Heat capacities and thermodynamic properties of MgNDC

One-three-dimensional metal-organic frameworks Mg_1.5(C₁₂H₆O₄)_1.5(C₃H₇NO)₂ (MgNDC) has been synthesized solvothermally and characterized by single crystal XRD, powder XRD, FT-IR spectra. The low-temperature molar heat capacities of MgNDC were measured by temperature modulated differential scanning calorimetry (TMDSC) over the temperature range from 205 to 470 K for the first time. No phase transition or thermal anomaly was observed in the experimental temperature range. The thermodynamic parameters of MgNDC such as entropy and enthalpy relative to reference temperature of 298.15 K were derived based on the above molar heat capacities data. Moreover, the thermal stability and decomposition of MgNDC was further investigated through thermogravimetry (TG)?Cmass spectrometer (MS). Three stages of mass loss were observed in the TG curve. TG?CMS curve indicated that the oxidative degradation products of MgNDC are mainly H₂O, CO₂, NO, and NO₂.     

Solid state of a new flavonoid derivative DA-6034

DA-6034 is a new synthetic flavonoid known to possess anti-inflammatory activity. The objective of this work was to investigate the existence of polymorphs and pseudopolymorphs of DA-6034. Six crystal forms, one hydrate form and five solvates, of DA-6034 have been isolated by recrystallization and characterized by differential scanning calorimetry (DSC), thermogravimetric analysis (TG), and powder X-ray diffractometry (PXRD). From the DSC and TG data it was confirmed that Form 1 is monohydrate; Form 2 is DMSO solvate; Form 3 is 1/2 DMSO solvate; Form 4 is 1/2 methyl ethyl ketone solvate; Form 5 is 1.5 H₂O, 1/2 acetic acid solvate; Form 6 is 1/2 H₂O, 1/4 butanol solvate. The PXRD patterns of the six crystal forms were different respectively. In the dissolution studies in pH 6.8 ± 0.05 buffer at 37 ± 0.5 °C, the solubility of solvates was higher than that of Form 1.     

Growth, optical, thermal, and conductivity behavior of nonlinear optical single crystals of CdHg(SCN)4(CH3OC2H5O)

In this study, organometallic nonlinear optical single crystal of Cadmium mercury thiocyanate glycol monomethyl ether was grown by slow evaporation technique at room temperature. The grown crystal was confirmed by single crystal XRD and FT-IR analysis. Optical and thermal properties of the sample were investigated by UV–Vis–NIR, TG–DTA and DSC technique. Using Tauc’s relation, the band gap of the crystal was estimated as 3.99 eV. The thermal studies confirm that the CMTG is thermally stable up to 105 °C. Photoluminescence and ac & dc conductivity measurements of the sample were also carried out and reported for the first time. The PL analysis confirms the suitability of the material for application in the blue–green region. The temperature dependences of ac & dc conductivities of CMTG were investigated, and the activation energies were found to be 0.098 and 0.045 eV, respectively. The SHG efficiency measurement confirms that the NLO efficiency of CMTG is nearly three times more efficient than urea.     

Synthesis, growth, thermal, optical, mechanical and dielectric studies of N-succinopyridine

Organic nonlinear optical (NLO) material, N-succinopyridine (NSP), was synthesised and bulk single crystals were grown from aqueous solution using isothermal solvent evaporation technique. The stoichiometric form of NSP has been confirmed by carbon–hydrogen–nitrogen analysis. NSP crystallizes in orthorhombic system with non-centrosymmetric space group P2₁2₁2₁ and unit cell dimensions a = 7.721(2) Å, b = 7.762(3) Å, c = 14.951(3) Å. The thermal stability, thermal decomposition and specific heat capacity of NSP have been investigated by thermogravimetric/differential thermal analysis, differential scanning calorimetric (DSC) analysis and modulated DSC analysis. A wide transparency window, 294–1,100 nm, useful for optoelectronic applications is indicated by UV–Vis–NIR studies. The NLO second harmonic generation efficiency analysis using Nd:YAG laser (1,064 nm) revealed that the SHG efficiency of NSP is about 1.2 times higher than that of standard potassium dihydrogen phosphate powder of comparable size and more importantly that it is phase-matchable. The room temperature mechanical behaviours of NSP have been tested using Vicker’s microhardness tester and the results were analysed through classical Mayer’s law. The dielectric behaviours such as dielectric constant, dielectric loss and ac conductivity of NSP single crystal have also been investigated as a function of frequency (20 Hz–1 MHz) and temperature (308–358 K).     

