Supramolecule-Originated Emission: A Room-Temperature Phosphorescence 2D Ionic H‑Bond Network from Nonemissive Aliphatic Derivatives

Supramolecular
materials exhibiting unique functions unavailable
from their individual components are attracting great attention. Here,
we report a novel supramolecule emission strategy, where the emission
originated from a two-dimensional (2D) ionic hydrogen bond (H-bond)
supramolecular network. High-quality crystals were obtained by rapid
self-assembly of liquid aliphatic amine and ketone. The 2D ionic H-bonding
network was characterized by single-crystal X-ray diffraction (XRD)
that shows a planar electron system similar to aromatic species. First-principles
calculations demonstrated that the charge-separated transition process
and high spin–orbital coupling constants of the rigid supramolecular
structure contribute to the enhanced singlet–triplet intersystem
crossing process. The emission could be well regulated via the substituents
of either the enol or amine part, and a maximum quantum efficiency
of 26% was realized. The emission system demonstrated stable room-temperature
phosphorescence (RTP), which is even hard to obtain for aromatic species,
and the lifetime reached 0.45 s with an 8% luminescence quantum yield.
For application, with liquid amine and enol as ink, high-quality RTP
patterns can be fabricated by computer-controlled precision printing.
Our findings will surely bring completely fresh thinking for photoluminescence
and other functions purely originated by the supramolecular structure.

具备单一组分无法实现的独特功能的超分子（supramolecular）材料正受到广泛关注。本研究报道一种全新的超分子发光策略，其发光源自二维（2D）离子氢键（H-bond）超分子网络。通过液态脂肪族胺与酮的快速自组装，可制备得到高质量晶体。借助单晶X射线衍射（XRD）对该二维离子氢键网络进行表征，结果显示其拥有与芳香族物种类似的平面电子体系。第一性原理计算表明，刚性超分子结构的电荷分离跃迁过程与较高的自旋轨道耦合常数，有助于增强单重态-三重态系间窜越过程。可通过烯醇或胺组分的取代基对发光性能进行精准调控，最高量子效率可达26%。该发光体系展现出稳定的室温磷光（RTP）性能——这一性能对于芳香族物种而言极难实现——其发光寿命可达0.45秒，发光量子产率达8%。在应用层面，以液态胺与烯醇作为油墨，可通过计算机控制的精密打印制备高质量室温磷光图案。本研究成果必将为纯由超分子结构衍生的光致发光及其他功能研究带来全新的思路。