Difluoroboron Complex Research Articles

Synthesis of Aminotroponyl-/Difluoroboronyl Aminotroponyl Deoxyuridine Phosphoramidites.

This report describes the chemical synthesis of aminotroponyl-conjugated deoxyuridine analog (at-dU) and its difluoroboron complex (dfbat-dU) and their phosphoramidites by using the versatile phosphorylating reagent 2-Cyanoethyl N,N-diisopropylchlorophosphoramidite. Tropolone is a non-benzenoid aromatic bioactive natural fluorescent molecule, possessing intramolecular charge transfer and metal chelating properties with transition metal ions such as Cu2+/ Zn2+/ Ni2+ . Its synthetic derivatives, 2-aminotropones also exhibit unique bioactivities and are considered potential therapeutic drug candidate. Recently, the fluorescence properties of aminotropone has improved by complexing with difluoroboron residue that generates aminotroponyl-BODIPY analog. These could be employed for the synthesis of at-dU/dfbat-dU containing DNA oligonucleotides for designing the 11 B/19 F-NMR/fluorescence-based DNA probes. © 2022 Wiley Periodicals LLC. Basic Protocol 1: Synthesis of N-propargyl-2-aminotropone (2) and difluoroboronyl N-propargyl-2-aminotropone (3) molecules. Basic Protocol 2: Synthesis of N-propargyl-2-aminotroponyl deoxyuridinyl (at-dU) phosphoramidites (7). Basic Protocol 3: Synthesis of difluoroboronyl N-propargyl-2-aminotroponyl deoxyuridinyl (dfbat-dU) phosphoramidites (10).

Synthesis and luminescence properties of the phenothiazine-functionalized β-diketonate difluoroboron complexes

In this article, a phenothiazine-functionalized mono-β-diketonate difluoroboron complex (PTZB) and a phenothiazine-functionalized bis-β-diketonate difluoroboron complex (DPTZB) were successfully synthesized and characterized by NMR and high-resolution mass spectrometry, and the structure of the phenothiazine-functionalized mono-β-diketonate difluoroboron complex (PTZB) was furtherly confirmed by single crystal X-ray diffraction. Their photophysical and electrochemical properties and thermal stability were systematically investigated by combining experiment and theoretical calculations. Both the complexes were found to exhibit high thermal stabilities with decomposition temperatures over 350 °C. The mono-β-diketonate difluoroboron complex (PTZB) exhibits strong red emission in toluene, while it shows weak emission in other common organic solvents. The bis-β-diketonate difluoroboron complex (DPTZB) exhibits weak emission in common organic solvents. Moreover, the mono-β-diketonate difluoroboron complex (PTZB) exhibits obvious aggregation-induced emission enhancement (AIEE) in toluene/n-hexane mixture.

BF4− as source for the preparation of BF2 bridged copper(II) dimethylglyoxime complexes

AbstractThe reaction of copper(II) tetrafluoroborate with dimethylglyoxime (H2dmg) leads to the formation of the dinuclear complexes [Cu2(dmg)(Hdmg)(EtOH)(H2dmg)]BF4 (1) and [Cu2(dmg ⋅ BF2)(Hdmg)(H2dmg)]BF4 (2). In 2, BF2 deriving from BF4− has been inserted into the oxime groups to form an O,O‐bidentate difluoroboron complex. Co‐crystallization of 1 and 2 impeded a thorough characterization of 2. In further attempts to prepare pure 2, the difluoroboron complexes [Cu(dmg ⋅ BF2)2(MeCN)] (3) and [Cu(dmg ⋅ BF2)(Hdmg)] (4) have been obtained. Attempts to isolate the BF2‐bridged ligand failed. Even though BF4− readily is decomposed to formally form BF2+ that is inserted into the resulting complexes and F−, the nascent F− ions are not a suitable F− source for organic fluorination reactions. Nevertheless, the described, facile route to prepare O,O‐bidentate difluoroboron complexes without the usage of the highly toxic BF3 ⋅ OEt2 but BF4− instead is of interest for synthetically working chemists.

