Accurately Modulating Binuclear Metal Nodes of Metal-Organic Frameworks for Oxygen Evolution.

The accurate manipulation of the species and locations of catalytic centers is crucial for regulating the catalytic activity of catalysts, which is essential for their efficient design and development. Metal-organic frameworks (MOFs) with coordinated metal sites are ideal materials for investigating the origin of catalytic activity. In this study, we present a Ni2-MOF featuring novel Ni-based binuclear nodes with open metal sites (OMSs) and saturated metal sites (SMSs). The nickel was replaced by iron to obtain Ni1Fe1-MOF. In the electrocatalytic oxygen evolution reaction, Ni1Fe1-MOF exhibited an overpotential and Tafel slope of 370 mV@10 mA cm-2 and 87.06 mV dec-1, respectively, which were higher than those of Ni2-MOF (283 mV@10 mA cm-2 and 39.59 mV dec-1, respectively), demonstrating the superior performance of Ni1Fe1-MOF. Furthermore, theoretical calculations revealed that iron as an SMS may effectively regulate the electronic structure of the nickel catalytic center to reduce the free energy barrier ΔG*OH of the rate-determining step.

Tracking the Stepwise Formation of a Water-Soluble Fluorescent Tb12 Cluster for Efficient Doxorubicin Detection.

Doxorubicin (DOX) is an anthraquinone drug used for the efficient treatment of a variety of tumors in human beings. Unfortunately, its poor biodegradability causes incomplete metabolism in the body. Therefore, it is of great significance to synthesize a sensitive and selective material for DOX detection. In this paper, we report a water-soluble Tb12 cluster and track its step-by-step formation (L → Tb1L1 → Tb2L1 → Tb2L2 → Tb3L2 → Tb4L2 → Tb12L6). Tb12 can be used to determine the presence of DOX, which quenches the luminescence of the Tb12 aqueous solution, and the detection limit can reach 13 nM (KSV = 8.7 × 105 M-1). Tb12 has advantages of high sensitivity and high selectivity for the detection of DOX in a simulated environment of human urine and serum.

Hierarchical Construction and Magnetic Difference of {Co12M12} (M = Co2+/Cd2+) Aggregates from {Co14} Cluster-Based Precursors in the Presence of Homo/Heterometal Salts.

The controllable construction and function expansion of some sophisticated aggregations represent a current hot topic in scientific research. In this paper, using a prefabricated {Co14} cluster as a synthetic precursor, a homometallic {Co24} and a heterometallic {Co12Cd12} giant cluster possessing similar dual-[M12] (M = Co/Cd) skeletons was prepared by reacting the precursor with excess CoCl2 and Cd(OAc)2 salts, respectively. The detailed structural information on {Co24} and {Co12Cd12} was characterized by single-crystal X-ray diffraction and further analyzed by X-ray photoelectron spectroscopy, inductively coupled plasma-mass spectroscopy, and scanning electron microscopy with energy dispersive X-ray (EDX) spectroscopy in the solid state. Compared to the {Co14} precursor, magnetic difference revealed that spin-canting and magnetic ordering had been enhanced in {Co24} and suppressed in {Co12Cd12} when dotted with diamagnetic Cd2+ ions.

In Situ Metal-Ligand Reactions under Solvent-Dependent Hydro(solvo)thermal Conditions: Structures, Mass Spectrometry, and Magnetism.

In this study, four in situ hydro(solvo)thermal metal-ligand reactions, including oxidation (H2L1), C-C coupling (H4L2), nitration (H2L3), and condensation (HL4-6), based on bis[3-(pyridin-2-yl)-1H-1,2,4-triazol-5-yl]methane (H2L0), in the presence of DyIII ions, were carried out. The in situ metal-ligand reaction gave six new ligands existing in eight novel DyIII coordination complexes, which were characterized by crystal structure, mass spectrometry, and magnetism.

Hierarchical Assembly of a {Co24} Cluster from Two Vertex-Fused {Co13} Clusters and Their Single-Molecule Magnetism.

