Photochemically-assisted synthesis and photophysical properties of difluoroboronated β-diketones with fused four-benzene-ring chromophores, chrysene and pyrene

Abstract

We investigated the photophysical properties of difluoroboronated β-diketones (BF2DK) with chrysene and pyrene skeletons (ChB and PyB, respectively) in solution and in the solid state. Acetylchrysenes, as the key precursors to ChBs, were photochemically prepared from the corresponding (acetylphenyl)naphthylethenes by means of a modified photocyclization method. The absorption and emission spectra of the BF2DKs were obtained in chloroform and acetonitrile, and the quantum yields and lifetimes of the fluorescence were determined. Excimeric fluorescence from PyB was absent even in highly concentrated solution. Based on the Lippert-Mataga analysis of the absorption and fluorescence features, the photophysical properties of the ChBs were discussed in comparison with those of PyB. The fluorescence states of the studied BF2DKs are shown to be of a charge-transfer character. The fluorescence quantum yields decrease with increasing the solvent polarity due to the enhanced internal conversion process. The fluorescence quantum yields in the solid state of the studied BF2DKs were determined, and it was found that PyB is fluorescent, whereas the fluorescence quantum yields of the ChBs depend on the substituted position of the chrysene moiety.

Methoxy‐Substituted Difluoroboron Benzoylacetonate Complexes with Color‐Tunable Phosphorescence

“…In previous reports, our group has explored the effects of π‐conjugation,, heteroaromatic groups, and heavy‐atom placement . Recently, other groups have reported additional substituents, such as phenanthrene, chrysene, amines, and more . In particular, Cano and co‐workers have also observed advantages in brightness and color‐tuning with alkoxy donors on BF 2 bdk dyes ,.…”

Synthesis, photophysical and electrochemical properties of novel and highly fluorescent difluoroboron flavanone β-diketonate complexes

“…1,2 The last decade has seen continued efforts to develop a new class of compounds known as organoboronic complexes. 3,4 The difluoroboron b-diketonates (BF 2 dbm) belonging to the tetracoordinate organoboron complexes are highly fluorescent and can present very useful photophysical properties, [1][2][3][4][5][6] with potential technological applications. The first compound of this type was synthetized by Morgan and Tunstall in 1924 through Claisen condensation reaction using only aromatic carbonyl compounds to obtain fluorescent organoboronic compounds.…”

“…5 The difluoroboron b-diketonate complexes are increasingly attracting more attention as fluorescent organic materials because they have so many advantages including easy preparation, high molar extinction coefficient, high quantum fluorescence yields and important photo physical properties. 4 Most of BF 2 dbm complexes reported showed a strong emission in solution 6 and further chemical modification at the aromatic ring substituents of the molecule and conjugation expansion allows for adjustments in emission color throughout the visible region up until NIR region. 7 Although the synthesis and photophysical characterization of many BF 2 dbm complexes has been described in the literature, 3,[8][9][10][11][12][13] only a few notable examples demonstrating their potential applications have been reported.…”

“…Difluoro-4,5-diphenyl-2,5-dihydro-[1,3,2]dioxaborinino[5,4c]chromen-1-ium-2-uide (4a). Flavanone 3a (0.91 mmol) and BF 3 Á Et 2 O (7.31 mmol) provided compound 4a as a yellow oil in 76% yield; R f : 0.60 (30% ethyl acetate/hexane, UV Lamp 365 nm); IR (cm À1 ): 3026, 1615, 1593, 1564, 1490, 1476, 1350, 1215, 1182, 1150, 1037, 750; 1 H-NMR (400 MHz, CDCl 3 ): d 6.58 (s, 1H),6.98 (d, 1H, J 12.0), 7.08-7.12 (m, 1H), 7.28-7.65 (m, 11 H), 8.05 (dd, 1H, J 8.0 and 1.6);13 C-NMR (100 MHz, CDCl 3 ): d 75.2, 104.4, 117.3, 118.4, 122.6, 127.5, 127.7, 127.8, 128.1, 128.5, 128.9, 129.2, 132.2, 133.3, 138.3, 139.1, 159.3, 177.4, 181.9; HRMS (ESI-TOF) m/z [M + H] + calcd for C 22 H 16 O 3 ÁBF 2 : 377.1155; found: 377.1161; CHCl 3 l abs = 404 nm, e = 0.5 Â 10 4 M À1 cm À1 , l em = 489 nm, F: 0.33721. t = 4.20 AE 0.03 ns, k r = 0.08 ns À1 , k nr = 0.16 ns À1 ; CH 3 CN l abs = 404 nm, e = 0.4 Â 10 4 M À1 cm À1 , l em = 502 nm, F = 0.20452, t = 6.56 AE 0.04 ns; THF: l abs = 369 nm, e = 0.3 Â 10 4 M À1 cm À1 , l em = 488 nm, F = 0.21117, t = 4.58 AE 0.03 ns, k r = 0.046 ns À1 .k nr = 0.172 ns À1 . 2,2-Difluoro-4-(4-metoxiphenyl)-5-phenyl-2,5-dihydro-[1,3,2]dioxaborinino[5,4-c]chromen-1-ium-2-uide (4b).…”