Colorimetric and turn-on fluorescent chemosensor with large stokes shift for sensitively probing cyanide anion in real samples and living systems

Cyanide anion is a ubiquitous chemical substance in the ecosystem, however, human daily life is severely threatened by its toxicity at any time. In this paper, a novel colorimetric and turn-on chemosensor 4-(4-(2,2-difluoro-6-methyl-2H-1,3,2-dioxaborinin-4-yl)buta-1,3-dien-1-yl)-N,N-dimethylaniline (NBF) for detecting cyanide anion was synthesized based on the 4-(dimethylamino)cinnamaldehyde and β-diketone difluoroboron complex. This fluorescent probe exhibited excellent spectroscopy properties such as large stokes shift, long emission wavelength, and good sensitivity. The detection limit of NBF towards cyanide ion was determined as low as 2.23 μM. Additionally, the detection mechanism towards cyanide ion was confirmed to be the nucleophilic addition interaction by high resolution mass spectrum (HRMS), 1H Nuclear Magnetic Resonance (NMR) titration, and quantum chemistry theory calculation. In addition, the probe NBF had been successfully utilized in detecting cyanide ions in water and food samples as well as imaging in the biological system, which broadened its practical application prospects.

Near-infrared thermally activated delayed fluorescence of D–π-A–π-D difluoroboron complex for efficient singlet oxygen generation in aqueous media

NIR TADF difluoroboron complex shows extremely small ΔEST, broad absorption range (350–650 nm), high1O2quantum yield (62%), and selective photodynamic killing of Gram-positive bacteria.

Excited-state dynamics of dipyrrolyldiketone difluoroboron complexes.

Anion-responsive photofunctional materials have been extensively studied because anions are important for biotic activity and constitute the building blocks of elegant supramolecular architectures. A number of fluorescent anion receptors that can probe anions in their environments have been reported, but the excited states of many of these molecules remain elusive. Studies on excited-state dynamics provide fruitful information for optimizing the emission properties, minimizing the photodegradation and photorelease of anions, and exploring novel photofunctions. In this study, we investigated the excited-state dynamics of an aryl-substituted dipyrrolyldiketone difluoroboron complex, a π-conjugated anion receptor, by time-resolved visible and infrared absorption spectroscopy and emission decay measurements combined with quantum chemical calculations. Anion binding was found to alter the radiative and nonradiative rate constants and the excited-state absorption of the anion receptor. In contrast, the molecular structures and binding abilities were similar in the S0 and S1 states.

Stereoisomeric selection upon adsorption: A structural and optical study of curcuminoid derivatives on ultrathin films of KCl on Au(111) and on bulk KCl(001)

