In vitro and in vivo antiproliferative activity on lung cancer of two acylhydrazone based zinc(II) complexes.

Two acylhydrazone based zinc(II) complexes [Zn(HL)2Cl2(CH3OH)2] (Zn1) and [ZnL(AC)]2 (Zn2) were synthesized from 3-(1-(salicyloylhydrazono)ethyl) pyridine (HL). Single crystal X-ray structure analyses showed that complexes Zn1 and Zn2 have a zero-dimensional monomer or dimer structure. Antiproliferative activity studies revealed that Zn1 and Zn2 are both more effective against A549 cells than cisplatin. The results of the reactive oxygen species (ROS) generation assay on A549 cells showed that both Zn1 and Zn2 induced apoptosis through ROS accumulation. The apoptosis-inducing and cell cycle arrest effects of Zn1 and Zn2 on A549 cells indicated that the antitumor effect was achieved through apoptosis induction and inhibition of DNA synthesis by blocking the G0/G1 phase of the cell cycle. What's more, the results of wound-healing assay showed that Zn1 and Zn2 could inhibit the migration of A549 cells. Western blot analysis further demonstrated that Zn1 and Zn2 induced cell apoptosis through the mitochondrial pathway, in which process, the expression level of cytochrome C, cleaved-PARP, cleaved-caspase 3 and cleaved-caspase 9 proteins increased while pro-caspase 3 and pro-caspase 9 expression decreased. In vivo anticancer evaluation demonstrated that both Zn1 and Zn2 complexes effectively inhibited tumor growth without causing significant toxicity in systemic organs.

Design of New Bis(1,2,3-triazol-1-yl)methane-Based Nitrogen Ligands: Synthesis and Coordination Chemistry.

The reaction between bis(1,2,3-triazol-1-yl)methane derivatives and nBuLi and various aldehydes, yielded novel neutral ligand precursors incorporating alcohol functional groups. The resulting compounds exhibited distinct characteristics depending on the steric hindrance of the aldehyde employed. In instances where aromatic aldehydes were utilized, functionalization occurred at the methine group bridging both triazole rings. Conversely, the use of pivalic aldehyde prompted functionalization at the C5 position of the triazole ring. These compounds were subsequently employed as ligand precursors in the synthesis of organometallic aluminum and zinc complexes, yielding dinuclear complexes with high efficiency. The structural elucidation of all compounds was accomplished through spectroscopic methods and validated by X-ray crystallography. Preliminary catalytic investigations into the coupling reaction of cyclohexene oxide and CO2 revealed that aluminum and zinc complexes catalyzed the selective formation of polyether and polycarbonate materials, respectively.

Antibacterial Photodynamic Therapy by Zn(II)-Curcumin Complex: Synthesis, Characterization, DFT Calculation, Antibacterial Activity, and Molecular Docking.

The increase in antibacterial drug resistance is threatening global health conditions. Recently, antibacterial photodynamic therapy (aPDT) has emerged as an effective antibacterial treatment with high cure gain. In this work, three Zn(II) complexes viz., [Zn(en)(acac)Cl] (1), [Zn(bpy)(acac)Cl] (2), [Zn(en)(cur)Cl] (3), where en=ethylenediamine (1 and 3), bpy=2,2'-bipyridine (2), acac=acetylacetonate (1 and 2), cur=curcumin monoanionic (3) were developed as aPDT agents. Complexes 1-3 were synthesized and fully characterized using NMR, HRMS, FTIR, UV-Vis. and fluorescence spectroscopy. The HOMO-LUMO energy gap (Eg), and adiabatic splittings (ΔS1-T1 and ΔS0-T1 ) obtained from DFT calculation indicated the photosensivity of the complexes. These complexes have not shown any potent antibacterial activity under dark conditions but the antibacterial activity of these complexes was significantly enhanced upon light exposure (MIC value up to 0.025 µg/mL) due to their light-mediated 1 O2 generation abilities. The molecular docking study suggested that complexes 1-3 interact efficiently with DNA gyrase B (PDB ID: 4uro). Importantly, 1-3 did not show any toxicity toward normal HEK-293 cells. Overall, in this work, we have demonstrated the promising potential of Zn(II) complexes as effective antibacterial agents under the influence of visible light.

