Cyclometalated Pt(II) complexes with tetradentate Schiff base ligands: Synthesis, photophysics, electrochemical studies and optical power limiting performance

Pt(II) complexes with tetradentate Schiff base ligands (Pt-1–Pt-5) were prepared, and their detailed photophysics were studied using steady-state, transient spectroscopies and density functional theory systematically. Pt-1–Pt-5 all exhibit ¹π,π* transitions and metal-to-ligand/intraligand charge transfer transitions in the UV–vis region. Meanwhile, these complexes are emissive in solution at room temperature (λ_em = 400–800 nm, Φ_em = 0.008–0.196). Triplet transient absorption (TA) demonstrated that except Pt-3, all complexes exhibit broad and strong triplet excited-state absorption from 400 to 750 nm. What's more, nonlinear transmission experiment demonstrated that Pt-1–Pt-5 show robust reverse saturable absorption (RSA) at 532 nm ns laser pulses. Among them, Pt-5 shows the strongest nonlinear absorption performance, which could potentially be used as optical power limiting (OPL) materials.