Zinc (II) and AIEgens: The “Clip Approach” for a Novel Fluorophore Family. A Review

Aggregation-induced emission (AIE) compounds display a photophysical phenomenon in which the aggregate state exhibits stronger emission than the isolated units. The common term of “AIEgens” was coined to describe compounds undergoing the AIE effect. Due to the recent interest in AIEgens, the search for novel hybrid organic–inorganic compounds with unique luminescence properties in the aggregate phase is a relevant goal. In this perspective, the abundant, inexpensive, and nontoxic d10 zinc cation offers unique opportunities for building AIE active fluorophores, sensing probes, and bioimaging tools. Considering the novelty of the topic, relevant examples collected in the last 5 years (2016–2021) through scientific production can be considered fully representative of the state-of-the-art. Starting from the simple phenomenological approach and considering different typological and chemical units and structures, we focused on zinc-based AIEgens offering synthetic novelty, research completeness, and relevant applications. A special section was devoted to Zn(II)-based AIEgens for living cell imaging as the novel technological frontier in biology and medicine.

Study of the Interaction of Zinc Cation with Azithromycin and its Significance in the COVID-19 Treatment: A Molecular Approach

Introduction: On account of the current COVID-19 pandemic, we have explored the importance of azithromycin and zinc in the treatment of the coronavirus disease by studying the interaction between the cation Zn++ and azithromycin with the tools of the semi-empirical quantum mechanics PM3 method. Methods: By this approach, the niche in which Zn++ is located was determined. Zn++ creates a strong clastic binding between an amine and a hydroxyl group located on the amino-hexose side-chain. Such an interaction serves as a shuttle and allows zinc cation to invade endocellular structures. Results: In this triple collaborative association, the role of hydroxychloroquine would be more that of a chaotropic agent at plasmic membranes, which facilitates access to the azithromycin-Zn++ equipage into key internal compartments. Conclusion: Finally, we show that both azithromycin and Zn++ are susceptible to play a direct role against the replication and the assembly of SARS-CoV-2 particles.

Crystal structure of {4-[10,15,20-tris(4-methoxyphenyl)porphyrin-5-yl]benzyl 2-diazoacetato}zinc(II)

In the title compound, [Zn(C50H36N6O5)], the ZnII cation is chelated by four pyrrole N atoms of the porphyrinate anion and coordinated by a symmetry-generated keto O atom of the diazoester group in a distorted square-pyramidal geometry. The mean Zn—N(pyrrole) bond length is 2.058 Å and the Zn—O(diazoester) bond length is 2.179 (4) Å. The zinc cation is displaced by 0.2202 (13) Å from the N4C20 mean plane of the porphyrinate anion toward the O atom; the involvement of this atom leads to a [100] polymeric chain in the crystal.

CATALYTIC INFLUENCE OF PYRIDINE ON COMPLEX-FORMING ABILITY OF OCTA(m-THREEFLUOROMETHYLPHENYL)PORPHYRAZINE AND HEXA(m-THREEFLUOROMETHYLPHENYL)BENZOPORPHYRASINE WITH ZINC ACETATE IN BENZENE

