Photochemical and thermal reactions of iron pentacarbonyl with dimethyldiacetylene (DMDA): spectral characterization of reaction complexes

A series of photochemical and thermal reactions has been carried out with iron pentacarbonyl and the conjugated alkadiyne dimethyldiacetylene (DMDA). One product (DMDA)Fe(CO)₆, was prepared directly from starting materials in tetrahydrofuran under photochemical conditions. Previously analogs of this complex had been prepared only under thermal conditions from complex intermediates. An X-ray analysis has established the structure of this complex; ¹³C NMR and other spectral data reported here are in agreement. Under thermal conditions in xylene, three isomeric forms of a tricarbonylferroleiron tricarbonyl (DMDA)₂Fe₂(CO)₆ complex were prepared. Separation and purification of two of these isomers was achieved; selected spectral data are reported. Infrared and mass spectra are also reported for the complex (DMDA)₂Fe(CO)₄ resulting from the photochemical reaction of starting materials in cyclohexane.     

Synthesis,spectral and thermal properties of macrocyclic zinc(II) complexes

The new zinc ternary complexes [Zn(cyclen)NO₃]ClO4 (I), [Zn₂(cyclen)₂(m-nic)](ClO₄)₃ (II), [Zn₂(cyclen)₂(m-pic)](ClO₄)₃ (III) (cyclen=1,4,7,10-tetraazacyclododecane; nic=nicotinic acid; pic=picolinic acid) were synthesized and their spectral and thermal properties were investigated. The compounds were characterized by elemental analysis, IR spectroscopy and TG/DTG, DTA methods. Moreover, the way of coordination of pyridinecarboxylate anions was proposed on the basis of the spectral data and consequently proved with results of X-ray structure analysis. This revised version was published online in August 2006 with corrections to the Cover Date.     

Interrelations between soil respiration and its thermal stability

Biological transformation of organic matter in soil is a crucial factor affecting the global carbon cycle. In order to understand these complex processes, soils must be investigated by a combination of various methods. This study compares the dynamics of biological mineralization of soil organic matter (SOM) determined via CO₂ evolution during an 80-day laboratory incubation with their thermo-oxidative stability determined by thermogravimetry (TG). Thirty-three soil samples, originating from a wide range of geological and vegetation conditions from various German national parks were studied. The results showed a correlation between the amount and rate of respired CO₂ and thermal mass losses of air-dried, conditioned soils occurring around 100?°C with linear coefficients of determination up to R ²?=?0.85. Further, correlation of soil respiration with thermal mass losses around 260?°C confirmed previous observations. The comparison of TG profiles from incubated and non-incubated soils underlined the importance of thermal mass losses in these two temperature intervals. Incubated soils had reduced thermal mass losses above 240?°C and conversely an increased mass loss at 100?C120?°C. Furthermore, the accurate determination of soil properties by TG such as soil organic carbon content was confirmed, and it was shown that it can be applied to a wider range of carbon contents as was previously thought. It was concluded that results of thermal analysis could be a helpful starting point for estimation of soil respiration and for development of methods revealing processes in soils.     

A two-dimensional infrared correlation spectroscopic study on the thermal degradation of poly(2-hydroxyethyl acrylate)-co-methyl methacrylate/SiO2 nanohybrids

Two-dimensional infrared (2D IR) correlation spectroscopy was applied to study the structural changes occurring in the decomposition of PHEA-co-MMA/SiO₂. Complicated absorption spectral changes were observed in the heating process. 2D IR analysis indicates that during heating, covalent bonds, (Si-O-C), between the polymer and the inorganic moiety were formed, which was the main factor in the improvement in thermal properties of the hybrids such as the decomposition temperatures (T_d). The thermal stability of the hybrids was also studied by solid-state ²⁹Si MAS NMR spectroscopy and TGA tests. Their results complemented each other well.     

Studies on the structure and thermal behaviour of the Mn—urea complex

The urea complex of manganese was synthesized and its structure established to be [Mn(Urea)(H₂O)₃Cl₂] from elemental analyses, IR and UV and visible spectroscopy and magnetic susceptibility measurements. The thermal behaviour has been studied by thermogravimetry (TG) in nitrogen and air atmospheres and differential thermal analysis (DTA) in air. TG analysis shows three main steps of decomposition leading to oxide formation in the final stage when the complex is heated in air, and MnCl₂ formation when it is heated in nitrogen. The kinetics of decomposition of the complex have been studied. Plots of the Coats—Redfern equation show two breaks from which three values of the activation energy are reported. From the results, it is concluded that decomposition of the complex is a heterogeneous process.     