We present the synthesis, structural characterization, and magnetic properties of two high-nuclearity cobalt clusters formulated as [Co13(µ3-OH)3(µ3-Cl)(dpbt)5(ptd)Cl10][Co(H2O)2Cl2]·(CH3)2CHOH (1) and [Co24(µ3-OH)6(µ3-Cl)2(dpbt)10(ptd)2Cl16]·2CH3CH2OH (2), respectively (H2dpbt = 5,5'-bis(pyridin-2-yl)-3,3'-bis(1,2,4-triazole) and H2ptd = 3-(pyridin-2-yl)-1,2,4-triazine-5,6-diol). Compound 1 is composed of an inner [Co4(µ3-OH)3(µ3-Cl)] cubane and an outer [Co9(dpbt)5(ptd)Cl10] defective adamantane. Compound 2 reveals a giant {Co24} cluster possessing a dual-[Co12] skeleton from 1. The hierarchical assembly from 1 to 2 has been established and tracked through high-resolution electrospray ionization (HRESI-MS) analyses from the solvothermal reaction mother solution. Magnetic studies of 1 and 2 revealed the highly correlated spins, a glasslike magnetic phase transition at ca. 8 K, and slow relaxation behavior of SMM nature in the lower-temperature region (below 4 K).

Ni(II) Complexes with Schiff Base Ligands: Preparation, Characterization, DNA/Protein Interaction and Cytotoxicity Studies.

In this study, two Ni(II) complexes, namely [Ni(HL1)2(OAc)2] (1) and [Ni(L2)2] (2) (where HL1 and HL2 are (E)-1-((1-(2-hydroxyethyl)-1H-pyrazol-5-ylimino)methyl)-naphthalen-2-ol) and (E)-ethyl-5-((2-hydroxynaphthalen-1-yl)methyleneamino)-1-methyl-1H-pyrazole-4-carboxylate, respectively), were synthesized and characterized by X-ray crystallography, Electrospray Ionization Mass Spectrometry (ESI-MS), elemental analysis, and IR. Their uptake in biological macromolecules and cancer cells were preliminarily investigated through electronic absorption (UV-Vis), circular dichroism (CD) and fluorescence quenching measurements. Bovine serum albumin (BSA) interaction experiments were investigated by spectroscopy which showed that the complexes and ligands could quench the intrinsic fluorescence of BSA through an obvious static quenching process. The spectroscopic studies indicated that these complexes could bind to DNA via groove, non-covalent, and electrostatic interactions. Furthermore, in vitro methyl thiazolyl tetrazolium (MTT) assays and Annexin V/PI flow cytometry experiments were performed to assess the antitumor capacity of the complexes against eight cell lines. The results show that both of the complexes possess reasonable cytotoxicities.

Antiviral Matrine-Type Alkaloids from the Rhizomes of Sophora tonkinensis.

Three new matrine-type alkaloids, (+)-5α-hydroxyoxysophocarpine (1), (-)-12ß-hydroxyoxysophocarpine (2), and (+)-5α-hydroxylemannine (3), along with 14 known analogues, (-)-sophocarpine (4), (-)-5α-hydroxysophocarpine (5), (-)-9α-hydroxysophocarpine (6), (+)-12α-hydroxysophocarpine (7), (-)-12ß-hydroxysophocarpine (8), (+)-oxysophocarpine (9), (+)-matrine (10), (+)-sophoranol (11), (+)-9α-hydroxymatrine (12), (-)-14ß-hydroxymatrine (13), (+)-oxymatrine (14), (+)-5α-hydroxyoxymatrine (15), (-)-14ß-hydroxyoxymatrine (16), and (+)-sophoramine (17), were isolated from the rhizomes of Sophora tonkinensis. Their structures were elucidated via spectrometric data analyses, and the absolute configurations were established by single-crystal X-ray diffraction and ECD data. Alkaloids 2, 6, 11, and 13 exhibited antiviral activity against the Coxsackie virus B3 (CVB3), with IC50 values of 26.62-252.18 µM, and alkaloids 7, 8, and 17 inhibited influenza virus A/Hanfang/359/95 (H3N2) replication with IC50 values of 63.07-242.46 µM.

