NOBF4 Research Articles

Serendipitous Conversion of an Acetylamino Dideoxy-Octonic Acid Derivate into a Functionalized Carbohydrate-Pyrazole Conjugate and Investigation of the Method´s General Applicability.

By treatment of the peracetylated methylester of 4-acetylamino-2,4-dideoxy-d-glycero-d-galacto-octonic acid (ADOA-PAE) with nitrosyl tetrafluoroborate, a serendipitous formation of a highly functionalized carbohydrate-pyrazole conjugate was observed in 95% yield. This observation is remarkable, as it involves a five-step one-pot synthesis that proceeds via an 1,3-acyl shift and a 1,5-electrocyclization, which usually requires thermal conditions; however, the reaction occurred at a temperature of 0 °C. Additionally, the excellent yield of the carbohydrate-decorated pyrazole and the regiospecificity of the cyclization are of particular interest, as regioselectivity is always a challenge in pyrazole synthesis. Subsequently, this novel access to pyrazoles starting from N-acetyl-allyl amides via nitrosation and electrocyclization was investigated. In addition, mechanistic studies for the formation of substituted pyrazoles of type were carried out.

Chemical transformation mechanism for blue-to-green emitting CsPbBr3 nanocrystals.

Recently, metal-halide perovskites have rapidly emerged as efficient light emitters with near-unity quantum yield and size-dependent optical and electronic properties, which have attracted considerable attention from researchers. However, the ultrafast nucleation rate of ionic perovskite counterparts severely limits the in-depth exploration of the growth mechanism of colloidal nanocrystals (NCs). Herein, we used an inorganic ligand nitrosonium tetrafluoroborate (NOBF4) to trigger a slow post-synthesis transformation process, converting non-luminescent Cs4PbBr6 NCs into bright green luminescent CsPbBr3 NCs to elucidate the concrete transformation mechanism via four stages: (i) the dissociation of pristine NCs, (ii) the formation of Pb-Br intermediates, (iii) low-dimensional nanoplatelets (NPLs) and (iv) cubic CsPbBr3 NCs, corresponding to the blue-to-green emission process. The desorption and reorganization of organic ligands induced by NO+ and the involvement of BF4- in the ligand exchange process played pivotal roles in this dissolution-recrystallization of NCs. Moreover, controlled shape evolution from anisotropic NPLs to NCs was investigated through variations in the amount of NOBF4. This further validates that additives exert a decisive role in the symmetry and growth of nanostructured perovskite crystals during phase transition based on the ligand-exchange mechanism. This finding serves as a source of inspiration for the synthesis of highly luminescent CsPbBr3 NCs, providing valuable insights into the chemical mechanism in post-synthesis transformation.

Spidermen Strategy for Stable 24% Efficiency Perovskite Solar Cells

AbstractThe interface energetics‐modification plays an important role in improving the power conversion efficiency (PCE) among the perovskite solar cells (PSCs). Considering the low carrier mobility caused by defects in PSCs, a double‐layer modification engineering strategy is adopted to introduce the “spiderman” NOBF4 (nitrosonium tetrafluoroborate) between tin dioxide (SnO2 and perovskite layers. NO+, as the interfacial bonding layer, can passivate the oxygen vacancy in SnO2, while BF4− can optimize the defects in the bulk of perovskite. This conclusion is confirmed by theoretical calculation and transmission electron microscopy (TEM). The synergistic effect of NO+ and BF4− distinctly heightens the carrier extraction efficiency, and the PCE of PSCs is 24.04% with a fill factor (FF) of 82.98% and long‐term stability. This study underlines the effectiveness of multifunctional additives in improving interface contact and enhancing PCE of PSCs.

The reaction of NOBF4 with antimony(III) corroles: Fluoride binding to antimony and regioselective nitration of the macrocycle

The reaction of antimony(III) corroles with nitrosonium tetrafluoroborate in the presence of air led to trans‐difluoroantimony(V) 3,17‐dinitro‐corrole complexes. A trans‐dinitrosylantimony(V) corrole compound has been proposed as a possible reaction intermediate that is subsequently converted into a trans‐dinitroantimony(V) corrole product. The formation of these intermediate species has been established via in situ FT‐IR spectra. This trans‐dinitroantimony(V) corrole species can transfer the nitro group to the β‐pyrrole positions (C3 and C17) of the corrole periphery via a radical pathway. The binding of fluoride to the axial positions of antimony(V) corrole occurs via nucleophilic attack of fluoride ion from BF4−. The trans‐difluoroantimony(V) 3,17‐dinitro‐corrole complexes are fully characterized via X‐ray crystallography, UV‐vis, FT‐IR, and NMR spectroscopy. They catalyze oxygenation reactions under photo‐redox conditions in presence of air and light at ambient temperature by forming singlet oxygen.