Synthesis and Characterization of Altaicadispirolactone

Altaicadispirolactone was synthesized via a simple route. In this route, levulinic acid was used as a starting material, and bromination followed by hydrolysis and BF₃ · OEt₂‐catalyzed cyclization were carried out. A single‐crystal ORTEP drawing has been created and more detailed crystallographic data of the compound has been obtained from X‐ray analysis.     

Molar heat capacities and standard molar enthalpy of formation of pyrimethanil butanedioic salt

A noval anilino-pyrimidine fungicide, pyrimethanil butanedioic salt (C₂₈H₃₂N₆O₄), was synthesized by a chemical reaction of pyrimethanil and butanedioic acid. The low-temperature heat capacities of the compound were measured with an adiabatic calorimeter from 80 to 380 K. The thermodynamic function data relative to 298.15 K were calculated based on the heat capacity fitted curve. The thermal stability of the compound was investigated by TG and DSC. The TG curve shows that pyrimethanil butanedioic salt starts to sublimate at 455.1 K and totally changes into vapor when the temperature reaches 542.5 K with the maximal speed of weight loss at 536.8 K. The melting point, the molar enthalpy (Δ_fus H _m), and entropy (Δ_fus S _m) of fusion were determined from its DSC curves. The constant-volume energy of combustion (Δ_c U _m) of pyrimethanil butanedioic salt was measured by an isoperibol oxygen-bomb combustion calorimeter at T = (298.15 ± 0.001) K. From the Hess thermochemical cycle, the standard molar enthalpy of formation was derived and determined to be Δ_f H _m ^o (pyrimethanil butanedioic salt)=?285.4 ± 5.5 kJ mol^?1.     

Variable temperature PXRD investigation of the phase changes during the dehydration of potassium Tutton salts

The thermal dehydration of the potassium Tutton salts K₂M(SO₄)₂·6H₂O (M = Mg, Co, Ni, Cu, Zn) was investigated using thermal gravimetric analysis (TG), differential scanning calorimetry (DSC), FTIR, and variable temperature powder X-ray diffraction. While each Tutton salts lost all six waters of hydration when heated to 500 K, the decomposition pathway depended on the divalent metal cation. K₂Ni(SO₄)₂·6H₂O lost all six waters in a single step, and K₂Cu(SO₄)₂·6H₂O consistently lost water in two steps in capped and uncapped cells. In contrast, multiple decomposition pathways were observed for the magnesium, cobalt, and zinc Tutton salts when capped and uncapped TG cells were used. K₂Zn(SO₄)₂·6H₂O lost the waters of hydration in a single step in an uncapped cell and in two steps in a capped cell. Both K₂Mg(SO₄)₂·6H₂O and K₂Co(SO₄)₂·6H₂O decomposed in a series of steps where the stability of the intermediates depended on the cell configuration. A greater number of phases were often observed in DSC and capped-cells TG experiments. A quasi-equilibrium model is presented that could explain this observation. These results highlight that experimental conditions play a critical role in the observed thermal decomposition pathway of Tutton salts.     

Crystal structure and physical properties of EuMo6S8 single crystals at ambient pressure

X-Ray analyses were performed at room temperature on single crystals of Eu_xMo₆S₈. Refinement of its crystal structure shows an upper stoichiometry of x = 1.0. Atomic positions and crystallographic data are given in full. Crystals were also characterized through their susceptibility and transport properties. All europium atoms are divalent as confirmed by the magnetization at low temperatures. A welldefined anomaly on the electrical resistivity at T_s = 107 K separates the metallic high-temperature rhombohedral phase from the low-temperature nonmetallic (triclinic) phase. Very large residual resistivity ratios obtained for stoichiometric crystals favor our interpretation that the Eu_1.0Mo₆S₈ low-temperature phase must be essentially semiconducting.     

