Photochemical grafting of diazonium salts on metals

4-Nitrobenzenediazonium may be photochemically grafted onto gold, copper and iron under visible and UV light. Thin nanometre layers are obtained and characterized by IRRAS, electrochemistry and ellipsometry.     

Facile electrochemical transformation of diazonium salts into carboxylic acids

The electrolyses of aryldiazonium tetrafluoroborates in dry DMF and Bu₄NHSO₄ as solvent-supporting electrolyte system, in the presence of CO₂ led to the corresponding arylcarboxylic acids in very good yields.     

Spontaneous grafting of diazonium salts: chemical mechanism on metallic surfaces

The spontaneous reaction of diazonium salts on various substrates has been widely employed since it consists of a simple immersion of the substrate in the diazonium salt solution. As electrochemical processes involving the same diazonium salts, the spontaneous grafting is assumed to give covalently poly(phenylene)-like bonded films. Resistance to solvents and to ultrasonication is commonly accepted as indirect proof of the existence of a covalent bond. However, the most relevant attempts to demonstrate a metal-C interface bond have been obtained by an XPS investigation of spontaneously grafted films on copper. Similarly, our experiments give evidence of such a bond in spontaneously grafted films on nickel substrates in acetonitrile. In the case of gold substrates, the formation of a spontaneous film was unexpected but reported in the literature in parallel to our observations. Even if no interfacial bond was observed, formation of the films was explained by grafting of aryl cations or radicals on the surface arising from dediazoniation, the film growing later by azo coupling, radical addition, or cationic addition on the grafted phenyl layer. Nevertheless, none of these mechanisms fits our experimental results showing the presence of an Au-N bond. In this work, we present a fine spectroscopic analysis of the coatings obtained on gold and nickel substrates that allow us to propose a chemical structure of such films, in particular, their interface with the substrates. After testing the most probable mechanisms, we have concluded in favor of the involvement of two complementary mechanisms which are the direct reaction of diazonium salts with the gold surface that accounts for the observed Au-N interfacial bonds as well as the formation of aryl cations able to graft on the substrate through Au-C linkages.     

Gold(III) diazonium complexes for electrochemical reductive grafting

Gold(III) diazonium complexes were synthesized for the first time and studied for electrochemical reductive grafting. The diazonium complex [CN-4-C(6)H(4)N≡N]AuCl(4) was synthesized by protonating CN-4-C(6)H(4)NH(2) with chloroauric acid H[AuCl(4)]·3H(2)O to form the ammonium salt [CN-4-C(6)H(4)NH(3)]AuCl(4), which was then oxidized by the one-electron oxidizing agent [NO]PF(6) in CH(3)CN. The highly irreversible reduction potential of 0.1 mM [CN-4-C(6)H(4)N≡N]AuCl(4) observed at -0.06 V versus Ag/AgCl in CH(3)CN/0.1 M [Bu(4)N]PF(6) encompasses both gold(0) deposition and diazonium reduction. Repeated scans showed the absence of the reduction peak on the second run, which indicates that surface modification with a blocking gold aryl film has occurred and is largely complete.     

Sterically hindered diazonium salts for the grafting of a monolayer on metals

An organic monolayer is obtained on Cu, Au, and SiH by electrografting 3,5-bis-tert-butyl benzenediazonium tetrafluoroborate, as evidenced by cyclic voltammetry, IR-ATR, and ellipsometry. This results from the bulky groups at the 3,5-positions that sterically hinder the growth of the layer.     

Syntheses of terminally functionalized polyisobutylene derivatives using diazonium salts

A new strategy for the synthesis of end‐functionalized polyisobutylene (PIB) oligomers is detailed. Commercially available vinyl‐terminated PIB oligomers were modified to form aniline‐terminated PIB via an aromatic electrophilic substitution reaction. The PIB‐bound aryl amines so formed were then converted into diazonium salts using isopentyl nitrite and an acid in methylene chloride. These salts served as versatile intermediates in synthetic reactions affording azo dye‐containing PIB derivatives and other terminally‐functionalized PIB derivatives not readily available by other reactions. The advantages and limitations of various name reactions including diazo couplings, Sandmeyer reactions, dediazoniations, and Heck reactions are discussed. The kinetics of polar substitution reactions at the termini of these nonpolar oligomers and the effects of solvent on these reactions were also examined. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Reaction of heterocyclic diazonium salts with hydrazones

