X-ray Structure Analysis Research Articles

Cytotoxicity and Apoptosis-Induction in MCF-7 Cells for New Pd(II) Complex Based on s-Triazine Ligand: Synthesis, Single Crystal X-ray Diffraction Analysis and Structural Investigations

The synthesis and X-ray structure analysis of the new [PdLCl2]*0.5 CH2Cl2 complex where L is hydrazono-s-triazine di-morpholine derivative, were presented. In the neutral inner sphere of this complex, the organic ligand L is acting as a NN-bidentate chelate via the pyridine and hydrazone N-atoms. The coordination configuration of the Pd(II) is completed by two chloride ions at cis-positions. The tetra-coordinated Pd(II) showed a distorted square planar geometry. The outer sphere comprised half methylene chloride molecule per [PdLCl2] as crystal solvent. The crystal stability is dominated by a number of weak C-H…N, C-H…Cl, and C-H…O non-covalent interactions. Based on Hirshfeld analysis, the H…H, N…H, H…Cl, O…H, Pd…C, and Cl…C intermolecular interactions contributed by 45.2, 9.3, 21.5, 5.8, 2.3, and 3.4%, respectively. DFT studies revealed closed shell characters for the Pd-N and Pd-Cl coordinate bonds. The net charge of Pd is also predicted to be 0.311 e and the amount of electron density transferred from the ligand groups is 1.689 e. The Pd(II) complex exhibited potent cytotoxic activity against MCF-7, HepG2, and A549 cells with IC50 values of 1.18, 4.74, and 5.22 μg/mL, compared to cisplatin with IC50 values of 4.1, 9.7, and 12.3 μg/mL, respectively. Additionally, it exhibited poor cytotoxicity against WISH cells with much higher IC50 values (IC50 = 37.2 μg/mL). Investigating apoptosis-induction, the Pd(II) complex induced apoptotic cell death by an 11-fold change in MCF-7 cells arresting the cell phase at the G0–G1 phase. Accordingly, Pd(II) complex can be developed as a promising anti-breast cancer agent.

Synthesis and X-ray Structure Analysis of the Polymeric [Ag2(4-Amino-4H-1,2,4-triazole)2(NO3)]n(NO3)n Adduct: Anticancer, and Antimicrobial Applications

A new Ag(I) adduct was synthesized by the reaction of 4-amino-4H-1,2,4-triazole (L) with AgNO3. Its chemical structure was approved to be [Ag2(L)2(NO3)]n(NO3)n utilizing elemental analysis, FTIR spectra, and single crystal X-ray diffraction (SC-XRD). According to SC-XRD, there are two independent silver atoms which are coordinated differently depending on whether the nitrate anion is coordinated or not. The coordination geometry of Ag1 is a slightly bent configuration while Ag2 has a distorted tetrahedral structure. The 4-amino-4H-1,2,4-triazole ligand and one of the nitrate groups adopt bridging mode, which connects the crystallographically independent Ag1 and Ag2 atoms resulting in the formation of two-dimensional coordination polymer. Hirshfeld surface analysis displays that the intermolecular O···H (34.0%), Ag···N (10.6%), H···H (10.4%), Ag···O (9.3%), and N···H (9.0%) contacts are the most abundant interactions. Regarding anticancer activity, the [Ag2(L)2(NO3)]n(NO3)n demonstrates stronger cytotoxic efficacy against lung (IC50 = 3.50 ± 0.37 µg/mL) and breast (IC50 = 2.98 ± 0.26 µg/mL) carcinoma cell lines than the anticancer medication cis-platin. The [Ag2(L)2(NO3)]n(NO3)n complex showed interesting antibacterial and antifungal activities compared to the free components (AgNO3 and 4-amino-4H-1,2,4-triazole). The investigated silver(I) complex exhibits remarkable antibacterial activity against E. coli (MIC = 6.1 µg/mL) that may be on par with Gentamycin (MIC = 4.8 µg/mL). As a result, the newly synthesized Ag(I) complex could be suggested for anticancer and antibacterial treatments.