Step-scheme perylenediimide supramolecular nanosheet and TiO2 nanoparticle composites for boosted water splitting performance

Adjusting the band gap of organic-inorganic composites by chemical bonding can effectively construct Step-scheme (S-scheme) heterojunctions, featuring properties of fast photogenerated charge migration and excellent photocatalytic performance. In this work, a novel perylene-3, 4, 9, 10-tetracarboxylicdiimide (PDI)-titanium dioxide (TiO2) heterojunction is elaborately synthesized through simple solvent compounding method. The monodispersed spherical TiO2 nanoparticles was prepared with the capping agents of oleylamine and oleic acid, and suffered by a ligand exchange process with nitrosonium tetrafluoroborate (NOBF4) to remove oleylamine and oleic acid. The NOBF4 ligands were further replaced by PDI super molecular nanosheets to obtain two dimensional (2D)-zero dimensional (0D) PDI-TiO2 composites. TiO2 nanoparticles are evenly anchored on the surface of PDI nanosheets with intimate contact. The PDI-TiO2 composites has emerged considerably superior activity in hydrogen evolution. The highest hydrogen evolution rate for PDI-TiO2composites with the PDI weight percentage of 2.4% was 9766 μmol h−1 g−1 under solar light irradiation, which is 2.56 times of TiO2-NOBF4 catalyst. Moreover, PDI-TiO2 composites possess stoichiometric overall water splitting performance with H2 and O2 release rates of 238.20 and 114.18 μmol h−1 g−1. The superior photocatalytic performance of PDI-TiO2 composites can be attributed to the dramatic increase in visible and NIR light absorption caused by π-π stacking structure of PDI, the prevented charge recombination by the S-scheme heterojunction, and the enhanced oxygen evolution by the stronger oxidation capability of PDI. PDI supramolecular nanosheets may work as a novel functional support for many types of semiconductor nanomaterials as graphene, which will display a wide range of application prospects in the energy and environmental fields.

Adaption of MAPbI3 perovskite with copper phthalocyanine inorganic hole transport layer via nitrosonium tetrafluoroborate additive to enhance performance and stability of perovskite solar cells

Due to their high resistance to real operational conditions, perovskite-based solar cells (PSCs) with dopant-free inorganic hole transport materials are good candidates for PSC commercialization. It should be noted that these types of PSCs have recorded lower power conversion efficiency (PCE) compared to Spiro-OMeTAD-based PSCs, with a recent PCE record of 25.8%. Here, we introduced nitrosonium tetrafluoroborate (NOBF4) into the perovskite precursor to improve hole carriers' transport between the perovskite layer and copper phthalocyanine (CuPc) layer. Electrochemical impedance spectroscopy (EIS) showed that NOBF4 additive reduces series resistance in PSC devices, which may be due to a band alignment between the valance band of perovskite and CuPc. In addition, due to a partial BF4− substitution with I− ions during the fabrication process, the crystallinity properties of the perovskite layer are tailored, leading to the formation of a film with larger grains. By employing NOBF4 material, in the obtained perovskite layer, a small unreacted lead iodide (PbI2) amount remained. In total, the NOBF4 additive brings a maximum efficiency of 16.77% for the target solar cell group, higher than the 14.42% for control devices. The target PSCs, compared with the control PSCs, showed improved air stability results from the suppressed PbI2 with enlarged perovskite grains.

Efficient and stable pure α-phase FAPbI3 perovskite solar cells with a dual engineering strategy: Additive and dimensional engineering approaches

Formamidinium lead triiodide (FAPbI3) perovskite solar cells (PSCs) with a certified 25.5% power conversion efficiency (PCE) are the most promising devices for next-generation of solar cells. Here, we focus on boosting the performance and stability of these types of PSCs through a two-step engineering method, first additive engineering based on propionic acid for 3D FAPbI3 PSCs. Second, post-treatment of 3D devices with a 2-(4-fluorophenyl)ethyl ammonium iodide (FPEAI) solution doped with nitrosonium tetrafluoroborate (NOBF4). This two-step approach improves carriers' lifetime and charges separation at 3D/2D perovskite/hole transport layer (HTL), tiding with improvements in photovoltaic properties of corresponding PSCs. Besides, NOBF4 p-type dopant increases hole mobility at the interface of the 3D/2D hybrid perovskite/HTL, thus providing a road towards more boosting efficiency and stability of PSCs through dimensional engineering. Leading to improved properties of the perovskite, the modified 3D/2D PSCs achieve a PCE of up to 23.18% with long-term shelf, thermal and operational stability.

