Characterization of the Compounds Released in the Gaseous Waste Stream during the Slow Pyrolysis of Hemp (Cannabis sativa L.)

This study aims to characterize and valorize hemp residual biomass by a slow pyrolysis process. The volatile by-products of hemp carbonization were characterized by several methods (TGA, UV-VIS, TLC, Flash Prep-LC, UHPLC, QTOF-MS) to understand the pyrolysis reaction mechanisms and to identify the chemical products produced during the process. The obtained carbon yield was 29%, generating a gaseous stream composed of phenols and furans which was collected in four temperature ranges (F1 at 20–150 °C, F2 at 150–250 °C, F3 at 250–400 °C and F4 at 400–1000 °C). The obtained liquid fractions were separated into subfractions by flash chromatography. The total phenolic content (TPC) varied depending on the fraction but did not correlate with an increase in temperature or with a decrease in pH value. Compounds present in fractions F1, F3 and F4, being mainly phenolic molecules such as guaiacyl or syringyl derivatives issued from the lignin degradation, exhibit antioxidant capacity. The temperature of the pyrolysis process was positively correlated with detectable phenolic content, which can be explained by the decomposition order of the hemp chemical constituents. A detailed understanding of the chemical composition of pyrolysis products of hemp residuals allows for an assessment of their potential valorization routes and the future economic potential of underutilized biomass.     

Modification of hemp shiv properties using water-repellent sol–gel coatings

For the first time, the hydrophilicity of hemp shiv was modified without the compromise of its hygroscopic properties. This research focused on the use of sol–gel method in preparation of coatings on the natural plant material, hemp shiv, that has growing potential in the construction industry as a thermal insulator. The sol–gel coatings were produced by cohydrolysis and polycondensation of tetraethyl orthosilicate (TEOS) using an acidic catalyst. Methyltriethoxysilane (MTES) was added as the hydrophobic precursor to provide water resistance to the bio-based material. Scanning electron microscopy (SEM) and focused ion beam (FIB) have been used to determine the morphological changes on the surface as well as within the hemp shiv. It was found that the sol–gel coatings caused a reduction in water uptake but did not strongly influence the moisture sorption behaviour of hemp shiv. Fourier transformed infrared (FTIR) spectroscopy shows that the coating layer on hemp shiv acts a shield, thereby lowering peak intensity in the wavelength range 1200–1800?cm^?1. The sol–gel coating affected pore size distribution and cumulative pore volume of the shiv resulting in tailored porosity. The overall porosity of shiv decreased with a refinement in diameter of the larger pores. Thermal analysis was performed using TGA and stability of coated and uncoated hemp shiv have been evaluated. Hemp shiv modified with sol–gel coating can potentially develop sustainable heat insulating composites with better hygrothermal properties.

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A Comparative Study of Pyrolysis Liquids by Slow Pyrolysis of Industrial Hemp Leaves,Hurds and Roots

This study assessed the pyrolysis liquids obtained by slow pyrolysis of industrial hemp leaves, hurds, and roots. The liquids recovered between a pyrolysis temperature of 275–350 °C, at two condensation temperatures 130 °C and 70 °C, were analyzed. Aqueous and bio-oil pyrolysis liquids were produced and analyzed by proton nuclear magnetic resonance (NMR), gas chromatography–mass spectrometry (GC-MS), and atmospheric pressure photoionization Fourier transform ion cyclotron resonance mass spectrometry (APPI FT-ICR MS). NMR revealed quantitative concentrations of the most abundant compounds in the aqueous fractions and compound groups in the oily fractions. In the aqueous fractions, the concentration range of acetic acid was 50–241 gL⁻¹, methanol 2–30 gL⁻¹, propanoic acid 5–20 gL⁻¹, and 1-hydroxybutan-2-one 2 gL⁻¹. GC-MS was used to compare the compositions of the volatile compounds and APPI FT-ICR MS was utilized to determine the most abundant higher molecular weight compounds. The different obtained pyrolysis liquids (aqueous and oily) had various volatile and nonvolatile compounds such as acetic acid, 2,6-dimethoxyphenol, 2-methoxyphenol, and cannabidiol. This study provides a detailed understanding of the chemical composition of pyrolysis liquids from different parts of the industrial hemp plant and assesses their possible economic potential.     