Heat capacities and thermodynamic properties of MgBTC

A novel two-dimensional metal organic framework MgBTC [MgBTC(OCN)₂·2H₂O, where BTC = 1,3,5-benzenetricarboxylate] has been synthesized solvothermally and characterized by single crystal XRD, powder XRD, FT-IR spectra. The low-temperature molar heat capacities of MgBTC were measured by temperature modulated differential scanning calorimetry (TMDSC) over the temperature range from 190 to 350 K for the first time. No phase transition or thermal anomaly was observed in the experimental temperature range. The thermodynamic parameters of MgBTC such as entropy and enthalpy relative to reference temperature of 298.15 K were derived based on the above molar heat capacities data. Moreover, the thermal stability and decomposition of MgBTC was further investigated through thermogravimetry (TG)-mass spectrometer (MS). Four stages of mass loss were observed in the TG curve. TG-MS curve indicated that the products of oxidative degradation of MgBTC are H₂O, N₂, CO₂ and CO. The powder XRD showed that the mixture after TG contains MgO and graphite.     

Influence of organic dyes on the thermal,mechanical, and optical properties of l-arginine trifluoroacetate (LATF) single crystals

Bulk single crystals of pure and organic dyes (rhodamine, amaranth, and methyl orange) admixture l-arginine trifluoroacetate were grown by slow evaporation technique. The cell parameters and crystallinity of pure and dyes-mixed LATF were confirmed by powder X-ray diffraction analysis. Thermal analysis (TG/DTA, DSC) reveals the purity of the sample and no decomposition is observed up to melting point. In the TG trace of pure LATF, methyl orange: LATF, amaranth: LATF and rhodamine: LATF it is observed that the crystals were thermally stable up to 488, 485, 483, and 484.14 K, respectively. The crystals are further characterized using UV–Vis analysis, microhardness analysis, and EDAX analysis. By plotting log P versus log d, the value of the work hardening coefficient "n" was found to be 1.95, 0.52, 0.8, and 0.88 for pure, methyl orange, amaranth, and rhodamine dyes-doped LATF grown crystals, respectively. Second harmonic generation efficiency of pure and dye admixture LATF crystals was measured using Kurtz and Perry powder test, the efficiency of methyl orange, amaranth, and rhodamine dyes-doped LATF crystal is 2.7, 2.6, and 2.07 times greater than KDP, where as the efficiency of LATF pure is 2.5 times greater than that of KDP.     

Structural characterization,phase transition and dielectric properties of 4-cyanopyridynium perchlorate monohydrate: [(4-CNC5H4NH)][ClO4]·H2O

Crystal structure of 4-cyanopyridynium perchlorate monohydrate ([(4-CNC₅H₄NH)][ClO₄]·H₂O) has been determined at 293 and 240 K as orthorhombic space group, Pnma and monoclinic space group, P2₁/c, respectively, by means of single crystal X-ray diffraction. At room temperature the perchlorate anion reveals significant disorder, which is realized by the splitting of two oxygen atoms into four sites. DSC, dilatometric and dielectric spectroscopy techniques show that the crystal undergoes phase transition at 286/288 K (on cooling/heating scans). [(4-CNC₅H₄NH)][ClO₄]·H₂O appears to be an insulator with relatively high activation energy of the order of 100 kJ/mol. The phase transition in the title crystal is believed to be related to the dynamics of the perchlorate anion.     

Use of polyethylene glycol in the process of sol–gel encapsulation of Burkholderia cepacia lipase

Lipases from Burkholderia cepacia were encapsulated using polyethylene glycol (PEG, M _w 1500) at various concentrations (0.5–3.0 %, w/v) as an additive during the sol–gel immobilisation process. Matrixes immobilized in the presence and absences of additives were characterized by thermal analysis [thermogravimetric (TG) and differential scanning calorimetry (DSC)], scanning electron microscopy (SEM), enzymatic activity, and total activity recovery yield (Ya). The addition of PEG increased the activity values, with Ya just above 1.0 % (w/v) in the presence of PEG. The additional of 1.0 % (w/v) PEG increased enzyme activity from 33.98 to 89.91 U g^?1 and the values of recovery yield were 43.0–91.4 %, compared to values of the samples without PEG. PEG enhanced the thermal stability of the matrix structure in the temperature range 50–200 °C, as confirmed by TG and DSC analyses. This was influenced by the presence of water bound to the matrix. The SEM micrographs clearly showed an increase in the number of deposits on the material surface, producing matrices with greater porosity.     

