Preparation and structural studies on the Bu2Sn(IV) complexes with aromatic mono- and dicarboxylic acids containing hetero {N} donor atom

Nine complexes of ^tBu₂Sn(IV)²⁺ were obtained in the solid state with ligands containing -COOH group(s) and aromatic {N} donor atom. The binding sites of the ligands were identified by FT-IR spectroscopic measurements. It was found that in most cases the -COO⁻ groups are co-ordinated in monodentate manner. Nevertheless, in some of our complexes, the -COO⁻ group forms bridges between two central {Sn} atoms resulting in the formation of an oligomeric structure, a motif that is characteristic only to the nicotinate compound. These pieces of information and the rationalisation of the experimental ¹¹⁹Sn Mössbauer nuclear quadrupole splittings, Δ, - according to the point charge model formalism - support the formation of octahedral (O_h) or trigonal bipyramidal (TBP) molecular structures. The X-ray diffraction analysis of one complex obtained as single crystal revealed the distortion of the TBP geometry towards square pyramidal (SP) one. This was rationalised by PM3 molecular modelling of the ^tBu₂Sn(pdc) complex. In the asymmetric unit, the two chemically similar but symmetry independent molecules form pseudo-dimers, in which the Sn?Sn separation amounts to ca. 6.4 Å. The crystal lattice is stabilised by C-H?O hydrogen bonding between individual molecules.     

Thermal characteristics of polyurethane foams incorporated with phase change materials

Thermal energy storage plays an important role in heat management because of the demand for developed energy conservation, and has applications in diverse areas, from building heating/cooling systems which enable solar energy incorporation into the structure, to textiles and clothings providing an enhanced thermal comfort. In this study, we aimed to improve thermal characteristics of polyurethane rigid foams that have been widely used for thermal insulation as the ultimate energy savers due to their ability to form sandwich structures with various facer materials. Through a laboratory-scale work, two paraffin waxes acting as phase change materials, namely n-hexadecane and n-octadecane, each of which is capable of managing large heat storage/release, were directly incorporated into the polyurethane foams at different ratios. Polymerization modified by means of n-alkane addition could be achieved without any adverse effect. In order to determine both structural and thermal characteristics, seven types of foams produced were examined by FT-IR, SEM, DSC analyses, calorimeter bomb and mechanical tests. Results show that polyurethane foams can be designed as thermal insulators equipped with an improved buffering function against temperature changes.     

Ag-MoO3催化丙烯直接气相环氧化反应的原位红外研究

制备了对丙烯直接气相环氧化具有较好催化性能的Ag-MoO3催化剂, 采用原位FT-IR技术研究了丙烯、环氧丙烷及丙烯+氧气的混合气在Ag和Ag-MoO3催化剂表面上的吸附及反应行为. 研究表明, 丙烯在Ag和Ag-MoO3催化剂表面上吸附后, 均不发生化学反应, 而环氧丙烷吸附后在较高温度下则发生开环和聚合反应直至产生积炭. 与Ag催化剂相比, 在Ag-MoO3催化剂上, MoO3的加入在降低催化剂活性的同时, 在一定程度上抑制了产物环氧丙烷的开环及深度反应, 使环氧丙烷的选择性提高. 另外, 在较低的反应温度和较短的滞留时间下, 环氧丙烷发生深度反应的程度明显降低.     

Characterization of cyclodextrin-modified infrared chemical sensors: Part I. Modeling the mechanisms of interaction

To explore the properties of cyclodextrins (CDs) as an optical sensing phase, the behavior of immobilized CD in interaction with analytes was studied in this work. CDs having different cavity sizes were immobilized onto the surface of infrared (IR) internal reflection-sensing element (IRE) to kinetically monitor the behavior of CD in interaction with analytes. Several aromatic compounds having various molecular sizes and functional groups were used to characterize the interaction mechanism. A two-layer modification method was proposed in this work, which utilized a thin hydrophobic film (polyvinyl benzyl chloride) to stick on the IRE and to covalently bond to the CDs through an ethylene diamine linker. The synthesized CD phases exhibited high stability in aqueous solution. To analyze the behavior during the formation of complexes between the guest molecules and the CD phases, we modeled the interaction behavior and treated the kinetic data with the theoretical equations developed in this work. The results indicate that the behavior of the interaction between guest molecules and CDs was explained by considering the formation of two types of complexes: adsorbed complexes and inclusion complexes. The formation of the inclusion complexes was relatively fast, the time required to reach equilibrium could be shorter than a few minutes. The adsorbed complexes were also observed, but their rate of formation was relatively slow; equilibrium could be reached at times greater than 60 min. Based on the signals observed under equilibrium conditions, the concentration of inclusion complexes was approximately three times than that of the adsorbed complexes.     