Synthesis and Structure Elucidation of Novel Spirooxindole Linked to Ferrocene and Triazole Systems via [3 + 2] Cycloaddition Reaction

In the present work, a novel heterocyclic hybrid of a spirooxindole system was synthesized via the attachment of ferrocene and triazole motifs into an azomethine ylide by [3 + 2] cycloaddition reaction protocol. The X-ray structure of the heterocyclic hybrid (1″R,2″S,3R)-2″-(1-(3-chloro-4-fluorophenyl)-5-methyl-1H-1,2,3-triazole-4-carbonyl)-5-methyl-1″-(ferrocin-2-yl)-1″,2″,5″,6″,7″,7a″-hexahydrospiro[indoline-3,3″-pyrrolizin]-2-one revealed very well the expected structure, by using different analytical tools (FTIR and NMR spectroscopy). It crystallized in the triclinic-crystal system and the P-1-space group. The unit cell parameters are a = 9.1442(2) Å, b = 12.0872(3) Å, c = 14.1223(4) Å, α = 102.1700(10)°, β = 97.4190(10)°, γ = 99.1600(10)°, and V = 1484.81(7) ų. There are two molecules per unit cell and one formula unit per asymmetric unit. Hirshfeld analysis was used to study the molecular packing of the heterocyclic hybrid. H···H (50.8%), H···C (14.2%), Cl···H (8.9%), O···H (7.3%), and N···H (5.1%) are the most dominant intermolecular contacts in the crystal structure. O···H, N···H, H···C, F···H, F···C, and O···O are the only contacts that have the characteristic features of short and significant interactions. AIM study indicated predominant covalent characters for the Fe–C interactions. Also, the electron density (ρ(r)) at the bond critical point correlated inversely with the Fe–C distances.     

Thiazole–Chalcone Hybrids as Prospective Antitubercular and Antiproliferative Agents: Design,Synthesis, Biological,Molecular Docking Studies and In Silico ADME Evaluation

Compounds bearing thiazole and chalcone pharmacophores have been reported to possess excellent antitubercular and anticancer activities. In view of this, we designed, synthesized and characterized a novel series of thiazole–chalcone hybrids (1–20) and further evaluated them for antitubercular and antiproliferative activities by employing standard protocols. Among the twenty compounds, chalcones 12 and 7, containing 2,4-difluorophenyl and 2,4-dichlorophenyl groups, showed potential antitubercular activity higher than the standard pyrazinamide (MIC = 25.34 µM) with MICs of 2.43 and 4.41 µM, respectively. Chalcone 20 containing heteroaryl 2-thiazolyl moiety exhibited promising antiproliferative activity against the prostate cancer cell line (DU-145), higher than the standard methotrexate (IC₅₀ = 11 ± 1 µM) with an IC₅₀ value of 6.86 ± 1 µM. Furthermore, cytotoxicity studies of these compounds against normal human liver cell lines (L02) revealed that the target molecules were comparatively less selective against L02. Additional computational studies using AutoDock predicted the key binding interactions responsible for the activity and the SwissADME tool computed the in silico drug likeliness properties. The lead compounds generated through this study, create a way for the optimization and development of novel drugs against tuberculosis infections and prostate cancer.     

