Nitrogen-containing analogues of boron difluoride benzoylacetonate: synthesis, structure, luminescence, and quantum chemical modeling

Design, Synthesis, and Crystallization‐Induced Emission of Boron Difluorides β‐Ketoiminates

“…Depending on the ligand activity, the synthesis can take place in the presence of different bases . Previously we synthesized the simplest of the nitrogen‐containing boron difluoride benzoylacetonate derivatives ( 2 a ) by boiling it in toluene with tributoxyborane (yield 82 %) …”

“…Unlike the synthesis of boron difluoride β‐ketominiates with a hydrogen substituent, the synthesis of complexes with a methyl substituent ( 3 a – e ) proceeds under more severe conditions as a result of the decrease in the reactivity of the respective enamine, which is due to the increase of the electron‐donor capacity of the substituent at the nitrogen atom. In the case of compound 3 a , calcium carbonate, a stronger proton acceptor, was used instead of tributoxyborane . The synthesis of similar complexes with the developed π system in the α position of the chelate cycle ( 3 b – e ) proceeds in toluene at temperatures up to 80 °C.…”

“…As was previously established for compounds 2 a and 3 a , the substitution of one of the oxygen atoms in boron difluoride β‐diketonate ( 1 a ) proceeds selectively for the oxygen atom next to the methyl group, which was corroborated by X‐ray data . Analysis of the 1 H NMR spectroscopic data for compounds 2 a – e and 3 a – e corroborates the selective substitution of the oxygen atom next to the methyl group: The position of the signal of the methyl group hydrogen atoms in the α position of the chelate ring around δ =2.29–2.39 ppm corresponds to the signal from hydrogen atoms of the methyl group conjugated with the C=N fragment.…”

“…Previously we synthesized boron difluoride β‐ketoiminates and studied their luminescence properties . To reveal the relationship between the luminescence properties and the features of the molecular structure of boron difluoride β‐ketoiminates, the range of ligands was extended significantly.…”

“…Reaction of the respective ligand with boron trifluoride etherate in toluene under heating resulted in the formation of a ketoiminate complex ( 2 a ) in high yield . However, upon reaction of boron trifluoride etherate with β‐ketoimines that had a hydrogen substituent at the nitrogen atom and a developed π system in the α position of the chelate ring ( 2 b – e ), an oxidation side reaction of the formed boron difluoride β‐ketoiminate into the β‐diketonate complex was observed (Scheme ).…”