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

Abstract

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.

Boron‐Salphen Conjugate based Molecular Probe Exhibiting Fluorescence On‐Off‐On Response in Detection of Cu2+ and ATP through Displacement Approach

“…The FTIR spectrum of compound 2 (azine intermediate) displayed characteristic vibrational frequencies at 3492 (phenolic À OH), 2972 (ArÀ H), 2929 (CÀ H), 1628 (aldimine, C=N), and 1595 (CÀ C) cm À 1 due to intramolecular hydrogen bonding between phenolic À OH and aldimine function (Figure S7). However, after reaction with boron new vibrational frequencies appeared at 3413, 2852-2969, 1473, 1599, 1622, 1167, 826 and 1078 cm À 1 probably due to À OH (phenolic), C=C, CÀ H (Ar, alkyl), -CH=N (aldimine), BÀ O, BÀ F and BÀ N stretching vibrations, [82] respectively (Figure S8). Upon interaction with Cu 2 + frequencies due to OH/NH vibration bands at 3413 and between ~1250 to 1400 cm À 1 disappeared completely.…”

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“…The HOMO represents the ability to donate an electron and the LUMO as electron acceptor represents the ability to obtain an electron. The positive and negative phases are given in red and green, respectively [78,79]. It can be seen from this gure, that the HOMO of molecule (a) is localized mainly on the tetraaza macrocyclic ligand and on the 1,2 substituted benzene while the LUMO is localized extensively over the whole molecule.…”

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