Ce(OTf)3-catalyzed [3 + 2] cycloaddition of azides with nitroolefins: regioselective synthesis of 1,5-disubstituted 1,2,3-triazoles.

The first example of rare earth metal-catalyzed [3 + 2] cycloaddition of organic azides with nitroolefins and subsequent elimination reaction is described. In the presence of a catalytic amount of Ce(OTf)3, both benzyl and phenyl azides react with a broad range of aryl nitroolefins containing a range of functionalities selectively producing 1,5-disubstituted 1,2,3-triazoles in good to excellent yields.

Marbofloxacin combined with heavy rare-earth ions makes better candidates for veterinary drugs: crystal structure and bio-activity studies.

Marbofloxacin (MB) is a newly developed fluoroquinolone antibiotic used especially as a veterinary drug. It may be regarded as the improved version of enrofloxacin owing to its antibacterial activity, enhanced bioavailability, and pharmacokinetic-pharmacodynamic (PK-PD) properties. In this study, nine heavy rare-earth ions (Y, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu) were selected in light of their potential antibacterial activity and satisfactory biosafety to afford the corresponding rare-earth metal complexes of MB: the MB-Ln series. Their chemical structures and coordination patterns were characterized using IR spectroscopy, HRMS, TGA, and X-ray single-crystal diffraction analysis. Our results confirmed that all the MB-Ln complexes yielded the coincident coordination modes with four MB ligands coordinating to the Ln(III) center. In vitro antibacterial screening on five typical bacteria strains revealed that the MB-Ln complexes exhibited antibacterial activities comparable with MB, as indicated by the MIC/MBC values, in which Escherichia coli and Salmonella typhi were the most sensitive ones to MB-Ln. Furthermore, the MB-Ln complexes were found to be much less toxic in vivo than MB, as suggested by the evaluated LD50 (50% lethal dose) values. All the MB-Ln series complexes fell in the LD50 range of 5000-15 000 mg kg-1, while the LD50 value of MB was only 1294 mg kg-1. Furthermore, MB-Lu, as the selected representative of MB-Ln, could effectively inhibit the activity of DNA gyrase, the same as MB, suggesting the primary antibacterial mechanism of the MB-Ln series. The results demonstrated the good prospects and potential of metal-based veterinary drugs with better drug performance.

2,4-Di-bromo-1,3-dihy-droxy-9H-xanthen-9-one.

The title compound, C13H6Br2O4, derived from xanthone, a fundamental structural framework of active ingredients in many medicinal plants, and was synthesized by bromination of 1,3-di-hydroxyxanthen-9-one with N-bromo-succinimide. The mol-ecular conformation is essentially planar, the dihedral angle between the benzene rings being 1.1 (4)°. This conformation is favorable for the formation of an intra-molecular O-H⋯O hydrogen bond between a hy-droxy group and the xanthone carbonyl group. In the crystal, mol-ecules are associated into chains along the b-axis direction via C=O⋯H-O hydrogen bonds involving the other hy-droxy group.

Double-stranded metallo-triangles: from anion-templated nonanuclear to cation-templated tetraicosanuclear dysprosium clusters.

Two double-stranded metallo-triangles, Dy9 and Dy24, with hexaple-C10H7PO32- bridges were constructed, and their magnetic properties were explored. Compared with the field-induced relaxation phenomenon of Dy9 templated with a chloride anion, Dy24 templated with a sodium cation exhibited zero-field single-molecule-magnet behavior.

Stepwise formation of a chemodynamic therapy agent of {Cu8} macrocyclic complex recognized by iodide ions.

