Thermoanalytical studies on complexes of clotrimazole with cyclodextrins

γ-Cyclodextrin and dimethyl-β-cyclodextrin were used as solubilizing agents for a very poorly water-soluble drug, an imidazole derivative antifungal agent, clotrimazole; with the aim of improving the physicochemical properties of the drug. Solid products were prepared by physical mixing, kneading, precipitation and spray-drying methods in 1:1 and 1:2 drug:cyclodextrin molar ratios. Drug interactions were studied by thermoanalytical methods such as DSC, DTA, TG and DTG, X-ray diffractometry and Fourier transformation-infrared spectroscopy. The results demonstrated the formation of inclusion complexes in some products. This revised version was published online in July 2006 with corrections to the Cover Date.     

Thermoanalytical studies on complexes of ketoconazole with cyclodextrin derivatives

Inclusion complexation between cyclodextrin derivatives (hydroxypropyl-β-cyclodextrin and methyl-β-cyclodextrin) and a very poorly water-soluble antifungal agent, ketoconazole, was studied. Solid products were prepared by physical mixing, kneading and spray-drying methods in four molecular ratios: 2:1, 1:1, 1:2 and 1:3. The possibility of complex formation between the drug and the cyclodextrins was studied by thermal analysis. Supplementary techniques, such as X-ray diffractometry and Fourier transformation-infrared spectroscopy, were also applied to interpret the results of the thermal study of the products. This revised version was published online in July 2006 with corrections to the Cover Date.     

Thermoanalytical and Spectral Study of Efaroxan Hydrochloride

The physicochemical characterization of the solid-state enantiomers and racemate of efaroxan hydrochloride (C13H17N2O+Cl-, M=252.5 g mol-1) was performed by thermoanalytical methods (differential scanning calorimetry, thermogravimetry and thermomicroscopy) and spectral methods (infrared spectrometry and X-ray diffractometry). The efaroxan enantiomers and racemate were shown to be unstable near the melting point. At the beginning of the decomposition, a loss of hydrogen chloride was observed. However when sealed pans were used, the compounds decomposed at higher temperature, allowing a precise evaluation of the melting enthalpies by means of differential scanning calorimetry. The nature of the racemate and its thermal stability were assessed by evaluating its free formation enthalpy. An enantiotropic solid-solid transformation (II→I) was noted for the racemate; the reverse process (I→II) follows zero-order kinetics. This revised version was published online in July 2006 with corrections to the Cover Date.     

FTIR spectroscopy and X-ray diffraction characterization of Nb doped sol-gel silica

Nb doped silica was prepared by the sol-gel method. The experimental variables were the pH (acidic and basic) and the Nb concentration (1.0–10.0 wt.%). The samples were calcined at 300°C and 600°C and analyzed by XRD, and FTIR. The TGA and DTA of the gels were also performed. From the XRD results the radial distribution function allowed us to establish the existence of the Si–O–Nb bond in the powders.     

X-ray emission and X-ray photoelectron studies of electron density distribution in Cu(II) complexes with 2-imidazoline nitroxides

Electron density distribution in Cu(II) complexes with 2-imidazoline nitroxides was investigated by X-ray emission and X-ray photoelectron spectroscopy. The structure of the highest occupied molecular orbital (HOMO) of the compounds is determined mainly by the interaction of the metal with the donor atoms of the ligands. Coordination of the nitroxide by the Cu(hfac)₂ acceptor matrix changes the shape of the CuL _α spectral line. The 3s X-ray photoelectron spectra provide evidence about the transfer of electron density to the copper atom in the complexes.     

