N. S. Akhmadullina

Unexpected participation of nucleophiles in the reaction of palladium(II) acetate with divalent 3d metals

The kinetics of reactions of palladium(II) acetate with cobalt(II), nickel(II), and copper(II) acetates were studied by spectrophotometry. These reactions produce heterobimetallic complexes PdII(μ-OOCMe)4MII(OH2)(HOOCMe)2, where M = Co, Ni, or Cu. These reactions are very slow in carefully dehydrated (<0.01% H2O) acetic acid, but are considerably enhanced by water or acetonitrile. Our data indicate that the activation of the kinetically inert ring structure of the initial palladium complex Pd3(μ-OOCMe)6 by means of the nucleophilic attack of an H2O or acetonitrile molecule is the key step of the reaction mechanism.

On the nature of the chemical bond in heterobimetallic palladium(II) complexes with divalent 3d metals

The complex Pd(μ-OOCMe)4Cu(OH2) · 2Pd3(μ-OOCMe)6 was synthesized and characterized by X-ray crystallography. In the heterometallic moiety of this complex, the PdII and CuII atoms are at an extraordinary short distance (2.521(3) Å). DFT quantum-chemical calculations of the geometric and electronic structure of a series of heterobinuclear paddlewheel complexes PdIIMII(μ-OOCMe)4L (M = ZnII, NiII, CuII, CoII, FeII; L = OH2 and NCH) and their formate analogues PdIIMII(μ-OOCH)4L (M = ZnII, NiII, FeII) showed that the extraordinary short Pd⋯M distance in all these complexes is caused only by the tightening effect of carboxylate bridges rather than by the metal-metal bond. The direct Pd-M interaction becomes possible only after removal of electrons from the antibonding orbitals and formation of oxidized complexes of the [PdIII(μ-OOCMe)4NiIII]2+ type.

Effect of dopant concentration on the phase composition and luminescence properties of Eu2+- and Ce3+-doped AlONs

Herein we report the synthesis of aluminum oxynitride (Al5O6N) doped with Eu2+ and Ce3+ and examine the effects of the dopant concentration and the nature of the rare-earth-containing precursor (europium and cerium oxides, Eu(acac)3, and Ce(acac)3) on its properties. At dopant concentrations above the solubility limit of rare-earth aluminates (EuAl12O19 and CeAl11O18) in aluminum oxynitride, we observed the formation of aluminum nitride and aluminum oxide (α-Al2O3) as individual phases. The concentration of the latter phase was higher when the rare-earth oxides were used. The emission intensity in the cathodoluminescence spectra of the samples was shown to have a maximum at Eu2+ and Ce3+ concentrations from 0.1 to 0.5 at %. Concentration quenching of luminescence was observed.

Ceramic materials and phosphors based on silicon nitride and sialon

This review covers some of the main trends in the field of synthesis and the applications of materials based on silicon nitride presented in publications over the past 10–15 years. Attention is paid to the technique for synthesizing nitride and oxynitride compounds and for the production of ceramic construction materials and phosphors in silicon nitride systems.

Gold(III) chloride and acetate complexes with bipyridine and phenanthroline

Cationic-anionic chloride complexes of gold(III), [(L)AuCl2]BF4 (L = 2,2′-bipyridine and 1,10-phenanthroline (Phen)), are synthesized. Their reactions and the reactions of complex [(Phen)AuCl2]Cl with silver(I) and sodium acetates are studied. The chloride ligands in complexes [(L)AuCl2]BF4 are easily substituted by the acetate ligands in the reaction with silver(I) acetate to form new carboxylate complexes [(L)Au(OAc)2]BF4. The reaction of complex [(Phen)AuCl2]Cl with sodium acetate in glacial acetic acid affords binary complex salt [(Phen)AuCl2][AuCl4], which is characterized by single-crystal X-ray diffraction analysis.

Radioluminescent properties of Eu2+-doped aluminum oxynitride

X-ray luminescence (XRL) and pulsed cathodoluminescence (PCL) spectra of Eu2+-doped aluminum oxynitride Al5O6N (prepared using the standard sol-gel technique) have been investigated. The radioluminescence spectra, concentration dependences of light yield and time parameters of luminescence process have been measured and discussed. Some peculiarities of luminescence spectra as well as the possible excitation mechanism of AL5O6N with Eu2+ dopants are discussed too.

