Pendant Pyridyl Research Articles

Synthesis of Molybdenum Complexes Bearing Pyridine-Based PNP-Type Pincer Ligands with Pendent Pyridyl Unit and Their Catalytic Activity for Ammonia Formation

Synthesis of Molybdenum Complexes Bearing Pyridine-Based PNP-Type Pincer Ligands with Pendent Pyridyl Unit and Their Catalytic Activity for Ammonia Formation

Molecular mechanism of action of imidazolium carbosilane dendrimers on the outer bacterial membrane – From membrane damage to permeability to antimicrobial endolysin

The outer bacterial membrane of drug-resistant bacteria is a significant barrier to many antimicrobials. Therefore, the development of new antibacterials primarily focuses on damaging the outer bacterial membrane of Gram-negative bacteria. Among many membrane-disrupting substances, the most promising are cationic dendritic systems. However, the mode of action may vary among different strains due to variations in the lipid compositions of the membrane. Here, we investigated the interaction of two types of cationic imidazolium carbosilane dendrimers: one with a single cationic group (methyl imidazolium) and the other with the same cationic group but attached to a functional group (a pendant pyridyl moiety), capable of establishing interactions with membranes through H-bonding or ion–dipole electrostatic interactions. We used different models of the outer membrane of Gram-negative bacteria – Escherichia coli, Pseudomonas aeruginosa, and Acinetobacter baumannii. Additionally, we assessed the combined effect of the dendrimers and the antibacterial endolysin on P. aeruginosa. Our results show that the mechanism of action depends on the type of dendrimer and the lipid composition of the membrane. We also demonstrate that the alteration of membrane fluidity and permeability to endolysin by the methyl imidazolium and pyridyl imidazolium dendrimers may play a more significant role in antimicrobial activity compared to membrane damage caused by positively charged dendrimers.

Mechanism-Guided Kinetic Analysis of Electrocatalytic Proton Reduction Mediated by a Cobalt Catalyst Bearing a Pendant Basic Site.

Cobalt polypyridyl complexes stand out as efficient catalysts for electrochemical proton reduction, but investigations into their operating mechanisms, with broad-reaching implications in catalyst design, have been limited. Herein, we investigate the catalytic activity of a cobalt(II) polypyridyl complex bearing a pendant pyridyl base with a series of organic acids spanning 20 pKa units in acetonitrile. Structural analysis, as well as electrochemical studies, reveals that the Co(III) hydride intermediate is formed through reduction of the Co(II) catalyst followed by direct metal protonation in the initial EC step despite the presence of the pendant base, which is commonly thought of as a more kinetically accessible protonation site. Protonation of the pendant base occurs after the Co(III) hydride intermediate is further reduced in the overall ECEC pathway. Additionally, when the acid used is sufficiently strong, the Co(II) catalyst can be protonated, and the Co(III) hydride can react directly with acid to release H2. With thorough mechanistic understanding, the appropriate electroanalytical methods were identified to extract rate constants for the elementary steps over a range of conditions. Thermodynamic square schemes relating catalytic intermediates proposed in the three electrocatalytic HER mechanisms were constructed. These findings reveal a full description of the HER electrocatalysis mediated by this molecular system and provide insights into strategies to improve synthetic fuel-forming catalysts operative through metal hydride intermediates.

Nickel(II) and Palladium(II) Complexes with η5:κ1(N)-Coordinated Dicarbollide Ligands Containing Pendant Pyridine Group.

A series of C- and B-substituted nido-carborane derivatives with a pendant pyridyl group was prepared. The synthesized compounds were used as ligands in the complexation reactions with bis(triphenylphosphine)nickel(II) and palladium(II) chlorides to give six new metallacomplexes with unusual η5:κ1(N)-coordination of the metal center. The single crystal structures of 1-(NC5H4-2'-S)-1,2-C2B10H11, 1-(NC5H4-2'-CH2S)-1,2-C2B10H11, Cs [7-(NC5H4-2'-CH2S)-7,8-C2B9H11] closo- and nido-carboranes and 3-Ph3P-3-(4(7)-NC5H4-2'-S)-closo-3,1,2-NiC2B9H10 and 3-Ph3P-3-(4(7)-NC5H4-2'-CH2S)-closo-3,1,2-NiC2B9H10 metallacarboranes were determined using single crystal X-ray diffraction.

