Dibenzoylmethanatoboron Difluoride Research Articles

Methoxylated bis(pentafluorophenyl)boron‐β‐diketonates: Synthesis, Optical Properties and Hydrolytic Stability

AbstractA series of methoxylated bis(pentafluorophenyl)boron‐β‐diketonates (dkB(C6F5)2) with intense emission has been synthesized and characterized by a variety of physicochemical methods. The photophysical properties of the synthesized compounds were thoroughly investigated by electronic absorption, steady‐state, and time‐resolved fluorescence spectroscopy in both solution and solid state. The studied compounds exhibit solvatochromic behavior attributed to the intramolecular charge transfer (ICT) nature of the first excited state. The formation of exciplexes between DBMB(C6F5)2 and benzene derivatives was also studied. Notably, the studied compounds display a complex luminescence profile in the solid state, featuring fluorescence, delayed fluorescence and phosphorescence emission. Furthermore, the hydrolytical stability of the complexes was assessed, demonstrating excellent resistance to hydrolysis. Estimated rate constants, determined at 60 °C, are significantly lower (90‐2000 times) than those observed for the well‐studied dibenzoylmethanatoboron difluoride (DBMBF2). The incorporation of pentafluorophenyl substituents at the boron atom enables the synthesis of highly fluorescent and hydrolytically stable boron chelate complexes, suitable for sensing and bioimaging applications in water‐containing environments.

Effect of α-Substitution on Dibenzoylmethanatoboron Difluoride on Evaporative Crystallization

Effect of α-Substitution on Dibenzoylmethanatoboron Difluoride on Evaporative Crystallization

A simple method for calibration of hybrid exchange–correlation functionals for precise calculations of fluorescence wavelengths of dibenzoylmethanatoboron difluoride exciplexes with benzene, alkylbenzenes and pyridine

A simple approach to precise calculation of fluorescence wavelengths of charge-transfer exciplexes formed by dibenzoylmethanatoboron difluoride (DBMBF2) with benzene, alkylbenzenes and pyridine by varying the percentage of Hartree–Fock exchange energy (HFX) in the hybrid BHHLYP exchange–correlation functional is proposed. A correlation revealed between the optimal HFX parameter and the degree of charge transfer (CT) in the exciplexes provides a basis for the pre-assessment of the required HFX parameter in the BHHLYP functional from the calculated CT value in an exciplex of interest.

Tetrachromophoric Derivatives of Dibenzoylmethanatoboron Difluoride Based on Stereoregular Cyclotetrasiloxanes: Synthesis and Properties.

A series of new tetrachromophoric systems based on stereoregular tetracyclosiloxanes and dibenzoylmethanatoboron difluoride derivatives have been synthesized and characterized by a complex of physicochemical methods. The photophysical properties of the synthesized compounds are studied by electronic absorption, steady-state, and time-resolved fluorescence spectroscopy. In the synthesized compounds, four dibenzoylmethanatoboron difluoride (DBMBF2)-based fluorophores are in an all-cis arrangement with respect to a cyclotetrasiloxane scaffold. DFT calculations predict that they can form H-type dimers, trimers, or tetramers with an antiparallel orientation of their ground-state dipole moments. Under UV excitation, solutions of these compounds in polar and nonpolar solvents exhibit complex fluorescence consisting of monomer- and excimer-like emissions with different lifetimes. Global fitting analysis reveals the presence of at least four kinetically distinguishable species in the excited state. The studied compounds in solutions have CIE chromaticity coordinates very close to the white color point and are promising objects for the development of next-generation single-emission materials for white illumination.

Polydimethylsiloxanes with Grafted Dibenzoylmethanatoboron Difluoride: Synthesis and Properties.