H2S-sensing properties of SnO2 produced by ball milling and different chemical reactions

In this work, the mechanochemical synthesis of a moderately agglomerated tin oxide (SnO₂) powders and the subsequent preparation of semiconductor gas sensors as prototypes, were studied. Tin (II) chloride (SnCl₂) powder was milled with calcium hydroxide (Ca(OH)₂) and potassium carbonate, (K₂CO₃) powder, respectively, in a ball mill at room temperature and in an air atmosphere. Heat treatment of milled mixtures at 400 °C resulted in the formation of a tetragonal phase, confirmed by X-ray diffraction (XRD). During milling in the presence of water, a high number of hydroxide (OH) groups are formed at the surface. When SnCl₂ was milled with K₂CO₃, no water was produced and the Fourier-transform infrared spectrum (FT-IR) of the powder has no surface hydroxyl deformations. On exposure to hydrogen sulfide (H₂S) gas, the particles, prepared from anhydrous powder, have higher sensitivity than these, prepared from hydrated powder. The SnO₂ thick film, prepared from anhydrous powder may be successfully applied to a H₂S gas sensor.     

DSC,FT-IR and NIR with Chemometric Assessment Using PCA and HCA for Estimation of the Chemical Stability of Oral Antidiabetic Drug Linagliptin in the Presence of Pharmaceutical Excipients

Pharmaceutical excipients should not interact with active substances, however, in practice, they sometimes do it, affecting the efficacy, stability and safety of drugs. Thus, interactions between active substances and excipients are not desirable. For this reason, two component mixtures of oral antidiabetic drug linagliptin (LINA) with four excipients of different reactivity, i.e., lactose (LAC), mannitol (MAN), magnesium stearate (MGS) and polyvinylpyrrolidone (PVP), were prepared in a solid state. A high temperature and a high humidity of 60 °C and 70% RH, respectively, were applied as stressors in order to accelerate the potential interactions between LINA and excipients. Differential scanning calorimetry (DSC) as well as Fourier transform infrared (FT-IR) and near infrared (NIR) spectroscopy were used to estimate the changes due to potential interactions. In addition, chemometric computation of the data with principal component analysis (PCA) and hierarchical cluster analysis (HCA) was applied to adequately interpret the findings. Of the excipients used in the present experiment, all of them were not inert in relation to LINA. Some of the interactions were shown without any stressing, whereas others were observed under high-temperature/high-humidity conditions. Thus, it could be concluded that selection of appropriate excipients for LINA is very important question to minimize its degradation, especially when new types of formulations with LINA are being developed and manufactured.     

FT-IR和HPLC对不同产地大黄药材的鉴别分析

目的 采用傅里叶变换红外光谱(FT-IR)和高效液相色谱(HPLC)方法对37批不同品种和产地的大黄药材进行分析.方法 分别采用FT-IR和HPLC测量37批大黄药材的红外光谱和液相指纹图谱,并对结果进行聚类分析.从每一产地中选择一批药材,分析红外原始光谱,并对原始光谱进行二阶导数处理,根据所得二阶导数光谱对各产地大黄...     

Non-Destructive Analysis of Chlorpheniramine Maleate Tablets and Granules by Chemometrics-Assisted Attenuated Total Reflectance Infrared Spectroscopy

Non-destructive analysis of chlorpheniramine maleate (CPM), pharmaceutical tablets, and granules was conducted by chemometrics-assisted attenuated total reflectance infrared spectroscopy (ATR-IR). For tablets, an optimum PLSR model with eight latent factors was obtained from area-normalized and standard normal variate (SNV) pretreated ATR-IR spectral data with correlation coefficients (R²) of calibration and cross-validation of 0.9716 and 0.9602, respectively. The model capability for the 42 test set samples was proven with R² between the reference and model prediction values of 0.9632, and a root-mean-square error of prediction (RMSEP) of 1.7786. The successive PLSR model for granules was constructed from SNV and first derivative pretreated ATR-IR spectral data with two latent factors and correlation coefficients (R²) of calibration and cross-validation of 0.9577 and 0.9450, respectively.     

FT-IR Method Limitations for β-Glucan Analysis

β-glucans are known as biological response modifiers. However, different sources can result in structural differences and as a result differences in their biological activity. The hot water extraction method allows to obtain, high molecular weight β-glucans without altering their structure by using strong chemicals, such as alkalis or acids. Analysis of β-glucans by FT-IR and NMR spectroscopy in solid state is superior to analysis in solution as it allows researchers to study the preserved structure of the extracted polysaccharides. FT-IR spectroscopy was used in this study to make side-by-side comparison analysis of hot water extracted β-glucans from different yeast sources. NMR spectroscopy was used to confirm findings made by FT-IR spectroscopy. Extracted β-glucans exhibit characteristic structure of β-1,3/1,6-linked glucans with noticeable levels of proteins, possibly in a form of oligopeptides, chitin and other impurities. β-glucans obtained from C. guilliermondii, P. pastoris and S. pastorianus exhibited higher protein content. Differences in mannan, chitin and α-glucan content were also observed; however, the species-specific structure of obtained β-glucans could not be confirmed without additional studies. Structural analysis of high molecular weight β-glucans in solid state by FT-IR spectroscopy is difficult or limited due to band intensity changes and overlapping originating from different molecules.     

蓝色圆珠笔字迹色痕FTIR光谱解析

本文系统解析了１０８种油墨色痕的傅立叶变换显微红外谱图。根据红外谱图的特征峰,识别了油墨中的溶剂、色科、树脂等组分,这为字迹色痕形成时间的无损分析奠定了基础。