Binary Systems of Nifedipine And Various Cyclodextrins in The Solid State. Thermal,FTIR, XRD studies

Nifedipine complexes with β-cyclodextrin (β-CD), γ-cyclodextrin (γ-CD), 2-hydroxypropyl-β-cyclodextrin (2HP-β-CD), randomly methylated-β-cyclodextrin (RM-β-CD) and heptakis(2,6-O-dimethyl)-β-cyclodextrin (DM-β-CD) have been prepared by both kneading and heating methods and their behaviour studied by differential scanning calorimetry (DSC), diffuse reflectance mid-infrared spectroscopy (FTIR) and X-ray diffractometry (XRD). DSC revealed the nifedipine melting endotherm with onset at approximately 171°C for the kneaded mixtures with β-CD, γ-CD and 2HP-β-CD, thus confirming the presence of nifedipine in the crystalline state, while some decrease in crystallinity was observed in the DM-β-CD kneaded mixture. With RM-β-CD, however, broadening and shifting of the nifedipine endotherm and reduction in its intensity suggested that the kneading could have produced an amorphous inclusion complex. These differing extents of interaction of nifedipine with the cyclodextrins were confirmed by FTIR and XRD studies. This revised version was published online in August 2006 with corrections to the Cover Date.     

Coordinating properties of [M(CO)5(CN)] [M=Cr; Mo; W] ligands: formation of ion pairs or dinuclear cyanide-bridged complexes, spectroscopic and X-ray diffraction studies

The reaction of sodium cyanopentacarbonylmetalates Na[M(CO)₅(CN)] (M=Cr; Mo; W) with cationic Fe(II) complexes [Cp(CO)(L)Fe(thf)][O₃SCF₃], [L=PPh₃ (1a), CN-Benzyl (1b), CN-2,6-Me₂C₆H₃ (1c); CN-Bu^t (1d), P(OMe)₃ (1e), P(Me)₂Ph (1f)] in acetonitrile solution, yielded the metathesis products [Cp(CO)(L)Fe(NCCH₃)][NCM(CO)₅] [M=W, L=PPh₃ (2a), CN-Benzyl (2b), CN-2,6-Me₂C₆H₃ (2c); CN-Bu^t (2d), P(OMe)₃ (2e), P(Me)₂Ph (2f); M=Cr, L=(PPh₃) (3a), CN-2,6-Me₂C₆H₃ (3c); M=Mo, L=(PPh₃) (4a), CN-2,6-Me₂C₆H₃ (4c)]. The ionic nature of such complexes was suggested by conductivity measurements and their main structural features were determined by X-ray diffraction studies. Well-resolved signals relative to the [M(CO)₅(CN)] moieties could be distinguished only when ¹³C NMR experiments were performed at low temperature (from −30 to −50 °C), as in the case of [Cp(CO)(PPh₃)Fe(NCCH₃)][NCW(CO)₅] (2a) and [Cp(CO)(Benzyl-NC)Fe(NCCH₃)][NCW(CO)₅] (2b). When the same reaction was carried out in dichloromethane solution, neutral cyanide-bridged dinuclear complexes [Cp(CO)(L)FeNCM(CO)₅] [M=W, L=PPh₃ (5a), CN-Benzyl (5b); M=Cr, L=(PPh₃) (6a), CN-2,6-Me₂C₆H₃ (6c), CO (6g); M=Mo, L=CN-2,6-Me₂C₆H₃ (7c), CO (7g)] were obtained and characterized by infrared and NMR spectroscopy. In all cases, the room temperature ¹³C NMR measurements showed no broadening of cyano pentacarbonyl signals and, relative to tungsten complexes [Cp(CO)(PPh₃)FeNCW(CO)₅] (5a) and [Cp(CO)(CN-Benzyl)FeNCW(CO)₅] (5b), the presence of ¹⁸³W satellites of the ¹³CN resonances (J_CW ∼ 95 Hz) at room temperature confirmed the formation of stable neutral species. The main ¹³C NMR spectroscopic properties of the latter compounds were compared to those of the linkage isomers [Cp(CO)(PPh₃)FeCNW(CO)₅] (8a) and [Cp(CO)(CN-Benzyl)FeCNW(CO)₅] (8b). The characterization of the isomeric couples 5a-8a and 5b-8b was completed by the analyses of their main IR spectroscopic properties. The crystal structures determined for 2a, 5a, 8a and 8b allowed to investigate the geometrical and electronic differences between such complexes. Finally, the study was completed by extended Hückel calculations of the charge distribution among the relevant atoms for complexes 2a, 5a and 8a.     

