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Thermal nonradiative depopulation processes of excited levels significantly influence the potential application of phosphors. The high efficiency of thermal quenching of luminescence can limit a phosphor's potential applications as well as reduce the temperature range in which such a material can be used. This work presents a new strategy of shifting of usable temperature range of luminescent thermometer based on Eu3+ ion emission that the molar ratio of (AsO4)3− in respect to (VO4)3− increases in YVxAs1−xO4 host material. Consequently, the thermometric performance of the luminescence thermometer based on the single band intensity ratio corresponding to the 5D0 → 7F1 of Eu3+ ions upon optical excitations matching to the 1A2(1T1) → 1B1(1T2) and 1E(1T1) → 1B1(1T2) electronic transition of (VO4)3− group can be optimized. As shown, the use of YV0.25As0.75O4:Eu3+ has an extended usable temperature range in respect to YVO4:Eu3+. This improvement, coupled with its high sensitivity (>1% K−1) make YV0.25As0.75O4:Eu3+ a more stable material for luminescence thermometer applications. The presented strategy for modulating the thermal properties of luminescent thermometers through the introduction of the (AsO4)3− groups is a step towards designing thermometers with on-demand thermometric performance. [ABSTRACT FROM AUTHOR]

By means of alternating current-electrochemical synthesis starting from a mixture of 2-imino-3-(prop-2-en-1-yl)-1,3-thiazolidin-4-one (3-allylpseudothiohydantoin, napt) and 2-allylamino-1,3-thiazol-4(5H)-one (allylaminopseudothiohydantoin, aapt) hydrochlorides and corresponding copper(II) salts five new π-complexes, [Cu(napt)Cl] (1), [Cu2(aapt)2Cl]NO3(2), [Cu2(aapt)2Cl]BF4(3), [Cu2(aapt)2Cl]ClO4(4) and [Cu2(aapt)2Cl]2SiF6·2H2O (5), were obtained and studied by X-ray single crystal diffraction and IR-spectroscopy. Napt and aapt molecules are selectively coordinated to Cu+depending on the anion type. In crystals of1and5, the organic ligands are attached to the metal in a chelating N,(C=C)-bidentate mode. The aapt molecule in2-4acts as a tridentate chelating ligand, being coordinated to the copper(I) ion through the heterocyclic N atom, carbonyl O atom, and C=C bond of allyl group, forming an original cationic [Cu2(aapt)2Cl]+fragment with both a bridging Cl–ion and O atom of the C=O group. In the presence of the doubly charged SiF62–anion, Cu(I) in5prefers to be bonded with two bridging Cl–ions, rather than the C=O group, causing [Cu2(aapt)2Cl]+units to associate into the infinite cationic chains. Crystals of3and4are the first known examples of the simultaneous BF4–/Cl–or ClO4–/Cl–participation in copper(I) π-complex formation. [ABSTRACT FROM PUBLISHER]

The crystal structure has been determined for (CH3NH3)2[KCo(CN)6] at temperatures 100 and 443 K. It crystallizes in the monoclinic space group C2/c (LT) and in the cubic one Fm3̅m (HT). The dielectric response has been investigated for single crystals of pure K3[A′(CN)6] and guest–hosts of (CH3NH3)2[KA′(CN)6], where A′ is a trivalent metal, Co or Fe. Their dielectric properties were measured in the frequency range between 135 Hz and 2 MHz in a wide temperature range between 200 and 460 K. The anisotropy of the electric permittivity for single crystals of (CH3NH3)2[KCo(CN)6] was analysed in terms of the crystal structure. The relaxation processes were observed in the case of the pure host K3Fe(CN)6 and the guest/host crystal (CH3NH3)2[KFe(CN)6]. The activation energies of the dielectric relaxation have been estimated to be equal to 44 and 40 kJ mol−1 for (CH3NH3)2[KFe(CN)6] and K3Fe(CN)6, respectively. The mechanism of the phase transitions found at 425 K and 421 K for (CH3NH3)2[KFe(CN)6] and (CH3NH3)2[KCo(CN)6], respectively, has been postulated. From the dielectric losses the value of the electric ac conductivity has been estimated and analyzed in terms of the activation process of the current carriers. [ABSTRACT FROM AUTHOR]

The multi component Fe74Hf4Ta1Cu1Gd1LaxSi15-xCu1Gd1LaxSi15-xB4 (x=0;7) alloys are promising candidates in the search for materials with unusual mechanical and magnetic properties. Amorphous nature of melt-spun samples was confirmed by X-ray diffractometry and Mössbauer spectroscopy. The X-ray diffraction patterns revealed a distinct amorphous halo. The low-field components of magnetic hyperfine field distributions on iron nuclei are observed in the Mssbauer spectra, with average hyperfine field values of 19.9 and 15.7 T for x=0 and x=7, respectively. Coercivity studied by vibrating sample magnetometer was about 12 A/m for x=0 and 82 A/m for x=7 at 300 K and about 600 A/m for x=0 and 1200 A/m for x=7 at 400 K. Remanence also changed with temperature, amounting to 0.64 T for x=0 and 0.36 T for x=7 at 300 K, while at 400 K it was 0.43 and 0.11 T for x=0 and x=7, respectively. It is shown that La addition has beneficial effect of shifting the Curie point towards lower temperatures together with the increase of magnitude of magnetization. [ABSTRACT FROM AUTHOR]

