Phase polymorphism of [Zn(DMSO)6](ClO4)2 studied by differential scanning calorimetry

Four solid phases of [Zn(DMSO)₆](ClO₄)₂ have been detected by differential scanning calorimetry (DSC). Specifically, the phase transitions were detected between: metastable phase KII ↔ supercooled phase K0 at , stable phase KIb ↔ stable phase KIa at , stable phase KIa ↔ stable phase K0 at . At T_m2 = 389 K crystals partially and at T_m1 = 465 K completely melts. From the entropy change values it was concluded that the phases: K0 and K0′ are the orientationally dynamically disordered phases, so called ODDIC crystals, and phases KIa, KIb and metastable KII are dynamically ordered but with some degree of positional disorder.     

Thermal properties of [Cr(NH3)6](BF4)3 studied by adiabatic and relaxation calorimetry

Four (solid–solid) phase transitions were detected in the temperature range of (9 to 300) K in polycrystalline [Cr(NH₃)₆](BF₄)₃ at T_C1 = 240.7 K, T_C2 = 108.0 K, T_C3 = 91.9 K, and T_C4 = 61.3 K by adiabatic calorimetry. The measurements by relaxation calorimetry were followed on lowering temperature from 20 K down to 0.35 K under six different external magnetic field values (9, 7, 5, 3, 1 and 0) T. For non-zero values of applied magnetic field well-defined Schottky anomaly appears. Magnetic heat capacity was calculated assuming the zero-field splitting for the decoupled Cr(III) ions. There is no discrepancy between the observed and calculated values. Isothermal magnetization curve recorded up to 5 T was measured at temperature of 1.8 K.     

Phase transitions, structural changes and molecular motions in [Zn(NH3)4](BF4)2 studied by neutron scattering, X-ray powder diffraction and nuclear magnetic resonance

Nuclear magnetic resonance (¹H NMR and ¹⁹F NMR) measurements performed at 90-295 K, inelastic incoherent neutron scattering (IINS) spectra and neutron powder diffraction (NPD) patterns registered at 22-190 K, and X-ray powder diffraction (XRPD) measurements performed at 86-293 K, provided evidence that the crystal of [Zn(NH₃)₄](BF₄)₂ has four solid phases. The phase transitions occurring at: T_C3=101 K, T_C2=117 K and T_C1=178 K, as were detected earlier by differential scanning calorimetry (DSC), were connected on one hand only with an insignificant change in the crystal structure and on the other hand with a drastic change in the speed of the anisotropic, uniaxial reorientational motions of the NH₃ ligands and BF₄⁻ anions (at T_C3 and at T_C2) and with the dynamical orientational order-disorder process (“tumbling”) of tetrahedral [Zn(NH₃)₄]²⁺ and BF₄⁻ ions (at T_C1). The crystal structure of [Zn(NH₃)₄](BF₄)₂ at room temperature was determined by XRPD as orthorhombic, space group Pnma (No. 62), a=10.523 Å, b=7.892 Å, c=13.354 Å and Z=4. Unfortunately, it was not possible to determine the structure of the intermediate and the low-temperature phase. However, we registered the change of the lattice parameters and unit cell volume as a function of temperature and we can observe only a small deviation from near linear dependence of these parameters upon temperature in the vicinity of the T_C1 phase transition.     

Phase Transition and Thermal Decomposition of [Cd(H2O)6](BF4)2

Phase transition and thermal decomposition of [Cd(H₂O)₆](BF₄)₂ were studied by differential scanning calorimetry (DSC), differential thermal analysis (DTA) and thermogravimetry (TG) methods. The solid-solid phase transition at T _C1=324 K and the melting point atT _melt.=391 K were registered. The thermal dehydration process starts just above T _C1 and continues up to T _melt.,where [Cd(H₂O)₄](BF₄)₂ in the liquid phase is formed. Then, dehydration and decomposition take place simultaneously until CdF₂ is obtained. Final products of the thermal decomposition were identified using quadrupole mass spectrometry (QMS) and X-ray diffraction methods. This revised version was published online in August 2006 with corrections to the Cover Date.     

Phase Transitions in Crystalline [M(H2O)6](ClO4)2 (M=Mg,Mn, Fe,Co, Ni,Cu, Zn,Cd and Hg)

The results of DSC measurements in the temperature range 140–370 K on nine crystalline compounds of the type [M(H₂O)₆](ClO₄)₂, where M=Mg, Mn, Fe, Co, Ni, Cu, Zn, Cd and Hg, are discussed. Anomalies detected in the DSC curves are related to the existence of solid-solid phase transitions and/or to the melting points of these compounds. In consequence of two different hypothetical structural modifications of [Fe(H₂O)₆](ClO₄)₂, two DSC curves are obtained. For the compounds with M=Fe, Cd and Hg, new phase transitions have been discovered. The transition temperatures of the other phase transitions are in good agreement with literature data obtained by adiabatic calorimetry. For the compounds with M=Mg, Ni and Cd, DTA measurements were also carried out and the melting points of theses compounds were established. This revised version was published online in August 2006 with corrections to the Cover Date.     

