Red-Emitting Tetraphenylethylene-Based Boron Thioketonates: Effect of Substitution and Study of Nonlinear Optical Properties

Abstract

We present tetraphenylethylene (TPE) and N,N-dimethylaniline (DMA)-substituted monothio-β-diketonate boron compounds. All O,S-chelated boron compounds showed red emission in solution as well as in the solid state. A comparison of O,O-chelated vs O,S-chelated compound reveals that the latter showed a pronounced red shift in both absorption and emission. Furthermore, the O,S-chelated compound showed the reduction potential at a less-negative position over the O,O-chelated compound. The marked red shift in O,S-chelated compounds indicates that there is a discernible enhancement in linear polarizability upon optical excitation, and consequently, we explore the nonlinear optical properties of the compounds at infrared wavelengths. The open-aperture Z-scan measurements using ultrashort pulses reveal the optical-limiting behavior of these compounds along with a greater nonlinear absorption for those variants, which exhibits a greater red shift in absorption and emission spectrum.