Ni(II) complexes with in-situ generated N, O-bidentate aroylhydrazone Schiff base ligands: One-pot synthesis, characterization, crystal structure, and in-silico studies

A series of novel aroylhydrazone-based Ni(II) complexes were synthesized by using analogous Schiff base ligands prepared in-situ by reacting 4-[(4-methylbenzyl)oxy]benzoylhydrazine with different aldehydes in the presence of Ni(II) acetate tetrahydrate. The correspondent [NiL2] complexes, 4-7, were characterized by physicochemical techniques, viz., molar conductance, magnetic susceptibility measurement, IR, NMR, and mass spectroscopic techniques. The single-crystal X-ray structural analyses of complexes 4, 6 and 7 showed a distorted square-planar geometry for Ni atoms with deprotonated ligands in trans-configuration bound via azomethine-N and carbonylate-O atoms. Next, quantum chemical methods were incorporated to investigate their thermochemical, molecular orbital, and electrostatic potential properties. Computer-aided drug design methods were also implemented to assess their medicinal, pharmacological, and toxicological properties. Molecular docking and interaction analyses disclosed their potential binding affinity against human lung Cytochrome P450 2A13 receptor protein. Pharmacokinetic and toxicological studies suggest their relatively safe drug administrative properties.

Novel Sulfone 2-Aminobenzimidazole Derivatives and Their Coordination Compounds: Contribution of the Ethyl and Phenyl Substituents on Non-Covalent Molecular Interactions; Biological Antiproliferative Activity

New sulfone 2-aminobenzimidazole derivatives were designed and synthesized. Their nickel(II), copper(II), zinc(II), cadmium(II) and mercury(II) compounds were obtained and fully characterized by spectroscopic and analytical techniques. Single crystal X-ray structural analysis was performed in order to study the relevant intra and inter non-covalent interactions, mainly H···π, lone pair···π, and π···π, highlighting the difference between the terminal ethyl and phenyl groups in such interactions. Dimeric and trimeric supramolecular syntons were found for some of these compounds. Additionally, their antiproliferative activity was investigated, finding that the copper(II) compounds with the sulfone phenyl derivative were the most active.

Dimethylsilanediol from silicone elastomers: Analysis, release from biopharmaceutical process equipment, and clearance studies

Polysiloxanes are considered one of the most important commercial families of synthetic elastomers. They are frequently employed in biopharmaceutical manufacturing equipment as flexible single-use solutions due to superior material properties and compatibility with diverse sterilization methods. Extractables and leachables (E&L) testing is essential in qualifying such equipment, involving extraction studies to assess the potential release of compounds from plastic components for risk assessment. Silicone releases oligomeric siloxanes and small hydrolysis products, with dimethylsilanediol (DMSD) being the main hydrolysis product found in significant concentrations in aqueous process solutions. DMSD presents challenges for analysis, requiring specifically tailored analytical methods to detect it, which are commonly not applied in standard E&L screening tests. In biopharmaceutical manufacturing, it is relevant to consider the potential of DMSD to repolymerize into silicone oil when specific process parameters are altered. This may lead to interactions with drug ingredients, including proteins, resulting in the formation of aggregates. We synthesized and characterized DMSD using X-ray structure analysis and established an HPLC method with a refractive index detector to investigate the release of DMSD from commercially available silicone tubing used in drug manufacturing following autoclaving and irradiation. Subsequently, we assessed typical biopharmaceutical downstream operations for effectively removing this compound from the process stream.

Features of (Benzo)Imidazo[2,1-b][1,3]thiazine Mezylates Reaction with Nucleophilic Reagents

Peculiarities of the course of the methanesulfo-derivatives of (benzo)imidazo[2,1-b][1,3]thiazines reac-tions with a number of nucleophilic reagents were studied. It was determined that they react nonselectively with potassium thiocyanate to form a mixture of thio- and isothiocyanate derivatives. When interacting with sodium azide, nucleophilic substitution competes with an elimination reaction. The latter is dominant in the reaction with sodium cyanide. The spatial structure of one of the isomer elimination products, 4H-benzo[4,5]imidazo[2,1-b][1,3] thiazine, was established by X-ray structural analysis.