A method for the preparation of polydimethylsiloxanes with grafted methoxy-substituted dibenzoylmethanatoboron difluoride has been described. The structures of prepared polymers were confirmed using NMR, IR spectroscopy and gel permeation chromatography methods. Their thermal properties were investigated using thermal gravimetric analysis, differential scanning calorimetry and thermomechanical analysis. The prepared polymers had good thermal (Td5% up to 393 °C) and thermo-oxidative (Td5% = 413 °C) stability. The polymers started to transit in a viscous flow state at about 40 °C (for 3 a) and at about 20 °C (for 3 b). The viscoelastic characteristics of prepared polymers were determined in the sinusoidal oscillating vibrations mode. It was shown that the studied polymers at low frequencies at room temperature are viscoelastic fluids (G′ < G″). Increasing the frequency led to inversion (crossover) of dependences G′ and G″, which indicated the transition of polymers from viscous to elastomeric behavior characteristics, and the beginning of the formation of a physical network. Optical properties were studied using electron absorption, steady-state and time-resolved fluorescence spectroscopy. It was shown that intramolecular H-dimers exist in the ground state. The polymers studied had a bright fluorescence in the solution and in the solid state, consisting of bands of monomer and excimer emission. Thermally-activated delayed fluorescence was observed in the solution and the solid state. The prepared polymers possess intriguing properties that make them useful as optical materials, sensors or imaging agents.

Intramolecular H-type dimer and excimer formation in dibenzoylmethanatoboron difluoride dyads connected via diphenylsiloxane linkers

A series of new dibenzoylmethanatoboron difluoride (DBMBF2) and methoxy-substituted DBMBF2 dyads linked via flexible diphenylsiloxane linkers of various length have been synthesized and characterized. The structure and optical properties of these compounds were studied by X-ray single-crystal measurements, electron absorption, and steady-state and time-resolved fluorescence spectroscopy. In the dyads under study, which are in an equilibrium between the open and folded conformations, the formation of intramolecular H-dimers in the ground state are observed. For the dyads in dilute solutions in various solvents, both monomer and excimer (through intramolecular excimer formation) emissions are observed at room temperature. The effect of solvent polarity and linker length on the formation of intramolecular excimers has been studied. The contribution of excimers into the total fluorescence spectrum decreases with increasing the solvent polarity, and the length of the siloxane linker. The studied dyads in hexane and cyclohexane solutions have CIE chromaticity coordinates very close to the white color point. The mechanofluorochromic properties of the synthesized dyads were studied.

Molecular Aggregation Dynamics via a Liquid-like Cluster Intermediate during Heterogeneous Evaporation as Revealed by Hyperspectral Camera Fluorescence Imaging.

A hyperspectral camera (HSC) is a camera with great potential to obtain spectral information at each pixel, together with spatial imaging. HSC fluorescence imaging enables the molecular aggregation dynamics of the evaporative crystallization process to be followed in real-time. The key intermediate liquid-like cluster state for the two-step nucleation mechanism is visualized by the fluorescence color changes of mechanochromic luminescent dibenzoylmethanatoboron difluoride derivatives. Three types of emissive species (Crystal, BG-aggregates, and Amorphous) are generated from monomers in solution (low order and density) via liquid-like cluster (high density and low order) during solvent evaporation. These emissive species have partially different aggregated states based on fluorescence decay and fluorescence excitation spectral measurements. In terms of crystallization dynamics, our results indicate that it is important not only to generate supersaturated states but also to maintain the survival time of the liquid-like cluster. Moreover, we demonstrate that HSC fluorescence imaging can be a powerful tool for visualizing heterogeneous molecular aggregation processes.

Nano-assembly and optical properties of difluoroboron dibenzoylmethane-polysilane

Aggregation of various fluorophores is a useful approach to build highly sensitive and selective fluorescent sensors. In this work, the ability of oligomeric polydiphenylsilanes to associate with fluorescent low molecular weight organic compound is illustrated by the formation of stable aggregates between poly[diphenyl-co-methyl(H)]silane and dibenzoylmethanatoboron difluoride in solution. The formation of these nano-structures in solution was investigated both experimentally using gel permeation chromatography, σ spectroscopy and fluorescence spectroscopy, and theoretically by molecular modeling. Thin films obtained from this solution have a characteristic morphology in which the nano-aggregates undergo a self-organizing process and form crystalline spherulites. Association between the fluorescent polysilane and the fluorescent diketonato boron complex proceeds with an increase of fluorescence (amplification efficiency up to 90%) through a FRET mechanism as a result of aggregation, a phenomenon that could be used in the development of fluorescent sensors.