In Situ Synthesis of Phenoxazine Dyes in Water: Application for “Turn‐On” Fluorogenic and Chromogenic Detection of Nitric Oxide**

AbstractThe synthesis of phenoxazine dyes was revisited in order to access these fluorescent N,O‐heterocycles under mild conditions. The combined sequential use of nitrosonium tetrafluoroborate (NOBF4) and triphenylphosphine enables the facile conversion of bis(3‐dimethylaminophenyl) ether into the methyl analogue of popular laser dye oxazine 1. The ability of nitrosonium cation (NO+) to initiate the domino reaction resulting in π‐conjugated phenoxazine molecules under neutral conditions, then led us to explore the feasibility of expanding it in aqueous media. Thus, we explored the use of reactive signaling molecule nitric oxide (NO) as a biological trigger of phenoxazine synthesis in water. The implementation of a robust analytical methodology based on fluorescence assays and HPLC‐fluorescence/‐MS analyses, have enabled us to demonstrate the viability of this novel fluorogenic reaction‐based process to selectively yield an intense “OFF‐ON” response in the near‐infrared (NIR‐I) spectral region. This study is an important step towards the popularization of the concept of “covalent assembly” in the fields of optical sensing, bioimaging and molecular theranostics.

Conjugated polymer electrolyte with nitrosonium tetrafluoroborate as the interlayer for polymer solar cells

High-performance devices can be achieved by lowering the work function of the cathode electrode. Herein, we synthesized polyelectrolyte that has functionality at the side chain, named PFB. In addition, a p-type dopant, NOBF4 (nitrosonium tetrafluoroborate), was used to enhance the performance of the polyelectrolyte. This polyelectrolyte was adapted as an interlayer to improve the performances of polymer solar cells (PSCs). The PSCs based on PFB and NOBF4-PFB demonstrate higher power conversion efficiency (PCE) of 9.41% and 9.51% than pristine PSC using PTB7-Th as a reference (8.7%).

Controlled Formation of a Protein Corona Composed of Denatured BSA on Upconversion Nanoparticles Improves Their Colloidal Stability.

In the natural fluidic environment of a biological system, nanoparticles swiftly adsorb plasma proteins on their surface forming a “protein corona”, which profoundly and often adversely affects their residence in the systemic circulation in vivo and their interaction with cells in vitro. It has been recognized that preformation of a protein corona under controlled conditions ameliorates the protein corona effects, including colloidal stability in serum solutions. We report on the investigation of the stabilizing effects of a denatured bovine serum albumin (dBSA) protein corona formed on the surface of upconversion nanoparticles (UCNPs). UCNPs were chosen as a nanoparticle model due to their unique photoluminescent properties suitable for background-free biological imaging and sensing. UCNP surface was modified with nitrosonium tetrafluoroborate (NOBF4) to render it hydrophilic. UCNP-NOBF4 nanoparticles were incubated in dBSA solution to form a dBSA corona followed up by lyophilization. As produced dBSA-UCNP-NOBF4 demonstrated high photoluminescence brightness, sustained colloidal stability after long-term storage and the reduced level of serum protein surface adsorption. These results show promise of dBSA-based nanoparticle pretreatment to improve the amiability to biological environments towards theranostic applications.

Dye-sensitized core–shell NaGdF4:Yb,Er@NaGdF4:Yb,Nd upconversion nanoprobe for determination of H2S

The core–shell NaGdF4:Yb,Er@NaGdF4:Yb,Nd upconversion nanoparticles (UCNPs) were successfully obtained with the method of co-precipitation, and the water-solubility of UCNPs was improved by the ligand exchange reaction between nitrosyl tetrafluoroborate (NOBF4) and nanoparticles. The IR-783 dye with negative charge and NOBF4-UCNPs with positive charge can bind together by electrostatic action to sensitize UCNPs through the energy transfer from IR-783 to UCNPs. However, with the presence of Na2S (a commonly used H2S donor), a highly selective reaction between H2S and IR-783, which destoried the structure of IR-783 and blocked the energy transfer, thus led to the quenching of luminescent intensity. Based on this, a sensing system for determination of H2S has been constructed successfully. The linear range of H2S detection by this system is 0.5–15 μM, and the detection limit is 34.17 nM. Furthermore, the dye-sensitized core–shell NaGdF4:Yb,Er@NaGdF4:Yb,Nd upconversion nanoprobe was applied to real sample analysis with satisfactory results.

