Benzenediazonium Tetrafluoroborate Research Articles

Facile synthesis of Ti3C2Tx MXene nanosheets using aryl diazonium tetrafluoroborate for multiple applications

The development of an HF-free and environmentally benign method for etching the middle aluminum layer (Al) from the Ti3AlC2-MAX phase is a challenging task in titanium carbide (Ti3C2Tx) MXene synthesis. Herein, we designed a diazonium salt-based ultrasonic method to prepare MXene. We have explored 4-carboxy benzene diazonium tetrafluoroborate (4-CBDF) as a delaminating agent, which can dissolve the Al layer directly from the MAX phase. 4-carboxy benzene diazonium (4-CBD+) ion promotes the intercalation as well as exfoliation simultaneously during the etching of the MAX phase and directly results in Ti3C2Txnanosheets without undergoing any additional delamination process. Synthesized MXene nanosheets show excellent photothermal performance with a conversion efficiency of 59 %. This MXene-coated GC electrode exhibits the highest capacitance of 1133 F/g at a current density 1 A/g, which maintains a retention capacitance of 91% even after 10,000 GCD cycles. The present method provides a fundamental insight into the development of MXene-based next-generation photothermal materials and supercapacitors.

3,5-Dimethoxy-2-[(4-methoxyphenyl)diazenyl]phenol

3,5-Dimethoxy-2-[(4-methoxyphenyl)diazenyl]phenol was synthesized by an azo-coupling reaction between 3,5-dimethoxyphenol and 4-methoxy benzenediazonium tetrafluoroborate. The structure of newly synthesized compound was elucidated based on 1H NMR, 13C NMR, ESI-MS, UV-Vis and FT-IR.

Study of the reaction of iodoarylation of phenylacetylene by benzenediazonium tetrafluoroborate

Anion-arylation reaction, as well as its partial case – Meerwein arylation reaction, is a valuable tool for construction of practically important compounds. Such reactions are mainly catalyzed by transition metals. In the same time, iodo-arylation is self-catalyzed reaction and does not require utilization of eco-unfriendly heavy-metal containing catalysts. However, there are only several reports concerning to this topic. In order to shed more light on the nature and distributions of products of this reaction, herein we thoroughly investigated iodoarylation reaction of phenylacetylene by benezenediazonium tetrafluoroborate in the presence of lithium iodide. Reaction has been performed at 0‑5°C in DMF. For analysis of reaction products and its ratio GC‑MS analysis have been applied. Seven main products of this reaction have been found. In the reaction mixture typical product of Sandmeyer reaction – iodobenzene (33.9 %) has been identified. Although in course of the reaction formation of dimethylaminobenzene (6.5 %) take place. Probably, formation of last is a result of benzene radical attack on the solvent (DMF). In the same time, formation of diiodostyrene (10.2 %) in reaction mixture was predictable, because it is well known that iodine anion easily can be oxidized by arenediazonium salts to elemental iodine, which further reacts with starting phenylacetylene. Further, orto- and para-iodobiphenyls (8.7 and 4.1 %, respectively) have been identified in the reaction mixture. Formation of such products was unexpected, however can be explained as subsequent arylation by Gomberg-Bachmann-Hey type reaction of formed iodobenzene. Finally, desired E- and Z-iodostilbenes have been formed in 36.6 % total yield with E/Z ratio close to 3:1. In conclusion, products of iodo-mediated reaction of benzenediazonium tetrafluoroborate with phenylacetylene in presence of lithium iodide have been investigated by GC‑MS analysis. Possible ways of formation of all identified compounds have been suggested. Key words : iodo-arylation, iodostilbenes, arenenediazonium salts, phenylacetylene, chromato-mass spectrometry.

“Click” Chemistry on Gold Electrodes Modified with Reduced Graphene Oxide by Electrophoretic Deposition

The coating of electrical interfaces with reduced graphene oxide (rGO) films and their subsequent chemical modification are essential steps in the fabrication of graphene-based sensing platforms. In this work, electrophoretic deposition (EPD) of graphene oxide at 2.5 V for 300 s followed by vapor treatment were employed to coat gold electrodes uniformly with rGO. These interfaces showed excellent electron transfer characteristics for redox mediators such as ferrocene methanol and potassium ferrocyanide. Functional groups were integrated onto the Au/rGO electrodes by the electro-reduction of an aryldiazonium salt, 4-((triisopropylsilyl)ethylenyl)benzenediazonium tetrafluoroborate (TIPS-Eth-ArN) in our case. Chemical deprotection of the triisopropylsilyl function resulted in propargyl-terminated Au/rGO electrodes to which azidomethylferrocene was chemically linked using the Cu(I) catalyzed “click” chemistry.

