Chelating Carboxylate Research Articles

Self-assembled carboxymethyl chitosan/zinc alginate composite film with excellent water resistant and antimicrobial properties for chilled meat preservation

A major way to reduce meat waste is to extend the shelf life of chilled meat with appropriate packaging. However, most of the packaging film cannot keep meat fresh because of its poor antibacterial and water resistance performance. In this paper, a composite film for chilled meat packaging was synthesized by simple self-assembly of zinc ions with chelating carboxyl groups. Introducing zinc ions into the composite system endows excellent water resistance and antibacterial properties to the film, which are demonstrated by the water vapor permeability and Escherichia coli and Staphylococcus aureus antibacterial tests. The as-prepared composite film also showed enhanced mechanical properties due to the formation of chelation bonds between zinc ions and carboxyl groups. Moreover, the chilled meat preservation test demonstrated the as-prepared composite film can significantly extend the shelf life of pork by five days, indicating its outstanding freshness preservation property. This work demonstrated a facile method to synthesize water-resistant and antimicrobial composite film, which can appear as an effective packaging material for chilled meat and offer a new idea to solve its short shelf-life problem.

Oxidation of thymol catalysed by a water-soluble Cu(II)-adipate-diphenylamine complex in a biphasic medium

A metal–organic framework involving a dicarboxylate (adipic acid) and dipyridylamine (dpya), [Cu2(dpya)(µ-adipate)].2ClO4·2H2O, has been synthesized by one-pot reaction and structurally characterized by X-ray diffraction. Pentacoordinated Cu(II) dimer complex links the adjacent Cu(dpya) units through chelating carboxylate oxygens of adipate dianion in a coordination pattern with the metal center. The centrosymmetric adipate-bridged dinuclear complex cations [Cu2(dpya)(µ-adipate)]2+ are assembled into pseudo-2D supramolecular networks through aromatic stacking interactions (4.108 Å) and also hydrogen bondings with counter ion with the coordinated water molecule. The catalytic performance of the compound was investigated for thymol (T) oxidation in organic solvents and water/hexane biphasic systems. Its selectivity was measured as 100 % for T to thymoquinone (TQ). A novel, simple, and efficient catalyst system (TOF = 400 h−1) was developed for the oxidation of T into a valuable derivate, TQ, using TBHP with subs./cat.(100) in a water/hexane biphasic system at 70 οC.

Solution-Grown Ternary Semiconductors: Nanostructuring and Stereoelectronic Lone Pair Distortions in I–V–VI2 Materials

Alkali pnictogen dichalcogenides─I–V–VI2 or APnCh2─have been identified as promising semiconducting materials for energy conversion devices. However, the controlled nanoscale synthesis and our understanding of the effects of cation ordering and stereochemically active lone pairs on the structures of these ternary compounds remain underdeveloped. Here, we use solution-phase chemistry to synthesize a family of APnCh2 materials, including LiSbSe2, NaSbS2, NaSbSe2, NaBiS2, and NaBiSe2. Our approach utilizes alkali metal hydrides (AH) or carboxylates, A(O2CR), PnPh3, and elemental chalcogens as synthetic precursors and oleylamine or 1-octadecene as solvents. Synthetic manipulation via fine-tuning of reaction temperature enables control over the degree of ordering caused by the Sb 5s2 lone pair-induced distortions in NaSbS2. Pair distribution function analysis demonstrates that the structure of the Sb-containing phases deviates much more from a disordered rock salt structure than that of the Bi-containing phases. This local distortion, induced by the Sb lone pair, leads to a previously unreported noncentrosymmetric NaSbS2 crystal structure, which is additionally supported by second-harmonic generation measurements. Infrared and multinuclear solid-state NMR spectroscopies show that oleylamine or chelating carboxylates and, in some cases, unreacted precursors (LiH and PnPh3) remain bound to the nanocrystalline surfaces. A deeper understanding of the local atomic environment, long-range ordering, surface chemistry, and optoelectronic properties of these materials may speed up their fundamental study and application.

