Triarylazoimidazole-ZnII, CdII, and HgII Complexes: Structures, Photophysics, and Antibacterial Properties

Novel triarylazoimidazoles containing strong electron donors (p-NEt2) or acceptors (p-NO2) by the azoaryl group, and their group 12 metal complexes were synthesized and fully characterized, including X-ray analysis for several complexes. Novel complexes exhibit red photo-luminescence emission (Φ up to  0.21) in a solution. Moreover, the antibacterial activity of complexes was tested against Gram-positive microorganism S. aureus and Gram-negative microorganism

Towards Anion Recognition and Precipitation with Water-Soluble 1,2,4-Selenodiazolium Salts: Combined Structural and Theoretical Study

The synthesis and structural characterization of a series of supramolecular complexes of bicyclic cationic pyridine-fused 1,2,4-selenodiazoles with various anions is reported. The binding of trifluoroacetate, tetrachloroaurate, tetraphenylborate, perrhenate, and pertechnetate anions in the solid state is regarded. All the anions interact with selenodiazolium cations exclusively via a pair of “chelating” Se· · · O and H· · · O non-covalent interactions, which make them an attractive, novel, non-classical supramolecular recognition unit or a synthon. Trifluoroacetate salts were conveniently generated via novel oxidation reaction of 2,2′-dipyridyl diselenide with bis(trifluoroacetoxy)iodo)benzene in the presence of corresponding nitriles. Isolation and structural characterization of transient 2-pyridylselenyl trifluoroacetate was achieved. X-ray analysis has demonstrated that the latter forms dimers in the solid state featuring very short and strong Se· · · O and Se· · · N ChB con-tacts. 1,2,4-Selenodiazolium trifluoroacetates or halides show good solubility in water. In contrast, (AuCl4 )−, (ReO4 )−, or (TcO4 )− derivatives immediately precipitate from aqueous solutions. Structural features of these supramolecular complexes in the solid state are discussed. The nature and energies of the non-covalent interactions in novel assembles were studied by the theoretical methods. To the best of our knowledge, this is the first study that regards perrhenate and pertechnetate as acceptors in ChB interactions. The results presented here will be useful for further developments in anion recognition and precipitation involving cationic 1,2,4-selenodiazoles. © 2022 by the authors. Licensee MDPI, Basel, Switzerland

High antibacterial activity and low toxicity of pyridoxal derivatives of chitosan and their nanoparticles

The pyridoxal derivatives of chitosan with various degrees of substitution (DS) were synthesized from low-, moderate- and high-molecular-weight chitosans by their reaction with pyridoxal followed by treatment with NaBH4. The derivative of moderate molecular weight and high DS demonstrated a maximum antibacterial activity against S. aureus and E. coli. The nanoparticles of this derivative obtained by ionic gelation are nontoxic, and they exhibit a high in vitro antibacterial effect, which slightly exceeds that of ampicillin and gentamicin. © 202

Novel Chalcogen Bond Donors Derived from [3+2] Cycloaddition Reaction between 2-Pyridylselenyl Reagents and Isocyanates: Synthesis, Structures and Theoretical Studies

A novel [3+2] cycloaddition reaction between 2-pyridylselenyl halides or trifluoroacetates and isocyanates is described herein. This new convenient methodology allows the synthesis of novel 3-oxo-1,2,4-selenodiazolium scaffolds, which are inaccessible by the known methods. The coupling proceeds efficiently for a broad scope of substrates under mild conditions and allows preparation of cationic 3-oxo-1,2,4-selenodiazolium salts in high yields. The mechanism was analyzed using DFT calculations, evidencing the concerted nature of the novel cycloaddition reaction. The new Se-containing heterocycles were demonstrated to be structurally easily tunable donors of the chalcogen bonding (ChB). Noncovalent interactions in the solid state were studied using DFT calculations, molecular electrostatic potential surfaces and the quantum theory of atoms-in-molecules

Ultrasound-assisted catalyst-free thiol-yne click reaction in chitosan chemistry: Antibacterial and transfection activity of novel cationic chitosan derivatives and their based nanoparticles

In this work, we demonstrate that the thiol-yne click reaction could be efficiently mediated by ultrasonic irradiation and implement the ultrasound-assisted thiol-yne click reaction to chitosan chemistry as a polymer-analogous transformation. We optimize power and frequency of ultrasound to preserve selectivity of the click reaction and avoid ultrasonic degradation of the chitosan polymer chain. Thus, we obtain a new water-soluble betaine. Using ionic gelation of the obtained betaine derivatives of chitosan, we prepare nanoparticles with a unimodal size distribution. Furthermore, we present results of antibacterial and transfection activity tests for the chitosan derivatives and their based nanoparticles. The derivative with a medium molecular weight and a high degree of substitution demonstrated the best antibacterial effect. It derived nanoparticles with a size of ca. 100 nm and ζ-potential of ca. +69 mV revealed even higher antibacterial activity, slightly superior to commercial antibiotics ampicillin and gentamicin. On the contrary, the obtained polymers possess a much more pronounced transfection activity as compared with their based nanoparticles and species with a low degree of substitution acts as the most efficient transfecting agent. Moreover, the obtained betaine chitosan derivatives as well as their derived nanoparticles are non-toxic. © 201