In situ FTIR spectroscopic study of the recently detected low‐temperature‐induced structural changes in isotactic polypropylene

The in situ Fourier transform infrared spectroscopic study of isotactic polypropylene showed that structural changes are induced at liquid nitrogen temperature, and start to show up in the FTIR spectra with heating from ?196 to +200 °C. This structural change leads to the detection of an abnormal behavior in the MIR absorption spectra of the investigated sample. Lowering the temperature brought the chains closer together and so increased the interchain interaction. At ?196 °C splitting of some regularity bands assigned to helical chains within the crystalline region was observed, showing that the regularity of the chains increases because of cooling. Heating the samples from liquid nitrogen temperature caused an opposite conformational disordering, which resulted in the appearance of several new broad bands in the ranges: 600–700, 1614–1640, and 3050–3550 cm^?1. These structural changes might be due to both twisting and folding of the chains, which gave rise to bands assigned to the various bending modes of CH₂ molecules, in addition to the rotational isomers (conformers) resulting from rotation of the vinyl and alkyne end groups. Moreover, our experimental study of the behavior of several regularity bands suggests that at temperatures in the vicinity of +120 °C another high temperature structural change resulting from the disordering of helical sequences in the noncrystalline region takes place. Differential scanning calorimetry thermograms of the thermally treated and an untreated sample were found to confirm the obtained results. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 2829–2842, 2005     

Phase behavior in mixtures of a homopolymer and a block copolymer 1. FTIR and DSC studies

Miscibility in blends of three styrene-butadiene-styrene and one styrene-isoprene-styrene triblock copolymers containing 28%, 30%, 48%, and 14% by weight of polystyrene, respectively, with poly(vinyl methyl ether) (PVME) were investigated by FTIR spectroscopy and differential scanning calorimetry (DSC). It was found from the optical clarity and the glass transition temperature behavior that the blends show miscibility for each kind of triblock copolymers below a certain concentration of PVME. The concentration range to show miscibility becomes wider as the polystyrene content and molecular weight of PS segment in the triblock copolymers increase. From the FTIR results, the relative peak intensity of the 1100 cm^-1 region due to COCH₃ band of PVME and peak position of 698 cm^-1 region due to phenyl ring are sensitive to the miscibility of SBS(SIS)/PVME blends. The results show that the miscibility in SBS(SIS)/PVME blends is greatly affected by the composition of the copolymers and the polystyrene content in the triblock copolymers. Molecular weights of polystyrene segments have also affected the miscibility of the blends. ©1995 John Wiley & Sons, Inc.     

醇和N,N-二甲基乙酰胺分子间相互作用的FTIR光谱研究

The association between alcohols and N,N-dimethylacetamide in carbon tetrachloride was investigated using FTIR spectroscopy at 298 K.The formation constants for 1∶1 and 1∶2 complexes were calculated using the method of Whetsel and Kagarise.The observed 1∶1 complex values were also verified using the method of Nash.The rate of change in C=O bond moment on complexing with alcohols increased with increasing acidity of alcohols.The formation constant and values of free energy change increased with the increase in carbon chain length of alcohols,which suggested that the degree of complex formation varied with the length of the carbon chain of alcohols.     

XRD and thermal studies of AgI confined in nm-size pores by forming porous silica-AgI composites

To investigate the nm-size dependence of structural and thermal properties for AgI, the formation of composites between AgI and porous silica with controlled pore diameters of 10, 15, 30, and 50 nm was examined. The introduction of AgI within the micropores of the porous silica was performed successfully by a salt-bridge precipitation method with using AgNO₃ and KI aqueous solutions. The AgI formed within the micropores was identified to be β/γ-AgI, independent of the pore size of 10-50 nm, by powder X-ray diffractometry. In differential scanning calorimetry, the composites showed thermal anomaly at around 150°C on heating due to the phase transition from β/γ -AgI to α -AgI as in the case of bulk crystalline AgI (T _trs=147°C). However, the transition temperature from α-AgI to β/γ -AgI on cooling decreased remarkably with the decrease of the pore size from 50 to 10 nm. The result indicates the possibility for AgI particles with diameter less than 10 nm to exist as α -AgI even below 100°C. This revised version was published online in July 2006 with corrections to the Cover Date.     