Thermodynamic properties and heat capacities of Co (BTC)1/3 (DMF) (HCOO)

A novel metal organic framework [Co (BTC)_1/3 (DMF) (HCOO)] _n (CoMOF, BTC = 1,3,5-benzene tricarboxylate, DMF = N,N-dimethylformamide) has been synthesized solvothermally and characterized by single crystal X-ray diffraction, X-ray powder diffraction, and FT-IR spectra. The molar heat capacity of the compound was measured by modulated differential scanning calorimetry (MDSC) over the temperature range from 198 to 418 K for the first time. The thermodynamic parameters such as entropy and enthalpy versus 298.15 K based on the above molar heat capacity were calculated. Moreover, a four-step sequential thermal decomposition mechanism for the CoMOF was investigated through the thermogravimetry and mass spectrometer analysis (TG-DTG-MS) from 300 to 800 K. The apparent activation energy of the first decomposition step of the compound was calculated by the Kissinger method using experimental data of TG analysis.     

Thermal behavior of cashew gum by simultaneous TG/DTG/DSC-FT-IR and EDXRF

Cashew gum, an exudate polysaccharide from Anacardium occidentale L., was purified by alcohol precipitation. Thermal behavior of this polysaccharide was investigated by simultaneous TG/DTG/DSC-FT-IR analysis performed under nitrogen and air atmospheres and heating rate of 10 K min^?1. TG/DTG curves under oxidative atmosphere were similar to the curves under N₂ atmosphere until 340 °C, however, it was observed a profile difference due to the presence of two DTG peaks at 430 and 460 °C. DSC results showed endothermic and exothermic events corroborating with TG/DTG curves. The Simultaneous TG/DSC-FTIR analysis revealed that evolved gases from the decomposition of cashew gum sample were CO₂, CO, and groups: O–H, C–H, C=O, C–C, and C–O, in nitrogen and air atmospheres. Energy dispersive X-ray fluorescence analysis from the ash showed that the elements in larger amounts are CaO, MgO, and K₂O.     

Growth and characterization of semiorganic NLO crystal of l-glutamic acid hydrochlorobromide (LGHCB)

Single crystals of nonlinear optical material l-glutamic acid hydrochlorobromide (LGHCB) were grown by slow evaporation technique from its aqueous solution. Optically good quality crystals of dimension 20 × 10 × 2 mm³ were obtained. The lattice parameters for the grown crystals were determined using single crystal X-ray diffraction study. The LGHCB crystal belongs to non-centrosymmetric P2₁2₁2₁ space group. The crystal structure was resolved by direct method and refined by full matrix least-square method using SHELXL-97. Using the powder X-ray diffraction study, the crystallinity of the grown crystal was confirmed and the diffraction peaks are indexed. From Fourier transform infrared spectroscopy study, the various functional groups present in LGHCB crystal were elucidated. The UV–Vis-NIR absorption spectrum was recorded in the range of 200–2,000 nm, and the lower cut off wavelength is ~235 nm. Optical band gap of the grown crystal was found to be 5.22 eV. Thermal properties of LGHCB crystal were studied by thermogravimetric analysis and derivative thermogravimetric analysis. The second harmonic generation efficiency of LGHCB crystal was confirmed by Kurtz’s powder technique.     

Effects of various fire-extinguishing reagents for thermal hazard of triacetone triperoxide (TATP) by DSC/TG

Acetone, hydrogen peroxide (H₂O₂), and sulfuric acid (H₂SO₄) are easily to produce triacetone triperoxide (TATP), which is an organic peroxide and a hazardous material. The aim of this study was to analyze the thermal hazard of various fire-extinguishing reagents mixed with TATP. Various functions of fire-extinguishing reagents may have different extent of reactions with TATP. Differential scanning calorimetry (DSC) and thermogravimetric analyzer (TG) were used to detect the thermal hazard and to evaluate the effect of fire-extinguishing reagents mixed with TATP under fire condition. TATP decomposed rapidly and final decomposition was calculated before 200 °C. Therefore, heat of decomposition (ΔH _d) of TATP was evaluated to be 2,500 J g^?1 by DSC under 2 °C min^?1 of heating rate. H₂O₂, acetone, and H₂SO₄ should not be mixed in a wastewater drum. TATP decomposed at 50 °C by DSC using O₂ of reaction gas that is an exothermic reaction and can decompose a large amount of heat. Therefore, TATP was applied to assess thermal pyrolysis by DSC employing N₂ of reaction gas that can analyze an endothermic reaction. Mass loss percentage of TATP was evaluated to be 100 % when the ambient temperature exceeds 110 °C by TG using O₂ or N₂ of reaction gas.     

