divalent state
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The reaction of N-(2-pyridyl)thiourea with CuCl2 in methanol yields four different crystalline products: yellow dimeric complex, [Cu2Cl2(μ-Cl)2(L)2] (1), red polymeric complex, [Cu3Cl8L2]n (2), orange crystalline product with ionic structure, L2[CuCl4] (3), and colourless ionic compound LCl (4), where L = 2-amino-[1,2,4]thiadiazolo[2,3-a]pyridin-4-ium cation as a result of oxidative cyclization of N-(2-pyridyl)thiourea. The crystal structures of all these crystalline products have been determined by single-crystal X-ray diffraction analysis. Compound 1 involves a copper(I) ion while in 2 and 3 the copper centre is in the divalent state. 1H NMR spectra for compounds 1–3 are identical and confirm deprotonated thioamide groups of N-(2-pyridyl)thiourea and the formation of a thiadiazolopyridinium cation in solution. The hydrogen bonding and π–π stacking interactions were investigated in the solid state. In addition, all crystalline products 1–4 exhibit also S···Cl bonding interactions which consolidate the complexes into networks. The X-ray diffraction analyses indicate the absence of other crystalline phases in the crude reaction mixture.

In this study, crednerite CuMnO2 nanostructures were prepared using a hydrothermal method at 100 °C with different amounts of NaOH mineralizator. Obtained nanostructured crednerite CuMnO2 with monoclinic structure (space group C2/m) exhibits two kinds of morphologies: nanobelts of the length of 1 - 1.5 µm and thickness of 15 - 25 nm, and nanoplatets being of 50 - 70 nm in diameter. Comparative studies of the preprepared samples reveal an intimate relationship between morphological and physical properties in nanostructured CuMnO2. A low NaOH concentration favours elongated crystal growth along the c-axis, creating nanobelt-shaped morphology. On the other hand, a strong base solution promotes the formation of nanoplates. Unique morphologies of nanostructured CuMnO2 affect distinct spectroscopic and magnetic properties. The nanobelt-shaped sample is characterized by the Raman active A1g mode at 637 cm-1 and a modified Curie-Weiss bahaviour. This phase exhibits two successive magnetic phase transitions: ferromagnetically at 9.2 K and antiferromagnetically at 42 K. Conversely, the nanoplate-shaped sample behaves typically as those reported in the literature, namely, the Raman active A1g mode at 688 cm-1 and low-dimensional magnetism with antiferromagnetic ordering below 62 K. The variation in the magnetic properties is presumably associated to the partial oxidation of Cu1+ and Mn2+ in the nanoplate-shaped sample compared to the divalent state of Cu2+ and trivalent Mn3+ ions in the nanobelt-shaped one.

AbstractThe fluorooxoborates Sr[B5O7F3] (Ccm21 (no. 36), Z = 4, a = 864.777(3) pm, b = 1001.037(4) pm, c = 810.110(5) pm, 630 refl., 68 param., RF = 0.061, RBragg = 0.051) and Sr[B5O7F3]:Eu2+ were synthesized via solid-state reactions from Sr(BF4)2 and B2O3. Doping was achieved by adding EuF3, which was reduced to its divalent state during the synthesis. Sr[B5O7F3] was investigated by infrared spectroscopy. Photoluminescence spectra of the doped compound revealed an Eu2+ 5d-4f emission in the UV regime peaking at 371 nm with a full width at half maximum (FWHM) of 21 nm upon excitation at 239 nm, which proves a weak coordination of europium by the anionic fluorooxoborate network.

AbstractEu2Mg4Si3 ≡ (2Eu2+)(4Mg2+)(3Si4−) is an electron-precise Zintl phase. Its Hf2Co4P3-type structure contains three crystallographically independent europium sites. The divalent state of europium was manifested through 151Eu Mössbauer spectroscopy. In the paramagnetic regime (T = 78 K) the isomer shifts range from −9.16 to −11.29 mm s−1. Eu2Mg4Si3 shows complex magnetic hyperfine field splitting at T = 5.7 K with a superposition of three subspectra with magnetic hyperfine fields of 5.4 (Eu2), 20.4 (Eu1) and 22.4 (Eu3) T.

A cobalt(III)–manganese(II) heterometallic dinuclear complex, [MnII{CoIII(µ-Himn)3}Cl2(CH3OH)], was prepared by a metalloligand approach. X-ray crystallographic analysis indicated that the metalloligand [CoIII(Himn)3] underwent mer/fac geometrical isomerization upon coordination to a Mn ion. Owing to the non-coordinating N–H bonds in the [CoIII(Himn)3] moiety, the heterodinuclear complex exhibited hydrogen bond interactions with the Cl− ligand of the neighboring complex to construct two-dimensional hydrogen-bond networks. The bond distances around the Mn center and the χMT value at 300 K indicate that the Mn center is in a divalent state. The temperature dependence of the χMT product and field dependence of the magnetization showed the isotropic nature of the MnII center.

The effect of X-rays on the valence state of Eu ions in a Y2O3 matrix has been studied by the EPR method. The effect of charge exchange of Eu ions (Eu3 + → Eu2 + → Eu3 +) in the Y2O3 structure has been found. The mechanism of europium reduction to the divalent state under the action of X-ray irradiation has been described.

AbstractThe aim of this paper is to study the effect of Mg2+ doping in place of Ni in LiNiPO4 compounds synthesized by solid state reaction method. As Mg is a relatively light and cheap, and is expected to stabilize the structure, it has been considered as a substituent for Ni. The structural and conductivity studies of the substituted phases are discussed in comparison with LiNiPO4. In this study, we have proposed cation-substituted compounds, LiNi1–xMgxPO4 (x = 0, 0.05, 0.1 and 0.15) where a part of the divalent state of Ni2+ is replaced with the corresponding amount of Mg2+ and where the charge compensation is maintained by lithium deficiency. It is possible to obtain the mentioned compounds because the pristine LiNiPO4 compound is stable in ambient atmosphere, which differs considerably from the LiCoPO4 compound.

AbstractIn the present paper the synthesis, photoand electroluminescent properties of new rare earth metal complexes prepared and studied at the Razuvaev Institute of Organometallic Chemistry during the last decade are reviewed. The obtained compounds give luminescence in UV, visible and NIR regions. The substituted phenolates, naphtholates, mercaptobenzothiazolate, 8-oxyquinolinolate, polyfluorinated alcoholates and chalcogenophosphinates were used as ligands. The synthesis and structure of unusual three–nuclear sulfidenitride clusters of Nd and Dy are described. The new excitation mechanism of ytterbium phenolates and naphtholates, which includes the stage of reversible reduction of Yb to divalent state and oxidation of the ligands in the excitation process, is discussed.

Red-emitting Mn 2+-doped AlN ( AlN:Mn 2+) phosphors were successfully prepared by a highly effective combustion synthesis method. The phase purity, morphology, element-composition and luminescence properties of the synthesized phosphors were investigated. X-ray diffraction (XRD) results show that the Mn 2+-doped into the AlN host did not induce a second phase and distort the structure significantly. Scanning electron microscopy (SEM) images display that the phosphors have an irregular shape with a particle size in the range of 1–5 μm. X-ray photoelectron spectroscopy (XPS) spectrum indicates that Mn ions are divalent state. The synthesized AlN:Mn 2+ phosphors exhibit a strong red emission centered at ~ 600 nm, which is ascribe to the 4T1(4G)–6A1(6S) transition of Mn 2+ under ultraviolet excitation. The emission intensity reaches its maximum when Mn 2+-doped concentration is 3 mol%.