Assembling Structures of Diphenylalanine Linked with Dibenzoylmethanatoboron Difluoride Depending on the Solvent as Probed by Fluorescence Changes

We synthesized directly linked diphenylalanine and dibenzoylmethanatoboron difluoride (DPA-BF2DBMb) and investigated the assembling structure. The aggregation forms and fluorescence of precipitated DPA-BF2DBMb depended on the solvent. Based on this result, the aggregation process of DPA can be controlled and new luminescent materials that show environment-induced color changes can be developed.

Synthesis and properties of new dibenzoylmethanatoboron difluoride dyads connected by flexible siloxane linkers

A series of novel dibenzoylmethanatoboron difluoride (DBMBF2) and methoxy-substituted DBMBF2 dyads linked via flexible dimethylsiloxane linkers of variable length were synthesized and characterized. Both monomer and excimer (trough intramolecular excimer formation) emissions are observed for the dyads in dilute dichloromethane solutions at room temperature. The excimers contribution into the total fluorescence spectrum decreases with increasing siloxane linker length. The parallel-sandwich conformation of intramolecular pre-excimers formed by two terminal DBMBF2 moieties is confirmed by DFT-based calculations.

Synthesis and fluorescence photoswitching of a diarylethene derivative having a dibenzoylmethanato boron difluoride complex

A fluorescent diarylethene derivative covalently linked to a dibenzoylmethanato boron difluoride complex (DAE-BF2DBM dyad 1) was synthesized and its fluorescence photoswitching properties were examined in solution, in nanoparticles and in powder solid. DAE-BF2DBM dyad 1 underwent reversible fluorescence photswitching associated with the photochromic reactions in THF solution as well as in the solid states such as nanoparticles and powders upon alternate irradiation with ultraviolet (UV) and visible light. In addition, the efficient fluorescence photoswitching property based on the intermolecular energy transfer process in the densely packed solid states was clearly observed.

Tetrahedral Silicon-Centered Dibenzoylmethanatoboron Difluorides: Synthesis, Crystal Structure, and Photophysical Behavior in Solution and the Solid State.

Four tetrahedral silicon-centered derivatives of dibenzoylmethanatoboron difluoride (DBMBF2 ) were synthesized and characterized. Their structural and optical features both in solution and the solid state were investigated by using X-ray crystallography, steady-state and time-dependent spectroscopy, and DFT-based calculations. In dilute solutions, the molar absorption coefficient increases from 40500 to 175200 M-1 cm-1 as the number of DBMBF2 fragments in a molecule increases from one to four, while, in contrast, the nonradiative rate constant of fluorescence decay decreases from 0.49 to 0.34. In the solid state, absorption and emission spectra depend on the degree of crystallinity and microcrystal size. The tris-DBMBF2 derivative forms fully overlapping dimeric structures that exhibit excimer-like fluorescence, which is accurately predicted by the quantum-chemical calculations. The mono-DBMBF2 derivative exhibits fully reverse mechanofluorochromic behavior.

An Experimental Complex for High-Performance Screening of Photoluminescent Chemosensor Materials

An experimental complex is described for conducting high-performance screening of the functional characteristics of photoluminescent chemosensor materials (CSMs) intended for determining volatile organic compounds in the gas phase and optimizing the characteristics of matrix sensors based on CSMs in multicomponent vapor-gas mixtures. The complex combines a system for the continuous generation of multicomponent gas-vapor mixtures, which allows automated control of the composition of the mixture and the concentration of its components in the range from 0.01 mg/m3 to saturated vapors, and a system for exciting and recording the photoluminescence spectra of samples. The experimental data obtained in the study of fluorescent responses of a set of CSM based on boron dibenzoylmethanatoboron difluoride (DBMBF2) in mixtures of aromatic substances.

Evaporative Crystallization of Dibenzoylmethanato Boron Difluoride Probed by Time-resolved Quartz Crystal Microbalance Responses with Fluorescence Changes

We have studied the evaporative crystallization of dibenzoylmethanato boron difluoride complex (BF2DBM) using the quartz crystal microbalance (QCM) technique and based on fluorescence changes. The ...