UV-cured hyperbranched polyester polythiol(H20-SH)-epoxy acrylate networks: Preparation,thermal and mechanical properties

A hyperbranched polyester polythiol(H20-SH) was synthesized and characterized by FTIR spectral analysis, ¹H-NMR spectral analysis and GPC analysis. H20-SH was added into the formulation of UV-curable epoxy acrylate networks based on thiol-acrylate chemistry. The effects of H20-SH on polymerization kinetics, thermal and mechanical properties of thiol-epoxy acrylate networks were investigated by Real-time infrared spectroscopy, dynamic mechanical analysis (DMA), thermogravimetric (TGA), tensile test and water absorption characterization. Results show that epoxy acrylate resin with the addition of H20-SH massively reduces oxygen inhibition, improves the uniformity of cured films and enhances the tensile strength of the films. However, the thermal stability and glass transition temperature (T_g) decreases with the increasing amount of H20-SH.     

Synthesis, crystal structure and thermal decomposition of a new copper propionate [Cu(CH3CH2COO)2]·2H2O

A new copper propionate complex was synthesised and characterized for application as precursor for CuO based oxide thin films deposition. The FT-IR and X-ray diffraction analyses have revealed the formation of a cooper propionate complex [Cu(CH₃CH₂COO)₂]·2H₂O. The crystal and molecular structure of a new copper propionate complex was determined by XRD on the copper propionate single crystal. The copper propionate complex has a binuclear structure, connected by bridging bidentate carboxylates groups and a Cu?Cu bond of 2.6 Å. The thermal decomposition of copper propionate has been investigated by thermal analysis using thermogravimetric (TG) and differential thermal analysis (DTA), differential thermal analysis coupled with quadrupole mass spectrometry-QMS, X-ray diffraction (XRD), Fourier transformed infrared spectroscopy (FT-IR) techniques. TG and XRD data indicate the reduction of Cu(II)-Cu(I,0) during the decomposition of copper propionate.     

Isolation, structural, spectral, and thermal studies of imperatorin micro-crystals from Prangos pabularia

Imperatorin (mol. formula = C₁₆H₁₄O₄, mol. mass = 270) micro-crystals were isolated from ethyl acetate extract of the root parts of the plant Prangos pabularia. The composition related structural, spectral, and thermal properties were investigated. All the crystals were found to have single phase with orthorhombic structure. UV–Visible spectrum showed both direct forbidden transition and indirect allowed transition. The calculated optical band gaps (E _g) were 3.64 and 3.70 eV for direct forbidden and indirect allowed transitions, respectively. From the thermal studies of these crystals, melting point, stability, and other relevant information was obtained, ensuring the suitability of the material for application in any device where the crystals may have to withstand this range of temperature.     

Preparation,thermal decomposition,and crystal structure of Zn(II) 2-chlorobenzoate complex with nicotinamide

A new Zn(II) 2-chlorobenzoate complex, [Zn(2-ClC₆H₄COO)₂(nad)₂] (nad = nicotinamide), was synthesized and characterized by elemental analysis, infrared (IR) spectroscopy, mass spectrometry, thermal analysis, and X-ray structure determination. The mechanism of thermal decomposition of the complex was studied by TG/DTG, DTA, IR spectroscopy, and mass spectrometry. The thermal decomposition is characterized as a two-step process. Zinc oxide was found as the final product of the thermal decomposition performed up to 900°C. Mass spectrometry was used to determine the volatiles released during thermal decomposition. The IR spectrum indicates that carboxylate is coordinated to zinc in monodentate coordination. [Zn(2-ClC₆H₄COO)₂(nad)₂] crystallizes in the monoclinic system, space group Pn, a = 10.376(2) Å, b = 10.100(1) Å, c = 12.604(1) Å, β = 100.79(1)°. The zinc is tetrahedrally coordinated by two nitrogens of nicotinamide and two oxygens of 2-chlorobenzoate.     