Synthesis and in vitro antifungal activity of selenium-containing chitin derivatives

Mild and ‘green’ ultrasound-assisted reaction of chitin with 3-(chloromethyl)[1,2,4]selenadiazolo[4,5-a]pyridin-4-ium bromide in water affords novel selenium-containing cationic chitin derivatives. The thus obtained chitin derivatives are water soluble and are characterized by high in vitro antifungal activity comparable with conventional antifungal drug Amphotericin B. © 202

Novel heterocyclic chitosan derivatives and their derived nanoparticles: Catalytic and antibacterial properties

The metal-assisted nitrone-nitrile cycloaddition reaction is apply to empower chitosan chemistry. The ultrasonic irradiation has proven to efficiently accelerate the cycloaddition affording new heterocyclic (1,2,4-oxadiazoline) chitosan derivatives and avoiding ultrasonic degradation of the chitosan macromolecules. By varying the nitrone nature, both water- and toluene-soluble chitosan derivatives were successfully synthesized. Relying on the ionic gelation approach nanoparticles of heterocyclic chitosan derivatives were prepared. Water-soluble chitosan derivative demonstrated a high antibacterial activity coupled with low toxicity. The toxicity of the synthesized heterocyclic chitosan derivatives and their based nanoparticles are comparable with those of the starting chitosan, while their antibacterial activity is superior. Toluene-soluble derivatives are shown to be efficient homogeneous catalysts towards monoglyceride synthesis via the epoxide ring opening. They efficiently catalyze selective conversion of fatty acids and glycidol into corresponding monoglycerides allowing one to simplify significantly the procedure for separating the reaction product from the catalyst for its recovery and reusage. © 2020 Elsevier B.V

Novel biopolymer-based nanocomposite food coatings that exhibit active and smart properties due to a single type of nanoparticles

We used nanoparticles which possess simultaneously active (antimicrobial, UV-protective and antioxidant) and smart (temperature sensing) properties. The nanoparticles (2Rh = 450 nm, PDI = 0.118 ± 0.014, ζ-potential = 21 mV and Tg = 8 ± 1 °C) are based on polyethylene glycol (PEG)/methyl cellulose (MC) core with anthocyanidin and sodium acetate, and chitosan/gallotannin-based shell. The core of nanoparticles acts as a temperature indicator, changing its color from colorless into deep purple at 8 °C, while the shell provides antimicrobial (due to chitosan), UV-protective and antioxidant (due to gallotannin) effects. We incorporated these nanoparticles into the chitosan matrix. The coatings demonstrated improved mechanical and barrier properties compared with the pure chitosan coating. The elaborated coatings pronouncedly improve the shelf-life of Ricotta cheese. Moreover, they serve as thermo indicators, which warn about cheese storage at an unacceptable temperature. Thus, we developed new coatings in which all properties are enabled by a single type of nanoparticles. © 2020 Elsevier Lt

Synthesis of Selenium-Containing Chitosan Derivatives and Their Antibacterial Activity

Abstract: The interaction of chitosan with 3-(chloromethyl)-[1,2,4]selendiazole[4,5-a]pyridin-4 bromide results in water-soluble, selenium-containing, cationic chitosan derivatives. Derivatives of chitosan with degrees of substitution of 0.15, 0.45, and 0.65 were obtained. These derivatives are characterized by a pronounced in vitro antibacterial activity against Staphylococcus aureus and Escherichia coli, and the antibacterial activity of the derivatives increases with an increase in their degree of substitution. The antibacterial activity of the highly substituted derivative is comparable to that of the conventional antibiotics ampicillin and gentamicin. © 2022, The Author(s)

Adducts of 2-Pyridylselenenyl Halides and Nitriles as Novel Supramolecular Building Blocks: Four-Center Se···N Chalcogen Bonding versus Other Weak Interactions

Supramolecular chemistry of chalcogenadiazoles is attracting an increasing attention due to its applications in materials chemistry. Chalcogen bonding allows a fine-tuning of the self-assembly and, therefore, modulation of physical properties when these compounds are employed. Here, we report a facile preparation of a broad scope of 1,2,4-selenadiazoles via coupling of 2-pyridylselenenyl halides with unactivated nitriles, that represent a novel type of supramolecular building blocks which eagerly engage in a variety of chalcogen bonding interactions. The substituent-dependent propensity of novel selenadiazoles for the formation of four-center Se···N chalcogen bonding is analyzed. Other weak interactions, which in some cases outcompete the formation of 2Se-2N squares, are described. The discovery of the adducts derived from α-halogenated nitriles, which form robust dimers featuring a very specific combination of 2Se-2N square, two Hal···Hal, and two Se···Hal noncovalent interactions, is presented. © 2021 American Chemical Society