Synthesis, Characterization, and DFT Calculations of a New Sulfamethoxazole Schiff Base and Its Metal Complexes.

A new Schiff base, 4-((1E,2E)-3-(furan-2-yl)allylidene)amino)-N-(5-methylisoxazol-3-yl) benzene-sulfonamide (L), was synthesized by thermal condensation of 3-(2-furyl)acrolein and sulfamethoxazole (SMX), and the furan Schiff base (L) was converted to a phenol Schiff base (L') according to the Diels-Alder [4 + 2] cycloaddition reaction and studied experimentally. The structural and spectroscopic properties of the Schiff base were also corroborated by utilizing density functional theory (DFT) calculations. Furthermore, a series of lanthanide and transition metal complexes of the Schiff base were synthesized from the nitrate salts of Gd, Sm, Nd, and Zn (L1, L2, L3, and L4), respectively. Various spectroscopic studies confirmed the chemical structures of the Schiff-base ligand and its complexes. Based on the spectral studies, a nine-coordinated geometry was assigned to the lanthanide complexes and a six-coordinated geometry to the zinc complex. The elemental analysis data confirmed the suggested structure of the metal complexes, and the TGA studies confirmed the presence of one coordinated water molecule in the lanthanide complexes and one crystalline water molecule in the zinc complex; in addition, the conductivity showed the neutral nature of the complexes. Therefore, it is suggested that the ligand acts as a bidentate through coordinates to each metal atom by the isoxazole nitrogen and oxygen atoms of the sulfur dioxide moiety of the SMX based on FTIR studies. The ligand and its complexes were tested for their anti-inflammatory, anti-hemolytic, and antioxidant activities by various colorimetric methods. These complexes were found to exhibit potential effects of the selected biological activities.

Plant growth-promoting traits of culturable seed microbiome of citrus species from Purvanchal Himalaya.

Despite Northeastern India being "Treasure House of Citrus Genetic Wealth," genetic erosion of citrus diversity poses severe concern with a corresponding loss in seed microbial diversity. The seed microbiome of citrus species unique to the Purvanchal Himalaya is seldom explored for their use in sustainable orchard management. Isolation and characterization of culturable seed microbiomes of eight citrus species, namely, Citrus reticulata Blanco, C. grandis (L.) Osbeck, C. latipes Tanaka, C. megaloxycarpa Lushaigton, C. jambhiri Lush, C. sinensis (L.) Osbeck, C. macroptera Montr, and C. indica Tanaka collected from NE India were carried out. The isolates were then screened for an array of plant growth-promoting (PGP) traits [indole acetic acid (IAA) production, N2 fixation, phosphate and zinc complex dissolution, siderophores, and Hydrogen Cyanide (HCN) production]. The pure culture isolates of seed microbiomes were capable of dissolving insoluble Ca3(PO4)2 (1.31-4.84 µg Pi ml-1 h-1), Zn3(PO4)2 (2.44-3.16 µg Pi ml-1 h-1), AlPO4 (1.74-3.61 µg Pi ml-1 h-1), and FePO4 (1.54-4.61µg Pi ml-1 h-1), mineralized phytate (12.17-18.00 µg Pi ml-1 h-1) and produced IAA-like substances (4.8-187.29 µg ml-1 h-1). A few isolates of the seed microbiome were also able to fix nitrogen, secrete siderophore-like compounds and HCN, and dissolve ZnSO4 and ZnO. The 16S ribosomal Ribonucleic Acid (rRNA)-based taxonomic findings revealed that Bacillus was the most dominant genus among the isolates across citrus species. Isolates CG2-1, CME6-1, CME6-4, CME6-5, CME6-9, CJ7-1, CMA10-1, CI11-3, and CI11-4 were identified as promising bioinoculants for development of microbial consortium having multifaceted PGP traits for nutritional benefits of nitrogen, phosphorus and zinc, and IAA hormonal benefits to citrus crops for better fitness in acid soils.

