Synthesis, spectroscopic and catalytic properties of some new boron hybrid molecule derivatives by BF2 and BPh2 chelation

• The two type of boron complexes have been synthesized and characterized.
• The boron complexes were used for transfer hydrogenation of aromatic ketones.
• Catalytic studies showed that all complexes are good catalytic precursors.
• The emission energies of boron complexes are significantly red-shifted in comparison with their free ligands.
• The best yield was achieved when [L3BPh2] complexes was used.

A new series of Schiff base ligands (L1–L3) and their corresponding fluorine/phenyl boron hybrid complexes [LnBF2] and [LnBPh2] (n = 1, 2 or 3) have been synthesized and well characterized by both analytical and spectroscopic methods. The Schiff base ligands and their corresponding fluorine/phenyl boron hybrid complexes have been characterized by NMR (1H, 13C and 19F), FT-IR, UV–Vis, LC–MS, and fluorescence spectroscopy as well as melting point and elemental analysis. The fluorescence efficiencies of phenyl chelate complexes are greatly red-shifted compared to those of the fluorine chelate analogs based on the same ligands, presumably due to the large steric hindrance and hard π → π∗ transition of the diphenyl boron chelation, which can effectively prevent molecular aggregation. The boron hybrid complexes were applied to the transfer hydrogenation of acetophenone derivatives to 1-phenylethanol derivatives in the presence of 2-propanol as the hydrogen source. The catalytic studies showed that boron hybrid complexes are good catalytic precursors for transfer hydrogenation of aromatic ketones in 0.1 M iso-PrOH solution. Also, we have found that both steric and electronic factors have a significant impact on the catalytic properties of this class of molecules.

A new series of the Schiff base ligands (L1–L3) and their corresponding boron hybrid complexes [LnBF2] and [LnBPh2] (n = 1, 2 or 3) have been synthesized and well characterized by both analytical and spectroscopic methods. The Schiff base ligands and their corresponding boron hybrid complexes have been characterized by Nuclear magnetic resonance spectra (1H, 13C and 19F NMR), elemental analyses, infrared spectra (FT-IR), ultraviolet–visible spectra (UV–Vis), mass spectra (LC–MS), melting point and fluorescence spectroscopy. Furthermore, these boron hybrid complexes were applied to the transfer hydrogenation of acetophenone derivatives to 1-phenylethanol derivatives in the presence of 2-propanol as the hydrogen source.Figure optionsDownload as PowerPoint slide