质子化三嗪衍生物的电子和光学性质
Electronic and Optical Properties of Protonated Triazine Derivatives
摘要：
共价有机框架（COFs）的独特的电子和光学性质在很大程度上取决于质子化，质子化是一种普遍存在的现象，在其中合成的溶液环境。由此产生的影响是不平凡的，似乎是至关重要的有趣的功能，这些材料。在含时密度泛函理论的量子力学框架下，我们从第一性原理出发研究了水溶液中三嗪和氨基质子化对COFs分子结构单元的影响.在所有考虑的情况下，我们发现，质子吸收导致的间隙减少和重组的电子结构，驱动质子的存在和带正电的质子化的物种和负的counterweight在其附近之间的静电吸引力。质子化引起的结构扭曲被发现只起很小的作用。带隙重整化和激子结合强度之间的相互作用决定了吸收起始的能量：当前者占上风时，观察到红移。此外，质子化后的分子轨道的空间和能量重排诱导分裂的最低能量峰和降低其振子强度相比，原始的同行。我们的研究结果提供了定量和微观的洞察质子化的三嗪衍生物的电子和光学性质的COFs的积木的作用。因此，它们有助于合理化这些材料的结构、性质和功能之间的关系。
英文摘要：
The peculiar electronic and optical properties of covalent organic frameworks (COFs) are largely determined by protonation, a ubiquitous phenomenon in the solution environment in which they are synthesized. The resulting effects are non-trivial and appear to be crucial for the intriguing functionalities of these materials. In the quantum-mechanical framework of time-dependent density-functional theory, we investigate from first principles the impact of protonation of triazine and amino groups in molecular building blocks of COFs in water solution. In all considered cases, we find that proton uptake leads to a gap reduction and to a reorganization of the electronic structure, driven by the presence of the proton and by the electrostatic attraction between the positively charged protonated species and the negative counterion in its vicinity. Structural distortions induced by protonation are found to play only a minor role. The interplay between band-gap renormalization and exciton binding strength determines the energy of the absorption onsets: when the former prevails on the latter, a red-shift is observed. Furthermore, the spatial and energetic rearrangement of the molecular orbitals upon protonation induces a splitting of the lowest-energy peaks and a decrease of their oscillator strength in comparison with the pristine counterparts. Our results offer quantitative and microscopic insight into the role of protonation on the electronic and optical properties of triazine derivatives as building blocks of COFs. As such, they contribute to rationalize the relationships between structure, property, and functionality of these materials.
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