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 the eyes. However, achieving strong OPL responses while maintaining high optical transparency and processability remains a challenge. Herein, we report a molecular design strategy to improve the OPL performance of a series of Pt(II) complexes (Pt-1a–Pt-2c) by incorporating trinuclear Pt centers and modulating the core-ethynyl ligand electronic interacations. The trinuclear Pt centers extended the triplet-state lifetimes (0.52–2.05 μs) and enhanced the excited-state absorption (ESA), while the core-ethynyl ligand interacations effectively tuned the ground- and excited-state properties. These complexes exhibited tunable nonlinear optical (NLO) and OPL properties at 532 nm, with a minimum normalized transmittance (T_min) in the range of 0.38–0.78. Notably, Pt-2b showed outstanding OPL performance with a nonlinear absorption coefficient (β_eff) and optical limiting threshold (F_OL) of 192.15 cm GW⁻¹ and 0.71 J cm⁻², respectively. In flexible films, Pt-2b@PDMS-1.00 wt% demonstrated markedly enhanced OPL performance (β_eff = 965.83 cm GW⁻¹, F_OL = 0.26 J cm⁻²), surpassing the performance of many reported OPL materials. This study provides valuable insights into designing transparent Pt(II) complexes with superior OPL properties, and highlights the promise of flexible films for photonic applications.