We present a combined scanning tunneling microscopy (STM), noncontact atomic force microscopy (nc-AFM), and differential reflectance spectroscopy (DRS) study aiming at the characterization of the relationship between structural and optical properties of a supramolecular assembly of a curcuminoid derivative adsorbed on two kinds of substrates: bilayers of KCl on Au(111) [2 ML KCl/Au(111)] and KCl(001) bulk. The molecule features a difluoroboron (${\mathrm{BF}}_{2}$) complex as well as cyano (CN) end groups, which induces an internal dipole moment of a few Debyes. The comparative study of the structural properties of the molecules adsorbed on 2 ML KCl/Au(111), which allows for STM characterization, and KCl bulk, which allows for nc-AFM and DRS characterization, shows that the molecular adsorption is similar on both substrates. STM and nc-AFM give evidence that the on-surface condensation of the molecules into supramolecular assemblies is steered by two main interactions: the molecule-substrate interaction between the CN end groups of the molecule and the cationic ${\mathrm{K}}^{+}$ species, as well as an in-plane intermolecular interaction involving ${\mathrm{BF}}_{2}$ and phenyl groups. Based on density functional theory calculations, we propose an epitaxial molecular structure described by a two-molecule unit cell forming an $8\ifmmode\times\else\texttimes\fi{}2$ supercell on the KCl surface that grows in form of ribbons along the $\ensuremath{\langle}100\ensuremath{\rangle}$ or $\ensuremath{\langle}010\ensuremath{\rangle}$ directions of the substrate, which are polar. Among several possible stereoisomers for the molecule, it is found that the balance between vertical and in-plane interactions selects the one whose size matches the distance between ${\mathrm{K}}^{+}$ species to condense on the substrate and not the most stable one stemming from the gas phase. Finally, optical spectroscopy in solvent and DRS measurements performed on the supramolecular assembly exhibit similar features identified as three absorption peaks tracing a $\ensuremath{\pi}\ensuremath{\rightarrow}{\ensuremath{\pi}}^{*}$ electronic transition followed by a vibronic progression, plus a broader band featuring a set of higher-energy transitions. Due to both the weak electrostatic interactions and a lack of $\ensuremath{\pi}\text{\ensuremath{-}}\ensuremath{\pi}$ interactions in the condensed molecular phase, DR spectra exhibit no major excitonic effect, but a nonrigid redshift of the molecular absorption band compared to the situation in solvent. This observation is found to be consistent with the isomer selection due to the transition from the gas phase to the on-surface condensed phase.

Two novel red-emitting fluorescent chemosensors for trace water determination with high sensitivity and large Stokes shift

Water plays a crucial role in human daily life and industrial production. However, the real-time detection technology for trace water still needed to be developed. In this paper, two red-emitting fluorescent receptors (HDBF and NDBF) for the recognition of water were designed and synthesized based on the β-diketone difluoroboron complex and natural product vanillin. The two fluorescent probes showed excellent optical properties such as large Stokes shifts (227 nm and 286 nm), long emission wavelengths (627 nm and 686 nm), and high fluorescence quantum yields (11.28% and 6.15%). The limits of detection of HDBF and NDBF for water were determined as low as 0.016% and 0.018%, respectively. Their detecting mechanism towards water was confirmed as the hydrogen-bonding interaction by 1H NMR titration analysis. Furthermore, the two fluorescent sensors were successfully utilized in probing trace water in 1,4-dioxane by utilizing wet cotton swab as carrier, which suggested their practical application value for trace water determination.

Chelate method for the synthesis of 3-amidino-substituted 4-pyridones

An efficient synthetic procedure to obtain 3-(N-benzoylamidino)-substituted 4-pyridones has been developed based on the reaction of difluoroboron complex of N-benzoyl-substituted diacylketene aminal with primary amines.

A highly fluorescent tri-nuclear boron complex with large Stokes shifts based on tripodal Schiff base: synthesis and photophysical properties

In this study, a new imine-based tripodal ligand and its difluoroboron complex were designed and synthesized. This trinuclear-boron complex was prepared for the first time and fully characterized by common spectroscopic techniques such as $$^{1}$$ H-NMR, $$^{13}$$ C-NMR, FT-IR, UV–Vis and MS analysis. The optical and fluorescence properties of complex were examined in $$\hbox {CHCl}_{{3}}$$ , THF, acetonitrile, EtOAc, DMF and DMSO. It was revealed that the obtained boron complex showed intense emission with large Stokes shifts in the range from 83 nm to 96 nm. As a result of quantification of fluorescence quantum yields, it has been observed that it has high quantum yield values up to 48%. The large Stokes shifts and high efficient emissions in the solutions of boron complex make it precious fluorophore for potential applications in materials science. SYNOPSIS: The synthesis and characterization of a new four coordinated trinuclear boron complex and its optical properties are reported. The results show that the obtained new fluorophore could be beneficial for fluorescent materials due to presenting large Stokes shifts and high efficient blue emissions.