Crystal structure and thermal analysis of diaquadi (1,2,4-triazol-5-one)zinc(II) ion nitrate

A new complex, diaquadi(1,2,4-triazol-5-one)zinc(II) ion nitrate formulated as {[Zn(TO)₂(H₂O)₂](NO₃)₂}_n (1) (1,2,4-triazole-5-one, abbreviated as: TO) was synthesized and characterized by elemental analysis, X-ray single crystal diffraction, infrared spectrum (IR), differential scanning calorimetry (DSC), thermogravimetric analysis and differential thermogravimetric analysis (TG-DTG). The X-ray structure analysis reveals that the complex is orthorhombic with space group Pbca and unit-cell parameters a=6.9504(2) Å; b=10.6473(3) Å; c=17.8555(5) Å. Based on the result of thermal analysis, the thermal decomposition process of the compound was derived. From measurement of the enthalpy of solution in water in 298.15 K, the standard molar enthalpy of solution of lignand TO and the complex were determined as 15.43±0.18 and 52.64±0.42 kJ mol^?1, respectively. In addition, the standard molar enthalpy of formation of TO(aq) was calculated as ?126.97±0.72 kJ mol^?1.     

Studies on the thermal behaviour of tris-[thallium(III)]-lactate

The interaction of TL(OH)₃, with excess lactic acid indicated the formation of Tl(LA)₃ where LA stands for the anion of lactic acid. The structure of the complex was predicted from elemental analyses and IR spectra. The thermal decomposition of the complex using TG, DTG and DTA gave supporting evidence for the predicted structure. The kinetics of thermal decomposition were also studied employing various computational methods.     

Studies of thermal properties of di(methacryloyloxymethyl)naphthalene–divinylbenzene (DMN–DVB) copolymer and its alkyl-bonded derivatives

This paper presents the thermal properties of highly crosslinked di(methacryloyloxymethyl)naphthalene–divinylbenzene (DMN–DVB) copolymeric microspheres containing polar groups in the structure and their alkyl-bonded derivatives. C₈ and C₁₈ alkyl chains were introduced into the aromatic rings of the DMN–DVB porous copolymer by means of the Friedel–Crafts reaction. As a source of C₈ and C₁₈ alkyl chains, octyl and octadecyl chlorides were used. It was necessary to check whether the introduction of alkyl chains into the structure of polymeric packing had an impact on its thermal properties. The studies were carried out by thermogravimetry coupled online with FTIR spectroscopy and differential scanning calorimetry in inert atmosphere (helium). It was stated that the modified materials showed 20 and 50% mass losses at higher temperatures than the non-modified one while 1% mass loss was observed at lower temperatures. Moreover, an analysis of volatile decomposition products was performed.

     

Crystal structure of Co(3-pic)2Cl2 and thermal behaviour of a new complex, Co(py)(3-pic)Cl2

A crystalline Co(3-pic)₂Cl₂ compound was obtained and its structure determined by X-ray diffraction. The structure is characterized by the presence of two conformationally different molecules. A new cobalt(II) complex of molecular formula Co(py)(3-pic)Cl₂ was also synthesized. It was characterized by spectroscopic methods (IR, FIR, Raman spectra), elemental analysis and thermogravimetry (TG, DTA, DTG) carried out in both the oxidative and inert atmosphere. Each of the thermal decomposition steps was interpreted and the influence of substituent position in the pyridine ring on the thermal stability of the complex was discussed.     

Spectral,thermal and magnetic studies of biacetylmonoxime isonicotinoylhydrazone complexes

The synthesis and characterization of Co(II), Ni(II), Cu(II), Zn(II), Cd(II) and UO²⁺₂ complexes of biacetylmonoxime isonicotinoylhydrazone (BMINH) are reported. Elemental-analysis, magnetic, thermal and spectral (IR, visible and NMR) measurements have been used to characterize the complexes. IR spectral data show that the ligand behaves in a bidentate and/or tridentate manner. An octahedral structure is proposed for the Ni(II) complexes, while a square-planar structure is proposed for both Co(II) and Cu(II) complexes, on the basis of magnetic and spectral measurements.     

