Kseniya I. Lugovik

The well-known fluorophore, namely 1,3,6,8-tetrakis[(trimethylsilyl)ethynyl]pyrene, has been studied profoundly as a fluorescent sensor toward nitroaromatic compounds in solutions and vapor phase. Three prototypes of fluorescent materials for vapor sensing were prepared via electrospinning and drop-casting onto the melamine formaldehyde foam with the fluorophore as a pure solid or as a dopant in the polystyrene matrix. It has been shown that this fluorophore and solid fluorescent materials based on it have high detection limits toward nitroaromatic compounds within the range of 10⁻⁸ to 10⁻⁹ M in acetonitrile solution and within the up to ppb range in the vapor phase. The model, expanding on Frisch’s permeation model, was utilized to characterize the fluorescence response of materials relative to vapor concentration and duration of exposure to vapor. All prototypes can be used as sensor materials exhibiting a good sensitivity and selectivity for the original hand-made sniffer for detecting nitro-containing explosives in the vapor phase for real-time application.

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 λ_em 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.

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.

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.

An efficient synthesis of a new series of di‐ and trisubstituted thiazoles (TZs) bearing aryl enamine side‐chains (ETZs) has been developed and the optical properties of these compounds compared with structural analogues containing the isoelectronic aza‐enamine group (ATZs). Spectral characterization demonstrated the difference in the absorption and fluorescence of the ETZs and ATZs in solution and the emergence of fluorescent ETZs in the solid state. The optimized structural geometries and weak intramolecular interactions, electronic characteristics of the ground and excited states, HOMO and LUMO analyses, changes in electron density after S₀ → S_1vexcitation and maps of electrostatic potential (MEPs) calculated by means of DFT have allowed us to estimate the particularities of the geometric and electronic structures of the ETZs and ATZs in the ground and excited states. The availability, synthetic simplicity, stability, large Stokes shifts and high sensitivity to the microenvironment (fluorosolvatochromic behaviour) make the obtained TZs a useful platform for the further design and synthesis of new effective compounds for applications in the field of fluorescence imaging.