Two N,N-chelated difluoroboron complexes containing phenanthroimidazole moiety: Synthesis and luminescence properties

Two new N,N-chelated difluoroboron complexes, PIBF2-Cz and PI-BODIPY, containing phenanthroimidazole moiety were synthesized and characterized by elemental analysis, NMR spectroscopy and MS. Their photophysical and electrochemical properties and thermal stabilities were investigated systematically. The results showed that these N,N-chelated difluoroboron complexes not only exhibit excellent thermal stabilities but also emit strong green emissions with photoluminescence quantum efficiency of 95.71% and 67.22% in chloroform solutions. Furthermore, based on these N,N-chelated difluoroboron complexes, the green organic light-emitting devices with a configuration of ITO/NPB (20 nm)/TBADN: difluoroboron complex (x wt%, 30 nm)/TPBi (30 nm)/Liq (2 nm)/Al (100 nm) have been successfully fabricated by vacuum-deposition method, in which the devices fabricated from PIBF2-Cz exhibited the best electroluminescence performance with a maximum brightness of 20290 cd/m2 and a maximum luminous efficiencies of 7.97 cd/A and a maximum external quantum efficiency (EQE) of 1.88%.

Theoretical Investigation of Difluoroboron Complex of Curcuminoid Derivatives with and without Phenyl Substituent (at Meso Position): Linear and Non‐Linear Optical Study

AbstractTwo difluoroboron curcumin analogs and their phenylated versions were studied for their photophysical and non‐linear optical properties based on comprehensive density functional theory approach. The ground state geometry optimization, vertical excitation, and the first excited state optimization were carried out using B3LYP and CAM−B3LYP functionals with 6–31G(d) basis set. The geometry of the difluoroboron curcumin analogs was found to remain planar in both the ground and excited states. The computed vertical excitation and emission values obtained with global hybrid functional are in good correlation with the observed values. The phenylated analogs show enhancement in the photophysical properties. The linear and non‐linear optical properties were computed using two global hybrids functionals (B3LYP and BHHLYP) and a range separated hybrid functional (CAM−B3LYP) with 6–31+G(d,p) basis set. The difluoroboron curcumin analogs without the phenyl substituent have larger polarizability and hyperpolarizabiliy parameters than the phenylated analogs. The polarizability and hyperpolarizabiliy were found to be comparable with the BHHLYP and CAM−B3LYP functionals.

β-Diketone derivatives: influence of the chelating group on the photophysical and mechanofluorochromic properties.

A diphenyl-boron β-diketonate complex was synthesized. Its photophysical properties were studied in solution and in the solid-state, and compared to those of its parent diketone and the corresponding difluoro-boron complex. TD-DFT calculations show that the molecular orbitals involved in the first Franck-Condon transition are very different for the three compounds studied. The difluoro-boron complex is strongly fluorescent in solution, and remains fluorescent in the solid-state. The free diketone turns to be very weakly fluorescent in solution and displays significant Aggregation Induced Enhanced Emission (AIEE) in the crystalline state, which can be explained by a rigidification of the molecule, while the diphenyl-boron complex is weakly fluorescent in solution as well as in the solid-state. For the free diketone and the difluoro-boron complex a mechanofluorochromic response is observed upon grinding the crystalline powder in a mortar, while for the diphenyl-boron complex no fluorescence emission change is detected under these conditions. Overall, this study shows that the nature of the chelating group has a crucial influence on the photophysical and mechanofluorochromic properties of β-diketonate complexes, leading to a wide variety of behaviors within the closely related structures of such derivatives.

Pyrimidine-containing β-iminoenolate difluoroboron complexes acting as non-traditional π-gelators and mechanofluorochromic dyes

A xerogel-based film based on a mechanofluorochromic dye of a β-iminoenolate difluoroboron complex could detect TFA vapor with high performance.

BF2 complexes of 1,3-diketones on the surface of phosphorus dendrimers: synthesis and study of the photoluminescence properties

Difluoroboron complexes of monomeric and dimeric diketones and of generations 0–4 of phosphorus dendrimers ended by diketone ligands are synthesized and characterized. Their photoluminescence properties are measured. All compounds exhibit an intense absorption band in the near UV region. Both model dimers and dendrimers show a marked hypsochromic shift of this absorption band compared with the monomeric difluoroboron complex. The fluorescence of the dioxaborine complex subunit in the multichromophoric dendritic architectures is quenched compared with the emission of the isolated monomeric fluorophore, presumably due to interactions between the terminal groups of dendrimers.