Supramolecular Immobilization of Adamantyl and Carboxylate Modified N-Heterocyclic Carbene Ligand on Cucurbituril Substrates.

Herein, the design, synthesis, supramolecular interactions and structural analysis of a novel bidentate carboxylate chelating N-heterocylic carbene (NHC) ligand is presented. The NHC structure was modified to strategically incorporate adamantyl moiety for the formation of a supramolecular complex with host molecules such as cucurbiturils. The adamantyl modified NHC ligand could potentially be used in recoverable homogeneous catalysts when Immobilized on a solid support via host–guest chemistry. As a versatile precursor, NHC ligand (8) was synthesized and characterized by 1H-NMR, 13C-NMR, FTIR, single crystal x-ray crystallography and elemental analysis. A proof-of-principle non-covalent immobilization of the NHC ligand (8) with a Cucurbit[7]uril (CB7) host was demonstrated using 1H-NMR titration.

Experimental and theoretical investigations on three DyIII4 single molecule magnets: structural and magneto-structural correlations.

The work in this report describes the syntheses, crystal structures, dc/ac magnetic behaviour, and theoretical calculations (both ab initio CASSCF and DFT) of three defect dicubane/planar butterfly type tetradysprosium(III) compounds of compositions [DyIII4L4(μ3-OH)2(carboxylate)2(dmf)2] (carboxylate = formate (1), acetate (2), propionate (3)), where H2L = 2-(2-hydroxy-3-ethoxybenzylideneamino)phenol. In the butterfly type structures, two DyIII centres (Dyb) occupy the body positions while two other (Dyw) units occupy the wing positions. SHAPE analyses reveal that the coordination geometries of the Dyb and Dyw centres, both octacoordinated, are triangular dodecahedron (TDD) and square antiprism (SAPR), respectively. Variable-temperature magnetic susceptibility measurements give an indication of weak antiferromagnetic interactions and variable-field magnetization measurements reveal strong anisotropy in all the three compounds. The variable-temperature/frequency in-phase/out-of-phase AC susceptibility data reveal that all these three compounds are SMMs with two relaxation channels under zero dc field; slow relaxation (SR) and fast relaxation (FR) processes could be assigned to the SAPR (Dyw) and TDD (Dyb) metal centres, respectively. The simulated Ueff and τ0 values are: 49.0 cm-1 and 1.76 × 10-7 s for 1, 30.3 cm-1 and 1.51 × 10-8 s for 2 and 23.4 cm-1 and 9.64 × 10-7 s for 3. Furthermore, ab initio CASSCF/RASSI-SO/SINGLE_ANISO calculations reveal that the ground state of DyIII centres are axial in nature with a dominating contribution from mJ = |±15/2>. The magnetization relaxation occurs via the first excited KD resulting in the large computed blocking barrier of Dyw (SAPR) centres compared to that of the Dyb (TDD) centres which corroborates the experimental measurements. The exchange parameters obtained from DFT calculations are generally in line with those obtained from the fitting of χMT vs. T in POLY_ANISO calculations. Interesting structural and magneto-structural correlations have been found, which are the major outcomes of this investigation.

Zn(II)-to-Cu(II) Transmetalation in an Amide Functionalized Complex and Catalytic Applications in Styrene Oxidation and Nitroaldol Coupling.

