Mandal Kalyanashis, Bansal Deepak, Kumar Yogendra, Shukla Jyoti, Mukhopadhyay Pritam
Supramolecular and Material Chemistry Lab, School of Physical Sciences, Jawaharlal Nehru University, Delhi, 110067, India.
Institute of Resource Ecology, Helmholtz-Zentrum Dresden-Rossendorf, Bautzner Landstrasse 400, 01328, Dresden, Germany.
Chemistry. 2020 Aug 17;26(46):10607-10619. doi: 10.1002/chem.202001706. Epub 2020 Jul 20.
Halogen-bonding interactions in electron-deficient π scaffolds have largely been underexplored. Herein, the halogen-bonding properties of arylene imide/diimide-based electron-deficient scaffolds were studied. The influence of scaffold size, from small (phthalimide) to moderately sized (pyromellitic diimide or naphthalenediimides) to large (perylenediimide), axial-group modification, and number of halo substituents on the halogen bonding and its self-assembly was probed in a set of nine compounds. The structural modification leads to tunable optical and redox properties. The first reduction potential ranges between -1.09 and -0.17 V (vs. SCE). Two of the compounds, that is, 6 and 9, have deep-lying LUMOs with values reaching -4.2 eV. Single crystals of all nine systems were obtained, which showed Br⋅⋅⋅O, Br⋅⋅⋅Br, or Br⋅⋅⋅π halogen-bonding interactions, and a few systems are capable of forming all three types. These interactions lead to halogen-bonded rings (up to 12-membered), which propagate to form stacked 1D, 2D, or corrugated sheets. A few outliers were also identified, for example, molecules that prefer C-H⋅⋅⋅O hydrogen bonding over halogen bonding, or noncentrosymmetric rather than centrosymmetric organization. Computational studies based on Atoms in Molecules and Natural Bond Orbital analysis provided further insight into the halogen-bonding interactions. This study can lead to a predictive design tool-box to further explore related systems on surfaces reinforced by these weak directional forces.
缺电子π骨架中的卤键相互作用在很大程度上尚未得到充分研究。在此，对基于亚芳基酰亚胺/二酰亚胺的缺电子骨架的卤键性质进行了研究。在一组九种化合物中，探究了骨架大小（从小的邻苯二甲酰亚胺到中等大小的均苯四甲酸二酰亚胺或萘二酰亚胺，再到大的苝二酰亚胺）、轴向基团修饰以及卤代取代基的数量对卤键及其自组装的影响。结构修饰导致了可调节的光学和氧化还原性质。第一还原电位在 -1.09至 -0.17 V（相对于饱和甘汞电极）之间。其中两种化合物，即6和9，具有较深的最低未占分子轨道，其值达到 -4.2 eV。获得了所有九个体系的单晶，这些单晶显示出Br⋅⋅⋅O、Br⋅⋅⋅Br或Br⋅⋅⋅π卤键相互作用，并且一些体系能够形成所有三种类型的相互作用。这些相互作用导致形成卤键环（最多12元环），这些环进一步扩展形成堆叠的一维、二维或波纹状片层。还发现了一些异常情况，例如，相比于卤键更倾向于形成C-H⋅⋅⋅O氢键的分子，或者是非中心对称而非中心对称的结构。基于分子中的原子和自然键轨道分析的计算研究为卤键相互作用提供了进一步的见解。这项研究可以导致一个预测性设计工具箱，以进一步探索由这些弱定向力增强的表面上的相关体系。