Pyrene-Containing Polyamines as Fluorescent Receptors for Recognition of PFOA in Aqueous Media.

The globally widespread perfluorooctanoic acid (PFOA) is a concerning environmental contaminant, with a possible toxic long-term effects on the environment and human health The development of sensible, rapid, and low-cost detection systems is a current change in modern environmental chemistry. In this context, two triamine-based chemosensors, L1 and L2, containing a fluorescent pyrene unit, and their Zn(II) complexes are proposed as fluorescent probes for the detection of PFOA in aqueous media. Binding studies carried out by means of fluorescence and NMR titrations highlight that protonated forms of the receptors can interact with the carboxylate group of PFOA, thanks to salt bridge formation with the ammonium groups of the aliphatic chain. This interaction induces a decrease in the fluorescence emission of pyrene at neutral and slightly acidic pH values. Similarly, emission quenching has also been observed upon coordination of PFOA by the Zn(II) complexes of the receptors. These results evidence that simple polyamine-based molecular receptors can be employed for the optical recognition of harmful pollutant molecules, such as PFOA, in aqueous media.

Zn2+ and Cu2+ Interaction with the Recognition Interface of ACE2 for SARS-CoV-2 Spike Protein.

The spike protein (S) of SARS-CoV-2 is able to bind to the human angiotensin-converting enzyme 2 (ACE2) receptor with a much higher affinity compared to other coronaviruses. The binding interface between the ACE2 receptor and the spike protein plays a critical role in the entry mechanism of the SARS-CoV-2 virus. There are specific amino acids involved in the interaction between the S protein and the ACE2 receptor. This specificity is critical for the virus to establish a systemic infection and cause COVID-19 disease. In the ACE2 receptor, the largest number of amino acids playing a crucial role in the mechanism of interaction and recognition with the S protein is located in the C-terminal part, which represents the main binding region between ACE2 and S. This fragment is abundant in coordination residues such as aspartates, glutamates, and histidine that could be targeted by metal ions. Zn2+ ions bind to the ACE2 receptor in its catalytic site and modulate its activity, but it could also contribute to the structural stability of the entire protein. The ability of the human ACE2 receptor to coordinate metal ions, such as Zn2+, in the same region where it binds to the S protein could have a crucial impact on the mechanism of recognition and interaction of ACE2-S, with consequences on their binding affinity that deserve to be investigated. To test this possibility, this study aims to characterize the coordination ability of Zn2+, and also Cu2+ for comparison, with selected peptide models of the ACE2 binding interface using spectroscopic and potentiometric techniques.

Distinguishing Plasmin-Generating Microvesicles: Tiny Messengers Involved in Fibrinolysis and Proteolysis.

A number of stressors and inflammatory mediators (cytokines, proteases, oxidative stress mediators) released during inflammation or ischemia stimulate and activate cells in blood, the vessel wall or tissues. The most well-known functional and phenotypic responses of activated cells are (1) the immediate expression and/or release of stored or newly synthesized bioactive molecules, and (2) membrane blebbing followed by release of microvesicles. An ultimate response, namely the formation of extracellular traps by neutrophils (NETs), is outside the scope of this work. The main objective of this article is to provide an overview on the mechanism of plasminogen reception and activation at the surface of cell-derived microvesicles, new actors in fibrinolysis and proteolysis. The role of microvesicle-bound plasmin in pathological settings involving inflammation, atherosclerosis, angiogenesis, and tumour growth, remains to be investigated. Further studies are necessary to determine if profibrinolytic microvesicles are involved in a finely regulated equilibrium with pro-coagulant microvesicles, which ensures a balanced haemostasis, leading to the maintenance of vascular patency.

Grafted dinuclear zinc complexes for selective recognition of phosphatidylserine: Application to the capture of extracellular membrane microvesicles.

