Search results for "Onium salts"
showing 10 items of 14 documents
Effect of quaternary ammonium salts on spectral properties of zinc octacarboxyphthalocyanine
2020
Abstract The paper presents results of the research on the influence of quaternary ammonium salts on UV–vis absorption and emission spectra of zinc octacarboxyphthalocyanine (ZnPcOC). Quaternary ammonium salts which show biological activity play a crucial role. In ZnPcOC solutions with a proper concentration of tetrabutylammonium salts (TBAX), a strong bathochromic shift band (λmax = 760 nm – “R” band) showing red fluorescence appears in time. The presence of tetrabutylammonium salt causes pH increase and, consequently, a gradual dissociation of carboxyl groups in ZnPcOC molecule. It seems that –COO— anions present in the ZnPcOC complex can interact with tetraalkylammonium cations, causing …
Protonation of Carbonate in Aqueous Tetraalkylammonium Salts at 25°C.
2006
Protonation constants of carbonate were determined in tetramethylammonium chloride (Me4NClaq 0.1≤I/mol kg−1 ≤4) and tetraethylammonium iodide (Et4NIaq 0.1≤I/mol kg−1 ≤1) by potentiometric ([H+]-glass electrode) measurements. Dependence of protonation constants on ionic strength was taken into account by modified specific ion interaction theory (SIT) and by Pitzer models. Literature data on the protonation of carbonate in NaClaq (0.1≤I/mol kg−1 ≤6) were also critically analysed. Both protonation constants of carbonate follow the trend Et4NI>Me4NCl > NaCl. An ion pair formation model designed to take into account the different protonation behaviours of carbonate in different supporting electr…
Synthèse de pinces à fluorures dérivées d'aminoacides pour l'imagerie TEP
2014
This thesis project, which is part of a collaboration between the Institut de Chimie Moléculaire de l’Université de Bourgogne and the Positron Emission Tomography Research Centre, is about the synthesis of fluoride pincers derived from amino acids based on 18F-B bond construction to get a new class of PET imaging agents. First, this project concerned the design, synthesis and characterisation of new boronato and trifluoroborato phosphonium amino acid salts. Quaternisation of o-boronate phenyl phosphine with β-iodo amino esters or γ-iodo amino ester leads to the corresponding salts without racemisation and in yields up to 88%. Saponification of boronato phosphonium amino esters afford the fr…
Synthesis of No-Carrier-Added 4-[18F]Fluorophenol from 4-Benzyloxyphenyl-(2-thienyl)iodonium Bromide
2011
4-[(18)F]Fluorophenol is a versatile synthon for the synthesis of more complex radiopharmaceuticals bearing a 4-[(18)F]fluorophenoxy moiety. In order to prepare 4-[(18)F]fluorophenol in no-carrier-added (n.c.a.) form only a nucleophilic labelling method starting from [(18)F]fluoride is suitable. In this paper a new, two step radiosynthesis starting from 4-benzyloxyphenyl-(2-thienyl)iodonium bromide and [(18)F]fluoride with subsequent deprotection is described, yielding n.c.a. [(18)F]fluorophenol in 34 to 36% radiochemical yield.
An insight into the functionalisation of carbon nanotubes by diazonium chemistry: Towards a controlled decoration
2014
The derivatisation of materials including iron, gold, and carbon by addition of diazonium salts is a reliable process to tune their interfacial interaction with the surrounding media. In this regard, the functionalisation of carbon nanostructures by diazonium chemistry is a versatile strategy to obtain soluble nanomaterials with degrees of functionalisation among the highest ever reported. Starting from these premises we have studied the functionalisation of multi-walled carbon nanotubes by addition of the aryl diazonium salts generated in situ by treatment of 4-methoxyaniline with isopentylnitrite. Following a thorough purification and characterisation protocol (UV-vis, TGA, ATR-IR, cyclic…
Modulation of the organic heterojunction behavior, from electrografting to enhanced sensing properties
2019
International audience; The energy barrier of an organic heterojunction built on ITO electrodes and made from a low conductive sublayer (Cu(F16Pc)) covered by a highly conductive semiconductor (LuPc2) is modulated by electrografting of organic layers before depositing the sublayer. Impedance spectroscopy clearly demonstrates the increase of the energy barrier at the ITO – sublayer interface. Additionally, the electrografting is a versatile and promising method for the tuning of heterojunctions. The I(V) characteristics of the heterojunctions are highly modified by the electrografting. The same electromodifications of electrodes carried out on LuPc2 resistors lead to a modification of their …
Pulse radiolysis and theoretical investigation on the initial mechanism of the e-beam polymerization of epoxy resins. The results obtained on (phenox…
2007
Abstract The radical cation of (phenoxymethyl)oxirane ( PGE ⋅ + ) is generated by pulse radiolysis in dichloromethane solution and by direct action of radiation on the title compound. In the pure system its UV–vis spectrum is characterized by two bands at 340 and 430 nm, such that the electronic structure corresponds to a dipole bearing the positive charge on the phenoxy side. At the same time, the phenoxy-oxirane bridge is weakened. Then, the radical cation fragments into a phenoxonium ion and an oxyranylmethyl radical ( k PGE - fragm = 1.16 × 10 7 s - 1 ) . The latter immediately rearranges to an allyloxyl radical by ring opening. It is then conceived that the action of onium salts, as ra…
Radical Cyclization and 1,5-Hydrogen Transfer in Selected Aromatic Diazonium Salts
2014
2-(Methyl(3-methyl-1-phenyl-1H-pyrazol-5-yl)carbamoyl)thiophene-3-diazonium hydrogen sulfate 20, 2-(methyl(3-methyl-isoxazol-5yl)carbamoyl)-benzenediazonium hydrogen sulfate 21 and 2-(methyl(phenyl)carbamoyl)-benzenediazonium hydrogen sulphate 22 were synthesized and reacted with a CuSO4/NaCl/ascorbic acid combination to give complex mixtures. The structures of the reaction products were elucidated, depending upon the pathways followed. Compound 20 almost exclusively afforded an Ar-5 cyclization product and trace amounts of the product derived from a competing Ar-6 Pschorr closure. In the case of compound 21, the Ar-6 cyclization was not observed, while the Ar-5 cyclization and 1,5-hydrogen…
NMR enantiodifferentiation of triphenylphosphonium salts by chiral hexacoordinated phosphate anions
2003
BINPHAT anion—rather than TRISPHAT—is an efficient NMR chiral shift reagent for triphenylphosphonium salts containing stereogenic centers on the aliphatic side-chain. BINPHAT—rather than TRISPHAT—anion is an efficient NMR (1H and 31P) chiral shift reagent for chiral triphenylphosphonium salts.
Unravelling Radicals Reactivity Towards Carbon Nanotubes Manipulation/Functionalization
2016
Carbon Nanotubes (CNTs) chemistry is under constant evolution, as a consequence of the deep interest of the scientific community in finding new applications for these versatile materials. New and old synthetic protocols are used for improving the control of the functionalization degree of the final materials and for offering to scientists the possibility to fine-tune their final properties. In this Review, we focus the attention on radical reactions, a class of protocols characterized by small number of steps, different degrees of functionalization and enhanced solubility of the final modified CNTs, in the desired environment. The most well-known protocols are analysed providing some releva…