Polymer-Protein Nanovaccine Synthesized via Reactive Self-Assembly with Potential Application in Cancer Immunotherapy: Physicochemical and Biological Characterization In Vitro and In Vivo.

Nanovaccines composed of polymeric nanocarriers and protein-based antigens have attracted much attention in recent years because of their enormous potential in the prevention and treatment of diseases such as viral infections and cancer. While surface-conjugated protein antigens are known to be more immunoactive than encapsulated antigens, current surface conjugation methods often result in low and insufficient protein loading. Herein, reactive self-assembly is used to prepare nanovaccine from poly(ε-caprolactone) (PCL) and ovalbumin (OVA)-a model antigen. A rapid thiol-disulfide exchange reaction between PCL with pendant pyridyl disulfide groups and thiolated OVA results in the formation of nanoparticles with narrow size distribution. High OVA loading (≈70-80wt%) is achieved, and the native secondary structure of OVA is preserved. Compared to free OVA, the nanovaccine is much superior in enhancing antigen uptake by bone marrow-derived dendritic cells (BMDCs), promoting BMDC maturation and antigen presentation via the MHC I pathway, persisting at the injection site and draining lymph nodes, activating both Th1 and Th2 T cell immunity, and ultimately, resisting tumor challenge in mice. This is the first demonstration of reactive self-assembly for the construction of a polymer-protein nanovaccine with clear potential in advancing cancer immunotherapy.

Crystal structure and Hirshfeld surface analysis of cyclo-tetra-bromido-1κ2Br,3κ2Br-tetra-kis-(μ2-2-{[(pyridin-2-yl)meth-yl]amino}-ethane-1-thiol-ato-κ3N,S:S)tetra-mercury(II).

The macrometallacyclic title compound, [Hg4Br4(C8H11N2S)4] or [((HgL 2)(HgBr2))2] (1) where HL = 2-{[(pyridin-2-yl)meth-yl]amino}-ethane-1-thiol, was prepared and structurally characterized. The Hg2+ complex crystallizes in the P21/c space group. The centrosymmetric Hg4S4 metallacycle is constructed from metal ions with alternating distorted tetra-hedral Br2S2 and distorted seesaw N2S2 primary coordination environments with pendant pyridyl groups. The backfolded extended chair metallacycle conformation suggests inter-actions between each of the bis-chelated mercury atoms and Br atoms lying above and below the central Hg2S4 plane. Supra-molecular inter-actions in 1 include a fourfold aryl embrace and potential hydrogen bonds with bromine as the acceptor. Hirshfeld surface analysis indicates that H⋯H (51.7%), Br⋯H/H⋯Br (23.0%) and C⋯H/H⋯C (9.5%) inter-actions are dominant.

Precious-Metal-Free CO2 Photoreduction Boosted by Dynamic Coordinative Interaction between Pyridine-Tethered Cu(I) Sensitizers and a Co(II) Catalyst.

Improving the photocatalytic efficiency of a fully noble-metal-free system for CO2 reduction remains a fundamental challenge, which can be accomplished by facilitating electron delivery as a consequence of exploiting intermolecular interactions. Herein, we have designed two Cu(I) photosensitizers with different pyridyl pendants at the phenanthroline moiety to enable dynamic coordinative interactions between the sensitizers and a cobalt macrocyclic catalyst. Compared to the parent Cu(I) photosensitizer, one of the pyridine-tethered derivatives boosts the apparent quantum yield up to 76 ± 6% at 425 nm for selective (near 99%) CO2-to-CO conversion. This value is nearly twice that of the parent system with no pyridyl pendants (40 ± 5%) and substantially surpasses the record (57%) of the noble-metal-free systems reported so far. This system also realizes a maximum turnover number of 11 800 ± 1400. In contrast, another Cu(I) photosensitizer, in which the pyridine substituents are directly linked to the phenanthroline moiety, is inactive. The above behavior and photocatalytic mechanism are systematically elucidated by transient fluorescence, transient absorption, transient X-ray absorption spectroscopies, and quantum chemical calculations. This work highlights the advantage of constructing coordinative interactions to fine-tune the electron transfer processes within noble-metal-free systems for CO2 photoreduction.

