Solid-state 13C NMR Spectroscopy Research Articles

Crystal structure of rilpivirine hydrochloride, N6H19C22Cl

A monoclinic C form of rilpivirine hydrochloride, (N6H19C22)Cl, has been obtained and characterized using solid-state 15N, 13C, and 35Cl NMR spectroscopy and multitemperature synchrotron X-ray powder diffraction. The title compound crystallizes in the monoclinic system (space group C2/c, #15) at both room (295.0(2) K) and low (100.0(2) K) temperatures. At room temperature, the following parameters are a = 19.43051(3), b = 13.09431(14), c = 17.10254(18) Å, β = 109.3937(7), V = 4104.48(9) Å3, and Z = 8. The folded molecular conformation of the cation is similar with that of free base rilpivirine with the exception of cyanovinyl group disposition. The anion links cations to infinite chains parallel to the crystallographic c axis using N–H⋯Cl bonds where both amino groups and the protonated pyrimidine ring take part in the H-bonding. The powder patterns have been submitted to the ICDD for inclusion in the Powder Diffraction File™ (PDF®).

Opposing patterns of carbon and nitrogen stability in soil organic matter fractions compared to whole soil

AbstractNitrogen (N) released from soil organic matter (SOM) is quantitatively important for crop uptake, even when adequate fertiliser N is supplied. Understanding of SOM has shifted to recognise distinct fractions that correlate with properties such as turnover time, carbon (C) and N content, and chemical composition. Yet, how these fractions relate to N supply from SOM is poorly understood. This study aimed to link N mobilisation and C stability in coarse (≥50 μm) and fine (≤50 μm) fractions, and evaluate the roles of these fractions in supplying N in cropping soil. Soils from long‐term continuous cotton, cotton‐vetch, and cotton‐wheat rotations and a nearby uncleared site (NV) were separated into coarse and fine fractions, left as whole soil, or dispersed and freeze‐dried as a fractionation control. Initial C chemistry in fractions and whole soils was measured by solid state 13C NMR spectroscopy. N mobilisation and CO2 loss were measured over a 14‐day incubation experiment. In the cropping soils, net immobilisation of N was measured in the separate fractions, while net mobilisation was found in the whole soils. In the NV soil, N mobilisation was greater in the fine fraction. C mineralisation followed the order fine fraction > fractionation control = coarse fraction > whole soil. C stability was best explained by physical protection within whole soil structure rather than chemical recalcitrance or mineral stabilisation. The results revealed an unexpected contrast between C and N mineralisation from SOM fractions and demonstrated the importance of soil aggregates for SOM stability. We show a cautionary impact of fractionation on C and N dynamic, highlighting the need for further research to understand the synergistic behaviour of SOM fractions in whole soils.

Single-Step Synthesis and Characterization of Non-Linear Tough and Strong Segmented Polyurethane Elastomer Consisting of Very Short Hard and Soft Segments and Hierarchical Side-Reacted Networks and Single-Step Synthesis of Hierarchical Hyper-Branched Polyurethane.

Polyurethane elastomers are among the most versatile classes of industrial polymers-typically achieved through a two-step synthesis of segmented block copolymers, comprising very long and soft segments that provide elasticity and significantly long and hard segments that provide strength. The present research focused on the design of a single-step synthesis of a new segmented polyurethane consisting of very short soft and hard segments, crosslinked by preferentially side-reacted hierarchical tertiary oligo-uret network structures, thus exhibiting significant strength, elasticity, and toughness. Despite the theoretically linear structure, both FTIR and solid-state 13C NMR spectroscopy analyses indicated the quasi-equal presence of urethane groups and tertiary oligo-uret structures in the resulting polymer, indicating a preferential consecutive side reaction mechanism. Thermal analysis indicated the significant crystallization of soft segments consisting of only four ethylene oxide units, which was, hereby, demonstrated to occur via an extended chain mechanism. Tensile mechanical properties included significant strength, elasticity, and toughness. Increasing the soft segment length led to a decreased tertiary oligo-uret secondary crosslinking efficacy. The preferential hierarchical side reaction mechanism was, hereby, further confirmed through the synthesis of a completely new type of hyper-branched polymer via diisocyanate and a mono-hydroxy-terminated reagent. The structure-property relations and reaction mechanisms demonstrated in the present research can facilitate the design of new polyurethanes of enhanced performance and processing efficacy for a variety of novel applications.