Mössbauer, vibrational spectroscopic and solution X-ray diffraction studies of the structure of iron(III) complexes formed with indole-3-alkanoic acids in acidic aqueous solutions

The chemical reactions between iron(III) and indole-3-acetic (IAA), -propionic (IPA), and -butyric (IBA) acids were studied in acidic aqueous solutions. The motivation of this work was that IAA is one of the most powerful natural plant-growth-regulating substances (phytohormones of the auxin series). Mössbauer spectra of the frozen aqueous solutions of iron(III) with indole-3-alkanoic acids as ligands (L), showed parallel reactions between Fe³⁺ and the ligands. Partly, it resulted in a complex formation which precipitated in aqueous solution and partly, in a redox process with iron(II) and the oxidised indole-3-alkanoic acids as products. The Mössbauer parameters of the Fe²⁺ species suggested a hexaaquo coordination environment. The chemical composition and coordination structure of the precipitated complexes were investigated using elemental analysis, Mössbauer spectroscopy, Fourier transform infrared (FTIR) and Raman spectroscopic techniques. The complexes were soluble in some organic solvents. So, Mössbauer, FTIR and solution X-ray diffraction measurements were carried out on the solution of complexes in acetone, hexadeutero acetone and methanol, respectively. The data obtained supported the existence of the μ-dihydroxo-bridging structure of the dimer: [L₂Fe<(OH)₂>FeL₂] (where L is indole-3-propionate, -acetate or -butyrate).     

Thermal and FTIR characterization of Cu/Si-Al and Cu-zeolite catalysts

Summary Thermal and FTIR studies on Cu/Si-Al by sol-gel and Cu/zeolite catalysts are compared by determining the effect of alumina and Cu incorporation into a SiO₂-Al₂O₃ and zeolite base support matrix. Hydroxyl groups formed during hydrolysis are more stable as the amount of alumina increases in the matrix. A proposed mechanism for metal incorporation involving the effect of alumina incorporation into the matrix is presented. This mechanism may explain the formation of different Cu-based structures.     

自组装金电极的电化学测试及其FTIR和AFM分析

利用交流阻抗谱测试了自组装免疫电极的抗原响应特性，对生物电极解离过程的机理进行了研究，用傅里叶变换红外反射光谱（FTIR）和原子力显微镜（AFM）对电化学实验过程进行了直观观测和定量分析。     

FTIR spectroscopic studies of layer systems transferred onto germanium supports

An ATR attachment was adapted to a FTIR spectrometer. The increased sensitivity makes it possible to measure spectra of transferred monolayers. The characteristic vibrational frequencies of the transferred multilayer systems of two different substance types (octadecanoic acid, octadecylamine) were investigated in dependence on the layer number. A direct correlation between the absorbance and the transferred substance quantity was found. The absence of interaction between the first layer and the germanium surface was evidenced by the lack of a difference between multilayer spectra divided by the layer number, and the measured spectrum of one layer.     

Electrochemical and FTIR spectroscopic studies of tyrosine oxidation at polycrystalline platinum surfaces in alkaline solutions

The electrochemical oxidation of tyrosine has been studied on polycrystalline platinum in sodium hydroxide using cyclic voltammetry and in situ Fourier transform infrared spectroscopy (FTIRS). According to infrared data, the first interaction of tyrosine through the carboxylate group on platinum is proposed. The results showed an onset for tyrosine oxidation at ca. 0.5 V with the formation of soluble formate ion as product. The sharp increase in the current vs potential slope from ca. 1.1 V obeys the detection of cyanate ions together with p-(methyl)-phenoxide ions. No adsorbed carbon monoxide as well as carbon dioxide was detected by this methodology in the whole studied potential range. These results contrast with those obtained in acid solution where two parallel reactions, one yielding the γ-lactone of hydroxy benzofurane and the other producing p-benzoquinone occurs for the oxidation of tyrosine on platinum. Dedicated to Prof. Dr. Teresa Iwasita on the occasion of her 65th birthday in recognition of her numerous contributions to interfacial electrochemistry.     

