Thermal and spectroscopic studies on a double-salt-type pyridine–silver perchlorate complex having κ1-O coordinated perchlorate ions

Abstract

A simple synthetic method was developed to prepare 4[Agpy 2 ClO 4 ]Á[Agpy 4 ]ClO 4 in a low-temperature decomposition process of [Agpy 4 ]ClO 4 . A detailed IR, Raman and far-IR study including factor group analysis has been performed, and the assignation of bands is given. The compound decomposes quickly with a multistep ligand loss process with the formation of [Agpy 2 ]ClO 4 and AgClO 4 intermediates and AgCl as an end product around * 85, * 350 and 450°C, respectively. During the first decomposition step, a small fraction of the ligands is lost in a redox reaction: perchlorate oxidizes the pyridine, forming carbon, carbon dioxide, water and NO, while it itself is reduced into AgCl. In the next step, when AgClO 4 forms after complete ligand loss and reacts with the carbon formed in the degradation of pyridine at lower temperatures and produces NO, CO 2 and H 2 O. This reaction becomes possible because the AgCl formed in the redox reactions makes a eutectic melt with AgClO 4 in situ, which is a favorable medium for the carbon oxidation reaction. AgCl is known to reduce the temperature of decomposition of AgClO 4 , in which process forms AgCl as well as O 2 and so is an autocatalytic process. The loss and degradation of pyridine ligand are endothermic; the redox reactions including carbon oxidation and AgClO 4 decomposition into AgCl and O 2 are exothermic. The amount of absorbed/evolved heats corresponding to these processes was determined by DSC both under N 2 and O 2 atmospheres. Keywords Pyridine-silver complexes Á Perchlorates Á Quasi-intramolecular solid-phase redox reaction Á Evolved gas analysis Á DSC Electronic supplementary material The online version of this article (

Thermal analysis of solvatomorphic decakis (dimethylammonium) dihydrogendodecatungstate hydrates

“…Since in our compounds there are strongly reducing cations and oxidizing anions, one can expect a thermally induced redox reaction between them. The occurrence of such kind of redox reactions within one compound having oxidizing and reducing components is well documented in the literature [11][12][13][14][15][16][17]. Since in inert atmosphere the decomposition steps are endothermic, one can conclude that the energy required for elimination of water and dimethylamine as well as the disruption of the lattice exceeds the exothermicity of the redox interaction.…”

Solid-Phase Quasi-Intramolecular Redox Reaction of [Ag(NH3)2]MnO4: An Easy Way to Prepare Pure AgMnO2

“…The silver content was removed and analyzed as AgCl (with HCl addition), whereas the manganese(II) content was determined gravimetrically as oxinate. 3 , 4 The excess oxalic acid was measured with titration using 0.02 M KMnO 4 according to the standard procedure. The ammonia content was removed with the addition of 10% NaOH, and the air/ammonia mixture was sucked out through a sulfuric acid solution using a vacuum (in order to avoid ammonia oxidation by the permanganate, we could not boil off the ammonia by heating).…”

“… 4 , 10 Although there is no information about the reductive thermal decomposition of silver permanganate ammonia (NH 3 ) complexes, other transition-metal permanganate complexes could easily be transformed into spinel-like mixed oxides (MMn 2 O 4 , where M = Cu, Zn, and Cd). 11 − 14 Our previous successful work on the synthesis and studies on the decomposition of compounds having redox-active cationic/anionic parts 3 , 4 , 10 prompted us to study ammonia complexes of silver permanganate as potential precursors in the low-temperature (<373 K) preparation of nanosized Körbl and CO oxidation catalysts.…”

AgNO3⋅NH4NO3 – an enigmatic double‐salt type “decomposition intermediate” of diamminesilver(I) permanganate

“…The compound 1 was prepared in the thermal decomposition reaction of compound 2 and the aqueous leaching of the decomposition residue following the method given in. [7] The detailed description of the applied instruments can be found in our previous publications: [11][12][13][14][15][16] IR (Bruker Alpha FT-IR spectrometer attenuated total reflection mode, 2 cm À 1 resolution), far-IR (BioRad-Digilab FTS-60 A, attenuated reflection mode, 4 cm À 1 resolution) UV(Jasco V-670 UV-Vis spectrophotometer equipped with NV-470 type integrating sphere), Raman (Horiba Jobin-Yvon LabRAM-type microspectrometer, l 532 nm Nd-YAG and 785 nm diode laser, an Olympus BX-40 optical microscope), and PXRD (Philips PW-1050 Bragg-Brentano parafocusing goniometer with Cu tube), TG-MS (TA Instruments SDT Q600 thermal analyzer coupled to Hiden Analytical HPR-20/QIC mass spectrometer), DSC (Perkin Elmer Diamond DSC).…”