Phase- and Halogen-Dependent Room-Temperature Phosphorescence Properties of Biphenylnitrile Derivatives

The
photophysical properties of halogenated biphenylnitrile derivatives
(X-BPhN, X = F, Cl, and Br) were systematically investigated,
and bromobiphenylnitrile (Br-BPhN)-based solids exhibit
phase-dependent room-temperature phosphorescence (RTP) characteristics.
The perfect crystalline, lower-quality crystalline, and amorphous
solids of Br-BPhN were prepared and exhibited different
RTP properties. Two kinds of crystals obtained by slow vacuum gradient
sublimation (crystal 1: high-quality crystal) and quick
solvent evaporation (crystal 2: low-quality crystal)
are attributed to an identical crystalline phase. The absolute phosphorescence
quantum yields (ΦP) for crystal 1 and crystal 2 are 9.1 and 6.0%, respectively, while the amorphous
sample Br-BPhN has an extremely low ΦP of 1.4%. Theoretical calculations and experimental results demonstrate
that multiple intermolecular interactions including halogen bond-induced
rigid supramolecular frameworks in the crystalline phase can enhance
the RTP of Br-BPhN-based solids. This contribution presents
a useful mode molecule to study the mechanism of organic RTP and may
provide a feasible approach to develop pure organic phosphors with
efficient RTP feature.

本研究系统考察了卤代联苯甲腈衍生物（X-BPhN，X=F、Cl、Br）的光物理性质，发现基于溴代联苯甲腈（Br-BPhN）的固体材料展现出相依赖型室温磷光（RTP）特性。研究人员制备了Br-BPhN的完美晶体、低品质晶体与无定形固体，三者呈现出截然不同的RTP性能。通过缓慢真空梯度升华制备的晶体1（高品质晶体）与快速溶剂挥发法制备的晶体2（低品质晶体），虽结晶过程不同，却同属一种晶相。晶体1与晶体2的绝对磷光量子产率（ΦP）分别为9.1%与6.0%，而Br-BPhN无定形样品的ΦP仅为1.4%，数值极低。理论计算与实验结果证实，晶相中包括卤键诱导的刚性超分子骨架在内的多种分子间相互作用，可强化Br-BPhN基固体的RTP性能。本工作为有机RTP机理研究提供了一种极具参考价值的模型分子，同时可为开发具备高效RTP特性的纯有机磷光材料提供可行思路。