Isoselective Polymerization of rac-Lactide by Magnesium Initiators Bearing Achiral Di(2-pyridyl)methyl Substituted Aminophenolate Ligands.

Reactions of achiral di(2-pyridyl)methyl substituted aminophenols L1-6H (2-{N-R3-N-[di(2-pyridyl)methyl]aminomethyl}-4-R1-6-R2-C6H2OH: R1 = R2 = tBu, R3 = nBu (L1H), R3 = nhexyl (L2H), R3 = cyclohexyl (L3H); R1 = R2 = cumyl, R3 = nBu (L4H), R3 = nhexyl (L5H), R3 = cyclohexyl (L6H)) with {Mg[N(SiMe3)2]2}2 ([L1-6H]:[Mg] = 1:1) afforded a series of magnesium silylamido complexes 1-6. In the solid state, the magnesium center of 3, 4, and 6 is penta-coordinated by the tetradentate aminophenloate ligand and one silylamido ligand to form a seriously distorted square-pyramidal geometry as confirmed by X-ray crystallography diffraction analysis. VT 1H NMR and ROESY experiments further indicate that these magnesium complexes are also five-coordinated in solutions where the coordination of either of the two pyridyl pendants to the magnesium center is maintained. Complexes 1-6 are highly active toward the ring-opening polymerization of rac-lactide (rac-LA) at r.t. both in toluene and in tetrahydrofuran, capable of polymerizing 500 equiv of monomer to high conversions just within minutes. Among them, complex 3 exhibited the highest iso-stereoselectivity, affording moderately isotactic polylactide in toluene (Pm = 0.75). It is found that the isoselectivities and activities of these magnesium complexes toward the polymerization of rac-LA are closely associated with the substituents at the ortho-position of the phenoxide unit and on the skeleton nitrogen atom of the ligand. On the basis of NMR spectroscopic studies, the formation of isotactic PLAs with dominant stereoblock sequences was witnessed by using these magnesium complexes as initiators, and the inequivalent coordination of two pyridyl pendant arms in these magnesium complexes might be the source of exerting isoselective control.

Ligand-Directed Metalation of a Gold Pyrazolate Cluster.

Solid "[AuL]" (HL = 3-[pyrid-2-yl]-5-tertbutyl-1H-pyrazole) can be crystallized as cyclic [Au3(μ-L)3] and [Au4(μ-L)4] clusters from different solvents. The crystalline tetramer contains a square Au4 core with an HT:TH:TH:HT arrangement of ligand substituents, which preorganizes the cluster to chelate to additional metal ions via its pendant pyridyl groups. The addition of 0.5 equiv of AgBF4 to [AuL] yields [Ag2Au4(μ3-L)4][BF4]2, where two edges of the Au4 square are spanned by Ag+ ions via metallophilic Ag···Au contacts. Treatment of [AuL] with [Cu(NCMe)4]PF6 affords the metalloligand helicate [Cu2Au2(μ-L)4][PF6]2, via oxidation of the copper and partial fragmentation of the cluster.

Triazolyl- vs Pyridyl-Functionalized N-Heterocyclic Carbene Complexes: Impact of the Pendant N-Donor Ligand on Intramolecular C-C Bond Formation.