The Impact of Halogen Substituents on the Synthesis and Structure of Co-Crystals of Pyridine Amides

Strategies for co-crystal synthesis tend to employ either hydrogen- or halogen-bonds between different molecules. However, when both interactions are present, the structural influence that they may exert on the resulting assembly is difficult to predict a priori. To shed some light on this supramolecular challenge, we attempted to co-crystallize ten aliphatic dicarboxylic acids (co-formers) with three groups of target molecules; N-(pyridin-2-yl)picolinamides (2Pyr-X), N-(pyridin-2-yl)nicotinamides (3Pyr-X), N-(pyridin-2-yl)isonicotinamides (4Pyr-X); X=Cl/ Br/ I. The structural outcomes were compared with co-crystals prepared from the non-halogenated targets. As expected, none of the reactions with 2Pyr-X produced co-crystals due to the presence of a very stable intramolecular N-H···N hydrogen bond. In the 3Pyr series, all six structures obtained showed the same synthons, –COOH···N(py) and –COOH···N(py)-NH, that were found in the non-halogenated parent 3Pyr and were additionally accompanied by structure directing X···O(OH) interactions (X=Br/I). The co-crystals of the unhalogenated parent 4Pyr co-crystals assembled via intermolecular –COOH···N(py) and –COOH···N(py)-NH synthons. Three of the analogues 4Pyr-X co-crystals displayed only COOH···N(py) and –COOH···N(py)-NH interactions. The three co-crystals of 4Pyr-X with fumaric acid (for which no analogues structures with 4Pyr are known) formed –COOH···N(py)-NH and –NH···O=C hydrogen bonds and showed no structure-directing halogen bonds. In three co-crystals of 4Pyr-I in which –COOH···N(py)-NH hydrogen bond was present, a halogen-bond based –I···N(py) synthon replaced the –COOH···N(py) motif observed in the parent structures. The structural influence of the halogen atoms increased in the order of Cl < Br < I, as the size of σ-holes increased. Finally, it is noteworthy that isostructurality among structures of the homomeric targets was not translated to structural similarities between their respective co-crystals.     

Physicochemical and Functional Properties of 2S, 7S,and 11S Enriched Hemp Seed Protein Fractions

The hemp seed contains protein fractions that could serve as useful ingredients for food product development. However, utilization of hemp seed protein fractions in the food industry can only be successful if there is sufficient information on their levels and functional properties. Therefore, this work provides a comparative evaluation of the structural and functional properties of hemp seed protein isolate (HPI) and fractions that contain 2S, 7S, or 11S proteins. HPI and protein fractions were isolated at pH values of least solubility. Results showed that the dominant protein was 11S, with a yield of 72.70 ± 2.30%, while 7S and 2S had values of 1.29 ± 0.11% and 3.92 ± 0.15%, respectively. The 2S contained significantly (p < 0.05) higher contents of sulfhydryl groups at 3.69 µmol/g when compared to 7S (1.51 µmol/g), 11S (1.55 µmol/g), and HPI (1.97 µmol/g). The in vitro protein digestibility of the 2S (72.54 ± 0.52%) was significantly (p < 0.05) lower than those of the other isolated proteins. The intrinsic fluorescence showed that the 11S had a more rigid structure at pH 3.0, which was lost at higher pH values. We conclude that the 2S fraction has superior solubility, foaming capacity, and emulsifying activity when compared to the 7S, 11S, and HPI.     

Supramolecular Diiodine-Bromostannate(IV) Complexes: Narrow Bandgap Semiconductors

Three supramolecular bromostannates(IV) with “trapped” diiodine molecules, Cat₂{[SnBr₆](I₂)} (Cat = Me₄N⁺ (1), 1-MePy⁺ (2) and 4-MePyH (3)), were synthesized. In all cases, I₂ linkers are connected with bromide ligands via halogen···halogen non-covalent interactions. Articles 1–3 were studied using Raman spectroscopy, thermogravimetric analysis, and diffuse reflectance spectroscopy. The latter indicates that 1–3 are narrow band gap semiconductors.     

