Blue Highly Fluorescent Boranil Derived from Anil Ligand: Synthesis, Characterization, Experimental and Theoretical Evaluation of Solvent Effect on Structures and Photophysical Properties

In this study, we report the design and the synthesis of a Schiff base; Anil and its corresponding Boron Difluoride complexe; Boranil. The synthesis procedure was carried out adopting new, optimized reaction conditions. The Boranil dye presents the advantage to be emissive in solution. 1H and 19F NMR along with FTIR confirmed both compound's structure. To gain a better understanding of the solvatochromic behavior of Anil and Boranil, the dependence of the absorption spectra on the solvent's polarity was studied in depth. Thus, UV-Vis spectroscopy was performed in five selected solvents. In addition to the solvent's polarity effect, the influence of BF2 moiety introduction on the molecule's photophysical properties was also evaluated. When examining different absorption spectra, we found that the title fluorescent dye exhibited weak solvatochromic (11 nm in THF) as well as a slight redshift broader and relatively more structured absorption spectra after complexation. Besides, we investigate the obtained key structure-property relationships through DFT and TD-DFT calculations using a 6-311++ G (d, p) basis set. Quantum chemical calculations allowed confirming proposed structures and understanding their electronic structure in larger details. Theoretical results also showed good agreement with the experimental findings. Finally, the frontier molecular orbitals were investigated to illustrate the pi-conjugation and charge transfer effect.