Microvesicles (MVs) are key markers in human body fluids that reflect cellular activation related to diseases as thrombosis. These MVs display phosphatidylserine at the outer leaflet of their plasma membrane as specific recognition moieties. The work reported in this manuscript focuses on the development of an original method where MVs are captured by bimetallic zinc complexes. A set of ligands have been synthetized based on a phenol spacer bearing in para position an amine group appended to a short or a longer alkyl chain (for grafting on surface) and bis(dipicolylamine) arms in ortho position (for zinc coordination). The corresponding dibridged zinc phenoxido and hydroxido complexes have been prepared in acetronitrile in presence of triethylamine and characterized by several spectroscopic techniques. The pH-driven interconversion studies for both complexes in H2O:DMSO (70:30) evidence that at physiologic pH the main species are mono-bridged by the phenoxido spacer. An X-Ray structure obtained from complex 2 (based on the ligand with the amine group on the short chain) in aqueous medium confirms the presence of a mono-bridged complex. Then, the complexes have been used for interaction studies with short-chain phospholipids. Both have established the selective recognition of the anionic phosphatidylserine model versus zwitterionic phospholipids (in solution by 31P NMR and after immobilization on solid support by surface plasmon resonance (SPR)). Moreover, both complexes have also demonstrated their ability to capture MVs isolated from human plasma. These complexes are thus promising candidates for MVs probing by a new approach based on coordination chemistry.

Syntheses, Characterization and Crystal Structures of Dicyanamide Bridged Polynuclear Copper(II) and Zinc(II) Complexes with Urease Inhibitory Activity.

A pair of structurally similar dicyanamide bridged copper(II) and zinc(II) complexes [CuL(dca)]n (1) and [ZnL(dca)]n (2), were prepared from the fluorine containing Schiff base 5-fluoro-2-(((2-hydroxyethyl)imino)methyl)phenol (HL). The compounds were characterized by physico-chemical methods. Structures of the complexes were confirmed by single crystal X-ray diffraction. The Cu atom in complex 1 is in square pyramidal coordination, whereas the Zn atom in complex 2 is in trigonal bipyramidal coordination. The copper complex has effective Jack bean urease inhibitory activity, with IC50 value of 0.14±0.12 µmol L-1.

Effective Ligand Design: Zinc Complexes with Guanidine Hydroquinoline Ligands for Fast Lactide Polymerization and Chemical Recycling.

In this study, the synthesis of two new guanidine hydroquinoline ligands served as basis for six new zinc guanidine complexes. Two of these complexes showed very high activity in the lactide polymerization under industrial conditions. The lactide polymerization was demonstrated in solution and melt conditions observing high activity and molar masses up to 90 000 g mol-1 . Density functional theory studies elucidated the high activity of the complexes associated with the influence of the ligand backbone and the use of triflate counterions. On the way towards a circular economy, polymerization and depolymerization go hand in hand. So far, guanidine complexes have only shown their good activity in the ring opening polymerization of esters, and guanidine complexes with pure N donors have not been tested in recycling processes. Herein, the excellent ability of zinc guanidine complexes to catalyze both polymerization and depolymerization was demonstrated. The two most promising zinc complexes efficiently mediated the methanolysis of polylactide into methyl lactate under mild reaction conditions.

Instantaneous High-Resolution Visual Imaging of Latent Fingerprints in Water Using Color-Tunable AIE Pincer Complexes.

Instant visualization of latent fingerprints is developed by using a series of water-soluble terpyridine zinc complexes as aggregation-induced emission probes in pure water, under UV light or ambient sunlight. By simply soaking, or spraying with an aqueous solution of the probe, bright yellow fluorescence images with high contrast and resolution are readily developed on various surfaces including tinfoil, glass, paper, steel, leather, and ceramic tile. Remarkably, latent fingerprints can be visualized within seconds including details of whorl and sweat pores. The color of emission can be tuned from blue to orange by modifying the pincer ligands, allowing direct imaging under sunlight. These inexpensive, water-resistant, and color-tunable probes provide a practical approach for latent fingerprints recording and analysis, security protection, as well as criminal investigation in different scenarios.