Colorless Polyimides Derived from 5,5'-bis(2,3-norbornanedicarboxylic anhydride): Strategies to Reduce the Linear Coefficients of Thermal Expansion and Improve the Film Toughness.

In this paper, novel colorless polyimides (PIs) derived from 5,5'-bis(2,3-norbornanedicarboxylic anhydride) (BNBDA) were presented. The results of single-crystal X-ray structural analysis using a BNBDA-based model compound suggested that it had a unique steric structure with high structural linearity. Therefore, BNBDA is expected to afford new colorless PI films with an extremely high glass transition temperature (Tg) and a low linear coefficient of thermal expansion (CTE) when combined with aromatic diamines with rigid and linear structures (typically, 2,2'-bis(trifluoromethyl)benzidine (TFMB)). However, the polyaddition of BNBDA and TFMB did not form a PI precursor with a sufficiently high molecular weight; consequently, the formation of a flexible, free-standing PI film via the two-step process was inhibited because of its brittleness. One-pot polycondensation was also unsuccessful in this system because of precipitation during the reaction, probably owing to the poor solubility of the initially yielded BNBDA/TFMB imide oligomers. The combinations of (1) the structural modification of the BNBDA/TFMB system, (2) the application of a modified one-pot process, in which the conditions of the temperature-rising profile, solvents, azeotropic agent, catalysts, and reactor were refined, and (3) the optimization of the film preparation conditions overcame the trade-off between low CTE and high film toughness and afforded unprecedented PI films with well-balanced properties, simultaneously achieving excellent optical transparency, extremely high Tg, sufficiently high thermal stability, low CTE, high toughness, relatively low water uptake, and excellent solution processability.

Anti-InlA single-domain antibodies that inhibit the cell invasion of Listeria monocytogenes

Listeriosis, caused by infection with Listeria monocytogenes, is a severe disease with a high mortality rate. The L. monocytogenes virulence factor, internalin family protein InlA, which binds to the host receptor E-cadherin, is necessary to invade host cells. Here, we isolated two single-domain antibodies (VHHs) that bind to InlA with picomolar affinities from an alpaca immune library using the phage display method. These InlA-specific VHHs inhibited the binding of InlA to the extracellular domains of E-cadherin invitro as shown by biophysical interaction analysis. Furthermore, we determined that the VHHs inhibited the invasion of L.monocytogenes into host cells in culture. High-resolution X-ray structure analyses of the complexes of VHHs with InlA revealed that the VHHs bind to the same binding site as E-cadherin against InlA. We conclude that these VHHs have the potential for use as drugs to treat listeriosis.

A saddle-shaped expanded porphyrinoid fitting C60.

We present the synthesis of a new type of an expanded porphyrinoid macrocycle with a saddle-shaped morphology and its complexation of C60 guest molecules. The new macrocycle contains four carbazole and four triazole moieties and can be readily synthesized via a copper-catalyzed click reaction. It shows specific photo-physical properties including fluorescence with a high quantum yield of 60%. The combination of the saddle-shaped geometry with the expanded π-system allows for host-guest interactions with C60 in a stacked polymer fashion. Evidence for the presence of a host-guest complex is provided both in solution by NMR spectroscopy and in the solid state by X-ray structure analysis.

Supramolecular Self-Assembly of the Zwitterionic Sn(IV)-Porphyrin Complex

[Sn(OSO3)2(TPyHP)](HSO4)2∙8H2O (1), an ionic Sn(IV)-porphyrin complex, was prepared by reacting [Sn(OH2)2TPyP] with dilute sulfuric acid. X-ray structural analysis revealed that the zwitterionic [Sn(OSO3)2TPyHP]2+ species consists of two anionic axial Sn–O–SO3 units and four peripheral pyridinium moieties, with an overall dicationic charge balanced by two hydrogen sulfate (HSO4−) counter-anions. Ionic hydrogen bonding between the oxygen atoms of axial sulfato ligands and the peripheral pyridinium groups of adjacent Sn(IV)-porphyrin cations led to the formation of a 1D channel filled with counter-anions and water molecules. The supramolecular self-assembly of 1 was further characterized using various spectroscopic techniques, including 1H NMR spectroscopy, elemental analysis, ESI-mass spectrometry, UV-vis spectroscopy, fluorescence spectroscopy, FT-IR spectroscopy, thermogravimetric analysis (TGA), and powder X-ray diffractometry. The zwitterionic [Sn(OSO3)2TPyHP]2+ complex is a structurally well-defined complementary scaffold involved in supramolecular self-assembly. This novel class of ion-assembled metalloporphyrin is a potential functional porphyrin material used in ion exchange applications.