Thermal behavior and thermodynamic properties of berberine hydrochloride

The low-temperature heat capacities of berberine hydrochloride were measured over the temperature range from 78 to 350 K by an adiabatic calorimeter. The thermodynamic functions H _T ? H _298.15 and S _T ? S _298.15 were derived from the heat capacity data. The results showed that the structure of berberine hydrochloride was stable over the temperature range from 78 to 350 K. The thermal stability of the compound was further tested by DSC and TG measurements. The results were in agreement with those obtained from adiabatic calorimetry experiment. The standard molar enthalpy of formation in the crystalline state of berberine hydrochloride was obtained from the standard molar energies of combustion in oxygen at T = 298.15 K, measured by a rotating-bomb combustion calorimeter.     

Studies on the characterisation of l-proline thiourea monohydrate nonlinear optical single crystal

l-Proline thiourea monohydrate nonlinear optical single crystal of size 65 × 15 mm² was grown by slow evaporation technique at room temperature. The grown crystal was characterised by single crystal XRD, absorption spectrum, FTIR, EDAX, Vicker’s microhardness test, DSC, dielectric and photoconductivity studies. Second harmonic generation efficiency of the grown crystal makes it a higher order second harmonic material with good conversion efficiency. The reported crystal is an efficient nonlinear optical material with good optical transparency, thermal, mechanical strength and dielectric property.     

Thermal analysis, phase transitions and molecular reorientations in [Sr(OS(CH3)2)6](ClO4)2

Thermal analysis (TG/DTG/QMS), performed for [Sr(OS(CH₃)₂)₆](ClO₄)₂ in a flow of argon and in temperature range of 295–585 K, indicated that the compound is completely stable up to ca. 363 K, and next starts to decompose slowly, and in the temperature at ca. 492 K looses four (CH₃)₂SO molecules per one formula unit. During further heating [Sr(DMSO)₂](ClO₄)₂ melts and simultaneously decomposes with explosion. Differential scanning calorimetry (DSC) measurements performed in the temperature range of 93–370 K for [Sr(DMSO)₆](ClO₄)₂ revealed existence of the following phase transitions: glass ? crystal phase Cr5 at T _g  ≈ 164 K (235 K), phase Cr5 → phase Cr4 at $ T_{\text{c6}}^{\text{h}} $  ≈ 241 K, phase Cr4 → phase Cr3 at $ T_{\text{c5}}^{\text{h}} $  ≈ 255 K, phase Cr3 → phase Cr2 at $ T_{\text{c4}}^{\text{h}} $  ≈ 277 K, phase Cr2 ? phase Cr1 at $ T_{\text{c3}}^{\text{h}} $  ≈ 322 K and $ T_{\text{c3}}^{\text{c}} $  ≈ 314 K, phase Cr1 ? phase Rot2 at $ T_{\text{c2}}^{\text{h}} $  ≈ 327 K and $ T_{\text{c2}}^{\text{c}} $  ≈ 321 K and phase Rot2 ? phase Rot1 at $ T_{\text{c1}}^{\text{h}} $  ≈ 358 K and $ T_{\text{c1}}^{\text{c}} $  ≈ 347 K. Entropy changes values of the phase transitions at $ T_{\text{c1}}^{\text{h}} $ and $ T_{\text{c2}}^{\text{h}} $ (?S ≈ 79 and 24 J mol^?1 K^?1, respectively) indicated that phases Rot1 and Rot2 are substantially orientationally disordered. The solid phases (Cr1–Cr5) are more or less ordered phases (?S ≈ 7, 10, 4 and 3 J mol^?1 K^?1, respectively). Phase transitions in [Sr(DMSO)₆](ClO₄)₂ were also examined by Fourier transform middle infrared spectroscopy (FT-MIR). The characteristic changes in the FT-MIR absorption spectra of the low- and high-temperature phases observed at the phase transition temperatures discovered by DSC allowed us to relate these phase transitions to the changes of the reorientational motions of DMSO ligands and/or to the crystal structure changes.