Synthesis, characterization, and photoluminescence properties of difluoroboron complexes with bis-β-diketone ligands

Abstract

Some novel difluoroboron bis-b-diketonates containing a pyridyl moiety were synthesized from diethyl 2,6-pyridinedicarboxylate via Claisen condensation with the corresponding aryl methyl ketones and followed by complexation with boron trifluoride etherate. Their spectroscopic behaviors were studied by FTIR, 1 H NMR, UV-Vis, and fluorescence spectroscopic techniques. The results indicated that difluoroboron bis-b-diketonates exhibited violet or blue fluorescence emission at 428-454 nm under UV illumination in DMSO and possessed high extinction coefficients. It was found that the nature of the substituents at benzene ring in bis-bdiketone ligands had a significant impact on the photoluminescence behaviors of difluoroboron complexes. The complex 5b exhibited the strongest photoluminescence intensity and highest quantum yield (U u = 0.93), due to two strong electrondonating methoxyl moieties in molecule and the compound 4b displayed the lowest photoluminescence intensity and quantum yield, assigned to the heavy atom effect of the chlorine atom in its molecule. The photoluminescence intensity and quantum yield of these difluoroboron complexes decreased in the sequence, 5b [ 2b [ 1b [ 3b [ 4b.

Pyrazolo[1,5‐a]pyrimidine‐Dioxaborinine Hybrid Dyes: Synthesis and Substituent Effect in the Photophysical Properties

“…Remember that fluorophores containing dioxaborinine core have been widely reported; [5–12,26,32–34] nevertheless, those bearing the pyrazolo[1,5‐ a ]pyrimidine ring are rare, although some interesting examples have been reported in our research group [16,17,22,29,35,36] . Fluorophores of extended π‐conjugation ( Py‐DB , R 2 ‐DB , and TPA‐DB 3 ) and with various substitutions such as phenyl ( Ph 2 ‐DB ), methoxyaryl ( Py‐DB , R 2 ‐DB , and Ar‐PP ), TPA ( TPA‐DB , TPA‐DB 3 , and TPA‐PP ), and coumarin ( Cum‐DB ) groups were used in this analysis.…”

“…498/532 98500 1300 65 DCM [À À ], Suhasini et al [30] 430/527 -4300 49 DMF [À À ], Haucke et al [34] 366/397 40700 2100 39 Toluene [20], Yang et al [32] 379/468 18000 5000 77 CyH [3], Tigreros et al [35] 502/570 129000 2400 61 DCM [1], Chaicham et al [33] 353/479 5100 7500 44 DCM [10], Castillo et al [36] 449/531 87100 3300 85 CHCl 3 [10], Tigreros et al [12] 347/477 17700 7900 69 THF [20], This work 386/454 40700 3900 93 DMSO [20], Wang et al [26] [a] If no information is reported by the authors in the respective work, we assume that such dyes are obtained starting from commercial substrates. distribution throughout the molecule due to the high πconjugation in this compound (Figure 2a).…”

“…Even though dioxaborinine derivatives have been widely studied, there are very few examples using β‐diketones with pyridine‐type nitrogen atoms (C=N) in a position close to the oxygen atoms that form the boron complex (e.g., dye DB‐Py in Scheme 1a at the top); [26] this circumstance could be the result of the inherent competition between the DB ring formation against similar systems where some ring atoms are replaced by nitrogen, for example, an oxadiazaborinine ( ODAB ) ring (Scheme 1a at the bottom) [27] . In addition, and to our knowledge, direct access to the DB ring is principally allowed from carbonyl compounds, mainly β‐diketone derivatives that are substrates relatively challenging to acquire due to multi‐step synthetic processes.…”

A highly selective chemosensor for nickel(II) based on fluorescence quenching of a bispyrazole derivative

“…The bis-b-diketone, 3,3 0 -pyridin-2,6-diyl-bis(1-phenylpropane-1,3-dione), was prepared by Claisen condensation of diethyl 2,6-pyridinedicarboxylate with acetophenone in toluene using sodium as condensing agent according to literature [16].…”