Biomass derived cellulose nanofiber loaded PVA-nanocurcumin coating for extending the shelf life of Mandarin oranges (Citrus reticulata)

The concern over agricultural waste disposal can be resolved by converting them into value-added products. Here, sustainable fruit coatings and films have been developed via. wealth from waste concept. The cellulose nanofibers (CNF) have been extracted from the waste onion skin. The isolated CNF has been characterised using scanning electron microscopy (SEM), transmission electron microscopy (TEM), optical microscopy (OM), dynamic light scattering (DLS) and solid-state 13C NMR spectroscopy. A combination of cellulose nanofiber (CNF) and nanocurcumin in polyvinyl alcohol (PVA) matrix has been used for the fabrication of coating over fresh mandarin oranges. The effect of nanocurcumin in PVA-CNF nanocomposite on the post-harvest maintenance of mandarin oranges has been investigated. The morphology of the prepared films is studied by SEM and atomic force microscopy (AFM). The quality of the orange fruits coated using the above formulation by dip coating method was analysed via. weight loss analysis, total soluble solid (TSS), pH, titrable acidity (TA) and antioxidant activities. It was found that the nanocurcumin incorporated PVA-CNF coating was effective in reducing mass loss and maintaining the physiochemical properties of oranges in comparison with other formulations. The developed method could be extended to use as food packaging films, which would be a sustainable solution for agricultural waste valorisation and plastic pollution. Through this research work, we propose an environment friendly approach for the preservation of fruits and vegetables.

Biodegradable Nanocomposites Based on Blends of Poly(Butylene Adipate-Co-Terephthalate) (PBAT) and Thermoplastic Starch Filled with Montmorillonite (MMT): Physico-Mechanical Properties.

Poly(butylene adipate-co-terephthalate) (PBAT) is widely used for production of biodegradable films due to its high elongation, excellent flexibility, and good processability properties. An effective way to develop more accessible PBAT-based bioplastics for wide application in packaging is blending of PBAT with thermoplastic starch (TPS) since PBAT is costly with prices approximately double or even triple the prices of traditional plastics like polyethylene. This study is focused on investigating the influence of TPS/PBAT blend ratio and montmorillonite (MMT) content on the physical and mechanical properties and molecular mobility of TPS-MMT/PBAT nanocomposites. Obtained TPS-MMT/PBAT nanocomposites through the melt blending process were characterized using tensile testing, dynamic mechanical thermal analysis (DMTA), and X-ray diffraction (XRD), as well as solid-state 1H and 13C NMR spectroscopy. Mechanical properties demonstrated that the addition of TPS to PBAT leads to a substantial decrease in the tensile strength as well as in the elongation at break, while Young's modulus is rising substantially, while the effect of the MMT addition is almost negligible on the tensile stress of the blends. DMTA results confirmed the formation of TPS domains in the PBAT matrix. With increasing TPS content, mobility of starch-rich regions of TPS domains slightly increases. However, molecular mobility in glycerol-rich regions of TPS domains in the blends was slightly restricted. Moreover, the data obtained from 13C CP/MAS NMR spectra indicated that the presence of TPS in the sample decreases the mobility of the PBAT chains, mainly those located at the TPS/PBAT interfaces.

Unexpected high alkyl carbon contents in organic matter-rich sandy agricultural soils of Northwest Central Europe