An atomically precise Cu(I) macrocyclic complex Cu8I was developed for chemodynamic therapy (CDT) research. The {Cu8} macrocyclic skeleton gradually forms with the selective recognition of iodide ions, and the monitoring of intermediate fragments during Cu8I formation using time-dependent electrospray ionization mass spectrometry indicates the following possible formation process: [Cu1] → [Cu2] → [Cu3] → [Cu4] → [Cu5I] → [Cu6I] → [Cu7I] → [Cu8I] when recognized by iodide ions. Furthermore, the Cu(I)-mediated Fenton-like reaction in Cu8I catalyzes the production of toxic ˙OH from H2O2, which results in efficient tumor suppression.

A Cu(I)-based Fenton-like agent inducing mitochondrial damage for photo-assisted enhanced chemodynamic therapy.

Increasing the reactive oxygen species (ROS) content at the tumor site is one of the effective strategies to promote intracellular oxidative stress and improve therapeutic efficiency. Herein, an atomically precise cinnamaldehyde-derived metal-organic Cu(I) complex (denoted as DC-OD-Cu) was rationally constructed. DC-OD-Cu could preferentially accumulate in the mitochondria of HeLa cells due to the mitochondria-targeting ability of triphenylphosphine, which was accompanied by the generation of large amounts of highly toxic hydroxyl radicals (˙OH) via Cu(I)-mediated Fenton-like reactions. Meanwhile, greater ROS generation jointly results in mitochondrial damage under white LED light irradiation. Furthermore, the in vitro and in vivo results suggested that DC-OD-Cu possesses favorable cytotoxicity and inhibits tumor growth. We believe that this research might provide a controllable strategy to construct multifunctional metal organic complexes for ROS-involved CDT.

Triaqua-(cyclo-hex-4-ene-1,2-dicarboxyl-ato-κO(1))(1,10-phenanthroline-κ(2)N,N')cobalt(II).

In the title compound, [Co(C(8)H(8)O(4))(C(12)H(8)N(2))(H(2)O)(3)], the Co(II) atom is coordinated by two N atoms from a bidentate 1,10-phenanthroline ligand, one O atom from a monodentate 4-cyclo-hexene-1,2-dicarboxyl-ate ligand and three water O atoms in a distorted octa-hedral geometry. The mononuclear mol-ecules are engaged in extensive intra- and inter-molecular O-H⋯O hydrogen-bonding inter-actions and π-π stacking inter-actions [centroid-centroid distance = 3.784 (3) Å], forming a three-dimensional supra-molecular network.

Crystal structure, assembly process, and single-molecule magnet behavior of a triangular prismatic {Co9} cluster.

Using the polydentate ligand of H4L with the CoII ion, a triangular prism-type nine-nucleus cluster [Co9(L)3(CH2OCH2OH)6]·3.5H2O ({Co9}-Eg, H4L = 6,6'-(1H,1'H-[3,3'-bi(1,2,4-triazole)]-5,5'-diyl)dipicolinic acid) was constructed. Ion fragmentation during the formation of the {Co9}-Eg cluster was tracked using time-dependent electrospray ionization mass spectrometry. In addition, we proposed two possible formation processes (i) H4L → CoL → Co2L → Co6L3 → Co7L3 → Co9L3 and (ii) H4L → CoL → Co2L → Co3L → Co5L2 → Co7L3 → Co9L3. Magnetic studies show that {Co9}-Eg exhibits slow relaxation under a static zero field at low temperature, which is the main characteristic of single molecule magnets (SMMs).

A triphenylphosphine coordinated cinnamaldehyde-derived copper(I) Fenton-like agent with mitochondrial aggregation damage for chemodynamic therapy.