3+2] cycloaddition reaction of metallacyclopropene with nitrosonium ion: isolation of aromatic metallaisoxazole.

The synthesis of metallaisoxazole by the [3+2] cycloaddition reaction of metallacyclopropene with nitrosonium tetra-fluoroborate has been achieved under mild conditions. Nuclear magnetic resonance spectra, X-ray crystallographic analysis, and density functional theory calculations all suggest that the metallaisoxazole exhibits an aromatic character.

Magnetic nanovector for the down regulating CD44 and imaging of microRNA34a

Abstract Background Magnetic nanoparticles (MNPs) enable the monitoring of therapeutic agent delivery by non-invasive and real-time magnetic resonance imaging (MRI), because this technique can rapidly acquire multi-informational high resolution images. And Modifying the surface of various inorganic nanoparticles has recently become important to the development of novel biomedical technologies including therapeutics, diagnosis and clinical imaging, it is important for the treatment of the cancer in the functional aspect of nanoparticles. In addition, it is known that microRNAs (miRNA, miR), 1-2 nucleotides of non-coding small RNA, regulate various cellular functions including proliferation, differentiation and apoptosis as well as diseases. Thus, synthetic complimentary oligonucleotides against miRNAs can be potentially used as a molecular mechanism-based theragnostics biomarker in cancers by simultaneously imaging. Methods Nitrosonium tetrafluoroborate (NOBF4) is used to replace the original ligands attached to the magnetic nano particles, stabilizing the magnetic nanoparticls in various polar, hydrophilic media, and then surface modified magnetic nanoparticles were complexed with miRNA targeting CD44 gene via electrostatic interaction to verify the specific gene-silencing effect. Results The synthesized magnetic nanovectors were facilitated in vitro CD44 down-regulation and visualization via magnetic resonance imaging in metastatic gastric cancer. Conclusions In summary, we successfully formulated theranostic nanovector, for effective gene therapy and imaging. Nanovectors we designed were contributed to effective gene carrying through PEG-Tiohl. Moreover, it has potential to be a MR imaging agents as well as gene therapy. Consequently, Successful magnetic nanovector developed in this paper can be expected to expand research on carrying efficient delivery for not only cancer detecting agent but also therapeutic miRNA agents. Legal entity responsible for the study The author. Funding Has not received any funding. Disclosure The author has declared no conflicts of interest.

Diastereoselective heterocyclization of geminal bromo-fluoro arylcyclopropanes by nitrosonium tetrafluoroborate: Access to 4-fluorinated isoxazolines and isoxazoles

A series of 5-aryl-4-bromo-4-fluoroisoxazolines was synthesized via nitrosation of 2-aryl-1-bromo-1-fluorocyclopropanes with NOBF4. It was shown that the E-isomers of the cyclopropanes react highly regio- and diastereoselectively leading exclusively to the E-isomers of the isoxazolines. The obtained 5-aryl-4-bromo-4-fluoroisoxazolines were transformed selectively into the corresponding 5-aryl-4-fluoro- or 5-aryl-4-bromoisoxazoles in good yields in the reaction with Lewis acids.

Dopant‐Dependent Increase in Seebeck Coefficient and Electrical Conductivity in Blended Polymers with Offset Carrier Energies

AbstractThe strong and counterproductive interrelationship of thermoelectric parameters remains a bottleneck to improving thermoelectric performance, especially in polymer‐based materials. In this paper, a compositional range is investigated over which there is decoupling of the electrical conductivity and Seebeck coefficient, achieving increases in at least one of these two parameters while the other is maintained or slightly increased as well. This is done using an alkylthio‐substituted polythiophene (PQTS12) as additive in poly(bisdodecylquaterthiophene) (PQT12) with tetrafluorotetracyanoquinodimethane (F4TCNQ) and nitrosyl tetrafluoroborate (NOBF4) as dopants. The power factor increases two orders of magnitude with the PQTS12 additive at constant doping level. Using a second pair of polymers, poly(2,5‐bis(3‐dodecylthiophen‐2‐yl)thieno[3,2‐b]thiophene (PBTTTC12) and poly(2,5‐bis(3‐dodecylthiothiophen‐2‐yl)thieno[3,2‐b]thiophene, (PBTTTSC12), with higher mobilities, decoupling of the Seebeck coefficient and electrical conductivity is also observed and higher power factor is achieved. Distinguished from recently reported works, these two sets of polymers possess very closely offset carrier energy levels (0.05–0.07 eV), and the microstructure, assessed using grazing incidence X‐ray scattering, and mobility evaluated in field‐effect transistors, are not adversely affected by the blending. Experiments, calculations, and simulations are consistent with the idea that blending and doping polymers with closely spaced energy levels and compatible morphologies to promote carrier mobility favors increased power factors.