Characterization of Ambroxol and Its Hydrochloride Salt Crystals by Bromine K-Edge X-Ray Absorption Near-Edge Structure Spectroscopy and X-Ray Crystal Structure Analysis.

Polymorphic crystals of ambroxol, forms I and II, and form A ambroxol hydrochloride crystals were characterized with bromine K-edge X-ray absorption near-edge structure (XANES) spectroscopy and single-crystal X-ray structure analysis. The XANES spectra had unique shapes depending on the crystal forms. Refined single-crystal structures revealed different interatomic interactions around bromine atoms, such as C-H…Br and N-H…Br hydrogen bonds, Br…O halogen bonds, and N-H…π interactions. Differences in these weak interactions could affect the electronic states of the bromines, resulting in differences in the XANES spectra. The results demonstrated that weak non-conventional interatomic interactions could alter the shape of XANES spectra. Hence, the spectra could be used for evaluating polymorphs of active pharmaceutical ingredients.

Cysteine Enrichment Mediates Co-Option of Uricase in Reptilian Skin and Transition to Uricotelism.

Uric acid is the main means of nitrogen excretion in uricotelic vertebrates (birds and reptiles) and the end product of purine catabolism in humans and a few other mammals. While uricase is inactivated in mammals unable to degrade urate, the presence of orthologous genes without inactivating mutations in avian and reptilian genomes is unexplained. Here we show that the Gallus gallus gene we name cysteine-rich urate oxidase (CRUOX) encodes a functional protein representing a unique case of cysteine enrichment in the evolution of vertebrate orthologous genes. CRUOX retains the ability to catalyze urate oxidation to hydrogen peroxide and 5-hydroxyisourate (HIU), albeit with a 100-fold reduced efficiency. However, differently from all uricases hitherto characterized, it can also facilitate urate regeneration from HIU, a catalytic property that we propose depends on its enrichment in cysteine residues. X-ray structural analysis highlights differences in the active site compared to known orthologs and suggests a mechanism for cysteine-mediated self-aggregation under H2O2-oxidative conditions. Cysteine enrichment was concurrent with the transition to uricotelism and a shift in gene expression from the liver to the skin where CRUOX is co-expressed with β-keratins. Therefore, the loss of urate degradation in amniotes has followed opposite evolutionary trajectories: while uricase has been eliminated by pseudogenization in some mammals, it has been repurposed as a redox-sensitive enzyme in the reptilian skin.

Noncovalent Modification of Cycloparaphenylene by Catenane Formation Using an Active Metal Template Strategy.

The active metal template (AMT) strategy is a powerful tool for the formation of mechanically interlocked molecules (MIMs) such as rotaxanes and catenanes, allowing the synthesis of a variety of MIMs, including π-conjugated and multicomponent macrocycles. Cycloparaphenylene (CPP) is an emerging molecule characterized by its cyclic π-conjugated structure and unique properties. Therefore, diverse modifications of CPPs are necessary for its wide application. However, most CPP modifications require early stage functionalization and the direct modification of CPPs is very limited. Herein, we report the synthesis of a catenane consisting of [9]CPP and a 2,2'-bipyridine macrocycle as a new CPP analogue that contains a reliable synthetic scaffold enabling diverse and concise post-modification. Following the AMT strategy, the [9]CPP-bipyridine catenane was successfully synthesized through Ni-mediated aryl-aryl coupling. Catalytic C-H borylation/cross-coupling and metal complexation of the bipyridine macrocycle moiety, an effective post-functionalization method, were also demonstrated with the [9]CPP-bipyridine catenane. Single-crystal X-ray structural analysis revealed that the [9]CPP-bipyridine catenane forms a tridentated complex with an Ag ion inside the CPP ring. This interaction significantly enhances the phosphorescence lifetime through improved intermolecular interactions.