Raman Characterization of Phenyl-Derivatives: From Primary Amine to Diazonium Salts

The objective of the present work is to use Raman spectroscopy for characterizing, the fate of phenyl-derivatives, from phenyl-amines to aryl-diazonium derivatives (ADD). Four ADD were investigated: (i) benzene diazoniumtetrafluoroborate (DS), (ii) 4-decyl benzene diazoniumtetrafluoroborate (DS-C10H21), (iii) 4-carboxybenzene diazoniumtetrafluoroborate (DS-COOH) and (iv) 4-(aminoethyl) benzene diazoniumtetrafluoroborate (DS-(CH2)2NH2). Raman investigation of the above ADD confirmed the existence of an N≡N bond stretching in the range of 2285-2305 cm-1. Moreover, the strong band related to CH in plane-bending and C-N-stretching modes in the 1073-1080 cm-1 range, is a signature of phenyl derivatives stemming from ADD. Furthermore, we analyzed and discuss the H-N- (ring) symmetric stretching modes and the ring-N, as well as the benzene-ring vibrational modes, the C-H related vibrations and the functions in para-position carried by the aromatic ring. The effect of structural changes, the conformational rearrangements from amines to ADD and the influence of the substituent located in the para-position on Raman modes, were examined as well. Finally, Raman experiments supported by Density Functional Theory (DFT) modeling allowed us to determine the crystalline structure of DS-COOH.

Unlocking the energy capabilities of micron-sized LiFePO4.

Utilization of LiFePO4 as a cathode material for Li-ion batteries often requires size nanonization coupled with calcination-based carbon coating to improve its electrochemical performance, which, however, is usually at the expense of tap density and may be environmentally problematic. Here we report the utilization of micron-sized LiFePO4, which has a higher tap density than its nano-sized siblings, by forming a conducting polymer coating on its surface with a greener diazonium chemistry. Specifically, micron-sized LiFePO4 particles have been uniformly coated with a thin polyphenylene film via the spontaneous reaction between LiFePO4 and an aromatic diazonium salt of benzenediazonium tetrafluoroborate. The coated micron-sized LiFePO4, compared with its pristine counterpart, has shown improved electrical conductivity, high rate capability and excellent cyclability when used as a ‘carbon additive free' cathode material for rechargeable Li-ion batteries. The bonding mechanism of polyphenylene to LiFePO4/FePO4 has been understood with density functional theory calculations.

Quantifying the electrochemical maleimidation of large area graphene

Abstract The covalent modification of large-area graphene sheets by p-(N-Maleimido)phenyl (p-MP) via electrochemical grafting of p-(N-Maleimido)benzenediazonium tetrafluoroborate (p-MBDT) is successfully demonstrated for the first time. The deposition process is monitored in-situ using the mass change of a graphene/SiNX:H/Au-coated quartz crystal microbalance(QCM) chip. The resulting mass increase correlates with a maleimide thickness of approximately 2.3 molecular layers. The presence of an infrared absorption band at 1726 cm-1 shows that maleimide groups were deposited on the substrates. Raman backscattering spectra reveal the presence of D and D′ modes of the graphene layer, indicating that p-MP forms covalent bonds to graphene. Using the mass change and charge transfer during the potential cycling the faradaic efficiency of the functionalisation process was deduced, which amounts to eta = 22%.

Synthesis of conducting azopolymers by electrochemical grafting of a diazonium salt at polypyrrole electrodes

In this paper we report a new strategy for obtaining conducting azopolymers having pendant azobenzene moieties via functionalization of polypyrrole by electrochemical reduction of 4-[(4′-nitrophenyl)azo]benzenediazonium tetrafluoroborate (NABDBF4−). The functionalization of polypyrrole films with 4′-nitroazobenzene (NAB) groups has been evaluated by cyclic voltammetry and by spectroscopic techniques such as XPS, Raman and UV–vis spectroscopy. Moreover, the third-order nonlinear optical response of NAB-functionalized polypyrrole has been investigated using the optical third-harmonic generation technique. All these investigations confirmed the presence at the polymeric films surface of the functional groups introduced by the electrochemical reduction of diazonium salt. The versatility of this methodology allows not only the functionalization of polypyrrole-type materials with chromophore groups, but can also be successfully applied to other conjugated polymer systems in order to create various photoresponsive materials.