Effective Utilisation of Halophyte Biomass from Saline Soils for Biorefinering Processes

The salinity of European soil is increasing every year, causing severe economic damage (estimated 1–3 million hectares in the enlarged EU). This study uses the biomass of halophytes—tall fescue (grass) and hemp of the Białobrzeskie variety from saline soils—for bioenergy, second generation biofuels and designing new materials—fillers for polymer composites. In the bioethanol obtaining process, in the first stage, the grass and hemp biomass were pretreated with 1.5% NaOH. Before and after the treatment, the chemical composition was determined and the FTIR spectra and SEM pictures were taken. Then, the process of simultaneous saccharification and fermentation (SSF) was carried out. The concentration of ethanol for both the grass and hemp biomass was approx. 7 g·L⁻¹ (14 g·100 g⁻¹ of raw material). In addition, trials of obtaining green composites with halophyte biomass using polymers (PP) and biopolymers (PLA) as a matrix were performed. The mechanical properties of the composites (tensile and flexural tests) were determined. It was found that the addition of a compatibilizer improved the adhesion at the interface of PP composites with a hemp filler. In conclusion, the grass and hemp biomass were found to be an interesting and promising source to be used for bioethanol and biocomposites production. The use of annually renewable plant biomass from saline soils for biorefinering processes opens up opportunities for the development of a new value chains and new approaches to sustainable agriculture.     

Thermodynamics and kinetics of DNA nanotube polymerization from single-filament measurements

DNA nanotubes provide a programmable architecture for molecular self-assembly and can serve as model systems for one-dimensional biomolecular assemblies. While a variety of DNA nanotubes have been synthesized and employed as models for natural biopolymers, an extensive investigation of DNA nanotube kinetics and thermodynamics has been lacking. Using total internal reflection microscopy, DNA nanotube polymerization was monitored in real time at the single filament level over a wide range of free monomer concentrations and temperatures. The measured polymerization rates were subjected to a global nonlinear fit based on polymerization theory in order to simultaneously extract kinetic and thermodynamic parameters. For the DNA nanotubes used in this study, the association rate constant is (5.99 ± 0.15) × 10⁵ M^–1 s^–1, the enthalpy is 87.9 ± 2.0 kcal mol^–1, and the entropy is 0.252 ± 0.006 kcal mol^–1 K^–1. The qualitative and quantitative similarities between the kinetics of DNA nanotubes, actin filaments, and microtubules polymerization highlight the prospect of building complex dynamic systems from DNA molecules inspired by biological architecture.     

3,4-Seco-Isopimarane Diterpenes from the Twigs and Leaves of Isodon Flavidus

Three isopimarane diterpenes [fladins B (1), C (2), and D (3)] were isolated from the twigs and leaves of Chinese folk medicine, Isodon flavidus. The chemical structures were determined by the analysis of the comprehensive spectroscopic data, and the absolute configuration was confirmed by X-ray crystallographic analysis. The structures of 1–3 were formed from isopimaranes through the rearrangement of ring A by the bond break at C-3 and C-4 to form a new δ-lactone ring system between C-3 and C-9. This structure type represents the first discovery of a natural isopimarane diterpene with an unusual lactone moiety at C-9 and C-10. In the crystal of 1, molecules are linked to each other by intermolecular O-H···O bonds, forming chains along the b axis. Compounds 1–3 were evaluated for their bioactivities against different diseases. None of these compounds displayed cytotoxic activities against HCT116 and A549 cancer cell lines, antifungal activities against Trichophyton rubrum and T. mentagrophytes, or antiviral activities against HIV entry at 20 µg/mL (62.9–66.7) µM. Compounds 1 and 3 did not show antiviral activities against Ebola entry at 20 µg/mL either; only 2 was found to show an 81% inhibitory effect against Ebola entry activity at 20 µg/mL (66.7 µM). The bioactivity evidence suggested that this type of compound could be a valuable antiviral lead for further structure modification to improve the antiviral potential.     