The Role of Water Molecules in Formation of Heterometallic Palladium Acetate Complexes with Cerium and Neodymium

The reactions of palladium(II) acetate with neodymium(III) and cerium(III) acetates in acetic acid containing a specified amount of water have been studied. The following homo- and heterometallic complexes have been synthesized and characterized by X-ray diffraction: Nd2(μ-OOCMe)2(μ,η2-OOCMe)2(η2-OOCMe)2(HOOCMe)2(OH2)2 · 4HOOCMe, [Pd(μ-OOCMe)4Ce(OH2)2(μ,η2-OOCMe)]2 · 2HOOCMe · 6H2O, [Pd(μ-OOCMe)4Ce(OH2)2(μ,η2-OOCMe)]2 · 14H2O, [Pd(μ-OOCMe)4M(HOOCMe)2(OH2)2]+ [Pd(μ-OOCMe)4M(μ-OOCMe)4Pd]− · 2MeCOOH · 1.5H2O (M = Nd, Ce), and {[Pd(μ-OOCMe)4Ce(OOCMe)4]2 [Pd4(μ-OOCMe)4]2(μ4-O)8CePd4}(OH)3 · 27H2O. From kinetic and structural data and optical spectra of reaction solutions, the conclusion was drawn that hydrolytic processes play a decisive role in complexation reactions.

Radiation-Induced Effects in Ce 3+ - and Eu 2+ -Doped Al 5 O 6 N

Polycrystalline Al5O6N samples have been prepared by sol–gel synthesis followed by carbothermal reduction and nitridation. X-ray luminescence (XRL) spectra and thermoluminescence (TL) curves of Ce3+- and Eu2+-doped aluminum oxynitride have been measured in the temperature range 5–380 K and analyzed. Working TL peaks have been detected in the range 150–250 K for the Al5O6N:Ce3+ sample and in the range 140–200 K for the Al5O6N:Eu2+ samples. There are also lower temperature peaks: in the ranges 10–60 and 20–100 K. The XRL spectra of the samples have been measured at temperatures of 8 (for the first time) and 300 K.

Luminescent properties of Eu2+ in AlON, SiAlON, Ca-SiAlON oxynitrides

The X-ray luminescence (XRL) properties of γ-AlON (γ-Al5O6N), β-SiAlON (Si6–nAlnOnN8–n, where n = 2 and 3) and Ca-α-SiAlON (Cam/2Si12−(m+n)Alm+nOnN16−n) oxynitride samples doped by Eu2+ were investigated. The strong correlation of luminescence spectra parameters of Eu2+ luminescence centers in dependence of oxynitride samples composition is observed. With fitting procedure the composition of XRL spectra with complex profile of investigated oxynitride samples of γ-AlON, β-SiAlON and Ca-α-SiAlON was identified and discussed.The X-ray luminescence (XRL) properties of γ-AlON (γ-Al5O6N), β-SiAlON (Si6–nAlnOnN8–n, where n = 2 and 3) and Ca-α-SiAlON (Cam/2Si12−(m+n)Alm+nOnN16−n) oxynitride samples doped by Eu2+ were investigated. The strong correlation of luminescence spectra parameters of Eu2+ luminescence centers in dependence of oxynitride samples composition is observed. With fitting procedure the composition of XRL spectra with complex profile of investigated oxynitride samples of γ-AlON, β-SiAlON and Ca-α-SiAlON was identified and discussed.

Transfer of the chelating ligands in the systems [LAuCl2]+-[PdCl4]2−: Synthesis and structure of the salt (NH4)0.20[(Bipy)AuCl2]1.04[(Bipy)PdCl2]0.96[AuCl4]0.76[PdCl4]0.24

The formation of binary complex salts containing gold(III) in the cation and palladium(II) in the anion in the systems [(Bipy)AuCl2]+-[PdCl4]2− occurs by transfer of the N,N-electron-donating chelating ligand bipyridine and the chloride ligands between the gold-containing cation and the palladium-containing anion. The resulting neutral salt [(Bipy)PdCl2] crystallizes together with the anion [AuCl4]− from acetonitrile-water (1 : 1-1 : 2, v/v) to give the complex salt (NH4+)0.20[(Bipy)AuCl2+]1.04[(Bipy)PdCl2]0.96[AuCl4−]0.76PdCl42−]0.24 with a total Au : Pd ratio of 3 : 2. The ammonium cation is formed from acetonitrile upon its hydrolysis most likely catalyzed by Pd complexes. Quantum-chemical calculations were performed to study the transfer of the chelating ligand theoretically.