Polyphenylene Wrapped Sulfur/Multi-Walled Carbon Nano-Tubes via Spontaneous Grafting of Diazonium Salt for Improved Electrochemical Performance of Lithium-Sulfur Battery

A novel conducting polymer polyphenylene is used to in situ wrap the MWCNT-core/Sulfur-shell composite via the spontaneous polymerization reaction process of benzenediazonium tetrafluoroborate (ArN2+ BF4−). The porous conductive polymer skin layer effectively prevents the dissolution of active sulfur and facilitates the diffusion of lithium ion towards to reaction site, due to the shortened diffusion distance. Moreover, this resulting architecture structure, Polyphenylene/S/MWCNTs, can accommodate the large volumetric expansion of sulfur during lithiation procedure, improving the cycling stability and rate capability of lithium-sulfur batteries. It delivers an initial discharge capacity of 1491.3mAh/g at 0.1C, and the remaining capacity is 1015.6mAh/g after 75 cycles. The as-prepared material also exhibits an excellent rate capability and cyclability at 0.5C, 1C and 5C. Our experimental results manifest that this composite is a potential candidate as cathode material for high performance lithium-sulfur batteries in the future.

The 2,4-dimethyl-7-pentafluorosulfanyl-5-(trifluoromethyl)dibenzo[b,d]thiophenium trifluoromethanesulfonate: The SF5-analog of Umemoto salt

The SF5-analog of the Umemoto salt was synthesized in just two steps by combining our recently reported SF5-biaryl synthesis, via Suzuki coupling with 4-(pentafluorosulfanyl)benzenediazonium tetrafluoroborate, with Magnier's one-pot synthesis of dibenzothiophenium salts employing CF3SO2Na and triflic anhydride. The trifluoromethylating power of this novel onium salt toward reactive arenes was tested in a survey study on small scale.

4‐(Pentafluorosulfanyl)benzenediazonium Tetrafluoroborate: A Versatile Launch Pad for the Synthesis of Aromatic SF5 Compounds via Cross Coupling, Azo Coupling, Homocoupling, Dediazoniation, and Click Chemistry

AbstractThe reagent 4‐(pentafluorosulfanyl)benzenediazonium tetrafluoroborate (1) was synthesized and isolated as a stable salt for the first time; its application in a wide assortment of transformations was subsequently investigated. A series of novel SF5‐bearing alkenes, alkynes, and biaryl derivatives were synthesized by employing Heck–Matsuda, Sonogashira, and Suzuki coupling protocols. Dediazoniation with TMSX (X = Hal; N3; and CN) and NH4SCN in [BMIM][BF4] as solvent furnished the corresponding p‐SF5–C6H4X derivatives. The azide derivative p‐SF5–C6H4N3 entered into click chemistry with phenylacetylenes to furnish the corresponding triazoles. The 4,4′‐bis(pentafluorosulfanyl)biphenyl was synthesized by homo‐coupling using Pd(OAc)2. The corresponding azo compounds were obtained through azo‐coupling with reactive aromatic nucleophiles (1,3‐dimethoxybenzene, 1,3,5‐trimethoxybenzene, 1,2,4‐trimethoxybenzene, aniline and phenol). Fluorodediazoniation in [BMIM][PF6] and [BMIM][BF4] selectively furnished the fluoro derivative p‐SF5–C6H4F. Dediazoniation in [BMIM][NTf2] gave p‐SF5–C6H4OS(O)(CF3)=NSO2CF3 as the major and p‐SF5–C6H4‐NTf2 as the minor products. Homolytic dediazoniation in MeCN/NaI gave the unsymmetrical biaryls p‐SF5–C6H4‐Ar (ArH = mesitylene and p‐xylene) along with p‐SF5–C6H4I. Analysis of the dediazoniation product mixtures indicated that dediazoniation of p‐SF5–C6H4N2+ BF4– in low nucleophilicity, highly ionizing, solvents (TfOH, TFE, HFIP, TFAH) is mainly heterolytic, while in MeOH it is mainly homolytic. The isodesmic reaction p‐SF5–C6H4+ + R‐C6H5 → SF5–C6H5 + p‐R‐C6H4+ (with R = NO2, CF3, H) was gauged by DFT at various levels and by PCM.