Bimetallic Iron–Palladium Catalyst System as a Lewis-Acid for the Synthesis of Novel Pharmacophores Based Indole Scaffold as Anticancer Agents

The Friedel–Crafts reaction between substituted indoles as nucleophiles with chalcones-based benzofuran and benzothiophene scaffolds was carried out by employing a highly efficient bimetallic iron–palladium catalyst system. This catalytic approach produced the desired bis-heteroaryl products with low catalyst loading, a simple procedure, and with acceptable yield. All synthesized indole scaffolds 3a–3s were initially evaluated for their cytotoxic effect against human fibroblast BJ cell lines and appeared to be non-cytotoxic. All non-cytotoxic compounds 3a–3s were then evaluated for their anticancer activities against cervical cancer HeLa, prostate cancer PC3, and breast cancer MCF-7 cell lines, in comparison to standard drug doxorubicin, with IC₅₀ values 1.9 ± 0.4 µM, 0.9 ± 0.14 µM and 0.79 ± 0.05 µM, respectively, and appeared to be moderate to weak anticancer agents. Fluoro-substituted chalcone moiety-containing compounds, 3b appeared to be the most active member of the series against cervical HeLa (IC₅₀ = 8.2 ± 0.2 µM) and breast MCF-7 cancer cell line (IC₅₀ = 12.3 ± 0.04 µM), whereas 6-fluroindol-4-bromophenyl chalcone-containing compound 3e (IC₅₀ = 7.8 ± 0.4 µM) appeared to be more active against PC3 prostate cancer cell line.     

Green Synthesis,Characterization, and Antibacterial Properties of Silver Nanoparticles Obtained by Using Diverse Varieties of Cannabis sativa Leaf Extracts

Cannabis sativa L. (hemp) is a plant used in the textile industry and green building material industry, as well as for the phytoremediation of soil, medical treatments, and supplementary food products. The synergistic effect of terpenes, flavonoids, and cannabinoids in hemp extracts may mediate the biogenic synthesis of metal nanoparticles. In this study, the chemical composition of aqueous leaf extracts of three varieties of Romanian hemp (two monoecious, and one dioecious) have been determined by Fourier-Transformed Infrared spectroscopy (FT-IR), high-performance liquid chromatography, and mass spectrometry (UHPLC-DAD-MS). Then, their capability to mediate the green synthesis of silver nanoparticles (AgNPs) and their pottential antibacterial applications were evaluated. The average antioxidant capacity of the extracts had 18.4 ± 3.9% inhibition determined by 2,2-diphenyl-1-picrylhydrazyl (DPPH^•) and 78.2 ± 4.1% determined by 2,2′-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt (ABTS™) assays. The total polyphenolic content of the extracts was 1642 ± 32 mg gallic acid equivalent (GAE) L⁻¹. After this, these extracts were reacted with an aqueous solution of AgNO₃ resulting in AgNPs, which were characterized by UV−VIS spectroscopy, FT-IR, scanning electron microscopy (SEM-EDX), and dynamic light scattering (DLS). The results demonstrated obtaining spherical, stable AgNPs with a diameter of less than 69 nm and an absorbance peak at 435 nm. The mixture of extracts and AgNPs showed a superior antioxidant capacity of 2.3 ± 0.4% inhibition determined by the DPPH^• assay, 88.5 ± 0.9% inhibition as determined by the ABTS^•+ assay, and a good antibacterial activity against several human pathogens: Escherichia coli, Klebsiella pneumoniae, Pseudomonas fluorescens, and Staphylococcus aureus.     

π–π Noncovalent Interaction Involving 1,2,4- and 1,3,4-Oxadiazole Systems: The Combined Experimental,Theoretical, and Database Study

A series of N-pyridyl ureas bearing 1,2,4- (1a, 2a, and 3a) and 1,3,4-oxadiazole moiety (1b, 2b, 3b) was prepared and characterized by HRMS, ¹H and ¹³C NMR spectroscopy, as well as X-ray diffraction. The inspection of the crystal structures of (1–3)a,b and the Hirshfeld surface analysis made possible the recognition of the (oxadiazole)···(pyridine) and (oxadiazole)···(oxadiazole) interactions. The presence of these interactions was confirmed theoretically by DFT calculations, including NCI analysis for experimentally determined crystal structures as well as QTAIM analysis for optimized equilibrium structures. The preformed database survey allowed the verification of additional examples of relevant (oxadiazole)···π interactions both in Cambridge Structural Database and in Protein Data Bank, including the cocrystal of commercial anti-HIV drug Raltegravir.     

