Jena Satyam, Thayyil Muhammed Munthasir Akkarakkaran, Pradhan Sambit, Kitahara Maho, Seika Suzuki, Imai Yoshitane, Thilagar Pakkirisamy
Department of Inorganic and Physical Chemistry, Indian Institute of Science, Bangalore, 560012, India.
Department of Applied Chemistry, Kindai University, Higashi-Osaka, Osaka, 577-8502, Japan.
Chemistry. 2023 Oct 26;29(60):e202301924. doi: 10.1002/chem.202301924. Epub 2023 Sep 21.
Circularly polarized luminescence (CPL) features of BINOL-decorated cyclotriphosphazenes (CPs) are reported for the first time. The luminescence dissymmetry factor (g ) of these compounds in chloroform solutions and polymethyl methacrylate (PMMA) thin films with wt 1 % doping concentrations are found to be 1.0×10 , and 2.9×10 , respectively. However, no CPL signal is observed for the pristine solids. The enantiomers (CP-(R)/CP-(S)) show ultraviolet photoluminescence (~350-360 nm) in solution and the solid state. These compounds show ~10 times larger absolute photoluminescence quantum yield (PLQY) than the simple BINOLs in the solutions state. In the solid state, CP-(R) shows larger PLQY than binaphthol-(R); in contrast, the S enantiomer shows lower PLQY than binaphthol-(S); this indicates that the isomer-dependent solid-state packing of these compounds plays a crucial role in controlling the PL. Thin films with more than 1 % doping concentration and pristine solids of these compounds do not show persistent room-temperature phosphorescence (pRTP) due to concentration-caused quenching. However, thin films with wt 1 % of these chiral emitters exhibit pRTP characteristics with a ~159-343 ms lifetime under vacuum. Theoretical calculations reveal that the cyclophosphazene acts as an optically innocent dendritic core, and the optical features of these compounds are dictated by the pendent BINOL chromophore.
首次报道了联萘酚修饰的环三磷腈（CPs）的圆偏振发光（CPL）特性。发现这些化合物在氯仿溶液和掺杂浓度为1 wt%的聚甲基丙烯酸甲酯（PMMA）薄膜中的发光不对称因子（g）分别为1.0×10 和2.9×10 。然而，原始固体未观察到CPL信号。对映体（CP-(R)/CP-(S)）在溶液和固态中均显示紫外光致发光（350 - 360 nm）。在溶液状态下，这些化合物的绝对光致发光量子产率（PLQY）比简单的联萘酚大10倍。在固态中，CP-(R)的PLQY比联萘酚-(R)大；相反，S对映体的PLQY比联萘酚-(S)低；这表明这些化合物的异构体依赖性固态堆积在控制PL中起关键作用。由于浓度猝灭，掺杂浓度超过1%的薄膜和这些化合物的原始固体不显示持久的室温磷光（pRTP）。然而，含有1 wt%这些手性发光体的薄膜在真空下表现出pRTP特性，寿命约为159 - 343 ms。理论计算表明，环磷腈作为光学惰性树枝状核心，这些化合物的光学特性由侧链联萘酚发色团决定。