Phase transitions and molecular motions in [Ni(ND3)6](ClO4)2

[Ni(ND₃)₆](ClO₄)₂ has three solid phases between 100 and 300 K. The phase transitions temperatures at heating (T_C1^h=164.1 K and T_C2^h=145.1 K) are shifted, as compared to the non-deuterated compound, towards the lower temperature of ca. 8 and 5 K, respectively. The ClO₄⁻ anions perform fast, picosecond, isotropic reorientation with the activation energy of 6.6 kJ mol⁻¹, which abruptly slow down at T_C1^c phase transition, during sample cooling. The ND₃ ligands perform fast uniaxial reorientation around the Ni-N bond in all three detected phases, with the effective activation energy of 2.9 kJ mol⁻¹. The reorientational motion of ND₃ is only slightly distorted at the T_C1 phase transition due to the dynamical orientational order-disorder process of anions. The low value of the activation energy for the ND₃ reorientation suggests that this reorientation undergoes the translation-rotation coupling, which makes the barrier to the rotation of the ammonia ligands not constant but fluctuating. The phase polymorphism and the dynamics of the molecular reorientations of the title compound are similar but not quite identical with these of the [Ni(NH₃)₆](ClO₄)₂.     

Nickel and copper complexes of cyclopropyltetrazole: crystal structures of [Ni(C3tz)6](BF4)2 and [Cu(C3tz)6](BF4)2

Cyclopropyltetrazole (C₃tz) and its nickel(II) and copper(II) complexes [M(C₃tz)₆](BF₄)₂] were isolated and characterized by elemental analyses, electronic spectroscopy, molar conductances, magnetic susceptibilities and single-crystal X-ray analyses.     

Phase transitions and molecular motions in [Cd(H2O)6](BF4)2 studied by DSC, H and F NMR and FT-MIR

Two solid phase transitions of [Cd(H₂O)₆](BF₄)₂ occurring on heating at T_C2=183.3 K and T_C1=325.3 K, with 2 K and 5 K hysteresis, respectively, were detected by differential scanning calorimetry (DSC). High value of entropy changes indicated large orientational disorder of the high temperature and intermediate phase. Nuclear magnetic resonance (¹H NMR and ¹⁹F NMR) relaxation measurements revealed that the phase transitions at T_C1 and T_C2 were associated with a drastic and small change, respectively, of the both spin-lattice relaxation times: T₁(¹H) and T₁(¹⁹F). These relaxation processes were connected with the “tumbling” motions of the [Cd(H₂O)₆]²⁺, reorientational motions of the H₂O ligands, and with the iso- and anisotropic reorientation of the BF₄⁻ anions. The cross-relaxation effect was observed in phase III. The line width and the second moment of the ¹H and ¹⁹F NMR line measurements revealed that the H₂O reorientate in all three phases of the title compound. On heating the onset of the reorientation of 3 H₂O in the [Cd(H₂O)₆]⁺², around the three-fold symmetry axis of these octahedron, causes the isotropic reorientation of the whole cation. The BF₄⁻ reorientate isotropically in the phases I and II, but in the phase III they perform slow reorientation only about three- or two-fold axes. A small distortion in the structure of BF₄⁻ as well as of [Cd(H₂O)₆]²⁺ is postulated. The temperature dependence of the bandwidth of the O-H stretching mode measured by Fourier transform middle infrared spectroscopy (FT-MIR) indicated that the activation energy for the reorientation of the H₂O did not change much at the T_C2 phase transition.     

Melting and thermal decomposition of [Ni(H2O)6](NO3)2

The two-stage melting process and the thermal decomposition of [Ni(H₂O)₆](NO₃)₂ was studied by DSC, DTA and TG. The first melting point at 328 K is connected with the small and the second melting point at 362 K with the large enthalpy and entropy changes. The thermal dehydration process starts just above ca. 315 K and continues up to ca. 500 K. It consists of three well-separated stages, but the sample mass loss at each stage depends on the experimental regime. However, irrespective of the chosen regime, the total of registered mass losses in stage one and two amounts to three H₂O molecules per one [Ni(H₂O)₆](NO₃)₂ molecule. The remaining three H₂O molecules are gradually freed in the temperature range of 440–500 K in the third stage of the dehydration. Above 580 K, anhydrous Ni(NO₃)₂ decomposes into NO and NiO. The gaseous products were identified by quadrupole mass spectrometer (QMS), and the solid product was identified by X-ray diffraction (XRD) analysis.     