Redox-Responsive Chiral Dopant for Quick Electrochemical Color Modulation of Cholesteric Liquid Crystal.

Here, we report the first redox-active chiral dopant FcD, which electrically alters its helical twisting power (HTP) for a cholesteric liquid crystalline (LC) medium and quickly changes the reflection color. FcD is composed of an axially chiral binaphthyl unit in conjunction with a redox-active ferrocene unit. A cholesteric LC phase of 4'-pentyloxy-4-cyanobiphenyl, doped with FcD (3.0 mol %), developed a blue reflection color. When nitrosyl tetrafluoroborate, a one-electron oxidant, was added to this cholesteric LC phase, FcD was oxidized to decrease its original HTP value by 13%, so that a green reflection color was developed. In the presence of a supporting electrolyte, the reflection color was electrochemically modulated using a sandwich-type glass cell with indium tin oxide electrodes. In quick response to the applied voltage of +1.5 V, the reflection color changed from blue to green within 0.4 s. When 0 V was applied, the reflection color returned to its original blue color. The FcD-doped cholesteric LC is characterized by its fastest electrochemical response and lowest operating voltage among those reported for electrically driven cholesteric LC devices.

Solution‐processed Tetrafluoroborate‐capped In2O3 Nanocrystal Thin‐Film Transistors

Colloidal oleic acid (OA) capped indium oxide nanocrystal (In2O3 NC) was synthesized by the hot injection method. Afterwards, the ligand exchange reaction between OA and nitrosyl tetrafluoroborate (NOBF4) afforded tetrafluoroborate‐capped indium oxide nanocrystals (In2O3‐BF4− NCs). In2O3‐BF4− NCs thin‐film transistor (TFT) devices were fabricated by spin coating, exhibiting an electron mobility of 7.3 × 10−3, 5 × 10−2, and 0.19 cm2/V/s for low‐temperature annealed In2O3‐BF4− NCs films at 80, 150, and 250 °C, respectively. An even higher mobility of 13.0 cm2/V/s was obtained by annealing the films at 350 °C, because of decreasing distance between the adjacent In2O3 NCs, enhancing the electronic coupling between the neighboring NCs on the NC film by the decomposition of inorganic ligand NOBF4. The temperature‐dependent behavior of the electron transport of In2O3‐BF4− NCs films annealed at different temperatures of 150, 250, and 350 °C for application in TFT device is also reported. We conclude that thermally activating electron transport mechanism through nearest neighbor hopping works for the In2O3 NC solid in the range from 223 to 323 K, and the activation energy decreases with increasing annealing temperatures.

A versatile synthesis of triarylantimony difluorides by fluorination of triarylstibanes with nitrosyl tetrafluoroborate and their antitumor activity

Triarylantimony difluorides were synthesized in moderate to excellent yields by oxidative fluorination of triarylstibanes with nitrosyl tetrafluoroborate (NOBF4) under aerobic conditions. This reaction is the first example of fluorination of trivalent organoantimony compounds using NOBF4 as a fluorinating agent. The triarylantimony difluorides exhibited good anti-proliferation activity against tumor cell lines. In particular, the IC50 of p-Tol3SbF2 (2c) was the lowest in each cell lines.

Nitrosation of adamantyl dichlorocyclopropanes as a new approach to adamantyl isoxazoles

Nitrosation of 2-(1-adamantylmethyl)-1,1-dichlorocyclopropane with either adduct NOCl•(SO3) n or nitrosonium tetrafluoroborate gives 3- and 4-(1-adamantylmethyl)-5-chloroisoxazoles in good yields. The presence of a linker between cyclopropane ring and adamantane moiety is essential for enabling nitrosation—heterocyclization of adamantyl 1,1-dichlorocyclopropanes.

ChemInform Abstract: Synthesis of Furoxans (1,2,5‐Oxadiazole 2‐oxides) from Styrenes and Nitrosonium Tetrafluoroborate in Non‐Acidic Media and Mechanistic Study.

AbstractThe products are obtained as a mixture of two regioisomers with the furoxan bearing an external N‐oxygen atom at the distal side from the aryl substituent being the major product.