Alcón Isaac, Reta Daniel, Moreira Iberio de P R, Bromley Stefan T
Institut de Química Teòrica i Computacional de la Universitat de Barcelona (IQTC-UB) , Departament de Ciència de Materiales i Química Física de la Universitat de Barcelona , C/Martí I Franqués 1 , 08028 Barcelona , Spain . Email:
Institució Catalana de Recerca i Estudis Avançats (ICREA) , 08010 Barcelona , Spain.
Chem Sci. 2017 Feb 1;8(2):1027-1039. doi: 10.1039/c6sc01412g. Epub 2016 Aug 31.
Triarylmethyls (TAMs) are prominent highly attractive open shell organic molecular building blocks for materials science, having been used in breakthrough syntheses of organic magnetic polymers and metal organic frameworks. With their radical π-conjugated nature and a proven capacity to possess high stability suitable chemical design, TAMs display a variety of desirable characteristics which can be exploited for a wide range of applications. Due to their particular molecular and electronic structure, the spin localization in TAMs almost entirely depends on the dihedral angles of their three aryl rings with respect to the central methyl carbon atom plane, which opens up the possibility of controlling their fundamental properties by twisting the three aryl rings. Aryl ring twist angles can be tuned to a single value by specific chemical functionalisation but controlling them by external means in organic materials or devices represents a challenging task which has not yet been experimentally achieved. Herein, through rational chemical design we propose two 2D covalent organic frameworks (2D-COFs) based on specific TAM building blocks. By employing computational modeling we demonstrate that it is possible to externally manipulate the aryl ring twist angles in these 2D-linked TAM frameworks by external mechanical means. Furthermore, we show this structural manipulation allows for finely tuning the most important characteristics of these materials such as spin localization, optical electronic transitions and magnetic interactions. Due to the enormous technological potential offered by this new class of material and the fact that our work is guided by real advances in organic materials synthesis, we believe that our predictions will inspire the experimental realization of radical-2D-COFs with externally controllable characteristics.
三芳基甲基（TAMs）是材料科学中极具吸引力的开壳有机分子构建块，已用于有机磁性聚合物和金属有机框架的突破性合成。由于其自由基π共轭性质以及经证实的具备高稳定性的合适化学设计能力，TAMs展现出多种可用于广泛应用的理想特性。由于其特殊的分子和电子结构，TAMs中的自旋定位几乎完全取决于其三个芳基环相对于中心甲基碳原子平面的二面角，这为通过扭曲三个芳基环来控制其基本性质提供了可能性。芳基环的扭转角可通过特定的化学官能化调节至单一值，但在有机材料或器件中通过外部手段控制它们是一项具有挑战性的任务，尚未通过实验实现。在此，通过合理的化学设计，我们提出了基于特定TAM构建块的两种二维共价有机框架（2D-COFs）。通过使用计算模型，我们证明可以通过外部机械手段在这些二维连接的TAM框架中外部操纵芳基环的扭转角。此外，我们表明这种结构操纵允许精细调节这些材料的最重要特性，如自旋定位、光电跃迁和磁相互作用。由于这类新型材料具有巨大的技术潜力，且我们的工作以有机材料合成的实际进展为指导，我们相信我们的预测将激发具有外部可控特性的自由基二维共价有机框架的实验实现。
