Star-Shaped Pt(II) Complexes with Excellent Optical Power Limiting Performance and Their Flexible Optical Limiters†

Abstract

Efficient optical power limiting (OPL) materials are crucial for protecting optical devices and eyes; however, the development of OPL materials with strong OPL response, high transparency, and easy processability still faces many challenges. This study presents a strategy to enhance the OPL performance of Pt(II) complexes (Pt-1a–Pt-2c) by increasing the number of metal centers and tailoring the electronic interactions between the cores and ethynyl ligands. The trinuclear Pt centers significantly extend the triplet-state lifetimes (0.52-2.05 μs) and enhance excited-state absorption (ESA), while the core-ethynyl ligand electronic interplays further modulate the ground- and excited-state properties of Pt-1a–Pt-2c, collectively improving OPL performance. Under ns pulsed laser irradiation, they exhibit tunable nonlinear optical (NLO) and OPL properties at 532 nm, with minimum normalized transmittance (Tmin) of 0.38-0.78. Among them, Pt-2b achieves superior OPL performance, with a nonlinear absorption coefficient (βeff) and optical limiting threshold (FOL) of 192.15 cm GW-1 and 0.71 J cm-2, respectively. In flexible films, Pt-2b@PDMS-1.00 wt% exhibits markedly enhanced OPL performance (βeff = 965.83 cm GW-1, FOL = 0.26 J cm-2), surpassing many reported OPL materials. This study provides valuable insights into improving the OPL responses of highly transparent Pt(II) complexes, while the fabrication of flexible films further broadens their potential applications in flexible photonic devices.