Highly Fluorescent Dianionic Polymethines with a 1,3,2-Dioxaborine Core

Abstract

The difluoroboron β-diketonate ring is ever more used for creating bright polymethine-type fluorophores for the visible and NIR range. Here, we report the synthesis and spectral properties of a series of dianionic cyanine dyes of the rare A1–π–A−π–A1 type, with the central dioxaborine ring (A) embedded into the polymethine chain and various electron-acceptor terminal groups A1. Depending on the nature of the end group, the maxima of their intensive (with molar extinctions up to 380 000 M–1 cm–1) and narrow long-wavelength absorption band lie in the range of 530–770 nm. Their absorption and fluorescence bands are nearly mirror-like and characterized by weak solvatochromism; the marked hypsochromic shifts are observed only when going from polar aprotic solvents to methanol. The designed dianionic dyes have fluorescence quantum yields up to 92 % in the visible range, and even for the NIR dyes, the values of 18–37 % are observed in DMF.

Trianionic 1,3,2‐Dioxaborine‐Containing Polymethines: Bright Near‐Infrared Fluorophores

“…Besides, considering the strong absorption of the obtained symmetric trianionic chromophores, the fluorescence brightness (ϵ⋅ Φ f ) of dyes 10 – 13 exceeds the magnitude of 200 000 M −1 cm −1 in DMF. The ϵ⋅ Φ f value of the brightest in the series dye 10 (313 000 M −1 cm −1 in DMF) greatly outperforms the known highly bright NIR fluorophores, such as BODIPY, [15] aza−BODIPY, [24] diketopyrrolopyrrole dyes, [9f] and dianionic dioxaborine‐containing polymethines [17d] . Though in MeOH the fluorescence of dyes 10 – 12 is nearly twice as weak as in DMF, their Φ f values in MeOH are still high, amounting to 0.42, 0.20, and 0.19, respectively.…”

“… [17e] Despite the non‐symmetric structure, these dyes are characterized by an intense absorbance ( ϵ up to 300 000 M −1 cm −1 ) and bright fluorescence ( Φ f up to 0.80) in the red and NIR spectral range. Recently we described the synthesis of deep‐colored dioxaborine‐containing dianionic polymethines of the A′‐π‐A‐π‐A′ type, which are characterized by even more impressive photophysical characteristics, with the ϵ and Φ f reaching 378 000 M −1 cm −1 and 0.90, respectively [17d] …”

Recent advances in the synthesis of luminescent tetra-coordinated boron compounds

“…Variable temperature emission experiments reveal that the regioisomer with the internal B-N bond showed temperature dependent structural dynamics which was supported by TD-DFT calculations. They 89 The same group also 90 synthesized and characterized Pt(II) complexes that contain dithienylethene (DTE) and B( ppy)Mes 2 as photochromic units (58)(59)(60). UV/Vis and NMR experiments showed that only DTE units of all the complexes undergo reversible photoisomerization under UV light irradiation.…”

“…Due to the extended π-conjugation, the boron-derivatives of curcuminoids exhibit strong absorption and emission in the visible region and NIR region depending on the substitution. 58,59 The effect of aryl groups in these boron-β-diketonates of curcuminoids (36) was studied by Canard and co-workers (Fig. 5).…”

Fluorescent probes based on acridine derivatives and their application in dynamic monitoring of cell polarity variation

“…Firstly, compounds 3, 5 or 6 were obtained by the reaction of malononitrile with isophorone, 3-hydro-3-methyl-2-butanone or 2-aminobenzenethiol, and compound 4 was obtained by the reaction of 3-hydroxy-3-methyl-2-butanone and ethyl 2-cyanoacetate using the existing methods. [25][26][27][28] Secondly, the acridine ring of the classical dye matrix was introduced into the probe structure, and probes 1a-d (yields: 26.9% (1a), 51.6% (1b), 17.8% (1c), and 84.8% (1d)) were synthesized by the reaction between 9-acridine carboxaldehyde and the cyano compounds 3-6. Their structures were characterized using IR, 1 H NMR, and 13 C NMR spectroscopy and HRMS analyses as shown in the ESI.…”