Chemodynamic therapy (CDT), which uses agents to induce cell death by decomposing endogenous hydrogen peroxide (H2O2) into highly toxic hydroxyl radicals (˙OH), has been recognized as a promising approach to treat cancer. However, improving the efficiency of ˙OH production is considered one of the biggest challenges that limits the therapeutic efficacy of CDT. Herein, to controllably and efficiently induce oxidative damage through the production of ˙OH, we developed a new metal complex CDT agent with atomically precise structural characteristics as a deviation from traditional nanomaterial-CDT agents. The obtained CDT agent, a cinnamaldehyde derived copper(I) complex (denoted Cin-OD-Cu), was found to be continuously enriched in the mitochondria of A2780 ovarian carcinoma cells, which was accompanied by the generation of large amounts of ˙OH via Cu(I)-mediated Fenton-like reactions of H2O2, thereby stimulating oxidative stress in the mitochondria and eventually leading to cell death. Moreover, in vivo experiments showed that Cin-OD-Cu was capable of effectively inhibiting tumor growth with excellent biocompatibility. We believe this research enriches the limited selection of atomically precise metal complex CDT agents in particular for reactive oxygen species-mediated treatments aimed at inducing mitochondria oxidative damage; we anticipate that it will provide new insights into the development of novel, atomically precise agents for CDT.

A triphenylphosphine coordinated Cu(I) Fenton-like agent with ferrocene moieties for enhanced chemodynamic therapy.

A triphenylphosphine coordinated Cu(I) complex of Fc-OD-Cu was rationally designed for chemodynamic therapy (CDT) of cancer. The complex was capable of generating a highly toxic hydroxyl radical (˙OH) via a Fenton-like reaction induced by Cu(I) moieties and simultaneously mediated by ferrocene moieties. As a result, the CDT efficiency of Fc-OD-Cu is higher than that of Ba-OD-Cu (without ferrocene moieties) and Fc-OD (without Cu(I) moieties).

Rational construction of a triphenylphosphine-modified tetra-nuclear Cu(I) coordinated cluster for enhanced chemodynamic therapy.

A triphenylphosphine-modified tetra-nuclear Cu(I) coordinated cluster was constructed for enhanced chemodynamic therapy (CDT) by increasing the number of metal centers. Once inside human bladder cancer (T24) cells, a larger amount of copper accumulated compared with the mono-nuclear Cu(I) complex; the additional copper could generate more •OH and then induce more obvious apoptosis via a Fenton-like reaction, thus further increasing the tumor inhibition effect and ultimately improving the CDT efficiency.

1-[2-(Pyrazin-2-ylsulfan-yl)eth-yl]pyrazine-2(1H)-thione.

The title multifunctional twisted organic ligand, C(10)H(10)N(4)S(2), contains a short C=S bond [1.671 (2) Å]. The dihedral angle between the two pyrazine rings is 39.83 (6)°. In the crystal, inter-molecular C-H⋯N and C-H⋯S hydrogen bonds result in the formation of a supra-molecular network.

Two novel chiral tetranucleate copper-based complexes: syntheses, crystal structures, inhibition of angiogenesis and the growth of human breast cancer in vitro and in vivo.

The single crystals of two novel chiral tetranucleate copper(II)-based complexes (TNCu-A and TNCu-B) containing L-methioninol-derived Schiff-bases were obtained. Their single structures were characterized by X-ray single crystal diffraction, infrared (IR) rays, elemental analysis, and liquid chromatography-mass spectrometry analysis. TNCu-A can effectively inhibit human umbilical vein endothelial cells (HUVECs) to form a tubular structure and it induces apoptosis of human triple-negative breast cancer MDA-MB-231 cells and HUVECs in vitro in a mitochondria dependent manner. Moreover, in vivo TNCu-A can remarkably inhibit the growth of triple-negative breast cancer from which MDA-MB-231 cells were xenografted into severely immunodeficient nude mice by inhibiting proliferation, inducing apoptosis of MDA-MB-231 cells by dramatically inhibiting the expression of the anti-apoptotic protein Bcl-2 and up-regulating the expressions of proapoptotic proteins caspase-9 and Bax, and simultaneously inhibiting tumor angiogenesis by decreasing the density of vascular endothelial cells and suppressing migration and even partially inducing apoptosis.