The mononuclear zinc(II) complex cis-[ZnL2(H2O)2] (1; L = 4-(pyridin-3-ylcarbamoyl)benzoate) was synthesized and characterized. By soaking crystals of 1 in a mixture of DMF-H2O solution containing a slight excess of Cu(NO3)2 × 3H2O a transmetalation reaction occurred affording the related copper(II) complex trans-[CuL2(H2O)2] (2). The structures of the compounds were authenticated by single crystal X-ray diffraction revealing, apart from a change in the isomerism, an alteration in the relative orientation of the chelating carboxylate groups and of the pyridine moieties. H-bond interactions stabilize both geometries and expand them into two-dimensional (2D) networks. The transmetalation was confirmed by SEM–EDS analysis. Moreover, the thermodynamic feasibility of the transmetalation is demonstrated by density-functional theory (DFT) studies. The catalytic activities of 1 and 2 for the oxidation of styrene and for the nitroaldol (Henry) C-C coupling reaction were investigated. The copper(II) compound 2 acts as heterogeneous catalyst for the microwave-assisted oxidation of styrene with aqueous hydrogen peroxide, yielding selectively (>99%) benzaldehyde up to 66% of conversion and with a turnover frequency (TOF) of 132 h−1. The zinc(II) complex 1 is the most active catalyst (up to 87% yield) towards the nitroaldol (Henry) coupling reaction between benzaldehyde and nitro-methane or -ethane to afford the corresponding β-nitro alcohols. The reaction of benzaldehyde with nitroethane in the presence of 1 produced 2-nitro-1-phenylpropanol in the syn and the anti diastereoisomeric forms, with a considerable higher selectivity towards the former (66:34).

Bidentate carboxylate linked TiO2 with NH2-MIL-101(Fe) photocatalyst: a conjugation effect platform for high photocatalytic activity under visible light irradiation

Interfacial conjugation was employed to engineering preparation of TiO2@NH2-MIL-101(Fe) heterojunction photocataysts through carboxylate bidentate linkage with TiO2 and NH2-MIL-101(Fe), which can enhance the electron transfer capability from metal-organic frameworks (MOFs) to TiO2 and photocatalytic activity. The carbon nanospheres derived from glucose act as reducing agent and template to synthesize oxygen vacancies TiO2 hollow nanospheres. Then, the oxygen vacancies were employed as antennas to connect 2-aminoterephtalic acid as bidentate carboxylate chelating linkage on TiO2, which have been proved by the density functional theory (DFT) calculations. Subsequently, NH2-MIL-101(Fe) was coordinatingly formed on the surface of TiO2. The conjugation effects between TiO2 and NH2-MIL-101(Fe) enhanced the electron transfer capability and could also induce the band tail states to narrow bandgap of the composites. Thus, the photodegradability of methylene blue was remarkably enhanced under visible light irradiation. The degradation rate of TiO2@17%NH2-MIL-101(Fe) was 0.131 min−1, which was about 3.5 and 65 times higher than that of NH2-MIL-101(Fe) and TiO2, respectively.

Zero/one-dimensional coordination complexes constructed from the carboxylate and multi-nitrogen chelating ligands: structural insights and photocatalytic degradation of organic dye

In the current study, two new coordination complexes with the chemical formulae of [Co(cbba)(bimb)](H2O) (1, H2cbba = 3-((3-carboxybenzyl)oxy)benzoic acid, bimb = 6,6′-bis(1H-benzo[d]imidazol-2-yl)-2,2’-bipyridine) and {[Co(pdc)(bimb)](DMF)}n (2, H2pda = pyrazine-2,5-dicarboxylic acid) have been successfully prepared by reaction of the Co(NO3)2·6H2O with the bimb ligand in the presence of different carboxylate ligands (H2cbba for 1 and H2pda for 2). The as-prepared two complexes have been determined via the elemental analysis, single crystal X-ray diffraction along with the powder X-ray diffraction. In addition, the photocatalytic activity of complex 2 toward the degradation of methyl violet (MV) in simulated polluted water was explored.

Synthesis, Crystal Structures and Photoluminescent Properties of One-Dimensional Europium(III)- and Terbium(III)-Glutarate Coordination Polymers, and Their Applications for the Sensing of Fe3+ and Nitroaromatics