Phase transitions of polycrystalline [Fe(H2O)6](ClO4)3 and [Cr(H2O)6](ClO4)3 studied by DSC

The effects of heat treatment on soymilk protein denaturation were studied by differential scanning calorimetry (DSC) and electrophoresis. Transition behavior of soymilk was studied by DSC. Three endotherms were found in DSC heating curves; the transition observed at around 70°C is attributed to the denaturation of 7S (b-conglycinin) and the transition at around 90°C is to 11S (glycinin). The denaturation temperature increased with the increasing soymilk protein content. The change of electrophoretic patterns after heat treatments indicated that soy proteins were dissociated into subunits, some of which coalesced. When the heating temperature is below their denaturation temperature, the protein fractions cannot completely be denatured even after heat exposure for extended periods of time. This revised version was published online in August 2006 with corrections to the Cover Date.     

DSC study of the phase transitions in [Ni(D2O)6](ClO4)2 and [Ni(H2O)6](ClO4)2

DSC measurements were carried out for [Ni(H₂O)₆](ClO₄)₂ (sampleH) and [Ni(D₂O)₆](ClO₄)₂ (sampleD) in the temperature range 300–380 K. For both compounds two anomalies on the DSC curves were detected. The results for sampleH are compared to those previously obtained using adiabatic calorimetry method. For both compounds studied in this work the high-temperature transition appears at the same temperature while the low-temperature one is shifted towards higher temperatures in sampleD. Disorder connected with H₂O or D₂O groups is suggested in the intermediate phase between the low- and high-temperature transitions.     

Network formation studied by temperature scanning brillouin scattering and differential scanning calorimetry techniques. II.

The reaction of 1,4‐butanediol diglycidyl ether (EP) with cis‐1,2‐cyclohexanedicarboxylic anhydride (CH) and triethylamine (TEA) as an initiator was studied with temperature scanning Brillouin spectroscopy (TSBS) and differential scanning calorimetry (DSC). The evolution of the reaction process (liquid–gel–solid) was investigated as a function of the epoxy molar fraction (x_EP), for sample compositions varying from an epoxy excess to an anhydride excess. The dependence of the final conversion factors αr_DSC and αr_TSBS and the kinetic parameters E_DSC and E_TSBS on x_EP is presented. A comparison of the experimental gelation point (Pgel) behavior and the expected theoretical one, described by the Flory theory, is also reported. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 39: 1326–1336, 2001     

Binding sites of [Ru(bpy)2(H2O)2](BF4)2 with sulfur- and histidine-containing peptides studied by electrospray ionization mass spectrometry and tandem mass spectrometry

The composition and binding sites of cis-[Ru(II)(bpy)2]2+-bound sulfur-containing peptides of Met-Arg-Phe-Ala, glutathione and oxidized glutathione, and also histidine-containing peptide of oxidized insulin B chain, were investigated by electrospray ionization mass spectrometry (ESI-MS) and tandem mass spectrometry (MS/MS). The composition of Ru(II)-containing peptides was precisely determined by ESI-MS, zoom scan and simulation of isotope distribution patterns. MS/MS analysis shows that, in sulfur-containing peptides, the Ru(II) complex prefers to anchor to a carboxyl group, although some other potential binding sites of thiol, thioether and N-terminal amino groups present in these peptides, and in oxidized insulin B chain, Ru(II) first anchors to His10, then either to the hydroxyl group of Thr27 or to the carboxyl group of Ala30. Its secondary structure and microenvironment surrounding the potential binding sites may affect the binding ability of cis-[Ru(II)(bpy)2]2+ to oxidized insulin B chain.     

Ni(II), Pd(II), Cu(II) And Zn(II) complexes with N-(2-Pyridyl)Carbonylaniline (L), Syntheses and X-Ray Crystal structures of [Cu(L)2(H2O)2](No3)2, [Cu(L)2(H2O)2](Clo4)2 and [Zn(L)2(H2O)2](Clo4)2

Reaction of the N-(2-pyridyl)carbonylaniline ligand (L) with Cu(NO₃)₂, Cu(ClO₄)₂, Zn(ClO₄)₂, Ni(NO₃)₂ and PdCl₂ gives complexes with stoichiometry [Cu(L)₂(H₂O)₂](NO₃)₂, [Cu(L)₂(H₂O)₂](ClO₄)₂, [Zn(L)₂(H₂O)₂] (ClO₄)_2, [Ni(L)₂(H₂O)Cl](NO₃) and PdLCl₂. The new complexes were characterized by elemental analyses and infrared spectra. The crystal structures of [Cu(L)₂(H₂O)₂](NO₃)₂, [Cu(L)₂(H₂O)₂](ClO₄)₂, and [Zn(L)₂(H₂O)₂](ClO₄)₂ were determined by X-ray crystallography. The cation complexes [M(L)₂(H₂O)₂] contain copper(II) and zinc(II) with distorted octahedral geometry with two N-(2-pyridyl)carbonylaniline (L) ligands occupying the equatorial sites. The hexa-coordinated metal atoms are bonded to two pyridinic nitrogens, two carbonyl oxygens and two water molecules occupying the axial sites. Both the coordinated water molecules and uncoordinated amide NH groups of the N-(2-pyridyl)carbonylaniline (L) ligands are involved in hydrogen bonding, resulting in infinite hydrogen-bonded chains running in one and two-dimensions.     