Dicarboxylic Acids Induced Tandem Transformation of Silver Nanocluster.

Structural transformation of metal nanoclusters (NCs) is of great ongoing interest regarding their synthesis, stability, and reactivity. Although sporadic examples of cluster transformations have been reported, neither the underlying transformation mechanism nor the intermediates are unambiguous. Herein, we have synthesized a flexible 54-nuclei silver cluster (Ag54) by combining soft (tBuC≡C-) and hard (nPrCOO-) ligands. The existence of weakly coordinated nPrCOO- enhances the reactivity of Ag54, thus facilitating the dicarboxylic acid to induce structural transformation. X-ray structural analyses reveal that Ag54 transforms to Ag28 cluster-based 2D networks (Ag28a and Ag28b) induced by H2suc (succinic acid) and H2glu (glutaric acid), whereas with H2pda (2,2'-(1,2-phenylene)diacetic acid), a discrete Ag28 cluster (Ag28c) is isolated. The key intermediate Ag17 that emerges during the self-dissociation of Ag54 was isolated by using cryogenic recrystallization and characterized by X-ray crystallography. The "tandem transformation" mechanism for the structure evolution from Ag54 to Ag28a is established by time-dependent electrospray ionization mass spectrometry (ESI-MS) and UV-vis spectroscopy. In addition, the catalytic activity in the 4-nitrophenol reduction follows the sequence Ag28c > Ag28b > Ag28a > Ag54 due to more bare silver sites on the surface of the Ag28 cluster unit. Our findings not only open new avenues to the synthesis of silver NCs but also shed light on a better understanding of the structural transformation mechanism from one cluster to another or cluster-based metal-organic networks induced by dicarboxylates.

Synthesis, X-ray Structure, and Hirshfeld Analysis of [Ag(3-amino-5,6-dimethyl-1,2,4-triazine)(NO3)]n: A Potent Anticancer and Antimicrobial Agent

The [Ag(3ADMT)(NO3)]n complex was synthesized by the self-assembly of 3-amino-5,6-dimethyl-1,2,4-triazine (3ADMT) and AgNO3. Its molecular structure was analyzed utilizing FTIR spectra, elemental analysis, and single crystal X-ray diffraction (SC-XRD). There is one crystallographically independent Ag atom, which is tetra-coordinated by two nitrogen atoms from two 3ADMT and two oxygen atoms from two nitrate anions where all ligand groups are acting as connectors between the Ag1 sites. The geometry around the Ag(I) center is a distorted tetrahedron with a AgN2O2 coordination sphere augmented by strong argentophilic interactions between Ag atoms, which assist the aggregation of the complex units in a wavy-like and coplanar pattern to form a one-dimensional polymeric chain. The O...H (37.2%) and N...H (18.8%) intermolecular interactions contributed significantly to the molecular packing based on Hirshfeld surface analysis. The [Ag(3ADMT)(NO3)]n complex demonstrates promising cytotoxicity against lung (IC50 = 2.96 ± 0.31 μg/mL) and breast (IC50 = 1.97 ± 0.18 μg/mL) carcinoma. This remarkable cytotoxicity exceeds those of 3ADMT, AgNO3, and the anticancer medication cis-platin towards the tested cancer cell lines. In addition, the complex has a wide-spectrum antimicrobial action where the high antibacterial potency of the [Ag(3ADMT)(NO3)]n complex against P. vulgaris (MIC = 6.1 µg/mL) and B. subtilis (MIC = 17.2 µg/mL) could be comparable to the commonly used drug Gentamycin (MIC = 4.8 µg/mL). These results confirm that the components of the [Ag(3ADMT)(NO3)]n complex work together synergistically, forming a powerful multifunctional agent that could be exploited as an effective antimicrobial and anticancer agent.