Carbon sequestration in Plaggic Anthrosols is most often investigated by bulk soil carbon inventories, without considering the form in which the carbon is stored (e.g., particulate or mineral-associated organic matter (OM), its capacity, or its chemical composition). Here, we focus on the unusual high organic carbon (OC) accumulation in sandy Plaggic Anthrosols and adjacent reference soils under agricultural use. In these soils, the mineral fraction ≤20 µm which is commonly assumed to be the major factor for OC stabilization, are very low in mass proportion. Soil organic matter (SOM) physical fractionation was done to evaluate the quantity and quality of OC in the topsoil (Ap horizon). For the fraction ≤20 µm (medium and fine silt-, and clay-sized particles), we measured the concentration of OC and calculated its OC storage capacity and contribution. The OC of the fraction ≤20 µm was radiocarbon-dated and analyzed for its chemical composition by solid-state 13C NMR spectroscopy. The highly sandy (∼90 % sand and coarse silt) soils showed an accumulation of OC much higher than the conventionally calculated saturation level controlled by the proportion of the fraction ≤20 µm. Unexpectedly, Plaggic Anthrosols and the respective reference soils showed similar fractional OC concentrations, radiocarbon ages, and OM composition. The isolated fraction ≤20 µm contained, on average, 81 % of the total soil OC in only 9 % of the corresponding soil mass. All soil fractions ≤20 µm are characterized by a high mean OC concentration in the topsoil (reference soils: 226 ± 66.5 mg OC g−1, Plaggic Anthrosols: 202 ± 59.0 mg OC g−1) with a C/N ratio of 15 on average for both soils. The OM composition of the fraction ≤20 µm was specifically rich in alkyl-C, with unusually low proportions of O-alkyl-C and low contents of aryl-C. The radiocarbon concentration (F14C) indicated that topsoil OM of the ≤20 µm fraction is stored for long time periods with high mean conventional radiocarbon ages (14C) not only for Plaggic Anthrosols (F14C: 0.92 ± 0.04; 14C: 639 yBP) but also for the reference soils (F14C: 0.93 ± 0.04; 14C: 575 yBP) and received low inputs of OC derived from recent photosynthesis. Our data indicate the existence of specific SOM accumulation processes in the investigated sandy agricultural soils, resulting particularly large SOM stocks which cannot be explained by mechanistic association of OM with mineral surfaces. It is not clear, if this inherited OM is stable under present-day soil and management conditions.

Hexakis-2-(β-carboxyethenylphenoxy)cyclotriphosphazene: Synthesis, Properties, Modeling Structure.

Condensation of hexakis-2-(formylphenoxy)cyclotriphosphazene with malonic acid yielded hexakis-2-(β-carboxyethenylphenoxy)cyclotriphosphazene (2-CEPP), whose structure was confirmed by 31P, 1H, 13C NMR spectroscopy and MALDI-TOF mass spectrometry. A quantum-chemical calculation for the 2-CEPP molecule using the ab initio methods in the 6-311G** basis set and the DFT-PBE0/6-311g** method was performed with geometry optimization of all parameters by the standard gradient method. The acid strength of 2-CEPP was theoretically estimated. Using the small-angle X-ray scattering method, it was found that 2-CEPP is an amorphous substance, which, when heated, can transform into a crystalline state. However, when heated at 370 °C, 2-CEPP undergoes decarboxylation and polymerization to form an insoluble heat-resistant product. The occurrence of decarboxylation and polymerization reactions in the formed styrene fragments was confirmed by thermal (differential-scanning calorimetry) and spectral (solid-state 13C NMR spectroscopy) analysis.

Metal- and Peroxide-Free Silicone Rubbers with Antibacterial Properties Obtained at Room Temperature

Metal- and peroxide-free silicone rubbers were obtained via a reaction between amino-containing poly(dimethylsiloxanes) (amino-terminated (APDMS-1) or a copolymer with pendant amino groups (APDMS-2)) and iodine-containing polysiloxanes (PIMSs) (Menshutkin reaction). Simple mixing of functional polymers at room temperature resulted in forming silicone materials. The formation of ammonium cross-links was confirmed using solid-state 1H and 13C NMR spectroscopy. The equimolar ratio of NH2 groups to the I-containing moiety (1:1) was the most optimal among other ratios (2:1 and 1:2) to carry out cross-linking and led to the highest cross-linking density according to the swelling measurements. PIMS/APDMS-1 (1:1) rubbers had the lowest average molecular weight of segments between cross-links Mc = 250 compared to PIMSs/APDMS-1 (1:2) and (2:1) with Mc = 1110 and 390, respectively. The obtained silicone rubbers showed antibacterial activity against Escherichia coli and Staphylococcus aureus and thereby could be applied in biomedicine and the food industry as antibacterial coatings and materials.