Diazonium Exchange and Migration of Pivaloyl Group upon Azo Coupling of β‐Enaminones

Abstract4,4‐Dimethyl‐1‐methylamino‐1‐phenyl‐2‐(substituted phenyldiazenyl)pent‐1‐en‐3‐ones (prepared upon azo coupling of 4,4‐dimethyl‐1‐methylamino‐1‐phenylpent‐1‐en‐3‐one 6a with the corresponding benzenediazonium tetrafluoroborates) react with another molecule of substituted benzenediazonium tetrafluoroborate (in dichloromethane in the presence of anhydrous sodium acetate) to form substituted 4,4‐bis(substituted phenyldiazenyl) derivatives 8. The second azo coupling is reversible. Derivatives 8 undergo either reverse cleavage of a diazonium ion or [1,3] sigmatropic rearrangement forming substituted formazane 9. In the case of the sequential use of two different diazonium tetrafluoroborates, the less electrophilic group splits off more easily. The structures of the products 9 were studied by means of X‐ray, 1H, 13C, 19F and 15N NMR and MALDI HRMS analyses. The formazans 9 exhibit a reduced mobility of the phenyl group adjacent to the pivaloyl group, giving rise to anisochronism of proton and carbon atoms, to eventually form conformers. The reduced mobility was observed by means of NMR spectroscopy. A temperature dependence of the spectral behaviour was also studied.

Attractive double-layer forces and charge regulation upon interaction between electrografted amine layers and silica

Amine functionalities have been introduced on glassy carbon surfaces through electrografting of 4-(2-aminoethyl)benzenediazonium tetrafluoroborate. The grafted layers were characterized by ellipsometry and by nanomechanical mapping in air and aqueous solutions using the atomic force microscopy PeakForce QNM mode. The layer was found to be 2.5nm thick with low roughness, comparable to that of the glassy carbon substrate. However, small semi-spherical features were observed in the topographical image, indicating a clustering of the grafted amine compound. The nanomechanical mapping also demonstrated some swelling of the layer in water and pointed toward an important contribution of electrostatic interactions for the tip-surface adhesion. The forces between an aminated glassy carbon surface and a μm-sized silica particle in aqueous solutions were measured at different ionic strength and pH-values. The results demonstrate that an attractive double-layer force predominates at large separations, and that the surface charge densities increase as the separation between the surfaces decreases. The degree of charge regulation on the aminated glassy carbon is significant. The relatively low surface charge density of the aminated glassy carbon is attributed to significant incorporation of counterions in the water-rich grafted layer.

Synthesis of new derivatives of a representative o-quinone scaffold by reduction at the electrode

The concomitant electrochemical reduction of 9,10-phenanthrenequinone and benzenediazonium tetrafluoroborate, under constant potential conditions (−0.5 V vs Ag/Ag+), has been performed in different organic solvents. An interesting entry to new C–C radical coupling products is here described. Another cathodic pathway where the anion radical intermediate acts as an EGB is also described. The electrochemical behaviour of both systems and mechanistic proposals are given.

Photoswitchable Azoheterocycles via Coupling of Lithiated Imidazoles with Benzenediazonium Salts

In contrast to azobenzenes, heterocyclic azo compounds are less well investigated. Phenylazoimidazoles would be versatile as photodissociable ligands (PDLs) because imidazole is an important donor in coordination chemistry. Here, we present the synthesis of 4- and 5-phenylazoimidazoles via a novel azo-coupling method. 1,2-Protected imidazole is lithiated in the 5-position and coupled with benzenediazonium tetrafluoroborate. Several new phenylazoimidazoles were prepared. They exhibit an excellent switching behavior. Upon irradiation of the trans isomers with UV light, >95% of the cis forms are obtained. Upon heating, a complete transformation back to the trans configuration was achieved. Back switching with visible light, however, is incomplete.

Stereoselective Synthesis of Aza Analogues of Isoaltholactone and Goniothalesdiol – New Applications of the Heck–Matsuda Reaction (Eur. J. Org. Chem. 36/2011)

AbstractThe cover picture shows the Heck–Matsuda reaction as the key step in the total synthesis of the aza analogue of the natural product isoaltholactone, which was isolated from several species of Goniothalamus. The stereoselective synthesis of this aza analogue was accomplished by Heck–Matsuda arylation between a chiral endocyclic enecarbamate and benzenediazonium tetrafluoroborate. This transformation not only forged the key carbon–carbon bond between the aryl group and the pyrrolidine moiety, but also placed the olefin functional group at the appropriate position for the construction of aza‐isoaltholactone. Moreover, the synthesis of a new nitrogen analogue of the natural compound goniothalesdiol was also accomplished by using an intermediate produced in the synthesis of aza‐altholactone, making the overall process more divergent. Details are discussed in the article by C. R. D. Correia et. al. on p. 7259 ff. magnified image

Highly Hydrophilic Surfaces from Polyglycidol Grafts with Dual Antifouling and Specific Protein Recognition Properties