Depending on the nature of the heteroring and the hydrazone, a formazan or a heterylazophenylhydrazone are formed in the reaction of an aryl hydrazone with the diazonium salt obtained from a heterocyclic amine. Disproportionate to form a triphenylformazan is also possible.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 8, pp. 1062–1064, August, 1972     

Reaction of 5-alkylidenerhodanines with diazonium salts

In the action of diazonium salts on 5-alkylidenerhodanines, azo compounds are formed by the replacement of one or two hydrogen atoms in the methyl group. In the case of 5-ethylidenerhodanines, the formation of an azorhodanine through the replacement of the alkylidene residue by an arylazo group takes place simultaneously. In the formazyl derivatives the long-wave absorption maximum is displaced hypsochromically by 15–20 nm as compared with the dyes having a single azo group.     

Maleimide-activated aryl diazonium salts for electrode surface functionalization with biological and redox-active molecules

A versatile and simple method is introduced for formation of maleimide-functionalized surfaces using maleimide-activated aryl diazonium salts. We show for the first time electrodeposition of N-(4-diazophenyl)maleimide tetrafluoroborate on gold and carbon electrodes which was characterized via voltammetry, grazing angle FTIR, and ellipsometry. Electrodeposition conditions were used to control film thickness and yielded submonolayer-to-multilayer grafting. The resulting phenylmaleimide surfaces served as effective coupling agents for electrode functionalization with ferrocene and the redox-active protein cytochrome c. The utility of phenylmaleimide diazonium toward formation of a diazonium-activated conjugate, followed by direct electrodeposition of the diazonium-modified DNA onto the electrode surface, was also demonstrated. Effective electron transfer was obtained between immobilized molecules and the electrodes. This novel application of N-phenylmaleimide diazonium may facilitate the development of bioelectronic devices including biofuel cells, biosensors, and DNA and protein microarrays.     

Reaction of some organomercury compounds with diazonium salts

Summary We were the first to replace a mercury atom attached to a saturated carbon atom by the arylazo group. The reaction of the p-nitro- and 2,4-dinitrophenyldiazonium fluoborates with ethyl -bromomercuriphenylacetate and with bromomercurimethyl tert-butyl ketone give the corresponding arylhydrazones in good yields.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 9, pp. 1711–1712, September, 1964     

Role of MXene surface terminations in electrochemical energy storage: A review

MXenes are a group of recently discovered 2D materials and have attracted extensive attention since their first report in 2011; they have shown excellent prospects for energy storage applications owing to their unique layered microstructure and tunable electrical properties. One major feature of MXenes is their tailorable surface terminations (e.g., −F, −O, −OH). Numerous studies have indicated that the composition of the surface terminations can significantly impact the electrochemical properties of MXenes. Nonetheless, the underlying mechanisms are still poorly understood, mainly because of the difficulties in quantitative analysis and characterization. This review summarizes the latest research progress on MXene terminations. First, a systematic introduction to the approaches for preparing MXenes is presented, which generally dominates the surface terminations. Then, theoretical and experimental efforts regarding the surface terminations are discussed, and the influence of surface terminations on the electronic and electrochemical properties of MXenes are generalized. Finally, we present the significance and research prospects of MXene terminations. We expect this review to encourage research on MXenes and provide guidance for usingthese materials for batteries and supercapacitors.     

On the reaction of 5-aminopyrimidine with diazonium salts

The reaction of 5-aminopyrimidine with benzenediazonium chloride, p-methylbenzenediazonium chloride and p-bromobenzenediazonium chloride is described. The reaction leads to a mixture of compounds, i.e. 1-aryl-3-(pyrimidin-5-yl)triazene ( 6 ), 5-amino-4-aryl-6-arylazopyrimidine ( 7 ) and 4-aryl-6-arylazo-5-hydroxypyrimidine ( 8 ). The yields are found to be strongly dependent on the substituent present in the diazonium salt. Attempts to rearrange 1-(p-bromophenyl)-3-(pyrimidin-5-yl)triazene ( 6c ) under basic and acidic conditions into a 1,2,3-triazole derivative failed.     

Fractional surface termination of diamond by electrochemical oxidation

The crystalline form of sp(3)-hybridized carbon, diamond, offers various electrolyte-stable surface terminations. The H-termination-selective attachment of nitrophenyl diazonium, imaged by AFM, shows that electrochemical oxidation can control the fractional hydrogen/oxygen surface termination of diamond on the nanometer scale. This is of particular interest for all applications relying on interfacial electrochemistry, especially for biointerfaces.