Organometallic Rh(Cp*) (Cp* = η5-pentamethylcyclopentadienyl) complexes with monodentate N-heterocyclic carbene (NHC) ligands bearing a pendant anthracenyl substituent have been shown to undergo intramolecular C-C coupling reactions. Herein, two bidentate NHC ligands substituted with pyridyl or triazolyl donor groups were prepared along with the corresponding MII/III (M = RuII, OsII, RhIII, IrIII) complexes. While the Rh(Cp*) complex featuring an NHC-triazole bidentate ligand underwent the equivalent reaction as the monodentate Rh(NHC) complex, i.e., it formed a polydentate ligand, the pyridyl-pendant derivative was unequivocally shown to be unreactive. This contrasting behavior was further investigated by density functional theory (DFT) calculations that highlighted significant differences between the two types of Rh(III) complexes with pendant pyridyl or triazolyl N-coordinating groups. Modeling of the reaction pathways suggests that the initial formation of a dicationic Rh(III) species is unfavorable and that the internal ligand transformation proceeds first by dissociation of the coordinated N atom of the pendant group from the Rh center. After the formation of a neutral η4-fulvene ligand via combined proton/single electron transfer, a cycloaddition occurs between the exo-ene bond of fulvene and the 9' and 10' positions on the pendant anthracenyl group. The resulting experimental UV-visible spectrum recorded in methanol of the polydentate triazolyl-based Rh species revealed the loss of the vibronic coupling typically associated with an anthracenyl functional group. Moreover, TD-DFT modeling indicates the presence of an equilibrium process whereby the N-coordination of the pendant triazolyl group to the RhIII center appears to be highly labile. Charge decomposition analysis (CDA) of the DFT-modeled species with the dissociated triazolyl group revealed a pseudo-η3-allylic interaction between the π-type MOs of the transformed anthracenyl group and the RhIII center; thus, the singly attached chelating ligand is classified as having rare nonadenticity.

Understanding the Effect of the Electron Spin Relaxation on the Relaxivities of Mn(II) Complexes with Triazacyclononane Derivatives.

Investigating the relaxation of water 1H nuclei induced by paramagnetic Mn(II) complexes is important to understand the mechanisms that control the efficiency of contrast agents used in diagnostic magnetic resonance imaging (MRI). Herein, a series of potentially hexadentate triazacyclononane (TACN) derivatives containing different pendant arms were designed to explore the relaxation of the electron spin in the corresponding Mn(II) complexes by using a combination of 1H NMR relaxometry and theoretical calculations. These ligands include 1,4,7-triazacyclononane-1,4,7-triacetic acid (H3NOTA) and three derivatives in which an acetate group is replaced by sulfonamide (H3NO2ASAm), amide (H2NO2AM), or pyridyl (H2NO2APy) pendants. The analogue of H3NOTA containing three propionate pendant arms (H3NOTPrA) was also investigated. The X-ray structure of the derivative containing two acetate groups and a sulfonamide pendant arm [Mn(NO2ASAm)]− evidenced six-coordination of the ligand to the metal ion, with the coordination polyhedron being close to a trigonal prism. The relaxivities of all complexes at 20 MHz and 25 °C (1.1–1.3 mM–1 s–1) are typical of systems that lack water molecules coordinated to the metal ion. The nuclear magnetic relaxation profiles evidence significant differences in the relaxivities of the complexes at low fields (<1 MHz), which are associated with different spin relaxation rates. The zero field splitting (ZFS) parameters calculated by using DFT and CASSCF methods show that electronic relaxation is relatively insensitive to the nature of the donor atoms. However, the twist angle of the two tripodal faces that delineate the coordination polyhedron, defined by the N atoms of the TACN unit (lower face) and the donor atoms of the pendant arms (upper face), has an important effect in the ZFS parameters. A twist angle close to the ideal value for an octahedral coordination (60°), such as that in [Mn(NOTPrA)]−, leads to a small ZFS energy, whereas this value increases as the coordination polyhedron approaches to a trigonal prism.

A 3D electropolymerized thin film based on an isoporphyrin and on a pyridine end-decorated molybdenum(II) halide cluster: Photoelectrochemical and impedance properties

Herein, the first example of formation of a 3D hybrid organic-inorganic copolymer based on an isoporphyrin and on a pyridine end-decorated molybdenum(II) halide cluster. The isoporphyrin copolymer thin film was obtained by electropolymerization of zinc-5,15-bis(p-tolyl)porphyrin in the presence of polyiodometalate with 6 pendant pyridyl ligands (((Bu4N)2[{Mo6I8}(OOC-C5H4N)6]). Electrogenerated porphyrin radical cation is a powerful electrophile which can rapidly react with the pyridine end-decorated Mo(II) halide cluster as nucleophile to form 3D copolymer containing stable isoporphyrin.The electropolymerization was monitored by electrochemical quartz crystal microbalance (EQCM). The copolymer was characterized by UV-Vis-NIR spectroscopy, X-ray photoelectron spectroscopy (XPS), electrochemistry, and atomic force microscopy (AFM). The existence of the radical of the isoporphyrin copolymer was proved by electron spin resonance spectroscopy (EPR).Interestingly, the UV-Vis-NIR spectra of the copolymer exhibited broadening and splitting of the Soret band as well as one additional band in the NIR between 750 nm and 1000 nm.The photoelectrochemical properties have been studied by electrochemical impedance spectroscopy and by photocurrent transient measurements under visible-NIR light irradiation.The 3D copolymer containing stable isoporphyrin radical exhibits interesting photocurrent response even under only NIR illumination.In the solid state, the 3D copolymer could be stored for over several months and even one year without any degradation under ambient conditions in air.

