Luminescent organoboron compounds derived from salicylidenebenzohydrazide: Synthesis, characterization, structure, and photophysical properties

• Synthesis and photophysical properties of new organoboron compounds derived from salicylidenebenzohydrazide.
• Push–pull model of boron complexes bonded to tridentate ONO ligands.
• Non-planar molecular structures determined by X-ray crystallography.

A series of substituted 2-hydroxysalicylidine benzohydrazides were converted into their phenyl-boron complexes in good yields upon reaction with phenylboronic acid. All new compounds were characterized by NMR, UV, IR, spectroscopy and mass spectrometry. The X-ray structures of two complexes demonstrate that the boron atoms adopt a tetrahedral geometry. The 11B NMR chemical shifts of the boron atom in the complexes are also consistent with the presence of tetracoordinate boron centres. The photophysical properties of the free benzohydrazide ligands and their boron complexes have been determined and display quantum yields below 1% with lifetimes in the range 10−10–10−11 s.

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