Chemical Structure of Organic Matter of Agrochernozems of Different Alocalization on the Slope

The chemical structure of organic matter (OM) pools in agrochernozems confined to different zones of denudation-accumulation has been studied by solid-state 13C-NMR spectroscopy. It was revealed that in the erosion zone there are two competing processes occurring simultaneously: the decomposition of the “old” OM of the earlier underlying horizon and the stabilization of the fresh OM that has arrived with plant remains of cultivated plants (dynamic replacement of OM). Analytical data allow us to assert that the processes of dynamic replacement of eroded OM in the erosive zone quite effectively compensate for the processes of OM decomposition, as evidenced by the highest C/N ratio of all the studied OM pools in the eroding agrochernozem, along with the absence of significant differences in the integral indicators of their chemical structure. However, the constant removal of the upper soil layer from the eroding agrochernozem during each erosion event does not allow one to fully compensate for the OM quantitative losses in it. During the transportation of eroded material to the accumulative zone, the most labile part of OM can be mineralized. Accordingly, the OM again entering the accumulative zone is more transformed than that of the eroding agrochernozem. Nevertheless, the alluvial agrochernozem is characterized by an increased level of C accumulation in the soil as a whole and in all the studied OM pools. Accordingly, it can be stated that the constant OM inputs from the eroding position with its subsequent burial with each subsequent erosion event, as well as the repacking/aggregation of newly deposited OM, very effectively contribute to the deposition of C in the accumulative zone.

Combined liquid hot water and sulfonation pretreatment of sugarcane bagasse to maximize fermentable sugars production

Sugarcane bagasse (SCB) is a widely available biomass feedstock currently used for ethanol production in various parts of the world. Here, we carried out a combined liquid hot water and neutral/alkaline sulfonation pretreatments of SCB at relatively low temperatures to maximize enzymatic hydrolysis yields. To describe multi-step pretreatments severities, analytical equations for modified combind severity factors (CSF´m) were introduced. Although the chemical composition of SCB after the liquid hot water pretreatment alone has not been significantly changed under tested conditions, this pretreatment led to an increase in the efficiency of its enzymatic hydrolysis. Furthermore, a combination of liquid hot water pretreatment (at 120 °C for 1 h) and sulfonation of SCB (at 120 °C for 2 h) resulted in excellent enzymatic hydrolysis yields. After alkaline sulfonation, glucose yields reached 99.6 ± 0.21% for autoclaved and alkaline sulfonated bagasse (AASB) and 97.47 ± 0.75% for boiled and alkaline sulfonated bagasse (BASB), whereas xylose yields were 86.9 ± 1.9% and 88.0 ± 1.8% for AASB and BASB, respectively. High enzymatic hydrolysis yields are in line with elevated CSF´m of the latter pretreatments. X-ray diffraction, confocal laser scanning microscopy, and solid-state 13C NMR spectroscopy analyses showed that the structural desorganization of bagasse after liquid hot water pretreatment associated to chemical modifications of lignin and its massive removal promoted by alkaline sulfonation led to efficient separation of carbohydrates and lignin, revealing underlying structural reasons of the observed efficient enzymatic hydrolysis.

A facile approach to undecylenic acid-functionalized stationary phases for per aqueous liquid chromatography

Green chromatography techniques using low-toxic mobile phase are getting increasingly attention in recent years. The core is developing stationary phases that possess adequate retention and separation under the mobile phase of high content water. Using thiol-ene click chemistry, an undecylenic acid-bonded silica stationary phase (UAS) was prepared in a facile manner. Elemental analysis (EA), solid-state 13C NMR spectroscopy and Fourier transform infrared spectrometry (FT-IR) confirmed the successful preparation of UAS. The synthesized UAS was employed for per aqueous liquid chromatography (PALC), which uses little organic solvent during separation. Due to the hydrophilic carboxy, thioether group and hydrophobic alkyl chains of the UAS, various categories of compounds (including nucleobases, nucleosides, organic acids and basic compounds) with different properties can achieve enhanced separation under the mobile phase of high content water compared with commercial C18 and silica stationary phases. Overall, our present UAS stationary phase shows excellent separation ability toward highly polar compounds and meets the requirements of green chromatography.