Two lanthanide–glutarate coordination polymers, viz. : {[Eu(C5H6O4)(H2O)4]Cl}n, (1) and [Tb(C5H7O4)(C5H6O4)(H2O)2]n, (2) have been synthesized and characterized by IR spectroscopy, thermogravimetric analysis, and X-ray crystallography. In 1, the Eu(III) ions are coordinated by four O atoms from two bidentate chelating carboxylate groups, one O atom from a bridging carboxylate group and four O atoms from water molecules adopting an EuO9 distorted tri-capped trigonal prismatic coordination geometry. In 2, the Tb(III) ions are coordinated by six O atoms from three bidentate chelating carboxylates, one O atom from a bridging carboxylate and two O atoms from water molecules to generate distorted tri-capped trigonal prismatic TbO9 polyhedron. In both compounds, the metal polyhedra share edges, producing centrosymmetric Ln2O2 diamonds, and are linked into [001] chains by bridging glutarate di-anions. The crystal structures are consolidated by O–H···O and O–H···Cl hydrogen bonds in 1, and O–H···O hydrogen bonds in 2. Compound 1 exhibits a red emission attributed to the 5D0 → 7FJ (J = 1–4) transitions of the Eu(III) ion, whereas 2 displays green emission corresponding to the 5D4 → 7FJ (J = 0–6) transitions of the Tb(III) ion. Both the compounds exhibit high sensitivity and selectivity for Fe3+ ions due to luminescence quenching compared with other metal ions, which include; Na+, Mg2+, Al3+, Cr3+, Mn2+, Fe2+, Co2+, Ni2+, Zn2+ and Cd2+. Compounds 1 and 2 also show high luminescence quenching sensitivity for 4-nitrophenol over the other aromatic and nitroaromatic compounds, namely; bromobenzene, 1,3-dimethylbenzene, nitrobenzene, 4-nitrotolune, 4-nitrophenol, 2,6-dinitrophenol and 2,4,6-trinitrophenol.

Molecular-Level Understanding of Continuous Growth from Iron-Oxo Clusters to Iron Oxide Nanoparticles.

The formation of inorganic nanoparticles has been understood based on the classical crystallization theory described by a burst of nucleation, where surface energy is known to play a critical role, and a diffusion-controlled growth process. However, this nucleation and growth model may not be universally applicable to the entire nanoparticle systems because different precursors and surface ligands are used during their synthesis. Their intrinsic chemical reactivity can lead to a formation pathway that deviates from a classical nucleation and growth model. The formation of metal oxide nanoparticles is one such case because of several distinct chemical aspects during their synthesis. Typical carboxylate surface ligands, which are often employed in the synthesis of oxide nanoparticles, tend to continuously remain on the surface of the nanoparticles throughout the growth process. They can also act as an oxygen source during the growth of metal oxide nanoparticles. Carboxylates are prone to chemical reactions with different chemical species in the synthesis such as alcohol or amine. Such reactions can frequently leave reactive hydroxyl groups on the surface. Herein, we track the entire growth process of iron oxide nanoparticles synthesized from conventional iron precursors, iron-oleate complexes, with strongly chelating carboxylate moieties. Mass spectrometry studies reveal that the iron-oleate precursor is a cluster comprising a tri-iron-oxo core and carboxylate ligands rather than a mononuclear complex. A combinatorial analysis shows that the entire growth, regulated by organic reactions of chelating ligands, is continuous without a discrete nucleation step.

Synthesis and Characterization of Cyclometalated NHC Platinum Complexes with Chelating Carboxylate Ligands

Platinum(II) complexes [Pt(C^C*)(acac)], where C^C* = 3‐R‐1‐(phenyl‐κC2)‐1H‐benzimidazol‐2‐ylidene‐κC2 (R = Me, Ph) and acac = pentane‐2,4‐dionate, reacted with functionalized acetic acids YCH2CO2H (Y = NMe2, SMe and PPh2) with elimination of acetylacetone to produce the bis‐chelate complexes of the type [Pt(C^C*)(YCH2CO2)]. Whereas the Pt(II) precursor with the less bulky methyl substituent (R) gave rise to single products having trans‐C(NHC),Y geometry, its phenyl congener reacted less selectively, affording exclusively the product with trans‐S,C(Ph) configuration for Y = SMe and mixtures of cis and trans isomers for Y = NMe2 and PPh2. These observations were well reproduced by different DFT functionals at the double‐ξ level of theory, which suggested rather small energy differences between the geometric isomers. The photophysical measurements showed that complexes [Pt(C^C*)(YCH2CO2)] are emissive in the blue region (λem 460–490 nm) with photoluminescence quantum yields up to 36 % and emission lifetimes in the range of 3–5 µs.

