Room Temperature NIR Phosphorescence from C64 Nanographene Tetraimide by π-Stacking Complexation with Pt(II)Porphyrin

Additional data to report https://doi.org/10.1002/anie.202406353:

Near Infrared (NIR) phosphorescence at room temperature is challenging to achieve for organic molecules due to a negligible spin-orbit coupling and a low energy gap leading to fast non-radiative transitions. Here, we show a supramolecular host–guest strategy to harvest the energy from the low-lying triplet state of C64 nanographene tetraimide 1. 1H NMR and X-ray analysis confirmed the 1:2 stoichiometric binding of a Pt(II)porphyrin on the two π-surfaces of 1. While the free 1 does not show emission in the NIR, the host–guest complex solution shows NIR phosphorescence at 77 K. Further, between 860–1100 nm room temperature NIR phosphorescence (λmax = 900 nm, τavg = 142 µs) was observed for a solid-state sample drop-casted from a preformed complex in solution. Theoretical calculations reveal a non-zero spin-orbit coupling between isoenergetic S1 and T3 of π-stacked [1·Pt(II)porphyrin] complex. External heavy atom induced spin-orbit coupling along with rigidification and protection from oxygen in the solid state promotes both the intersystem crossing from the first excited singlet state into the triplet manifold and the NIR phosphorescence from the lowest triplet state of 1.

补充数据请参阅https://doi.org/10.1002/anie.202406353：

室温下实现有机分子的近红外（Near Infrared, NIR）磷光极具挑战，这是由于有机分子的自旋轨道耦合（spin-orbit coupling）可忽略不计，且能隙较低，会引发快速的非辐射跃迁。本文报道了一种超分子主客体策略，可从C64纳米石墨烯四酰亚胺1的低能三重态中获取能量。氢核磁共振（1H NMR）与X射线分析证实，铂(II)卟啉（Pt(II)porphyrin）在1的两个π表面以1:2的化学计量比结合。游离态的1并未表现出近红外发射，但其主客体复合物溶液在77 K下可观察到近红外磷光。进一步研究发现，将溶液中预先形成的复合物通过滴涂法制备的固态样品，在860–1100 nm波段范围内展现出室温近红外磷光（最大波长λmax = 900 nm，平均寿命τavg = 142 µs）。

理论计算表明，π堆叠的[1·Pt(II)porphyrin]复合物中，等能的S1与T3态之间存在非零的自旋轨道耦合。外重原子诱导的自旋轨道耦合，结合固态下的刚性化效应与氧气隔绝作用，同时促进了从第一激发单重态到三重态多重态的系间窜越，以及1的最低三重态所产生的近红外磷光。