A Family of Highly Fluorescent and Membrane-Permeable Bis(BF₂) Acyl-Pyridinylhydrazine Dyes with Strong Solid-State Emission and Large Stokes Shifts: The BOAPH Fluorophores

Abstract

Organic small-molecule fluorescent chromophores have become essential to modern chemical, biological, and materials related investigations. Herein, a straightforward synthesis and subsequent borylation were presented to form a novel family of bisBF 2 -anchoring acyl-pyridinylhydrazine, which we named BOAPH. The chromophore enjoys outstanding structural diversities owing to varied acyl chlorides and N-heteroarenylhydrazides. These resultant BOAPH dyes are confirmed by NMR, HRMS, and single-crystal X-ray structure analysis. Their spectroscopic properties were studied, and most of the strong absorbance and bright fluorescence with maximum wavelengths centered in the range of 400 and 650 nm. More importantly, they exhibit promising fluorescence quantum yields up to 0.79 in solution and solid states, good photostability, and large Stokes shifts. Furthermore, a respective BOAPH dye with a paradimethylaminophenyl group exhibited the interesting ability of ultrafast staining and two-photon imaging, which can specifically label lipid droplets of living cells immediately without the need for incubation.

Recent Advances in Highly Fluorescent Hydrazine-Inserted Pyrrole-Based Diboron-Anchoring Fluorophores: Synthesis and Properties

“…Recently, organic boron fluorescent platforms have been explored as interesting and versatile hetero-cyclic dyes because chelation with boron atoms could efficiently enhance rigidity of the rotational freedom of the various nonfluorescent ligands and turn them into highly fluorescent fluorophores, accompanied by intensively increased chem-stability and photostability. [9][10][11][12][13] In particular, tetracoordinate boron-chelating molecules with NN, NO or OO bidentate ligands forming six-membered or five-Template for SYNLETT Thieme membered rings have been the subject owing to their rich and unique properties. 12,13 Better known by the trademark BODIPY (boron dipyrromethene, bora-3a,4a-diaza-s-indacene, Figure 1), as a most successful fluorophore, has been significantly studied owing to their easy synthesis, simple modification and tunable photophysical properties.…”

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

“…232 Indole-pyridine, hydrazine, pyrrolyl-acylhydrazone, bipyridyl, pyridyl pyrrolide and semihemiporphyrazine based boron compounds were also studied for their tuneable photophysical properties. [237][238][239][240][241][242][243][244][245][246]…”

Versatility of the Amino Group in Hydrazone‐Based Molecular and Supramolecular Systems

“…Therefore, certain structural requirements must be met to achieve the greatest possible geometric and interactional complementarity between the associating partners. [2] In this sense, hydrazone-based systems are attractive because the triatomic framework C=N-N, properly functionalized, allows generating highly fluorescent dyes after rigidifying the hydrazone framework with the BF 2 moiety, [41][42][43] pockets of different sizes and can promote the recognition of a great variety of cations and anions. [44] The acidic nature of the NÀ H proton, as we will address shortly, constitutes a fundamental part of these processes.…”