Liposomal Formulations of a New Zinc(II) Complex Exhibiting High Therapeutic Potential in a Murine Colon Cancer Model.

Colorectal cancer is the second leading cause of cancer-related mortality. Many current therapies rely on chemotherapeutic agents with poor specificity for tumor cells. The clinical success of cisplatin has prompted the research and design of a huge number of metal-based complexes as potential chemotherapeutic agents. In this study, two zinc(II) complexes, [ZnL2] and [ZnL(AcO)], where AcO is acetate and L is an organic compound combining 8-hydroxyquinoline and a benzothiazole moiety, were developed and characterized. Analytical and spectroscopic studies, namely, NMR, FTIR, and UV-Vis allowed us to establish the complexes' structures, demonstrating the ligand-binding versatility: tetradentate in [ZnL(AcO)] and bidentate in [ZnL2]. Complexes were screened in vitro using murine and human colon cancer cells cultured in 2D and 3D settings. In 2D cells, the IC50 values were <22 µM, while in 3D settings, much higher concentrations were required. [ZnL(AcO)] displayed more suitable antiproliferative properties than [ZnL2] and was chosen for further studies. Moreover, based on the weak selectivity of the zinc-based complex towards cancer cell lines in comparison to the non-tumorigenic cell line, its incorporation in long-blood-circulating liposomes was performed, aiming to improve its targetability. The resultant optimized liposomal nanoformulation presented an I.E. of 76% with a mean size under 130 nm and a neutral surface charge and released the metal complex in a pH-dependent manner. The antiproliferative properties of [ZnL(AcO)] were maintained after liposomal incorporation. Preliminary safety assays were carried out through hemolytic activity that never surpassed 2% for the free and liposomal forms of [ZnL(AcO)]. Finally, in a syngeneic murine colon cancer mouse model, while free [ZnL(AcO)] was not able to impair tumor progression, the respective liposomal nanoformulation was able to reduce the relative tumor volume in the same manner as the positive control 5-fluorouracil but, most importantly, using a dosage that was 3-fold lower. Overall, our results show that liposomes were able to solve the solubility issues of the new metal-based complex and target it to tumor sites.

Crystal structure of bis-(ammonium) bis-[penta-aqua-(di-methyl-formamide)-zinc(II)] deca-vanadate tetra-hydrate.

The crystalline product (NH4)2[Zn(C3H7NO)(H2O)5]2[V10O28]·4H2O was success-fully isolated from an H2O/DMF solvent combination by evaporation at ambient temperature. The salt crystallizes in the P21/n space group. Imidazole, initially used in the synthesis but not present in the product, and DMF solvent appear to affect the synthesis and crystallization as structural-directing agents. In the title compound, the complex cation [Zn(H2O)5(DMF)]2+ acts as a counter-ion without being directly coordinated to the deca-vanadate anion. An extensive framework of hydrogen bonds integrates the whole architecture as evidenced by X-ray crystallography. The polyoxometalate [V10O28]6- lies on a center of symmetry while the complex cation [Zn(H2O)5(DMF)]2+ links three adjacent anions through a set of 2 + 2 + 3 hydrogen bonds.

Distinct Bimetallic Cooperativity Among Water Reduction Catalysts Containing [CoIII CoIII ], [NiII NiII ], and [ZnII ZnII ] Cores.