Influence of cadmium(II) source upon the formation of a discrete monomer [Cd(κ2-OC(O)tBu)2(H2O)2] and a trinuclear heterobimetallic 1D CP, {Na2[Cd(μ5-κ3:κ3-OAc)(μ3-κ2:κ3-OC(O)tBu)(μ3-κ1:κ2-OC(O)tBu)2]·2tBuC(O)OH}∞

The reaction of CdCl2·2.5H2O with two equiv of aq. NaOH followed by treatment of the resulting solution with two equiv of pivalic acid gave [Cd(κ2-OC(O)tBu)2(H2O)2] (1) in 83% yield while the aforementioned reaction with Cd(OAc)2·2H2O as Cd2+ source afforded a trinuclear heterobimetallic 1D-CP, {Na2[Cd(μ5-κ3:κ3-OAc)(μ3-κ2:κ3-OC(O)tBu)(μ3-κ1:κ2-OC(O)tBu)2]·2tBuC(O)OH}∞ (2) in 90% yield. Complexes 1 and 2 were characterized by elemental analyses, IR spectroscopy, solution 1H and 13C {1H} NMR spectroscopy and solid state CP-MAS 13C{1H} NMR spectroscopy, TG-DTA analyses and single crystal X-ray diffraction. The phase purity of 2 was also verified by powder X-ray diffraction. Complex 1 represents the first structurally characterised discrete mononuclear cadmium(II) carboxylate complex which is known to contain a pair of chelating carboxylate ligand, while 2 represents the first structurally characterized trinuclear heterobimetallic 1D-CP formed through aggregation via covalent coordinate bond.

Magnetofluorescent nanohybrid comprising polyglycerol grafted carbon dots and iron oxides: Colloidal synthesis and applications in cellular imaging and magnetically enhanced drug delivery.

Multifunctional nanohybrids are attracting increasing attention for potential biomedical applications such as bioimaging and drug delivery due to their combined advantages of individual components. However, challenges in the improvement of their synthesis and colloidal stability to facilitate practical biomedical applications still remain. In this work, we report an efficient synthetic approach to fabricate magnetofluorescent nanohybrid (IO-PG-CD) comprising fluorescent carbon dots (CDs) and magnetic iron oxide nanoparticles (IOs) through polyglycerol (PG) mediated covalent linkage in aqueous media. CDs and IOs are first grafted with PG layer, and then functionalized with carboxyl and amino groups, respectively. The resulting CD-PG-COOH and IO-PG-NH2 handled as simple chemical compounds are integrated through EDC/NHS crosslinking to obtain the desired IO-PG-CD nanohybrid. The unprecedented hydrophilicity of PG layer endows IO-PG-CD nanohybrid with excellent colloidal stability in various physiological media, facilitating biomedical applications in vitro and in vivo. IO-PG-CD nanohybrid exhibits low cytotoxicity and its uptake by cells can be obviously enhanced by external magnetic attraction. The internalized IO-PG-CD nanohybrid emits multicolor fluorescence as observed by confocal fluorescence microscopy, demonstrating much better photostability than the nanoparticle labeled with organic dye. Taking advantage of enormous chelating carboxyl groups on the surface of IO-PG-CD nanohybrid, platinum-based anticancer drug was loaded on the surface (IO-PG-CD/Pt) through complexation and delivered into cancer cells in a magnetically enhanced manner, killing the cancer cells efficiently in vitro. Moreover, in vivo cancer therapy indicates that the external magnetic attraction also obviously improves the anticancer efficacy of IO-PG-CD/Pt in HeLa subcutaneous xenografts.