Solvent-free functionalization of sawdust with quaternary ammonium groups: Application to the biosorption of two anionic dyes

The improvement of sawdust reactivity through simple chemical modification strategies represent an interesting method to extend the field of application or improve the natural performances of this abundant and available waste. In this work, sawdust was modified with Glycidyltrimethylammonium chloride (GTAC), an organic compound bearing a quaternary ammonium group. The objective was to obtain a modified sawdust with a permanent cationic charge. The modification of the material was confirmed by solid state 13C NMR and FTIR spectroscopy. The anion exchange capacity of modified sawdust (Sa-G) was demonstrated by the ability of sawdust to exclusively adsorb cations before modification and anions after modification. This anionic exchange property was applied for the adsorption of two anionic dyes (Procion Red MX-5B (PR) and Evans Blue (EB)). Generally, the material was more effective in acidic conditions due to the acid-base properties of sawdust. Compared to EB, the less charged and smaller PR adsorbs more quantitatively on the material and with faster kinetics (Equilibrium reached after only 30 min, while more than 24 h were needed in the case of EB). Thermodynamic study also reveals an exothermic process in the case of PR and endothermic in the case of EB. Under optimal conditions, the maximum adsorption capacities were 121.8 μmol g−1 for PR and 103.1 μmol g−1 for EB. Desorption tests showed that the material can be recycled by desorption of dyes in 0.1 M sodium hydroxide solution. After 5 adsorption-desorption cycles performance losses of only 15% for EB and 30% for PR were recorded.

Solid state 13C NMR spectroscopy as a tool for identification of counterfeit Viagra tablets and guide for develop new identification approach of falsified product

Counterfeit drugs are a global problem that is directly related to the safety and effectiveness of pharmacotherapy. The black market for counterfeit products is constantly growing and related to the wide availability through online shopping. Therefore, there is a constant need to develop analytical methods that would allow for the unambiguous identification of counterfeit products from the original ones. One of such techniques is solid-state NMR spectroscopy, which allows for direct registration and analysis of spectra of multicomponent solid forms of pharmaceutical formulations. The paper explores the possibility of using this technique in the identification of counterfeit Viagra tablets. In this study, solid-state NMR has been used to detect the non-pharmacopoeial cellulose present in the samples of counterfeit Viagra tablets. Besides, the NMR results allowed to develop a rapid dying technique that can be used to distinguish between the counterfeit and original drug. It has been shown that solid-state NMR spectroscopy allows for numerous analyses such as identification of counterfeit products, assessment of the composition of analyte, estimation of qualitative differences between the original and falsified product, and the development of simple analytical methods based on tablets composition differences.

An Ultrastable Tetrabenzonaphthalene-Linked conjugated microporous polymer functioning as a high-performance electrode for supercapacitors

BackgroundConjugated microporous polymers (CMPs) have been applied widely in several energy storage applications. Triphenylamine derivatives are good electrode materials that can be processed into SC devices because of their high charge mobilities, unique electronic properties, and high redox activity. MethodsWe prepared two novel tetrabenzonaphthalene-linked conjugated microporous polymers (TBN-pH CMPs) through [4 + 2] and [4 + 3] Schiff-base condensations of 2,7,10,15-tetra(4-formylphenyl)tetrabenzonaphthalene (TBN-PhCHO) with tetrakis(4-aminophenyl)ethene (TPE-4NH2) and tris(4-aminophenyl)amine (TPA-3NH2), respectively. Fourier transform infrared, and solid-state 13C NMR spectroscopy investigated the structures of the as-prepared CMPs. Significant FindingsThese CMPs, had large surface areas and outstanding thermal stability at temperatures of up to 400 °C, making them suitable for use as electrodes in supercapacitor (SC) systems. Indeed, the TBN-TPA CMP–based electrode had high specific capacitances (251 F g− 1 measured at 0.5 A g–1) and capacity retentions (94%, measured after 5000 cycles at 10 A g–1) when tested in three-electrode systems. We attribute the remarkable electrochemical activity and conductivity of the TBN-TPA CMP electrode to its large specific surface area (230 m2 g–1) and chemical structure featuring stacking of the benzene rings of its redox-active triphenylamine moieties.