Three binuclear species [LCoIII 2 (µ-Pz)2 ](ClO4 )3 (1), [LNiII 2 (CH3 OH)2 Cl2 ]ClO4 (2), and [LZnII 2 Cl2 ]PF6 (3) supported by the deprotonated form of the ligand 2,6-bis[bis(2-pyridylmethyl) amino-methyl]-4-methylphenol were synthesized, structurally characterized as solids and in solution, and had their electrochemical and spectroscopic behavior established. Species 1-3 had their water reduction ability studied aiming to interrogate the possible cooperative catalytic activity between two neighboring metal centers. Species 1 and 2 reduced H2 O to H2 effectively at an applied potential of -1.6 VAg/AgCl , yielding turnover numbers of 2,820 and 2,290, respectively, after 30 minutes. Species 3 lacked activity and was used as a negative control to eliminate the possibility of ligand-based catalysis. Pre- and post-catalytic data gave evidence of the molecular nature of the process within the timeframe of the experiments. Species 1 showed structural, rather than electronic cooperativity, while species 2 displayed no obvious cooperativity. DFT methods complemented the experimental results determining plausible mechanisms.

New thiosemicarbazone-based Zinc(II) complexes. In vitro cytotoxicity competing with cisplatin on malignant melanoma A375 cells and its relation to neuraminidase inhibition.

New thiosemicarbazone-based zinc(II) complexes were synthesized to study their cytotoxicity on A375 malignant melanoma cells. The complexes containing salicylidene (Zn1a), 3-methoxy-salicylidene (Zn1b) or 4-methoxy-salicylidene (Zn1c) moiety were characterized by analytical and spectroscopic methods. Anticancer potential of the complexes was determined by MTT test and HUVEC endothelial cells line was used to comprehend the effect on normal cells. Zn1b with an IC50 of 13 µM was found to be highly cytotoxic against A375 cancer cells, more effective than cisplatin (IC50: 37 µM). Zn1a and Zn1c did not have a negative effect on cell viability in the normal cells and gave the impression that they are more advantageous than cisplatin in this respect. Further, the ability of Zn1a-c to inhibit neuraminidase enzyme and its role in cytotoxicity was discussed. The test revealed that the Zn1b with 3-methoxy substituent exhibited higher inhibition activity against the neuraminidase than the Zn1a and Zn1c as analogical to the cytotoxicity results. In neuraminidase inhibition, IC50 values of Zn1b and Zn1c were 14 and 66 µM, respectively. These concentrations were very close to the cytotoxicity concentrations for Zn1b and Zn1c. The findings may indicate the role of neuraminidase enzyme inhibition in cell death for Zn1b and Zn1c.

Zinc 1,2,4-triazolo[1,5-a]pyrimidine Complexes: Synthesis, Structural Characterization and their Effect Against Chagas Disease.

BACKGROUND: The World Health Organization catalogues illnesses such as Chagas disease as neglected diseases, due to the low investment in new drugs to fight them. The search for novel and non-side effects anti-parasitic compounds is one of the urgent needs of the Third World. The use of triazolopyrimidines and their metal complexes have demonstrated hopeful results in this field. OBJECTIVE: This work studies the antiparasitic efficacy against Trypanosoma cruzi strains of a series of zinc triazolopyrimidine complexes. METHODS: A series of Zn complexes has been synthesized by the reaction between the triazolopyrimidine derivatives 7-amino-1,2,4-triazolo[1,5-a]pyrimidine (7atp) and 5,7-dimethyl-1,2,4-triazolo[1,5- a]pyrimidine (dmtp) with Zn(SO4) · 7H2O, ZnCl2, and Zn(NO3)2 · 6H2O salts. The complexes have been analyzed by spectroscopic and thermal assays and X-ray diffraction methods have been used to dilucidate the crystalline structure of one of them. The antiparasitic efficacy was tested in vitro against Trypanosoma cruzi to compare the trypanocidal effect of different ligands and counteranions to fight Chagas disease. RESULTS: The efficacy of these compounds against Trypanosoma cruzi has also been tested to compare the influence of different ligands and counteranions on the trypanocidal effect against Chagas disease. CONCLUSION: Antiproliferative tests corroborate the synergistic trypanocidal effect of the triazolopyrimidine coordination complexes.

Zinc Complexes with 1,3-Diketones as Activators for Sulfur Vulcanization of Styrene-Butadiene Elastomer Filled with Carbon Black.