Doped porous carbon nanostructures with N[sbnd]Co[sbnd]O catalytic active sites for efficient electrocatalytic oxygen reduction reaction

A cobalt metal-organic framework constructed by 4-(4-pyridyl)-benzoic acid was used as the precursor to afford a series of Co nanoparticles embedded and N/O-doped porous carbon materials CoNOC-Tc-t (where Tc represents the carbonization temperature and t represents the carbonization time), which possess high surface area, hierarchically micro-, meso- and macropores, and high graphitization as well as the uniformly enchased NCoO catalytic active sites derived from pyridine nitrogen atom and chelating carboxylate coordinated octahedral cobalt (II) center. These CoNOC-Tc-t porous carbon nanostructures have demonstrated prominent catalytic activities toward oxygen reduction reaction (ORR) in alkaline medium. Compared with commercial Pt/C catalyst, the CoNOC-800-1 (annealed at 800 °C for 1 h) exhibits excellent selectivity via an efficient four-electron-dominant ORR process, as well as the superior durability and methanol tolerance, making it a cost-effective Pt-free ORR electrocatalyst. More importantly, the novelly designed NCoO catalytic active sites are proposed and well demonstrated by experiments, which provides a promising approach to develop heteroatom-doped carbon-based electrocatalytic materials.

Synthesis and structural characterization of dinuclear cerium(III) and erbium(III) complexes of nicotinic acid or 2-aminobenzoic acid

A cerium(III) complex, [Ce2(NA)6(H2O)4] (1) and an erbium(III) complex, [Er2(2-AMB)6(H2O)4]·3H2O (2), where NA = nicotinic acid and 2-AMB = 2-aminobenzoic acid, have been prepared and characterized by IR spectroscopy, thermogravimetric analysis and X-ray crystallography. The single crystal analysis reveals that both complexes are dinuclear. In 1, the two cerium(III) ions are bridged by carboxylate groups of four nicotinate ligands. Each cerium atom in 1 is nine-coordinate and exhibits a distorted monocapped square antiprism geometry. The Ce(III) ions are coordinated by seven oxygen atoms of the carboxylate groups and two oxygen atoms of water molecules. In 2, each Er(III) ion is eight-coordinated adopting a distorted ErO8 dodecahedral geometry. The Er(III) ions are bound to four oxygen atoms of the chelating carboxylate ligands, to one oxygen each from the two bridiging carboxylates, and two oxygen atoms of water molecules. In 2 there is an intramolecular hydrogen bond forming a six-membered ring between the NH2 group and one of the carboxylate oxygens in each of the six 2-AMB ligands. In the crystal packing, the molecules of 1 and 2 are associated through O(or N)–H⋯O and O–H⋯N hydrogen bonds. In 2 the intermolecular hydrogen bonding results in a 3D supramolecular network structure.

Dynamic behaviour in nicotinate-bridged binuclear ruthenium(IV) complexes

The isonicotinic acid adduct [Ru(η3:η3-C10H16)Cl2(p-NC5H4CO2H)] 1 and nicotinate and isonicotinate bridged binuclear complexes [Ru2(η3:η3-C10H16)2Cl3(μ-κN,O,O′-NC5H4CO2)] 2 and 3 are reported. Complexes 2 and 3 exist as mixtures of diastereoisomers and are dynamic in water saturated chloroform solution with complexes involving bidentate chelating carboxylate ligands in equilibrium with unidente carboxylate aquo complexes [Ru2(η3:η3-C10H16)2Cl3(OH2)(μ-κN,O-NC5H4CO2)].

Syntheses and single crystal X-ray diffraction analysis of five isostructural 2D MOCCs

Five two-dimensional metal–organic coordination compounds (MOCCs) have been solvothermally synthesized by the combination of 2-aminonicotinic acid (ANA) and transition metal ions, viz. Co(II), Ni(II), Cu(II), Zn(II) and Cd(II), in water–ethanol mixed solvent. They are formulated as [Co(C6H5N2O2)2], (Co–ANA); [Ni(C6H5N2O2)2], (Ni–ANA) [Cu(C6H5N2O2)2], (Cu–ANA), [Zn(C6H5N2O2)2], (Zn–ANA) and [Cd(C6H5N2O2)2], (Cd–ANA). Single crystal X-ray diffraction studies for the complexes Co–ANA, Ni–ANA and Cd–ANA have also been carried out. These three complexes crystallize in the tetragonal crystal system with the space group P41212. The metal ions in all these complexes have an octahedral coordination environment. The six coordinations are satisfied by two pyridine N-atoms from two different ANA ligands and four oxygen atoms from two chelating carboxylate groups of another two ANA ligands. The topological motif of the coordination network is defined as 2-periodic net or square lattice (sql). These complexes were further characterized by elemental, FT-IR spectral, thermal and powder X-ray diffraction analyses.

