Thermal decomposition of double complex compounds of 3D metals.

The paper is devoted to the study of thermolysis of double complex compounds (DCС) of metalsin the I transition series. 30 DCСwith various combinations of metal-central atoms (Co-Fe, Cu-Fe, Ni-Fe Cr-Fe, Cr-Co,) and ligands (ammonia, urea (ur), ethylenediamine (en), 1,3-diaminopropane (tn), cyanide, oxalate and nitrite anions) were synthesized and characterized. A complete study of the thermal proper-ties of these DCCs in three atmospheres was carried out: oxidizing (air), inert (Ar, N2, partly He) and re-ducing (H2), in the temperature range of 20–1000°Cand at constant heating rate of 10°C/min. The solid and gaseous thermolysis products were studied. In the air solid thermolysis products are represented by mixtures of central ions oxides or mixed oxides of the MIMII2O4type. The main gaseous products of thermolysis underthe temperature below 300°Cinclude NH3, HNCO (for urea DCС) and HCN (for cya-nocomplexes), and above 300°C —СО2. In addition, undecomposed ligands, CO, nitrogen oxides and probably nitrogen are presented in the gas phase. Thermolysis of the studied DCCgoesin the most com-plex way in inert atmospheres. Solid thermolysis products are heterogeneous mixtures of metals (Cu, Fe), solid solutions of CoxFe1-x, Ni3Fe intermetallic compounds, oxides, carbides and nitrides of central ions and amorphous carbon; the content of the latter reaches 58% of the initial content in the complex. The gaseous products of thermolysis include the same compounds, except for CO2, as in the atmosphere of air, but also in different ratios. In an H2atmosphere, all studied DCCs, except Cr-containing ones, are re-duced to the sum of central ions —Cu + Fe or solid solutions Co-Fe and Ni-Fe, practically free of carbon. Gaseous products are the same as in an inert atmosphere, butan increased yield of NH3and a reduced yield of CO2and/or HCN speak in favor of partial hydrogenation of the ligands to hydrocarbons. A review of the catalytic properties of solid products of DCC thermolysis (~170 samples) showed that about 1/3 of themare active in model reactions (catalytic decomposition of hydrogen peroxide, thermal decomposi-tion of ammonium perchlorate).

THERMAL BEHAVIOR OF DOUBLE COMPLEXES [Co(NH3)6][Fe(CN)6] AND [CO(en)3][Fe(CN)6]·2H2O

Thermal behavior of double complex compounds (DCC) of first transition metal row has been studied on the example of [СоA6][Fe(CN)6] (A = NH3, C2H8N2/2) in oxidative(air), inert(argon, nitrogen, helium) and reductive(hydrogen) atmospheres. The analysis of solid and gaseous thermolysis products has been performed for separate temperature ranges. The TG curves of the thermolysis first stage coincide with each other for all the investigated atmospheres up to approximately 300 °C. DCC [Со(NH3)6][Fe(CN)6] (I) and [Со(en)3][Fe(CN)6] (II) undergo to first stage of thermal decomposition with the removal of the part of neutral ligands and 1-2, but not more as 3 CN groups in temperature range of 160-300 and 200-350°С in oxidative and 160-400 and 210-550 °С, in inert medium, respectively. DCC I forms the intermediate [(NH3)2CoFeC4N3], [(NH3)2.6CoFe(CN)5] and [(NH3)3CoFe(CN)4.3] at 330, 350 и 430 °С in atmosphere of air, argon and hydrogen. For DCC II the intermediates are not registered. At temperatures above 300 °C the TG curves diverge and relate already to the interaction of thermolysis products with the gaseous medium. The thermolysis in argon and hydrogen is accompanied by partial reduction of ligands and central atoms of DCCs, thermolysis in the air atmosphere - complete oxidation of ligands and central ions. The thermal behavior of DCC is compared with the thermal behavior of 3d metals cationic complexes on base of literature data. The thermolysis of all the DCC and cation complexes discussed here proceeds with the removal of neutral ligands in the temperature range of 50-400 °C. For citation:Pechenyuk S.I., Domonov D.P., Gosteva A.N., Semushina Yu.P., Shimkin A.A. Thermal behavior of double complexes [Co(NH3)6][Fe(CN)6] and [Co(en)3][Fe(CN)6]·2H2O. Izv. Vyssh. Uchebn. Zaved. Khim. Khim. Tekhnol. 2018. V. 61. N 4-5. P. 49-56

Luminescence Properties of Transition-Metal Ions in Double Complex Salts

The luminescence spectra and radiative lifetimes of a series of d3 and d6 double complex compounds with bipyridine (bip), phenanthroline (phen), ammonia and ethylenediamine (en) ligands in the cations and chloride, cyanide, thiocyanide and oxalate (ox) ligands in the anions have been investigated at temperatures down to 2 K. Although energy transfer between the component ions is predicted from the Förster and Dexter theory to be effective due to the finite overlap of the donor emission and the acceptor absorption spectra, no emission could be detected for most of the double complexes. Only [Ru(bip)3]tr-[Cr(NH3)2(NCS)4]2, [Ru(bip)3][PtCl6] and [Cr(d4-en)3] [Rh(SCN)6] exhibit characteristic luminescence spectra which in part are enhanced compared to their component emissions. For rationalizing the results, radiationless deactivation by various decay channels which compete with the energy transfer mechanism must be considered.