Inclusion complex of ketoconazole and p-sulfonic acid calix[6]arene improves antileishmanial activity and selectivity against Leishmania amazonensis and Leishmania infantum

Many previous studies presented the effectiveness of ketoconazole (KTZ) against leishmaniasis. However, the bioavailability and therapeutic efficacy of free KTZ are limited due to its low aqueous solubility. In this study, an inclusion complex (IC6HKTZ) was prepared with p-sulfonic acid calix[6]arene (CX6SO3H) to improve the solubility and efficacy of KTZ against Leishmania amazonensis and Leishmania infantum promastigotes. A linear increase in KTZ solubility as a function of CX6SO3H concentration was verified using the phase-solubility diagram. The resulting diagram was classified as AL-type and a 1:1 host–guest stoichiometry was assumed to prepare IC6HKTZ by freeze-drying. FTIR, TG/DSC, XRD, and solid-state 13C NMR spectroscopy analyses were performed to confirm the formation of IC6HKTZ. The solubility enhancement of KTZ by 120.00 μM CX6SO3H was about 95 times. The IC50 values of IC6HKTZ and free KTZ were 3.95 and 14.35 μM for Leishmania amazonensis and 6.74 and 17.47 μM for Leishmania infantum, respectively. The viability of DH82 macrophages was not affected by CX6SO3H. These results show that CX6SO3H is a new supramolecular carrier system that improves antileishmanial activities to KTZ for the treatment of cutaneous and visceral leishmaniasis.

Design Hybrid Porous Organic/Inorganic Polymers Containing Polyhedral Oligomeric Silsesquioxane/Pyrene/Anthracene Moieties as a High-Performance Electrode for Supercapacitor.

We synthesized two hybrid organic-inorganic porous polymers (HPP) through the Heck reaction of 9,10 dibromoanthracene (A-Br2) or 1,3,6,8-tetrabromopyrene (P-Br4)/A-Br2 as co-monomers with octavinylsilsesquioxane (OVS), in order to afford OVS-A HPP and OVS-P-A HPP, respectively. The chemical structures of these two hybrid porous polymers were validated through FTIR and solid-state 13C and 29Si NMR spectroscopy. The thermal stability and porosity of these materials were measured by TGA and N2 adsorption/desorption analyses, demonstrating that OVS-A HPP has higher thermal stability (Td10: 579 °C) and surface area (433 m2 g-1) than OVS-P-A HPP (Td10: 377 °C and 98 m2 g-1) due to its higher cross-linking density. Furthermore, the electrochemical analysis showed that OVS-P-A HPP has a higher specific capacitance (177 F g -1 at 0.5 A F g-1) when compared to OVS-A HPP (120 F g -1 at 0.5 A F g-1). The electron-rich phenyl rings and Faradaic reaction between the π-conjugated network and anthracene moiety may be attributed to their excellent electrochemical performance of OVS-P-A HPP.

Polybenzodiazine Aerogels: All-Nitrogen Analogues of Polybenzoxazines─Synthesis, Characterization, and High-Yield Conversion to Nanoporous Carbons

Tetrahydroquinazoline (THQ) was designed as an all-nitrogen analogue of main-stream benzoxazine monomers. THQ solutions in DMF gelled at 100 °C via HCl-catalyzed ring-opening polymerization to polybenzodiazine (PBDAZ) wet gels, which were dried in an autoclave with supercritical fluid CO2 to aerogels. These as-prepared PBDAZ-100 aerogels undergo ring-fusion aromatization at 240 °C under O2. This oxidized form is referred to as PBDAZ-240. Chemical identification of PBDAZ-100 and PBDAZ-240 relied on consideration of all nine possible polymerization pathways, in combination with elemental analysis, infrared and solid-state 13C NMR spectroscopy, and 15N NMR spectroscopy of aerogels from the selectively 15N-enriched THQ monomer. Fully oxidized PBDAZ-240 aerogels were carbonized at 800 °C under Ar to carbon aerogels with 61% w/w yield and with retention of the nanomorphology of the parent PBDAZ-100 aerogels. Direct pyrolysis of PBDAZ-100 at 800 °C, i.e., without prior oxidation, resulted in only 40% w/w yield and complete loss of the fine nanostructure. The evolution of PBDAZ-240 aerogels along pyrolysis toward carbonization was monitored using progressively higher pyrolysis temperatures from 300 to 800 °C under Ar. Aerogels received at 600 and 800 °C (referred to as PBDAZ-600 and PBDAZ-800, respectively) had relatively high surface areas (432 and 346 m2 g–1, respectively), a significant portion of which (79% in both materials) was assigned to micropores. The new polymer aerogels, together with polybenzoxazine aerogels, comprise a suitable basis set for comparing N-rich versus O-rich porous carbons as adsorbers.

