctly different from normal graphene patches, and thus also exhibit nice application prospects. In view of these, in this project, we theoretocally design various bio-inspired carbon-based polycyclic conjugated molecular patches, and investigate their multiradical characters and spin coupling regulation mechanism and their effects on molecular magnetisms, singlet-fission and other function propcesses. We establish the effective multiradical modification schemes and spin-unit coupling schemes. We study how the molecular thermal vibrations affect the multiradical characters and spin coupling interactions of these designed multiradical molecules and their assemblies. On the basis of the calculational study of the electronic structures and spin coupling properties of these systems, we mainly use ab initio molecular dynamics simulation technique to explore the dynamic regularity of the spin couplings, especially the potential transient magnetic coupling regularity of them, and establish reasonale structure-spin coupling property relationship. Further, we also want to develop newly efficient methods to calculate the dynamic magnetic coupling mechaism of the complicated structures. This work can have practical implicance in uncovering the thermally excited spin coupling regulation regularity of the species with tunable magnetic coupling properties and exploring and designing novel spintronics molecular devices.

鉴于各类低尺寸碳基稠环类石墨烯分子片分子设计及自旋电子学研究一直是新型碳基材料领域的热点课题；分子的内在热振动属性，可诱导分子结构涨落从而赋予其丰富的动态自旋电子学特性；各种特殊的生物分子片（如卟啉）呈现了正常类石墨烯片所不具备的特殊性质，在仿生材料方面也呈现出美好应用前景，本项目拟理论设计仿生稠环共轭多自由基分子片，探讨其多自由基特性及自旋耦合调控机制以及对分子磁性、单态裂变等功能过程的影响，建立有效的多自由基化修饰以及自旋单元组合方案。研究分子热振动对此类仿生稠环多自由基分子及其组装体自旋耦合的影响规律。利用从头算分子动力学方法研究其动态规律，开发潜在的瞬变磁耦合规律。建立此类仿生稠环多自由基分子及其组装体结构与动态自旋耦合之间的构效关系。发展动态磁耦合机制的有效计算模拟方法。此工作对揭示具有可变磁耦合特性的分子体系热激自旋耦合调控规律、开发新型的自旋电子学器件具有重要意义。

自旋态或磁性可转换的有机双自由基碳基磁性材料在自旋电子学、数据存储等方面具有广泛的应用而备受关注。各类低尺寸碳基稠环类石墨烯分子片设计及自旋电子学研究一直是新型碳基材料领域的热点课题。本项目围绕多自由基功能化的仿生碳基共轭稠环分子及其组装体这类新型的类石墨烯片的结构、动态自旋性质及有关演化动力学等有关问题，用计算及分子动力学模拟方法从分子层次上研究并开发设计了具有良好磁性质的新型的仿生及类石墨烯稠环碳基材料分子及其组装体的分子结构及磁耦合性质的构效关系，揭示了其磁耦合机制及动态磁耦合规律，取得了预期的成果。基于卟啉、类石墨烯片、DNA碱及碱对结构等具有一定π共轭度的生物分子，设计开发了具有双自由基特性的新型仿生稠环碳基共轭分子片，即具有显性及隐性开壳层的仿生稠环分子磁子，建立了合理的功能磁性目标的修饰方案。揭示了多自由基特性及自旋耦合调控机制以及对分子磁性等功能过程的影响，建立了有效的多自由基化修饰以及自旋单元组合方案。澄清了分子的振动模式、结构涨落对此类稠环共轭分子片潜在磁性的诱导机制以及分子间和分子内热振动的耦合作用规律，研究了分子动力学因素对修饰分子磁性的影响，并给出其动态磁耦合变化规律。特别阐明了光诱导、质子转移、氧化还原、应变等手段所诱导出的丰富铁磁和反铁磁的自旋电子学特性规律及调控模式。在此基础上，进一步研究了稠环类衍生物组装相关问题，揭示了纳米级分子磁性组装体的静态与动态磁耦合特征。表明了二维金属卟啉片自旋磁序列对应变具有快速响应以及应变效应实现的四种可能的磁特性（铁磁/FM, 亚铁磁/FIM，反铁磁/AFM1和AFM2）以及它们之间的转化，实现了磁性调控。发现了含有NV缺陷的二维卟啉结构具有优异的电子性能和稳定的磁性。本项目为开发新型的基于仿生碳基共轭稠环多自由基分子体系的磁性纳米材料提供重要的理论指导信息。