Zinc oxide nanoparticles (N-ZnO) and zinc complexes with 1,3-diketones of different structures were applied instead of microsized zinc oxide (M-ZnO) to activate the sulfur vulcanization of styrene-butadiene rubber (SBR). The influence of vulcanization activators on the cure characteristics of rubber compounds, as well as crosslink density and functional properties of SBR vulcanizates, such as tensile properties, hardness, damping behavior, thermal stability and resistance to thermo-oxidative aging was explored. Applying N-ZnO allowed to reduce the content of zinc by 40% compared to M-ZnO without detrimental influence on the cure characteristic and performance of SBR composites. The activity of zinc complexes in vulcanization seems to strongly depend on their structure, i.e., availability of zinc to react with curatives. The lower the steric hindrance of the substituents and thus the better the availability of zinc ions, the greater was the activity of the zinc complex and consequently the higher the crosslink density of the vulcanizates. Zinc complexes had no detrimental effect on the time and temperature of SBR vulcanization. Despite lower crosslink density, most vulcanizates with zinc complexes demonstrated similar or improved functional properties in comparison with SBR containing M-ZnO. Most importantly, zinc complexes allowed the content of zinc in SBR compounds to be reduced by approximately 90% compared to M-ZnO.

Ring-Opening Copolymerization of Cyclohexene Oxide and Cyclic Anhydrides Catalyzed by Bimetallic Scorpionate Zinc Catalysts.

The catalytic activity and high selectivity reported by bimetallic heteroscorpionate acetate zinc complexes in ring-opening copolymerization (ROCOP) reactions involving CO2 as substrate encouraged us to expand their use as catalysts for ROCOP of cyclohexene oxide (CHO) and cyclic anhydrides. Among the catalysts tested for the ROCOP of CHO and phthalic anhydride at different reaction conditions, the most active catalytic system was the combination of complex 3 with bis(triphenylphosphine)iminium as cocatalyst in toluene at 80 °C. Once the optimal catalytic system was determined, the scope in terms of other cyclic anhydrides was broadened. The catalytic system was capable of copolymerizing selectively and efficiently CHO with phthalic, maleic, succinic and naphthalic anhydrides to afford the corresponding polyester materials. The polyesters obtained were characterized by spectroscopic, spectrometric, and calorimetric techniques. Finally, the reaction mechanism of the catalytic system was proposed based on stoichiometric reactions.

Molecular docking identification for the efficacy of some zinc complexes with chloroquine and hydroxychloroquine against main protease of COVID-19.

Vast amount of research has been recently conducted to discover drugs for efficacious treatment of corona virus disease 2019 (COVID-19). The ambiguity about using Chloroquine/ Hydroxychloroquine to treat this illness was a springboard towards new methods for improving the adequacy of these drugs. The effective treatment of COVID-19 using Zinc complexes as add-on to Chloroquine/ Hydroxychloroquine has received major attention in this context. The current studies have shed a light on molecular docking and molecular dynamics methodologies as powerful techniques in establishing therapeutic strategies to combat COVID-19 pandemic. We are proposing some zinc compounds coordination to Chloroquine/ Hydroxychloroquine in order to enhance their activity. The molecular docking calculations showed that Zn(QC)Cl2(H2O) has the least binding energy -7.70 Kcal /mol then Zn(HQC)Cl2(H2O) -7.54 Kcal /mol. The recorded hydrogen bonds were recognized in the strongest range of H Bond category distances. Identification of binding site interactions revealed that the interaction of Zn(QC)Cl2(H2O)with the protease of COVID-19 results in three hydrogen bonds, while Zn(HQC)Cl2(H2O) exhibited a strong binding to the main protease receptor by forming eight hydrogen bonds. The dynamic behavior of the proposed complexes was revealed by molecular dynamics simulations. The outcomes obtained from Molecular dynamics calculations approved the stability of Mpro-Zn(CQ/HCQ)Cl2H2O systems. These findings recommend Zn (CQ) Cl2H2O and Zn (HCQ) Cl2H2O as potential inhibitors for COVID-19 Mpro.