Turn-on exciplex fluorescence induced by complexation of nonfluorescent pentafluorinated dibenzoylmethanatoboron difluoride with benzene and its derivatives

A new pentafluorinated derivative of (dibenzoylmethanato)boron difluoride (5F-DBMBF2) was synthesized and studied as an “off–on” fluorescent probe for benzene derivatives with a reversible detection capability.

Exciplexes of Fluorinated and Methylated Derivatives of Dibenzoylmethanatoboron Difluoride with Benzene and Toluene on the Surface of Trimethylsilylated Aerosil

It has been shown that the introduction of electron-donating or electron-withdrawing groups in the para-position of dibenzoylmethanatoboron difluoride (DBMBF2) makes it possible to control the fluorescenсe characteristics of fluorophore exciplexes with methylbenzenes (MB). The fluorescent properties of DBMBF2/MB exciplexes at the gas–solid interface have been studied using the example of DBMBF2 adsorbed on the surface of trimethylsilylated aerosil.

Interaction of hydroxy substituted dibenzoylmethanatoboron difluoride with hydrated ammonia in solution: A combined spectroscopic and computational study

UV–Vis absorption spectroscopy and quantum chemistry are employed to study the spectral features of a new organoboron dye ortho-hydroxy dibenzoylmethanatoboron difluoride (OHDBMBF2). The compound shows promise for the detection of hydrated ammonia thanks to the ability to interact with proton acceptors. Specifically, a color change from colorless to red and a new long-wavelength absorption band at 500 nm have been noted after consecutive injections of ammonia and water into the solution of the dye. According to the DFT and TDDFT calculations, the response of OHDBMBF2 to hydrated ammonia is caused by the deprotonation reaction. Based on the results of the theoretical simulations, the nature of the absorption bands of the neutral and anionic forms of the dye has been explained.

The molecular structure and absorption spectrum of hydroxy substituted dibenzoylmethanatoboron difluoride in solution: A theoretical and experimental study

Electronic spectroscopy and quantum chemistry are used to study the structure and absorption spectra of the hydroxy substituted dibenzoylmethanatoboron difluoride (OHDBMBF2) in solutions. Introducing a hydroxy group in the diketonate moiety allows the dye to form intermolecular complexes with proton acceptors, such as solvents or analytes, thus making it a promising chemical sensor. Our calculations show that donor oxygen-containing solvents break the intramolecular hydrogen bond OH···Odik and form an intermolecular OH···Osolv bond thus disrupting the coplanarity of the dye and affecting the position and shape of its absorption bands. The spectra calculated with explicit solvent combined with polarizable continuum model (PCM) better agree with the experiment than those calculated only within PCM.

Ink-Jet Printing of Chemosensing Layers Based on Surface-Functionalized Silica Nanoparticles

Silica nanoparticles (SNPs) with a diameter of 100 nm and surface-modified by covalently linked dibenzoylmethanatoboron difluoride have been synthesized and characterized. Suspensions of SNPs in dichloroethane are used as ink suitable for the microvalve ink-jet printing of sensing layers. It is demonstrated that SNP-based thin films are sensitive for methylbenzene vapors and could be a good candidate as a printed sensor. Responses of sensing films to methylbenzene vapors are analyzed using multivariate nonlinear regression.

Cooperative effects of o- and m-methyl groups on the intramolecular charge-transfer emission properties of dibenzoylmethanatoboron difluorides.

The photophysical properties of o-tolyl-, m-tolyl-, and p-xylyl-substituted asymmetric diaroylmethanatoboron difluorides in a mixture of CH2Cl2 and c-C6H12, and in the crystalline state were determined. In solution, the fluorescence (FL) properties of these substances are controlled by the position and number of methyl groups on the phenyl rings. An especially interesting finding is that FL from the p-xylyl derivative occurs from an excited state which possesses intramolecular charge-transfer character caused by the o- and m-methyl groups cooperatively. The results of X-ray crystallographic analysis reveal that these asymmetric diaroylmethanatoboron difluorides form dyads through orbital overlap of neighboring molecules. This phenomenon governs the unique FL properties of these substances in the solid state.