Abstract: The structure of [C3N2H5]4[Bi2Br10]·2H2O, (PBB) was determined by single crystal X-ray diffraction at 100K. It crystallizes in the monoclinic space group C2/m, with a =12.992(4)Å, b =16.326(5)Å, c =8.255(3)Å, β =108.56°(3), V =1659.9(9)Å3 and Z =2. The structure consists of discrete binuclear [Bi2Br10]4− anions, ordered pyrazolium cations and water molecules. The crystal packing is governed by strong N–H⋯O and weak O–H⋯Br hydrogen bonds. A sequence of structural phase transitions in PBB was established on the basis of differential scanning calorimetry and dilatometric studies. Two reversible first-order phase transitions were found: (I→II) at 381/371K (on heating/cooling) and (II→III) at 348/338K. Dielectric response near both phase transitions is characteristic of crystals with the “plastic-like” phases. Over the phase III a low frequency dielectric relaxator is disclosed. The possible molecular motions in the PBB compound are characterized by the 1H NMR studies. The infrared spectra of polycrystalline compound in the temperature range 300–380K are reported for the region 4000–400cm−1. The observed spectral changes through the structural phase transition III→II are attributed to an onset of motion both of the pyrazolium cations and water molecules. [Copyright &y& Elsevier]

This brief review discusses the coordination behaviour of π-coordinated copper(I) in the structures of [Cu2(µ-dapp)(NH2SO3)4]⋅2H2O (1), [C4H12N2][Cu2(µ-dapp)(NH2SO3)6]⋅2H2O (2), [Cu2 (µ-dapp)(H2O)6] (SiF6)2⋅2H2O (3), [Cu2 (µ-dapp)(NO3)4(H2O)2]⋅2H2O (4), [Cu(µ-ahmta)(NO3)(H2O)](NO3)⋅H2O (5), and [Cu(µ-ahmta)(H2O)2](BF4)2⋅H2O (6) complexes (dapp = N,N'-diallylpiperazinium(2+), ahmta = N-allylhexamethylenetetraminium), obtained as single crystals by means of an alternating current electrochemical technique. The above π-complexes are formed respectively by CuSO3NH2, Cu2SiF6, CuNO3, and CuBF4 salts, unknown in a free state. [ABSTRACT FROM AUTHOR]

The crystal structure has been determined for (CH3NH3)2[KCo(CN)6] at temperatures 100 and 443 K. It crystallizes in the monoclinic space group C2/c (LT) and in the cubic one Fm3̅m (HT). The dielectric response has been investigated for single crystals of pure K3[A′(CN)6] and guest–hosts of (CH3NH3)2[KA′(CN)6], where A′ is a trivalent metal, Co or Fe. Their dielectric properties were measured in the frequency range between 135 Hz and 2 MHz in a wide temperature range between 200 and 460 K. The anisotropy of the electric permittivity for single crystals of (CH3NH3)2[KCo(CN)6] was analysed in terms of the crystal structure. The relaxation processes were observed in the case of the pure host K3Fe(CN)6 and the guest/host crystal (CH3NH3)2[KFe(CN)6]. The activation energies of the dielectric relaxation have been estimated to be equal to 44 and 40 kJ mol−1 for (CH3NH3)2[KFe(CN)6] and K3Fe(CN)6, respectively. The mechanism of the phase transitions found at 425 K and 421 K for (CH3NH3)2[KFe(CN)6] and (CH3NH3)2[KCo(CN)6], respectively, has been postulated. From the dielectric losses the value of the electric ac conductivity has been estimated and analyzed in terms of the activation process of the current carriers. [ABSTRACT FROM AUTHOR]

Abstract: The hypothetically reversible [Cu(I)(diallylsulfoxide)] [Cu(II)(diallylsulfide)] system was examined by FTIR spectroscopy and X-ray diffraction. It is stated that the Cu4OCl6 body centered adamantanoid cages, appearing at both the substrate and product sites, act as a template to promote the oxidation of diallylsulfide to diallylsulfoxide or Cu(I) to Cu(II), thus making the reaction irreversible. Each of these two adamantanoid cores possesses a different point symmetry as well as self assembly mode to form two polymorphs of the [Cu4OCl6(diallylsulfoxide)4] complex. Their polymorphic relationships based on the symmetry homology S 4 ← Td → C 3, as well as the distortion in the Cu(II) coordination geometry, are discussed. [Copyright &y& Elsevier]