The Antifungal Action Mode of N-Phenacyldibromobenzimidazoles

Our study aimed to characterise the action mode of N-phenacyldibromobenzimidazoles against C. albicans and C. neoformans. Firstly, we selected the non-cytotoxic most active benzimidazoles based on the structure–activity relationships showing that the group of 5,6-dibromobenzimidazole derivatives are less active against C. albicans vs. 4,6-dibromobenzimidazole analogues (5e–f and 5h). The substitution of chlorine atoms to the benzene ring of the N-phenacyl substituent extended the anti-C. albicans action (5e with 2,4-Cl₂ or 5f with 3,4-Cl₂). The excellent results for N-phenacyldibromobenzimidazole 5h against the C. albicans reference and clinical isolate showed IC₅₀ = 8 µg/mL and %I = 100 ± 3, respectively. Compound 5h was fungicidal against the C. neoformans isolate. Compound 5h at 160–4 µg/mL caused irreversible damage of the fungal cell membrane and accidental cell death (ACD). We reported on chitinolytic activity of 5h, in accordance with the patterns observed for the following substrates: 4-nitrophenyl-N-acetyl-β-d-glucosaminide and 4-nitrophenyl-β-d-N,N′,N″-triacetylchitothiose. Derivative 5h at 16 µg/mL: (1) it affected cell wall by inducing β-d-glucanase, (2) it caused morphological distortions and (3) osmotic instability in the C. albicans biofilm-treated. Compound 5h exerted Candida-dependent inhibition of virulence factors.     

Structural Insight into the Binding of Cyanovirin-N with the Spike Glycoprotein,Mpro and PLpro of SARS-CoV-2: Protein–Protein Interactions,Dynamics Simulations and Free Energy Calculations

The emergence of COVID-19 continues to pose severe threats to global public health. The pandemic has infected over 171 million people and claimed more than 3.5 million lives to date. We investigated the binding potential of antiviral cyanobacterial proteins including cyanovirin-N, scytovirin and phycocyanin with fundamental proteins involved in attachment and replication of SARS-CoV-2. Cyanovirin-N displayed the highest binding energy scores (−16.8 ± 0.02 kcal/mol, −12.3 ± 0.03 kcal/mol and −13.4 ± 0.02 kcal/mol, respectively) with the spike protein, the main protease (M^pro) and the papainlike protease (PL^pro) of SARS-CoV-2. Cyanovirin-N was observed to interact with the crucial residues involved in the attachment of the human ACE2 receptor. Analysis of the binding affinities calculated employing the molecular mechanics-Poisson–Boltzmann surface area (MM-PBSA) approach revealed that all forms of energy, except the polar solvation energy, favourably contributed to the interactions of cyanovirin-N with the viral proteins. With particular emphasis on cyanovirin-N, the current work presents evidence for the potential inhibition of SARS-CoV-2 by cyanobacterial proteins, and offers the opportunity for in vitro and in vivo experiments to deploy the cyanobacterial proteins as valuable therapeutics against COVID-19.     

A Capillary Electrophoresis-Based Method for the Measurement of Hydroxychloroquine and Its Active Metabolite Desethyl Hydroxychloroquine in Whole Blood in Patients with Rheumatoid Arthritis

A capillary electrophoresis method was developed to detect and measure hydroxychloroquine (HCQ) and its active metabolite desethyl hydroxychloroquine (DHCQ) in whole blood in patients with rheumatoid arthritis. The best separation in terms of peak area reproducibility, migration time, peak shape, and resolution of adjacent peaks was obtained in a 60 cm, 75 µm i.d. uncoated fused-silica capillary using a background electrolyte mixture of an aqueous 55 mmol/L TRIS solution brought to pH 2.6 with phosphoric acid and methanol (85:15) and a voltage and a temperature of separation of 20 kV and 30 °C, respectively. Analytes were separated in less than 12 min, with excellent linearity (R² ≥ 0.999) in the concentration range of 0.5–8 µmol/L. The recovery of analytes spiked in whole blood was 99–101% for HCQ and 98–99% for DHCQ. Analysis of five samples from patients with rheumatoid arthritis receiving HCQ 400 mg daily yielded mean steady-state concentrations of 2.27 ± 1.61 and 1.54 ± 0.55 μmol/L for HCQ and DHCQ, respectively, with a HCQ to DHCQ ratio of 1.40 ± 0.77.     

