Yanqing Wang, Na Li, Liangwen Chu, Zelin Hao, Junyu Chen, Jiang Huang, Junlin Yan, Hongtao Bian, Pengfei Duan*, Jing Liu*, and Yu Fang. Angew. Chem. Int. Ed., 2024, 63, e202403898.

Molecular self-assembly has been recognized as an effective strategy to enhance circularly polarized luminescence (CPL), representing one of the most important areas in CPL field. However, the commonly reported supramolecular CPL-active materials, typically formed through enthalpically driven assembly of amphiphilic fluorophores, often exhibiting thermo disassembly of fluorescent advanced structures and significantly weakening the chiroptical properties. Apparently, improving the circularly polarized luminescence dissymmetry factor (g_lum), luminescence efficiency (QY), and thermal quenching resistance of chiral materials poses a significant challenge.

To address these challenges, we present an innovative strategy utilizing the entropically driven self-assembly of amphiphilic phosphorescent platinum(II) complexes (L-Pt) with tetraethylene glycol chains, resulting in unique temperature dependencies. The entropically driven self-assembly of L-Pt leads to a synergistic improvement in phosphorescence emission efficiency (QY was amplified from 15% at 25 °C to 53% at 60 °C) and chirality, both in the ground state and the excited state (g_lum value has been magnified from 0.04 × 10^-2 to 0.06) with increasing temperature. Notably, we observed reversible modulation of phosphorescence and chirality observed over at least 10 cycles through successive heating and cooling, highlighting the intelligent control of luminescence and chiroptical properties by regulating intermolecular interactions among neighboring L-Pt molecules. Importantly, the QY and g_lum of the L-Pt assembly in solid state were measured as 69% and 0.16 respectively, representing relatively high values compared to most self-assembled CPL systems. This study marks the pioneering demonstration of dual thermo-enhancement of phosphorescence and CPL and provides valuable insights into the thermal effects on high-temperature and switchable CPL materials.

Figure 1 Dual Enhancement of Phosphorescence and Circularly Polarized Luminescence through Entropically Driven Self-Assembly of a Platinum(II) Complex

Figure 2 The unique temperature-dependent luminescence properties of L-Pt assemblies

Figure 3 The advanced structure of L-Pt assemblies

First Authors: Wang Yanqing and Li Na, master’s candidates, Shaanxi Normal University

Correspondence Authors: Prof. Liu Jing, Shaanxi Normal University; Researcher Duan Pengfei, National Center for Nanoscience and Technology

Full Text Link: https://doi.org/10.1002/anie.202403898