Homopolymer grafts from α-tert-butoxy-ω-vinylbenzyl-polyglycidol (PGL) were prepared on gold and stainless steel (SS) substrates modified by 4-benzoyl-phenyl (BP) moieties derived from the electroreduction of the parent salt 4-benzoyl benzene diazonium tetrafluoroborate. The grafted BP aryl groups efficiently served to surface-initiate photopolymerization (SIPP) of PGL. In similar conditions, SIPP of hydroxyethyl methacrylate (HEMA) permitted the production of PHEMA grafts as model surfaces. Water contact angles were found to be 66°, 15°, and 0° for SS-BP, SS-PHEMA, and SS-PPGL, respectively. The spontaneous spreading of water drops on SS-PPGL was invariably observed with 1.5 μL water drops. PPGL thus appears as a superhydrophilic polymer. Resistance to nonspecific adsorption of proteins of PPGL and PHEMA grafts on gold was evaluated by surface plasmon resonance (SPR) using antibovine serum albumin (anti-BSA). The results conclusively show that PPGL-grafts exhibit enhanced resistance to anti-BSA adsorption compared to the well-known hydrophilic PHEMA. PPGL grafts were further modified with BSA through the carbonyldiimidazole activation of the OH groups providing immunosensing surfaces. The so-prepared PPGL-grafted BSA hybrids specifically interacted with anti-BSA in PBS as compared to antimyoglobin. It is clear that the superhydrophilic character of PPGL grafts opens new avenues for biomedical applications where surfaces with dual functionality, namely, specific protein grafting together with resistance to biofouling, are required.

ChemInform Abstract: Synthetic Methods and Reactions. Part 160. Preparation of Phenyl Alkyl Ethers and Phenyl Esters from Benzenediazonium Tetrafluoroborate with Alkoxytrimethylsilanes and Trimethylsilyl Esters.

ChemInform Abstract: Synthetic Methods and Reactions. Part 160. Preparation of Phenyl Alkyl Ethers and Phenyl Esters from Benzenediazonium Tetrafluoroborate with Alkoxytrimethylsilanes and Trimethylsilyl Esters.

Reaction of metals with benzenediazonium tetrafluoroborate in aprotic solvents

Abstract The reaction of metals and glassy carbon with benzenediazonium tetrafluoroborate (BDFB) in aprotic solvents has been studied. During contact of Pt, Au, Ag, Pd, or V with glassy carbon in concentrated diazonium salt solution no change of color was observed. For Al, Ca, Cr, Cu, Fe, Ga, In, Mg, Li, Na, or Zn the process was accompanied by a rapid solution color change, rapid N2 release and the loss of metal sample mass. The copper metal ionization-dissolution was studied by ultraviolet and visible absorption spectroscopy, along with gravimetric and volumetric measurements. A dissolution mechanism was proposed based on kinetic, infrared, and X-ray diffraction data. The 432 nm absorption band appearing after Cu-BDFB reaction indicates formation of the mixed complex [Cu(N2C6H5·(N≡C-CH3)3]+ where the copper atom is covalently bonded to the azophenyl radical and coordinated to acetonitrile (ACN). This complex is thermodynamically unstable and decomposes slowly to a colorless crystalline and a black amorphous phase. The crystalline phase was identified as [Cu(NC-CH3)4]BF4. The amorphous phase is a mixture of products formed by azophenyl and phenyl radical condensation.

Fabrication, Characterization, and Optoelectronic Properties of Layer-by-Layer Films Based on Terpyridine-Modified MWCNTs and Ruthenium(III) Ions

A novel full-conjugated 4-(2,2′:6′,2′′-terpyrid-4′-yl) benzenediazonium tetrafluoroborate (diazo-tpy) was synthesized and used for surface modification of materials, such as quartz wafers, ITO glass, silicon, and multiwalled carbon nanotubes (MWCNTs). Under UV irradiation, the diazonium group of diazo-tpy is decomposed and the residual terpyridine group is covalently anchored to the surface of substrates. The obtained tpy-modified MWCNTs (tpy-MWCNTs) have good solubility in common organic solvents. TGA and HRTEM analyses confirmed that terpyridine groups have been symmetrically grafted on MWCNTs. The thickness of the tpy-modified monolayer is about 2.3 nm, which is approximately 2 times the axial length of the 4-(2,2′:6′,2′′-terpyrid-4′-yl)phenyl group. The introduction of terpyridine groups on the surface of MWCNTs provides a coordination site to complex with metal ions. Multilayer films were fabricated from tpy-MWCNTs and ruthenium ions [Ru(III)] via the layer-by-layer self-assembled (LBL SA) technique ...