A–X⋯σ Interactions—Halogen Bonds with σ-Electrons as the Lewis Base Centre

CCSD(T)/aug-cc-pVTZ//ωB97XD/aug-cc-pVTZ calculations were performed for halogen-bonded complexes. Here, the molecular hydrogen, cyclopropane, cyclobutane and cyclopentane act as Lewis base units that interact through the electrons of the H–H or C–C σ-bond. The FCCH, ClCCH, BrCCH and ICCH species, as well as the F₂, Cl₂, Br₂ and I₂ molecular halogens, act as Lewis acid units in these complexes, interacting through the σ-hole localised at the halogen centre. The Quantum Theory of Atoms in Molecules (QTAIM), the Natural Bond Orbital (NBO) and the Energy Decomposition Analysis (EDA) approaches were applied to analyse these aforementioned complexes. These complexes may be classified as linked by A–X···σ halogen bonds, where A = C, X (halogen). However, distinct properties of these halogen bonds are observed that depend partly on the kind of electron donor: dihydrogen, cyclopropane, or another cycloalkane. Examples of similar interactions that occur in crystals are presented; Cambridge Structural Database (CSD) searches were carried out to find species linked by the A–X···σ halogen bonds.     

Stability of Manganese(II)–Pyrazine, –Quinoxaline or –Phenazine Complexes and Their Potential as Carbonate Sequestration Agents

Carbonate sequestration technology is a complement of CO₂ sequestration technology, which might assure its long-term viability. In this work, in order to explore the interactions between Mn²⁺ ion with several ligands and carbonate ion, we reported a spectrophotometric equilibrium study of complexes of Mn²⁺ with pyrazine, quinoxaline or phenazine and its carbonate species at 298 K. For the complexes of manganese(II)–pyrazine, manganese(II)–quinoxaline and manganese(II)–phenazine, the formation constants obtained were log β₁₁₀ = 4.6 ± 0.1, log β₁₁₀ = 5.9 ± 0.1 and log β₁₁₀ = 6.0 ± 0.1, respectively. The formation constants for the carbonated species manganese(II)–carbonate, manganese(II)–pyrazine–carbonate, manganese(II)–quinoxaline–carbonate and manganese(II)–phenazine–carbonate complexes were log β₁₁₀ = 5.1 ± 0.1, log β₁₁₀ = 9.8 ± 0.1, log β₁₁₀ = 11.7 ± 0.1 and log β₁₁₀ = 12.7 ± 0.1, respectively. Finally, the individual calculated electronic spectra and its distribution diagram of these species are also reported. The use of N-donor ligand with π-electron-attracting activity in a manganese(II) complex might increase its interaction with carbonate ions.     

Synthesis,Experimental and Theoretical Study of Azidochromones

A series of 2-(haloalkyl)-3-azidomethyl and 6-azido chromones has been synthetized, characterized and studied by theoretical (DFT calculations) and spectroscopic methods (UV-Vis, NMR). The crystal structure of 3-azidomethyl-2-difluoromethyl chromone, determined by X-ray diffraction methods, shows a planar framework due to extended π-bond delocalization. Its molecular packing is stabilized by F···H, N···H and O···H hydrogen bonds, π···π stacking and C–O···π intermolecular interactions. Moreover, AIM, NCI and Hirshfeld analysis evidenced that azido moiety has a significant role in the stabilization of crystal packing through weak intermolecular interactions, where analysis of electronic density suggested closed-shell (CS) interatomic interactions.