Fluorescent boron complexes based on new N,O-chelates as promising candidates for flow cytometry.

This study presents the synthesis and optical properties of a new class of bright green-yellow fluorescent dyes with potential applications in bioimaging. A facile synthetic route via the chelation of aryl(hetaryl)aminoacryloylthiophene scaffolds with a BF2 fragment is presented. The photophysical properties of the dyes are attributed to the nature and position of electron-donating and electron-withdrawing substituents. Upon coordination to a BF2 fragment, characteristic emission was observed, with λem ranging from 503 to 543 nm and quantum yields of 0.14-0.42. Compared with parent aryl(hetaryl)aminoacryloylthiophenes, a significant red shift in absorption (up to 480 nm in solution) and emission (up to 543 nm in solution and 610 nm in the solid state) and high chemical stability and photostability were observed. The electron-accepting character of the substituents on the terminal aromatic ring or replacing this fragment with pyridine or pyrazine moieties resulted in increased quantum yields. To gain insight into the electronic structures and optical properties, quantum mechanical calculations were performed. The results of (TD-)DFT calculations supported the structural and spectroscopic data and showed the features of electronic distribution in the frontier molecular orbitals and active electrophilic and nucleophilic sites in the compounds investigated. Synthesized BF2 complexes are promising dyes for cell imaging and flow cytometry owing to their ready penetration and accumulation in cells.

Detection of nitroaromatic explosives by new D-π-A sensing fluorophores on the basis of the pyrimidine scaffold.

A series of D-π-A- type dyes based on pyrimidines, bearing various thiophene linkers, have been studied as sensing fluorophores. Fluorescence studies have demonstrated that the emission of all derivatives is sensitive to the presence of nitroaromatic explosives, such as 2,4,6-trinitrophenol (PA), 2,4,6-trinitrotoluene (TNT), and 2,4-dinitrotoluene (DNT), in their acetonitrile solutions. The detection limits of fluorophores to PA, TNT, and DNT proved to be in the range from 5.83 × 10(-6) to 2.38 × 10(-7) mol/L, 1.70 × 10(-4) to 8.40 × 10(-6) mol/L, and 8.39 × 10(-5) to 6.87 × 10(-6) mol/L, respectively. The theoretical investigation into the quenching mechanism in the presence of fluorophore has been performed. All compounds have shown a good efficiency as sensor materials when tested as elements of the original device «Nitroscan¼ for detecting nitro-containing explosives in vapor phase (Plant "Promautomatika", Ekaterinburg, Russia). Graphical Abstract ᅟ.

Highlights on the Road towards Highly Emitting Solid-State Luminophores: Two Classes of Thiazole-Based Organoboron Fluorophores with the AIEE/AIE Effect.

Developing a novel, small-sized molecular building block that may be capable of emitting light in the solid state is a challenging task and has rarely been reported in the literature. BF2 -containing dyes seem to be promising candidates towards this aim. Two series of new N^NBF2 complexes showing aggregation-induced emission (AIE) and aggregation-induced emission enhancement (AIEE) were designed and synthesized by means of a new protocol, which improved on the traditional method by employing microwave irradiation. The optical and photophysical properties of the BF2 complexes were investigated in depth. The synthesized complexes showed fluorescence in both solution and the solid state and, in a mixture of tetrahydrofuran/water, may aggregate into fluorescent nanoparticles. The experimental investigation was supported by quantum mechanical calculations. Their availability, stability, large Stokes shifts, and aggregation capabilities, along with their solid-state emission capability, render this new class of BF2 complexes promising AIEE/AIE fluorophores for further applications in the fields of fluorescence imaging and materials science.

Synthesis of 5-Acyl-2-Amino-3-Cyanothiophenes: Chemistry and Fluorescent Properties.

Independent of the substrate structure and reaction conditions, 3-amino-2-cyanothioacrylamides, which contain two active electrophilic centers, were shown to interact with various active halo methylene compounds under mild conditions to afford 5-acyl-2-amino-3-cyanothiophenes as the only products. A series of new polyfunctional thiophene derivatives with a rare combination of functionalities were synthesized, and their photophysical properties were experimentally and computationally investigated. The calculated electronic characteristics of the ground and excited states were compared to the experimental results, which provided a good understanding of the relationship between the optoelectronic properties and the molecular structures. After absorption of light quanta, the systems populate an intramolecular charge-transfer (ICT) Franck-Condon state, and emission occurs from a twisted ICT minimum.

The new facile and straightforward method for the synthesis of 4H-1,2,3-thiadiazolo[5,4-b]indoles and determination of their antiproliferative activity.

A series of 4H-1,2,3-thiadiazolo[5,4-b]indoles were synthesized by novel tandem of oxidative cyclization of 3-alkoxycarbonylhydrazonoindoline-2-thiones, 1,5-H-shift and elimination of tert-butoxy(ethoxy)carbonyl group. The simple method for their modifications by the reactions with electrophilic agents were elaborated and as a result of the synthetic investigation a number of N-alkyl-, N-acyl- and N-sulfonyl-4H-1,2,3-thiadiazolo[5,4-b]indoles were prepared in good yields. Preliminary biological tests for the three examples of synthesized compounds with different substituents at the nitrogen atom indole ring have shown that the biological behavior of the investigated 1,2,3-thiadiazolo[5,4-b]indoles is substantially directed by this structural fragment.