D–π–A-Type Pyrene Derivatives with Different Push–Pull Properties: Broadband Absorption Response and Transient Dynamic Analysis
Ruipeng Niu, Yuxiao Wang, Xingzhi Wu, Shuang Chen, Xueru Zhang, Yinglin Song
Abstract
The nonlinear absorption properties and excited-state dynamics of two linear D−π–A pyrene derivatives (B1 and B2) with different push–pull properties were investigated and compared. The transient absorption spectra provide information about their excited states, revealing a transition from the local excited (LE) state to the charge transfer (CT) state in each of the compounds. The Z-scan measurements show that both derivatives exhibit reverse saturable absorption at multiple excitation widths (fs, ps, and ns). Combined with quantum chemical calculations, the experimental results indicate that B1 (with pyrene as the donor) shows superior two-photon absorption (TPA) at shorter wavelengths (≤650 nm) because of more π–π* transition and that the stronger CT to the pyrene group contributes to the resonance enhancement of the TPA of B2 (with pyrene as the acceptor) at near-infrared wavelengths. In addition, both compounds exhibit satisfactory optical limiting performance, while the thresholds of B2 are 0.0029–0.01 and 0.092 J/cm2 under excitation by femtosecond (532–900 nm) and picosecond (532 nm) pulses, respectively.