DNA/protein interactions, cell cycle arrest and apoptosis study of potent cytotoxic Pt(II) complexes with reduced side-effects

A series of platinum(II) complexes (C1–C6), incorporating an intercalating substituted benzimidazole (2-aminomethylbenzimidazole) and varied leaving groups such as chloride, chelating carboxylates, and thiols, was synthesized to achieve more potent and specific metallodrugs. Spectroscopic titrations, viscosity and electrophoresis measurements revealed that the complexes bound to DNA via an intercalative mode. The complexes were also found to have high affinity towards serum albumin, BSA. Cell viability experiments against three human cancer cell lines (A549, MCF-7, MDA-MB-231) in vitro indicated that the antitumor activities were comparable with cisplatin and its successors, with the greatest efficiency towards A549. Interestingly, complexes C1–C4 were 1.3–1.6 times more potent than cisplatin towards MDA-MB-231 cells. The complexes generate lower degrees of oxidative stress and are almost non-toxic to normal L6 myotubes, indicative of selective toxicity for tumor cells over normal cells. Further studies with A549 cell line revealed that the inhibition of cancer cell proliferation by the complexes is brought about by a combination of cell cycle arrest at the G2/M phase and induction of a caspase-mediated apoptosis.

Four isostructural lanthanide coordination polymers based on rare coordinated citric acid: Syntheses, structures, magnetisms and luminescence

Four new isostructural lanthanide coordination polymers [Ln(Hcit)(H2O)2·2H2O]n (H4cit=citric acid) (Ln=Sm (1), Gd (2), Er (3), Nd (4)) have been synthesized under hydrothermal method by using citric acid, melamine as well as Sm(NO3)3·6H2O (1), Gd(NO3)3·6H2O (2), Er(NO3)3·6H2O (3), Nd(NO3)3·6H2O (4), and structurally characterized by FT-IR, thermogravimetric analyses (TGA), powder X-ray diffraction (PXRD), elemental analyses and X-ray single-crystal diffraction. The X-ray single-crystal diffraction analyses demonstrated that Hcit3- ligand adopt the rare coordination mode to connect the metal atoms of complexes 1–4 by chelating carboxyl group, single coordinated carboxyl group and hydroxyl group, forming left-handed and right-handed helical chains, which are further connected to 2D layer structures by Ln–O bonds. Furthermore, complex 1 displayed good fluorescence at solid state; complexes 1 and 3 exhibited antiferromagnetic behaviors, while complex 2 displayed ferromagnetic behavior.

Anchoring of a Carboxyl-Functionalized Norbornadiene Derivative to an Atomically Defined Cobalt Oxide Surface

We have investigated the anchoring of the molecular energy carrier norbornadiene (NBD) to an atomically defined oxide surface. To this end, we synthesized a carboxyl-functionalized NBD derivative, namely 1-(2′-norbornadienyl)pentanoic acid (NBDA), and deposited it by physical vapor deposition (PVD) under ultrahigh vacuum (UHV) conditions onto a well-ordered Co3O4(111) film grown on Ir(100). In addition, we performed a comparative growth study with benzoic acid (BA) under identical conditions which was used as a reference. The interaction and orientation of NBDA and BA with the oxide surface were monitored in situ during film growth by isothermal time-resolved infrared reflection–absorption spectroscopy (TR-IRAS), both below and above the multilayer desorption temperature. The thermal behavior and stability of the films were investigated by temperature-programmed IRAS (TP-IRAS), with help of density functional (DF) calculations. BA binds to Co3O4(111) under formation of a symmetric chelating carboxylate wi...