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.

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.

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).

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).

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.

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.

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.

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.

A simple and feasible atom-precise biotinylated Cu(i) complex for tumor-targeted chemodynamic therapy.

A simple and feasible atom-precise biotinylated Cu(i) complex, which can catalyze H2O2 overexpressed commonly in the tumor microenvironment to produce ˙OH through a Fenton-like reaction, was prepared and employed as an effective agent for tumor-targeted chemodynamic therapy.

Constructing an unprecedented {MnII38} matryoshka doll with a [Mn18(CO3)9] inorganic core and magnetocaloric effect.

An unprecedented inner [Mn18(CO3)9] inorganic core and [Mn20] metal-organic periphery compose a high-nuclearity homometallic single-valent {MnII38} molecular aggregate with a [Mn6] ⊂ [Mn12] ⊂ [Mn8] ⊂ [Mn12] matryoshka doll-like skeleton that displays a significant magnetocaloric effect (MCE).

Ring-forming transformation associated with hydrazone changes of hexadecanuclear dysprosium phosphonates.

{Dy16(µ6-C10H7PO3)2(µ5-C10H7PO3)8(spch)8(µ3-OH)2(µ2-OH)2(µ2-AcO)6(µ3-COO)2(DMF)2(H2O)6}·0.5CH3OH·4.5H2O (1) and {Dy16(µ5-C10H7PO3)4(µ3-C10H7PO3)12(µ2-C10H7PO3H)8(opch)4(DMF)8(MeOH)4}·2.5CH3OH·3H2O (2), where H2spch is ((E)-N'-(2-hydroxybenzylidene)pyrazine-2-carbohydrazide, C10H7PO3H2 is 1-naphthylphosphonic acid and H2opch is (E)-N'-(2-hydroxy-3-methoxybenzylidene)pyrazine-2-carbohydrazide, were successfully synthesized by varying the hydrazone ligands in the Dy-phosphonate system. It is important that the ellipsoidal core experiences a ring forming structural transformation to the supramolecular square motif upon the incorporation of an ortho-methoxy substituent into the hydrazone. Alternating-current (ac) magnetic susceptibility studies of 1 and 2 suggest that similar single molecule magnet behaviors occur for these two complexes. The result represents an effective molecular assembly tactic to develop highly complicated lanthanide coordination clusters through the multicomponent self-assembly of the coalescence of phosphonate- and hydrazone-based ligands and metal salts.

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.

Two novel chiral tetranucleate copper-based complexes: crystal structures, nanoparticles, and inhibiting angiogenesis and the growth of human breast cancer by regulating the VEGF/VEGFR2 signal pathway in vitro.

The single crystals of two novel copper(ii)-based complexes containing l-methioninol-derived Schiff bases were obtained and characterized. The nanoparticles of these complexes were prepared and their cellular uptake was measured in MDA-MB-231 cells and HUVECs. It was found that these complexes could remarkably induce apoptosis, inhibit proliferation, suppress migration and metastasis, and inhibit angiogenesis and the growth of triple-negative breast cancer derived from MDA-MB-231 cells in vitro. Meanwhile, these complexes exhibit anticancer and antiangiogenic functions by activating the important protein molecules VEGFR2, FAK, AKT and Erk1/2 or their phosphorylated molecules p-VEGFR2, p-FAK, p-AKT, and p-Erk1/2 in the VEGF/VEGFR2 signaling pathway, collapsing the mitochondrial membrane potential, and damaging the level of reactive oxygen species.

A novel sandwich shaped {CoCoMo} cluster with a Co triangle encapsulated in two capped CoIIICoMoO40 fragments.

A novel discrete {Co14Mo24} nanoscale cluster, {CoIII2CoII10Cl2(dpbt)3(H2O)2[CoIIMoV12O31(CH3O)9]2}·24CH3OH (1) (here, dpbt = 5,5'-di(pyridin-2-yl)-3,3'-bi(1,2,4-triazole)), with a triangular Co4 core encapsulated in two novel capped Co-substituted Keggin-type Co5Mo12O40 anions, has been isolated from alkaline methanol solution. The high-resolution electrospray ionization mass spectrum (HRESI-MS) of microcrystalline 1 in MeOH/CH2Cl2 (v : v = 2 : 1) was recorded. Two prominent overlapping peaks in the range of m/z = 2740-2840 and 1820-1880 for the discrete fragments of [CoIII2CoII12MoV24O62Cl2(dpbt)3(H2O)2(CH3O)x(OH)18-x-2H]2- (x = 9-18, F1) and [CoIII2CoII12MoV24O62Cl2(dpbt)3(H2O)2(CH3O)x(OH)19-x-2H]3- (x = 6-13, F2), respectively, are obtained, confirming the {Co14Mo24} composition in 1. In addition, weak anti-ferromagnetic interactions in 1 are observed.

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.

Synthesis, characterization, DNA/protein interaction and cytotoxicity studies of Cu(II) and Co(II) complexes derived from dipyridyl triazole ligands.

Four different transition metal complexes containing dipyridyl triazole ligands, namely [Cu(abpt)2Cl2]·2H2O (1), [Cu(abpt)2(ClO4)2] (2), [Co2(abpt)2(H2O)2Cl2]·Cl2·4H2O (3) and [Co2(Hbpt)2(CH3OH)2(NO3)2] (4) have been designed, synthesized and further structurally characterized by X-ray crystallography, ESI-MS, elemental analysis, IR and Raman spectroscopy. In these complexes, the both ligands act as bidentate ligands with N, N donors. DNA binding interactions with calf thymus DNA (ct-DNA) of the ligand and its complexes 1~4 were investigated via electronic absorption, fluorescence quenching, circular dichroism and viscosity measurements as well as confocal Laser Raman spectroscopy. The results show these complexes are able to bind to DNA via the non-covalent mode i.e. intercalation and groove binding or electrostatic interactions. The interactions with bovine serum albumin (BSA) were also studied using UV-Vis and fluorescence spectroscopic methods which indicated that fluorescence quenching of BSA by these compounds was the presence of both static and dynamic quenching. Moreover, the in vitro cytotoxic effects of the complexes against four cell lines SK-OV-3, HL-7702, BEL7404 and NCI-H460 showed the necessity of the coordination action on the biological properties on the respective complex and that all four complexes exhibited substantial cytotoxic activity.