Novel hybrid motifs of 4-nitroimidazole-piperazinyl tagged 1,2,3-triazoles: Synthesis, crystal structure, anticancer evaluations, and molecular docking study

4-((4-(1-benzyl-2-methyl-4-nitro-1H-imidazole-5-yl)piperazine-1-yl)methyl)-1-substituted-1H-1,2,3-triazole motifs are designed and synthesized via click chemistry. The reaction of 1-(N1-benzyl- 2-methyl-4-nitro-1H-imidazole- 5-yl)-4-(prop-2-yn-1-yl) piperazine 5 as new scaffold with diverse primary azides to selectively produce 1,4-disubstituted-1,2,3-triazoles 9a–k, 10a–c and 11a–q. Physicochemical methods: when 1H NMR, 13C NMR, and HRMS are utilized to fully characterize all synthesized compounds. X-ray structural determination and analysis for compound 9a is also performed. The newly designed chromophores are assessed for their anti-proliferative potency against three selected human cancer cell lines (MCF-7, HepG2, and PC3), and one normal cell line (Dermal/Fibroblast). Compounds 9g and 9k have shown potent activities against the MCF-7 cell line with IC50 values of (2.00 ± 0.03 μM) and (5.00 ± 0.01 μM) respectively. ADMET studies and Molecular docking investigations are performed on the most active hybrid nitroimidazole derivatives 9g and 9k with 4-hydroxytamoxifen (4-OHT) at the human estrogen receptor alpha (hER) during binding active sites to study the ligand–protein interactions and free binding energies at atomic levels. The triazole ring in the 9g derivative forms a hydrogen bond with Asp58 with distance 3.2 Å. And it is found that polar contact with His231 amino acid residue.In silico assessment of the compounds showed very good pharmacokinetic properties based on their physicochemical values, also the ADMET criteria of the most active hybrid systems are within the acceptable range.

Treatment of Substandard Rocket Fuel 1,1-Dimethylhydrazine via Its Methylene Derivative into Heterocycles Based on Pyrrolo-[3,4c]Quinolines, Cyclododeca[b]piran and Pyrrole.

1,1-Dimethylhydrazine (Heptil, rocket fuel (UDMH)) is characterized by extremely high toxicity, teratogenicity and the ability to constantly absorb water from the atmosphere, losing its energy characteristics. In this regard, as well as due to the alternative fuel ("Angara") transition, there is a need for UDMH utilization in huge amounts. A more benign approach involves its immediate reaction with a formalin solution to form 1,1-dimethyl-2-methylene hydrazone (MDH), which is significantly less toxic by an order of magnitude. MDH can then be polymerized under acidic conditions, and the resulting product can be burned, yielding a substantial amount of nitrogen oxides. We propose an alternative to incineration by involving MDH in organic synthesis. We studied the reactions of MDH and its analog N,N-dimethyl-2-(methylenamino)ethane-1-amine (MDEA) with available CH-acids: tetracyanoethylated ketones (TCEKs) based on cyclohexanone, 4-propylcyclohexanone, 2-methylcyclohexanone, cyclododecanone and tetracyanoethane. The structures synthesized were confirmed by IR, 1H, 13C NMR and mass spectroscopy methods. MDH-based adducts were also identified by X-ray structural analysis. TCEKs and MDH, as well as TCEK based on cyclohexanone and MDEA, form bi- and tricyclic structures: pyrrolo [3,4c]-quinolines (using TCEKs based on cyclohexanone and 4-propylcyclohexanone), epiminomethanoquinoline-3,4-dicarbonitrile (using TCEK based on 2-methylcyclohexanone) and cyclododec[b]pyran-3,4-dicarbonitrile (using TCEK based on cyclododecanone). MDH and TCNEH2 formed a pyrrole derivative. Thus, we synthesized the structures that are of interest for molecular design and pharmaceutical chemistry.