Thermal behaviour of emulsions studied by differential scanning calorimetry

This article is a review about the ways in which solidification and the melting may occur within emulsions submitted to steady cooling and heating performed in a differential scanning calorimeter. Simple, multiple and mixed emulsions are considered. Due to nucleation phenomena creating supercooled and supersaturated liquids, the DSC curves obtained during cooling and heating are quite different. The influence of a solute in the disperse phase is described in detail. Some implications about the instabilities of emulsions due to mass transfer phenomena are described.     

Polymorphism and thermal decomposition of [Ni(DMSO)<Subscript>4</Subscript>]I<Subscript>2</Subscript>

Tetrakis(dimethyl sulphoxide)nickel(II) bis(iodide) was studied by thermogravimetry (TG) and simultaneous differential thermal analysis (SDTA) and differential scanning calorimetry (DSC). The gaseous products of the decomposition were on-line identified by a quadrupole mass spectrometer (QMS). Thermal decomposition of the title compound proceeds in three main stages. In the first stage, which starts just above ca. 419 K, the compound loses two dimethyl sulphoxide (DMSO) molecules per one formula unit and small amount of iodide ion. In the second stage (464–552 K) the next DMSO ligands and the iodide ion simultaneously are released. In the last stage (552–900 K) NiSO4 is created which next decomposes to NiO and SO₃.     

Temperature modulated differential scanning calorimetry (TMDSC) in the region of phase transitions. Part 2: some specific results from polymers

By means of four different examples (pressure crystallised, gel crystallised, nascent and highly stretched polyethylenes (PEs)) it is shown that temperature modulated DSC offers advantages against common DSC. It is possible to see dynamic processes inside the sample during melting. This way we found (i) that during melting of high pressure crystallised PE the so-called ₂-process (known from DMA) takes place, (ii) the lamellae doubling in gel crystallised UHMWPE can be seen in TMDSC signals, though no balance heat flow rate is visible in the common DSC, (iii) the same is true for the recrystallisation in nascent and highly stretched PE many degrees before the melting peak appears. To separate these results from the measured curves the knowledge of the heat transport into and within the sample is needed. A simple low pass filter model has proved its worth for this purpose.     

Herstellung keramischer Pulver. IX. Zur Bildung von NiMn2 O4 und ZnMn2O4 durch Zersetzung von [Ni(H2O)6] (MnO4)2 und [Zn(H2O)6] (MnO4)2

Preparation of Ceramic Powders. IX. NiMn₂O₄ and ZnMn₂O₄ Formation by Decomposition of [Ni(H₂O)₆] (MnO₄)₂ and [Zn(H₂O)₆] (MnO₄)₂ Improved preparation of Ba(MnO₄)₂ from BaMnO₄ is reported. Thermal or hydrothermal decomposition of [Ni(H₂O)₆] (MnO₄)₂ yields intermediately an amorphous manganate(IV) which forms crystalline NiMnO₃ and α-Mn₂O₃ in the range T > 400°C. NiMn₂O₄ is formed above 730°C in accordance with the phase diagram. On the other hand, ZnMn₂O₄ is already at 300°C obtained from [Zn(H₂O)₆](MnO₄)₂ at hydrothermal conditions.     

Derivate des Flußspat-Typs: [Fe(NH3)6][TaF6]2 und [Ni(NH3)6][TaF6]2

Derivatives of the Fluorite Type: [Fe(NH₃)₆][TaF₆]₂ and [Ni(NH₃)₆][TaF₆]₂ Light blue single crystals of [Fe(NH₃)₆][TaF₆]₂ and [Ni(NH₃)₆][TaF₆]₂ are obtained from 36 : 1 : 6 molar mixtures of (NH₄)F, iron/nickel and tantalum powders, respectively, in sealed Monel metal ampoules at 400 °C. They both crystallize isotypic with [Co(NH₃)₆][PF₆]₂ (cubic, Fm-3m, Z = 4, a = 1259.0(2)/1260.4(2) pm) in a structure that can be derived from the basic fluorite-type of structure according to [Ca][F]₂≡[Fe(NH₃)₆][TaF₆]₂, for example.