Pluronic Micelle-Mediated Tissue Factor Silencing Enhances Hemocompatibility, Stemness, Differentiation Potential, and Paracrine Signaling of Mesenchymal Stem Cells.

Mesenchymal stem/stromal cells (MSCs) evoke great excitement for treating different human diseases due to their ability to home inflamed tissues, suppress inflammation, and promote tissue regeneration. Despite great promises, clinical trial results are disappointing as allotransplantation of MSCs trigger thrombotic activity and are damaged by the complement system, compromising their survival and function. To overcome this, a new strategy is presented by the silencing of tissue factor (TF), a transmembrane protein that mediates procoagulant activity. Novel Pluronic-based micelles are designed with the pendant pyridyl disulfide group, which are used to conjugate TF-targeting siRNA by the thiol-exchange reaction. This nanocarrier design effectively delivered the payload to MSCs resulting in ∼72% TF knockdown (KD) without significant cytotoxicity. Hematological evaluation of MSCs and TF-KD MSCs in an ex vivo human whole blood model revealed a significant reduction in an instant-blood-mediated-inflammatory reaction as evidenced by reduced platelet aggregation (93% of free platelets in the TF-KD group, compared to 22% in untreated bone marrow-derived MSCs) and thrombin–antithrombin complex formation. Effective TF silencing induced higher MSC differentiation in osteogenic and adipogenic media and showed stronger paracrine suppression of proinflammatory cytokines in macrophages and higher stimulation in the presence of endotoxins. Thus, TF silencing can produce functional cells with higher fidelity, efficacy, and functions.

Stimuli-Responsive Proteinosomes Based on Biohybrid Shell Cross-Linked Micelles

A new method of stimuli-responsive proteinosome fabrication with the shell cross-linked micelle as a template is reported in this research. A thermoresponsive diblock copolymer poly[di(ethylene glycol) methyl ether methacrylate]-b-poly[poly(ethylene glycol) methyl ether methacrylate-co-pyridyl disulfide methacrylamide] [PDEGMA-b-P(PEGMA-co-PDSMA)] was synthesized and self-assembled into micelles with PDEGMA cores and P(PEGMA-co-PDSMA) shells at the temperature above its lower critical solution temperature (LCST). Reduced bovine serum albumin (BSA) molecules with six thiol groups were used to cross-link the shells of the micelles by reacting with the pendant pyridyl disulfide groups on the P(PEGMA-co-PDSMA) block. At a temperature below the LCST of the polymer, the PDEGMA cores were dissolved in water, affording proteinosomes with a size of about 50 nm and capsule-like structures. The proteinosome was also thermoresponsive with a phase transition temperature at 35 °C. The fabrication of the proteinosome had no obvious influence on the structure and activity of BSA, and BSA retained most of its secondary structure and esterase-like activity. Because the BSA molecules were connected to the polymer chains through disulfide bonds, they could be released upon addition of dithiothreitol. The in vitro cell viability evaluation and the cellular uptake assay demonstrated that the proteinosome showed low toxicity to NIH 3T3 and 4T1 cells and could be internalized into the 4T1 cells.