The complexation of octa(m-threefluoromethylphenyl)porphyrazine and hexa(m-three-fluoromethylphenyl)benzoporphyrazine with zinc acetate in the pyridine-benzene system was studied. It was preliminary established that the electron absorption spectrum of octa(m-threefluoromethylphenyl)porphyrazine and hexa(m-threefluoromethylphenyl)benzoporphyrazine in benzene contains a split Q-line in the visible spectrum, which is typical for the D2h symmetry of the π-chromophore of the molecule. The kinetically controlled reaction of formation of the zinc complex with the studied porphyrazines is observed only at a pyridine concentration in benzene of more than 0.09 mol/l. The reaction proceeds in the concentration range from 0.09 to 0.25 mol / l in benzene. Complexation is accompanied by an increase in the molecule symmetry from D2h to D4h, which indicates the formation of a zinc complex with octa(m-threefluoromethylphenyl)porphyrazine and hexa(m-threefluoromethylphenyl)benzoporphyrasine. It was found that the complexation is observed in a fairly narrow range of concentrations of pyridine in benzene, which made it impossible to determine the reaction order on the base. Considering the pronounced proton acceptor ability of the studied porphyrazines, a possible scheme of the mechanism includes the initial stage of the acid-base interaction of the macrocyclic molecule with pyridine to form the H-complex, followed by the entry of the zinc cation into the coordination region of the porphyrazine macrocycle. It was found that the rate of complexation of octa(m-threefluoromethylphenyl)porphyrazine and hexa(m-threefluoromethylphenyl)benzoporphyrasine with zinc acetate increases with an increase in the concentration of pyridine in benzene at sufficiently low values of the activation energy of the process. This is due not only to the electron-acceptor influence of the nitrogen meso-atoms and substituents in the pyrrole rings of porphyrazine, which increase the polarity of the NH-bonds, but also to the proton-acceptor ability of pyridine, which supports the removal of NH-groups protons from the macrocycle region. It was found that benzo-substitution in octa(m-threefluoromethylphenyl)porphyrazine does not affect the rate and activation parameters of zinc complex formation, which indicates a close protonisation of intra-cyclic NH-bonds of porphyrazine molecules.Forcitation:Osipova G.V., Petrov O.A. Catalytic influence of pyridine on complex-forming ability of octa(m-threefluoromethylphenyl)porphyrazine and hexa(m-threefluoromethylphenyl)benzoporphyrasine with zinc acetate in benzene. Izv. Vyssh. Uchebn. Zaved. Khim. Khim. Tekhnol. 2018. V. 61. N 7. P. 31-36

Isoform-selective HDAC1/6/8 inhibitors with an imidazo-ketopiperazine cap containing stereochemical diversity

A series of hydroxamic acids linked by different lengths to a chiral imidazo-ketopiperazine scaffold were synthesized. The compounds with linker lengths of 6 and 7 carbon atoms were the most potent in histone deacetylase (HDAC) inhibition, and were specific submicromolar inhibitors of the HDAC1, HDAC6 and HDAC8 isoforms. A docking model for the binding mode predicts binding of the hydroxamic acid to the active site zinc cation and additional interactions between the imidazo-ketopiperazine and the enzyme rim. The compounds were micromolar inhibitors of the MV4-11, THP-1 and U937 cancer cell lines. Increased levels of histone H3 and tubulin acetylation support a cellular mechanism of action through HDAC inhibition. This article is part of a discussion meeting issue ‘Frontiers in epigenetic chemical biology’.

Assessment of some nutrient contents and enzyme activity in early germinating bean of two soybean varieties (Glycine max) DT84 and DT2008

Soybeans have become widly important and popular due to a high demand of plant protein and fiber. Besides, grains of soybean contain abundance of vitamines, minerals and bioactive compounds such as isoflavone, gama- aminobutyric acid... However, some antinutrient compounds such as tripsin inhibitor and phytate are available in these grains. In this paper, nutrient compounds (protein, lipid, polysaccharide and dissolved minerals) and enzymes of early germinating seeds of soybean varieties (DT84 and DT2008) were evaluated and compared to those of non-germinating beans in order to determine a suitable germinating period for food processing. Experimental results showed that: Activities of enzymes (protease, amylase and phytase) in early germinating soybeans were higher than those in dry beans. Those enzymes have made major changes in nutrient compounds of soybeans: proteins, polysaccharides and lipids reduced. Especially, the content of phytate, an antinutrient factor, reduced signicantly (17.0-48.9% in DT84 variety and 28.0-60.7% in DT2008 variety) during early germinating period of soybeans. However, easy uptake minerals (calcium, iron and zinc ions), reduced sugars and peptides were significantly increased. In detail, the increase in dissolve iron cation was 10.31-12.13%, calcium cation was 31.56-35.75% and zinc cation was 31.38-43.32%. These results confirmed the positive effect of germinating soybeans in food processing.