Cg…Cg interactions driven 1D polymeric chains bridged by lattice solvents in N3-(2-pyridoyl)-4-pyridinecarboxamidrazone Pb(II) complex

This study will shed light on the non-covalent interactions present in the N3-(2-pyridoyl)-4-pyridinecarboxamidrazone Pb(II) complex [(L)Pb(CH3OH)(H2O)2] and their significance in the context of crystal packing and material properties. The complex was synthesized and characterized using single crystal X-ray structural analysis, providing valuable insights into its molecular structure. Our focus was on analyzing the non-covalent interactions in the crystal structure, where these interactions played a crucial role in the formation of one-dimensional network chains observed in the crystal. To quantitatively analyze these interactions, we employed Hirshfeld surfaces analysis. Furthermore, we performed density functional theory computational studies to calculate the molecular geometry and global reactive parameters, allowing us to gain a better understanding of the properties of the novel molecule. The molecular electrostatic potential was plotted to visualize the charge distribution and identify the electrophilic and nucleophilic sites in the molecule. Finally, we explored the non-covalent interactions and electron charge density distribution using the QTAM and NCI models, providing further insights into the complex's behavior. This study contributes to the understanding of non-covalent interactions in the context of crystal growth and design, and expands the knowledge of the structural and electronic properties of the N3-(2-pyridoyl)-4-pyridinecarboxamidrazone Pb(II) complex.

Alkyne as a Latent Warhead to Covalently Target SARS-CoV-2 Main Protease.

There is an urgent need for improved therapy to better control the ongoing COVID-19 pandemic. The main protease Mpro plays a pivotal role in SARS-CoV-2 replications, thereby representing an attractive target for antiviral development. We seek to identify novel electrophilic warheads for efficient, covalent inhibition of Mpro. By comparing the efficacy of a panel of warheads installed on a common scaffold against Mpro, we discovered that the terminal alkyne could covalently modify Mpro as a latent warhead. Our biochemical and X-ray structural analyses revealed the irreversible formation of the vinyl-sulfide linkage between the alkyne and the catalytic cysteine of Mpro. Clickable probes based on the alkyne inhibitors were developed to measure target engagement, drug residence time, and off-target effects. The best alkyne-containing inhibitors potently inhibited SARS-CoV-2 infection in cell infection models. Our findings highlight great potentials of alkyne as a latent warhead to target cystine proteases in viruses and beyond.

Rare coordination behavior of triethanolamine ligand in [Cu(H3tea)2](3,4-dimethoxycinnamate)2·2H2O: Synthesis, characterization, single crystal X-ray structure determination, Hirshfeld calculation and molecular docking studies

Herein, unusual and rare coordination behavior of triethanolamine (H3tea) ligand in copper(II) carboxylate complex; [Cu(H3tea)2](3,4-DMC)2·2H2O; DMC = 3,4-dimethoxycinnamate, has been explored and structurally reported for the first time. Synthesis and crystallization of the complex has been achieved at ambient conditions using methanol-water (4:1 v/v) as a solvent mixture after very slow evaporation. Furthermore, the complex is characterized by elemental analyses, spectroscopic methods (UV–Visible, FT-IR) and structure elucidation has been carried out by single crystal X-ray structure analyses. X-ray structure determination of the complex revealed the presence of [Cu(H3tea)2]2+ as a cation and two moieties of 3,4-dimethoxycinnamate as anions forming a second sphere coordination complex. Various weak (non-covalent) interactions such as CH∙∙∙O, and OH∙∙∙O impart an important role in the lattice stabilization of a second sphere coordination complex. Hirshfeld surface calculations clearly revealed the existence of interplay of non-covalent interactions in lattice stabilization. The theoretical calculation also suggested the total interaction energies in this complex, i.e. 32.6 kj.mol−1. In addition, molecular docking investigations of this complex clearly showed that there is substantial protein-ligand interaction with best binding scores of -7.2, -7.3, -7.9 kcal/mol against 4GKU, 3W4P, 5CGX and -5.8, -7.8 kcal/mol against 4HFZ, 1D5R proteins lesser than parent acid i.e. 3,4-dimethoxycinnamic acid indicating the potential of this complex; [Cu(H3tea)2](3,4-DMC)2·2H2O as antibacterial and anticancer agent respectively.