Fluxional dynamics of terpyridine ligand in [Ru(bpy-d8)2(η2-tpy)]2+ complex

Herein, we report the fluxional dynamic behaviour of terpyridineligand in [Ru(bpy-d8)(η2-tpy)]2+ 1. Reaction of Ru(bpy-d8)2Cl2·2H2O with 2,2′:6′,2′′-terpyridine in refluxing methanol afforded 1. Complex 1 has been characterized by 1H NMR spectroscopic analysis. Variable temperature 1H NMR data reveals that the pendant pyridine ring of the tpy ligand in Ru(bpy-d8)2(tpy)]2+ rotates which effects the adjacent ring protons. Moreover, protonation of 1 with trifluoroacetic acid (TFA) confirms that peripheral N on the pendant pyridyl ring of the tpy ligand affects the chemical shifts of protons on the tpy pendant pyridyl ring.&#x0D; Bangladesh J. Sci. Ind. Res.55(4), 253-260, 2020

Steric Effect of a Capping Ligand on the Formation of Supramolecular Coordination Networks of Ni(II): Solid-State Entrapment of Cyclic Water Dimer.

Supramolecular dimer of water is the simplest of the small water clusters [(H2O)n, n = 2–10]. During the course of our work on supramolecular coordination networks of three-component systems (divalent metal ion, tridentate capping ligand, and ditopic carboxylate linker), a cyclic water dimer is found to be entrapped in the network of [Ni2(6-Mebpta)2(adc)2]·2H2O (1) (6-Mebpta = 2-methyl-N-((6-methylpyridin-2-yl)methyl)-N-(pyridin-2-ylmethyl)propan-2-amine and adc = acetylenedicarboxylate). Based on the single-crystal structure of 1, the water dimer plays an important role in connecting the bis(adc) bridged dinickel synthons to form a one-dimensional (1D) supramolecular network. To emphasize the role of 6-Mebpta in the judicious choice of components for 1, one simple modification to it by having another methyl group in the second pendant pyridyl group to make 6,6′-Me2bpta (2-methyl-N,N-bis((6-methylpyridin-2-yl)methyl)propan-2-amine) did not allow the formation of any water cluster in [Ni(6,6′-Me2bpta)(adc)(H2O)]·H2O (2), where a different coordination environment around Ni(II) is also observed. Further quantification of the difference in supramolecular interactions observed in 1 and 2 has been assessed by Hirshfeld surface analysis. Both 1 and 2 are obtained in good yields at room temperature (methanol as solvent) and are further characterized by elemental analysis, Fourier transform infrared (FTIR) and Raman spectroscopy, powder X-ray diffraction, and thermogravimetric analysis.

Luminescent Copolymer‐Rhenium(I) Hybrid Materials via Picolylamine‐Modified Poly(pentafluorophenyl acrylate)

AbstractThe synthesis and photophysical properties of well‐defined polymer‐rhenium(I) hybrid materials is described. Reversible addition‐fragmentation chain transfer polymerization of pentafluorophenyl acrylate yields a parent homopolymer that serves as a reactive scaffold for the preparation of a series of new statistical copolymers containing pendent pyridyl functional groups in conjunction with various other repeat unit species. Attachment of [Re(CO)3(phen)]+ fragments via coordination through the pendent pyridyl groups yields the hybrid metal‐copolymer materials. Photophysical studies confirm successful rhenium coordination as judged from the absorption and emission profiles of the hybrid materials and further verify that the polymeric scaffold has no discernable effect on the luminescent properties of the coordinated rhenium species.

Probing into the electrochemistry of four nickel(II) and cobalt(II) complexes with azadiphosphine ligands (PNP) and their catalysis on proton reduction

In this work, four complexes of Co(II) and Ni(II), [Co(L1)2(CH3CN)](ClO4)2 (1), [Ni(L1)2](ClO4)2 (2), [Co(L2)2(CH3CN)](ClO4)2 (3) and [Ni(L2)2](ClO4)2 (4) were synthesized by reacting the perchlorate hydrate of M(II) (M = Co and Ni) with the ligands, Ph2PN(cyclohexyl)PPh2 (L1) and Ph2PN(pyridin-2-ylmethyl)PPh2 (L2), respectively. The complexes were fully characterized, and their absolute structures were determined using X-ray single crystallographic analysis. The cobalt complexes (1 and 3) exhibited two reductions in acetonitrile, one reversible reduction at about −0.65 V and the other at about −2.0 V at which catalytic reduction of proton was observed. The two reductions were assigned to Co(II) → Co(I) and Co(I) → Co(0) processes, respectively. The reduction of Ni(II) → Ni(I) was negatively shifted by about 300 mV compared to the cobalt analogues and the process showed two closely located reversible reductions due to geometric isomerization between the square planar (Sp) and tetrahedral (Td) geometries, of which the Td isomer was first reduced due to the lower energy level of its frontier orbitals. The second reduction of the Ni(II) complexes (2 and 4) was invisible in the potential range examined. Upon addition of acetic acid, it shifted positively by over 300 mV and showed catalysis on proton reduction. The shift was attributed to proton-coupled electron transfer (PCET) effect which was further enhanced by the pendant pyridyl group in ligand L2. The nickel complexes showed much higher activity than cobalt analogues in the catalysis on proton reduction and the pendant base group could synergistically enhance the activity of the complex (4).