Confined rapid thermolysis/FTIR/ToF studies of imidazolium-based ionic liquids

Rapid scan FTIR spectroscopy and time-of-flight (ToF) mass spectrometry were utilized to study thermal decomposition of three imidazolium-based ionic liquids, with 1-ethyl-3-methyl-imidazolium (emim) as the cation, and NO₃⁻, Cl⁻, and Br⁻ as the anions. The thermal decomposition involved heating rates of 2000 K/s and temperatures to 435 °C in an ambient inert gas at 1 atm. Using sub-milligram quantities of each compound, examinations of the evolution of gas-phase species revealed that the most probable sites for proton transfer and subsequent secondary reactions were primarily the methyl group and secondarily the ethyl group. The ring appeared to remain intact, as there was no evidence of the formation of HCN, imines or related products. The most reactive compound is [emim]NO₃, since the nitrate group served as a strong oxidizer and reacted strongly with the methyl/ethyl groups at the elevated temperatures to produce common final products from combustion.     

Determination of low levels of free fibres of chrysotile in contaminated soils by X-ray diffraction and FTIR spectroscopy

A new analytical method for the determination of low levels (0.01–1 wt%) of free fibres of chrysotile in contaminated clayey, sandy and sandy-organic soils is described. The detection limit of 0.01 wt% is reached with an enrichment of free fibres of chrysotile in the sample using a standard laboratory elutriator for sedimentation analysis. The chrysotile quantitative determination is performed both by X-ray powder diffraction, using the internal standard and reference intensity ratio methods, and by Fourier-transform infrared absorption spectroscopy. The procedure can be successfully applied to different soils after removal, by a thermal treatment, of the matrix components which can interfere. This straightforward method fulfils the request of public institutions and private companies for an appropriate quantitative determination of chrysotile-free fibres in contaminated soils.     

DSC and X-ray studies on side-chain crystallization of comb-like polymers

Thermal properties of acrylate and methacrylate monomers containing long-fluorocarbon chains (H(CF₂)_nCH₂OCOCH=CH₂, (F_nA) and H(CF₂)_nCH₂OCOC(CH₃)=CH₂, (F_nMA), wheren=6, 8, 10) and their comb-like polymers have been investigated by differential scanning calorimeter (DSC) and X-ray diffraction. The comb-like polymers (PF₁₀A and PF₁₀MA) with sufficiently long-fluorocarbon chains showed a simple melting and crystallizing behavior. For the fusion of PF₁₀A in 1st heating, enthalpy change H _f was 18 kJ mol^–1 and entropy change S _f was 45 J K^–1 mol^–1, while for PF₁₀MA the values H _f and S_f were 5.3 kJ mol^–1 and 14 J K^–1 mol^–1, respectively. Melted PF₈A crystallized slowly, whereas PF₈MA with same fluorocarbon chain and also both of PF₆A and PF₆MA with shorter fluorocarbon chains can hardly crystallize by the aggregation of side-chains. Effects of the length of side-chain and the flexibility of main chain on the side-chain crystallization of comb-like polymers are clear. Crystallization process of the methacrylate monomers was sensitively affected by the scanning rate of DSC measurement and the length of fluorocarbon chains.     

Intramolecular carbonyl?carbonyl interactions in W, Mo and Fe complexes containing the η-N-maleimidato ligand: X-ray, DFT and AIM studies

The crystal structures of (η⁵-C₅H₅)W(CO)₃(η¹-N-maleimidato) and (η⁵-C₅H₅)Fe(CO)₂(η¹-N-maleimidato) complexes were determined by single crystal X-ray diffraction. The molecular geometries of both structures are compared with those of the Mo analog of the W complex and ethyl-N-maleimide in order to find a relation between the geometrical features and the rate constants of the addition reaction of the sulfhydryl group of biomolecules to the ethylenic bond of the maleimidato fragment. For a deeper insight into the problem DFT calculation were performed. An analysis of atomic charges, using the CHELPG scheme, and of theoretical electron density function, using the AIM theory, was performed. In the (η⁵-C₅H₅)W(CO)₃(η¹-N-maleimidato), likewise in its Mo analog, the carbonyl?carbonyl interaction was found both for experimental and calculated structures. It is probably the first approach to explain this type of intramolecular interactions acting in organometallic compounds. This interaction can play the essential role in the reaction mechanism of nucleophilic addition to the maleimidato moiety. The AIM investigations indicate also the differences in the character of bonding between the η-N-maleimidato ligand and the central metal atom.