Asymmetric Dipyrrin and F-BODIPYs Conjugated to Terminal Alkynes and Alkenes.

An asymmetric meso-H dipyrrin featuring a conjugated terminal alkyne substituent was converted to its corresponding difluoro boron complex, and the extent of π-conjugation was extended using Sonogashira cross-coupling. Treatment of the alkyne-substituted dipyrrin with BF3·OEt2 and NEt3 revealed the reactivity of the conjugated terminal alkyne toward Lewis-activated electrophilic substitution and led to the isolation of F-BODIPYs bearing terminal bromovinyl and enol substituents.

Relating stacking structures and charge transport in crystal polymorphs of the pyrrole-based π-conjugated molecule

We present a theoretical study on charge transport in crystal polymorphs of the pyrrole-based π-conjugated molecule, the dipyrrolyldiketone difluoroboron complex. The ab initio all-electron fragment molecular orbital calculations were carried out to evaluate electronic couplings for charge transfer in three crystal polymorphs. The electron and hole carrier mobilities were estimated on the basis of the master equation combined with the Marcus theory. We found that utilizing the polar diketone difluoroboron unit as the π-conjugated molecule results in the large molecular interactions and electronic couplings. We demonstrate the impact of crystal packing structures on the anisotropy of charge transport, highlighting the dimensionality of charge-transfer networks varying from zero-dimensional behavior of charge localization to three-dimensional behavior of isotropic charge transport. We further elucidate the effects of different π-π stacking modes on the electronic couplings and intermolecular interactions, which underlie the relationship between the crystal packing structures and charge transport.

Carbazole modified salicylaldimines and their difluoroboron complexes: effect of the tert-butyl and trifluoromethyl terminal groups on organogelation and piezofluorochromism

Luminescent nanofibers were generated from nontraditional π-gelators based on salicylaldimines and their difluoroboron complex bearing tert-butyl carbazole and trifluoromethylbenzene.

Multi-stimuli-responsive fluorescence of a highly emissive difluoroboron complex in both solution and solid states

A highly fluorescent emissive difluoroboron complex (TC) was designed, synthesized and characterized. The absolute fluorescence quantum yields of TC are 33.0% in the solid state and 26.0% in the solution state. The results of X-ray diffraction analysis demonstrate that the rigid structure, the intermolecular hydrogen bonding and the well-ordered as well as loose molecular packing are the major reasons for the high fluorescence emission. Moreover, the colors and fluorescence emission of TC can be switched by external stimuli including grinding and acids/bases. Powder X-ray diffraction (PXRD) investigation verifies that the crystalline–amorphous state transformation between the original and ground states might be attributed to the mechanochromic luminescence properties. The high fluorescence emission and multi-stimuli-responsive fluorescence properties reveal that TC can be used as rewritable information storage, security ink and a fluorescence indicator for acids/bases.

Carbazole-based salicylaldimine difluoroboron complex with crystallization-induced emission enhancement and reversible piezofluorochromism characteristics

New salicylaldimine difluoroboron complex TCB with tert-butyl group was designed and synthesized. The novel luminogen showed a crystallization-induced emission enhancement (CIEE) effect. Amorphous samples of TCB emitted yellow green light with 6.4% solid-state absolute fluorescence quantum yield (ΦF). In contrast, the crystals of TCB showed intense green light emission with 69.0% ΦF. Moreover, it exhibited reversible piezofluorochromic (PFC) behavior with contrast colors between green and yellow green. The powder XRD studies suggested that the destruction of a crystalline state into an amorphous state is responsible for piezofluorochromism. As a result, the salicylaldimine difluoroboron complex could be applied as a new building block of CIEE-active PFC materials.