Photodimerization of enaminoketonatoboron difluorides

Synthesis, structure and spectral study of two types of novel fluorescent BF2 complexes with heterocyclic 1,3-enaminoketone ligands

“…There are two main types of these complexes, classified as N, N double-dentate and O, O double-dentate compounds, BODIPY (boradipyrromethene) [1][2][3][4] and 1,3,2-dioxaborine [5][6][7][8] are their corresponding representatives. However, there are few reports [9][10][11] available on the generation of difluoroboron complexes with N, O double-dentate ligands. Although we have reported [12] the synthesis and X-ray crystallography of a difluoroboron complex containing the N, O double-dentate ligand derived from a Schiff 0 s base of salicyaldehyde, its poor quantum yield and low fluorescence intensity compelled us to explore other approaches to such compounds.…”

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

“…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.…”

“…As was previously found for compounds 2 a and 3 a through analysis of the X‐ray data, unlike the respective β‐diketonate analogue ( 1 a ), one observes the disorder of the quasi‐aromaticity of the chelate cycle. The C−C bond by the nitrogen atom is longer than that by the oxygen atom; the C−N bond length corresponds to that of a double bond, and the C−O bond length is equal to that of a single bond.…”

“…The C−C bond by the nitrogen atom is longer than that by the oxygen atom; the C−N bond length corresponds to that of a double bond, and the C−O bond length is equal to that of a single bond. Disorder of the quasi‐aromaticity is observed for nitrogen‐containing analogues of boron difluoride dibenzoylmethanate as well . These data allow us to conclude that there is a diene structure in the chelate cycle of boron difluoride β‐ketoiminates …”

“…As follows from the quantum chemistry calculations of the geometry of molecules of boron difluoride β‐ketoiminates ( 2 a – e and 3 a – e ) in the ground state, in all β‐ketoiminate complexes one observes a disorder of the chelate cycle symmetry (Table ), which is in good agreement with the X‐ray data of compounds 2 a and 3 a . The data shown in Table clearly demonstrate that while C−C and C−O bonds of molecules of all the β‐diketonate complexes under study ( 1 a – e ) are pairwise equaled, the lengths of the C 2 −C 3 bonds in compounds 2 a – e and 3 a – e are significantly larger than those of C 3 −C 4 bonds, and the C 2 −N bond lengths are significantly larger than those of C 4 −O bonds.…”