Effect of Changing Anion on the Crystalline Structure, Crystal Structure, Hirschfield Surface, IR and NMR Spectroscopy of Organic Salts and Hybrid Compounds: C<sub>6</sub>H<sub>4</sub>(NH<sub>3</sub>)<sub>2</sub>Cl<sub>2</sub> (I), <i>β</i>-[C<sub>6</sub>H<sub>10</sub>N<sub>2</sub>]<sub>2</sub>ZnCl<sub>4</sub> (II), Respectively

Two organic-inorganic hybrid materials, C6H4(NH3)2∙Cl2 (I) and β-[C6H10N2]2ZnCl4 (II), have been synthesized by hydrothermal method. These two materials are one of the hybrid materials have emerged as one of the most brilliant components classes. These extraordinary compounds synergistically combine the desired physical properties of both organic and inorganic components into a single compound offering the possibility to achieve great improvement over time in terms of science across various sectors. Their structures were determined by XRD pattern investigations and single crystal X-ray diffraction. These two compounds are crystallized in the monoclinic system; C2/c space group. In the both structures, the anionic-cationic entities are interconnected by hydrogen bonding contacts and p-p Interaction forming three-dimensional networks. Intermolecular interactions were investigated by Hirshfeld surfaces and the contacts of the four different chloride atoms in (II) were compared. The vibrational absorption bands were identified by infrared spectroscopy. These compounds were also investigated by solid state13C NMR spectroscopy.

Effects of Corn Straw and Biochar Returning to Fields Every Other Year on the Structure of Soil Humic Acid

Returning straw and biochar to the fields can change the structure of humic acid in soil and affect the content of soil organic matter. However, returning straw and biochar to the fields in successive years also increases the insect pests of crops and causes nitrogen competition, thus increasing the soil burden. Therefore, to provide a theoretical basis for the study of the time effect of returning fields, three treatments were set in this paper to study the effects of straw and biochar returning every other year on the soil organic matter and humic acid (HA) structure. Elements, Fourier transform infrared spectroscopy (FTIR), thermogravimetric spectroscopy (TG), three-dimensional fluorescence spectroscopy, and solid state 13C-NMR spectroscopy were used to comprehensively investigate the structural characteristics of humic acid in soil. The results showed that after straw and biomass charcoal are returned to the field every other year, compared with 2018, after planting in 2020, the average content of soil organic carbon will increase by 29.49% and 36.14%, respectively. HA showed a phenomenon of increased aliphatic property and decreased aromaticity; aromatic carbon of HA decreased, while alkyl carbon and alkoxy carbon increased; the molecular structure of HA developed toward simplification. In the short term, the effect of biomass charcoal returning was more significant. This study can be used as a reference for the research on the time effect of returning straw and biomass carbon to the fields, and can also provide a basis for the research on the composition of humus after returning organic materials to the fields.

Synthesis and thermal properties of novel bismaleimides containing cardo and oxazine structures and the thermal transition behaviors of their polymer structures

In this work, three bismaleimides containing cardo and ortho-oxazine structures, with dual advantages of bismaleimide and benzoxazine resin, were synthesized. Their chemical structures were characterized by Fourier transform infrared (FT-IR) spectroscopy and nuclear magnetic resonance (NMR) spectroscopy. The kinetics of curing and kinetic model were investigated by non-isothermal differential scanning calorimetry. The curing reaction of the bismaleimide was studied by in-situ FT-IR spectroscopy. Studies showed that both bismaleimide and benzoxazine provided the new structure with better thermal stability and solubility, compared to similar type of materials and commercial bismaleimides. Additionally, the further thermal rearrangement of the internal structure of the polymer at high temperature formed a benzoxazole structure with higher thermal stability. The rearrangement due to thermal changes was confirmed by in-situ FT-IR and solid-state 13C-NMR spectroscopy. Microscale combustion calorimetry (MCC) showed that both, bismaleimide and benzoxazole resins, were formed after thermal rearrangement and had excellent flame-retardant properties.