In this study, the sequential extraction method was applied to extract selected potentially toxic elements (PTEs) (Cd, Cr, Cu, Fe, Ni, Pb and Zn) in river sediments collected from the Blood River situated in Seshego area, Limpopo Province, South Africa. The study aimed to assess a possible trend of mobilisation of these elements from sediment to water. The accuracy of the sequential extraction method was confirmed by analysing sediment-certified reference material, and quantitative percentage recoveries ranging from 86 to 119%, 81 to 111% and 77 to 119% were achieved for exchangeable, reducible and oxidisable fractions, respectively. The potential risk of the PTEs in sediments was evaluated. The calculated values of contamination factor (CF) as well as risk assessment code (RAC) for Cd, Cu, Ni and Pb revealed the mobility of these elements. The PTEs in river sediments are at a high toxicity-risk level and could therefore cause a threat to organisms dwelling in sediments and humans via consumption of crops irrigated with the polluted river water.

The structures of the mono- and the dihalogenated N-unsubstituted 2-aminobenzamides were characterized by means of the spectroscopic (¹H-NMR, UV-Vis, FT-IR, and FT-Raman) and X-ray crystallographic techniques complemented with a density functional theory (DFT) method. The hindered rotation of the C(O)–NH₂ single bond resulted in non-equivalence of the amide protons and therefore two distinct resonances of different chemical shift values in the ¹H-NMR spectra of these compounds were observed. 2-Amino-5-bromobenzamide (ABB) as a model confirmed the presence of strong intramolecular hydrogen bonds between oxygen and the amine hydrogen. However, intramolecular hydrogen bonding between the carbonyl oxygen and the amine protons was not observed in the solution phase due to a rapid exchange of these two protons with the solvent and fast rotation of the Ar–NH₂ single bond. XRD also revealed the ability of the amide unit of these compounds to function as a hydrogen bond donor and acceptor simultaneously to form strong intermolecular hydrogen bonding between oxygen of one molecule and the NH moiety of the amine or amide group of the other molecule and between the amine nitrogen and the amide hydrogen of different molecules. DFT calculations using the B3LYP/6-311++G(d,p) basis set revealed that the conformer (A) with oxygen and 2-amine on the same side predominates possibly due to the formation of a six-membered intramolecular ring, which is assisted by hydrogen bonding as observed in the single crystal XRD structure.

The ambident electrophilic character of the 5-bromo-2-hydroxychalcones and the binucleophilic nature of 2-aminothiophenol were exploited to construct the 2-aryl-4-(4-bromo-2-hydroxyphenyl)benzo[1,5]thiazepines. The structures and conformation of these 2-aryl-4-(4-bromo-2-hydroxyphenyl)benzo[1,5]thiazepines were established with the use of spectroscopic techniques complemented with a single crystal X-ray diffraction method. Both ¹H-NMR and IR spectroscopic techniques confirmed participation of the hydroxyl group in the intramolecular hydrogen-bonding interaction with a nitrogen atom. SC-XRD confirmed the presence of a six-membered intramolecularly hydrogen-bonded pseudo-aromatic ring, which was corroborated by the DFT method on 2b as a representative example in the gas phase. Compounds 2a (Ar = -C₆H₅), 2c (Ar = -C₆H₄(4-Cl)) and 2f (Ar = -C₆H₄(4-CH(CH₃)₂) exhibited increased inhibitory activity against α-glucosidase compared to acarbose (IC₅₀ = 7.56 ± 0.42 µM), with IC₅₀ values of 6.70 ± 0.15 µM, 2.69 ± 0.27 µM and 6.54 ± 0.11 µM, respectively. Compound 2f, which exhibited increased activity against α-glucosidase, also exhibited a significant inhibitory effect against α-amylase (IC₅₀ = 9.71 ± 0.50 µM). The results of some computational approaches on aspects such as noncovalent interactions, calculated binding energies for α-glucosidase and α-amylase, ADME (absorption, distribution, metabolism and excretion) and bioavailability properties, gastrointestinal absorption and blood–brain barrier permeability are also presented.

The conformation of the title compounds was determined in solution by ¹H-NMR spectroscopy and in solid state by single-crystal X-ray diffraction (XRD) complemented with density functional theory. The compounds were found to exist exclusively in solution and solid state as trans-2-aminochalcone epoxides with strong intramolecular hydrogen bonding interaction between the amino and carbonyl groups. These 2-aminochalcone epoxides experienced a solvent effect in DMSO-d₆, which resulted in an anomalous chemical shift for the α-hydrogen signal, presumably due to complexation of solute molecules with DMSO. The solute–solvent interaction would probably fix the trans conformation of epoxyketone such that α-H is more accessible to both aryl rings, and in turn, experience their combined anisotropic effect. Intermolecular interactions in the crystal structures were confirmed and quantified using the Hirshfeld surface analysis. Moreover, the trans stereochemistry of the α-epoxyketones facilitated direct one-pot sequential sulfuric acid-mediated ring opening and aryl migration to afford the corresponding 3-arylquinolin-4(1H)-ones (azaisoflavones).

Selenium can either be essential or toxic depending on the concentration and oxidation state. In this study, the concentrations of inorganic selenium [Se(IV)] in water samples were determined in the presence of hexavalent selenium [Se(VI)} in water. Water samples were collected from ten different sampling sites in Blood and Mokolo Rivers in Limpopo Province, South Africa. A solid phase extraction (SPE) method with Dowex 1 × 2 resin (chloride form) as an adsorbent material was used to preconcentrate and separate Se(IV) selectively in the presence of Se(VI) in water samples. Concentrations of Se(IV) were quantified by inductively coupled plasma-mass spectrometry (ICP-MS) and ranged from 0.0411 to 0.820 µg/L and 0.135 to 2.79 µg/L in Blood and Mokolo Rivers, respectively. The presence of Se(IV) in water samples collected from Blood and Mokolo Rivers suggests that industrial and agricultural activities around these rivers have an impact on water quality.

The structures and content variations of biomolecules can be seen using fluorophores and fluorophores-based probes or labels, which have advanced significantly in the wide spectrum of areas of biomedicine. Studying biological systems requires the use of organic fluorophores, which are made possible by modern microscope imaging techniques. The visualisation of biomolecule synthesis, conformational changes, and interactions in biological systems through fluorescence imaging, is one of the most potent bioanalytical methods. Mostly fluorescence imaging methods for biomedical studies primarily use fluorescent dyes and nanoparticles due to the insufficient fluorescence of biological device. Fluorophores and fluorophores-based probes or labels, which have made major advancements in a wide range of biomedical fields, can be used to observe the structures and content fluctuations of biomolecules. Organic-based fluorescent compounds have been widely used in biomedicine as raw materials for production of flexible imaging and sensing devices. Modern microscope imaging techniques enable the use of organic fluorophores, which are necessary for studying biological systems. Red/near-infrared emitting fluorophores have recently attracted a lot of scientific attention because they enable bioimaging applications with reduced autofluorescence interference and light scattering, two key hurdles to deep-tissue imaging, as well as reduced photodamage and photobleaching. Herein, we looked at the effectiveness and limitations of the current techniques for transforming significant organic fluorophores’ cores into derivatives with extended wavelengths of emission. Together, we discuss key sensing properties and typical applications of these fluorophores to produce molecular probes for biological analytes. Finally, we listed certain crucial elements to take into account when synthesising new fluorophores.