Synthesis, Photophysical, Electrochemical, and Non-linear Optical Properties of Triaryl Pyrazole-based B-N Coordinated Boron Compounds.

We report here a set of triaryl pyrazole based B-N coordinated boron compounds (11-17) synthesized by electrophilic aromatic borylation strategy. All the pyrazole boron compounds were thoroughly characterized using multinuclear NMR spectroscopy, LC-MS, and single crystal X-ray diffraction analysis (for 12-17). The photoluminescence measurements of 11-17 revealed that the emission peak maxima were tuned based on the substitution on N-phenyl. The photophysical and electrochemical properties were further supported by theoretical calculations. Z-scan based investigations at 515 nm pump wavelength showed that B-N coordination led to enhancement of nonlinear absorption (two-photon absorption (TPA)) in these compounds if an electron deficient moiety is attached. It has also been observed that an appropriate choice of moiety allows to optimally maneuver the molecular polarizability of the π-system and consequently, assists in controlling the third-order nonlinear optical response.