Fused polycyclic compounds: Synthesize, enhancing TPA cross-section by modifying torsional multiple ring

Four fused polycyclic compounds (DNBT, DNTB, DNPY, and DNNM) with different substituents were designed and synthesized to achieve excellent nonlinear optical materials. Broadband reverse saturation absorption performance based on TPA was carried out by Z-scan. Transient absorption spectrum showed that the different substituents can significantly regulate the ultrafast kinetic processes of their excited states. The relationship between excited states charge structure and nonlinear optical properties were studied by density functional theory (DFT) and sum over states (SOS) model. TPA of these compounds is modulated by local excitation in DBPy and TA fragments. Intra-molecular charge transfer weakens the TPA cross-section. These compounds are potential optical limiting (OL) materials in visible light range. The clear mechanism show that the nonlinear optical properties of organic materials can be improved purposefully through theoretical and experimental methods.