Synthesis, structural characterization and antiproliferative potential of copper 4′-phenyl-terpyridine complexes constructed from building block reaction

Reactions between 4′-phenyl-terpyridine (L0) and Cu(II) nitrate resulted in the formation of complex [Cu(NO3)2L0](H2O) (1). Further reaction of this compound as a building block with sodium citrate, sodium benzoic and a tetra-methylpyridyl functionalized Cyclam ligand led to the compounds as [Cu(L0)2](NO3)2(H2O)1.5 (2), [Cu(ONO2)L0(OCOC6H5)](1.5H2O)(0.5CH3CN) (3) and [Cu2(NO3)2(L0)2L](NO3)2(H2O)2 (4), respectively. The four compounds were characterized by Elemental analysis, IR, UV–vis, and single crystal X-ray diffraction. Moreover, the thermal stability of 1 and 4 were determined by TG-DTA. In 1, 3 and 4, Cu ion is coordinated with one terpyridine motif and two oxygen atoms or one oxygen and one nitrogen atoms from two auxiliary ligands, resulting in a distorted CuN3O2 or CuN4O tetragonal pyramid geometry, while 2 is a sandwich structure, forming a regular-octahedron CuN6 coordination structure. The functionalized cyclam ligand L shows only one conformation with two pendant pyridyl groups coordinating to two copper ions and the other two being free in a para-mode conformation. The separation between the two copper ions in one molecule is 14.9398 (9) Å. Three human cancer cell lines were used for antiproliferative potential: human lung cancer cell line (A549), human colon cancer cell line (HCT-8) and human breast cancer cell line (MCF-7). The results have shown that these copper compounds have good inhibitory effects on cancer cells, which are better than that of the commonly used clinical drug cisplatin.

Crystal structure of imidazo[1,5-a]pyridinium-based hybrid salt (C13H12N3)2[MnCl4

A new organic-inorganic hybrid salt [L]2[MnCl4] (I) where L + is the 2-methyl-3-(pyridin-2-yl)imidazo[1,5-a]pyridinium cation, is built of discrete organic cations and tetra-chlorido-manganate(II) anions. The L + cation was formed in situ in the oxidative cyclo-condensation of 2-pyridine-carbaldehyde and CH3NH2·HCl in methanol. The structure was refined as a two-component twin using PLATON (Spek, 2020 ▸) to de-twin the data. The twin law (-1 0 0 0-1 0 0.5 0 1) was applied in the refinement where the twin component fraction refined to 0.155 (1). The compound crystallizes in the space group P21/c with two crystallographically non-equivalent cations in the asymmetric unit, which possess similar structural conformations. The fused pyridinium and imidazolium rings of the cations are virtually coplanar [dihedral angles are 0.89 (18) and 0.78 (17)°]; the pendant pyridyl rings are twisted by 36.83 (14) and 36.14 (13)° with respect to the planes of the remaining atoms of the cations. The tetra-hedral MnCl4 2- anion is slightly distorted with the Mn-Cl distances falling in the range 2.3469 (10)-2.3941 (9) Å. The distortion value of 0.044 relative to the ideal tetra-hedron was obtained by continuous shape measurement (CShM) analysis. In the crystal, the cations and anions form separate stacks propagating along the a-axis direction. The organic cations display weak π-π stacking. The anions, which are stacked identically one above the other, demonstrate loose packing; the minimum Mn⋯Mn separation in the cation stack is approximately 7.49 Å. The investigation of the fluorescent properties of a powdered sample of (I) showed no emission. X-band EPR data for (I) at 293 and 77 K revealed broad fine structure signals, indicating moderate zero-field splitting.