A supramolecular polymeric chain in the cobalt(II) complex with diclofenac: synthesis,crystal structure,spectroscopic, thermal and antioxidant activity

Abstract

A cobalt(II) complex with empirical formula [Co(dicl)₂·(H₂O)₃]·MeOH (where dicl?=?diclofenac) was synthesized and characterized by elemental analysis, flame atomic absorption spectroscopy (FAAS), infrared spectroscopy (FTIR) and thermal decomposition techniques (TGA). The crystal structure of the complex was determined by single crystal X-ray diffraction technique. The compound crystallizes in the monoclinic space group I2/a. Apical water molecules link adjacent cobalt(II) ions forming polymeric chains along the crystal a axis. The thermal behavior of the complex was studied by TG/DTG/DTA, TG/MS and TG/FTIR methods under non-isothermal conditions in air. Upon heating [Co(dicl)₂·(H₂O)₃]·MeOH decomposes progressively to metal oxides, which are the final products of pyrolysis. Furthermore, antioxidant activity of the complex was examined.     

Synthesis and thermal properties of cellulose-based polycaprolactones

Cellulose-based polycaprolactone (CAPCL) sheets were prepared from cellulose acetate (CA) and ϵ-caprolactone (CL). Thermal properties of the obtained CAPCL's were studied by differential scanning calorimetry (DSC), thermogravimetry (TG) and TG-Fourier transform infrared spectrometry (TG-FTIR). The glass transition temperatures (T_g 's) of CAPCL decreased with increasing CL/OH ratio, until CL/OH ratio reached 15 and then increased above that ratio. Melting of CAPCL was observed when CL/OH ratio was over 10. The thermal degradation temperatures (T_d 's) of CAPCL increased from ca. 350 °C to 390 °C with increasing CL/OH ratio. The results obtained by TG-FTIR analysis of CAPCL showed that gases with OH, CH, C=O, C-O-C groups evolved by thermal degradation.     

Characterization and thermal analysis of thiourea and bismuth trichloride complex

A complex of thiourea and bismuth trichloride has been synthesized. Its composition is Bi₃Cl₉[SC(NH₂)₂]₇. Crystallographic data are a = 7.141(2) Å, b = 8.820(3) Å, c = 16.365(5) Å, α = 99.389(4)°, β = 95.422(4)°, γ = 106.177(4)°, triclinic system. There are the mononuclear anion [BiCl₅SC(NH₂)₂]^2? and the dinuclear cation {Bi₂Cl₄[SC(NH₂)₂]₆}²⁺ with the Bi–Cl–Bi bridge bonds in the complex. The electric conductance of the absolute methanol solution contained the complex indicates that the complex is an ionic compound. Raman spectra indicate that the bismuth ion is coordinated by the sulfur atoms of the thiourea. The thermal analysis verifies the structure of complex. The TG–MASS curves show the structure rearrangement in the complex at about 118 °C. The DSC curves and calculation means that the structure rearrangement is irreversible.     

A novel photo and thermal stable dysprosium complex with tetraphenylimidodiphosphinate acid

The first Dy(III) tetraphenylimidodiphosphinate complex Dy(Tpip)₃ was synthesized and characterized by elemental analysis, IR, TG, and X-ray diffraction analysis. The aryl-functionalised imidodiphosphinate ligand (Tpip) provides a bidentate anionic site that leads to a hexa-coordinate dysprosium complex [Dy(Tpip)₃]. The X-ray single-crystal structural analysis indicates that the structure crystallizes to a trigonal system with a space group $P\bar 3$ a = 23.4638(17), c = 21.3207(18) Å, and Z = 6. It shows excellent thermal stability with no obvious weight loss below 400°C. The luminescence experiment shows that the complex exhibits the typical luminescence of Dy₃₊ ion in the visible region. The photo stability of Dy(Tpip)₃ is very good and the emission intensity remains above 94% as it of before excited upon excitation for 3600 s.     

Effect of the spatial network structure and cross-link density of diene rubbers on their thermal stability and fire hazard

The paper presents the results of investigating the effect of the density and spatial network structure of diene rubbers (NBR and SBR) on their thermal properties and fire hazard. The rubbers were either conventionally cross-linked by means of sulfur and organic peroxide or nonconventionally with the use of iodoform (CH₃I). Based on thermo-kinetic analysis, the destruction activation energy of the elastomers investigated and their vulcanizates was determined under air and inert gas. The analysis of particular stages of their thermal decomposition was also presented. During the combustion of the elastomeric materials obtained, it has been found that their fire hazard depends not only on the elastomer chemical structure but also on the method of its cross-linking.