Metal-organic Hybrid Research Articles

Piezochromic Porous Metal-Organic Framework.

Pressure changes the color of a new type of metal-organic porous hybrid material CoBbcDabcoH2O. It is built of Co2+ cations linked by 1,4-benzenedicabroxylate (Bdc) anions and 1,4-diazabicyclo[2.2.2]octane (Dabco) molecules into 2-D grid-like sheets, interconnected through OH···O bonds of water molecules to carboxylate H-acceptors. This first piezochromic MOF, stable in air and in many solvents, is an ideal ultraprecise sensor for pressure calibration. The color changes are due to strains generated by pressure in the highly asymmetric crystal field of Co2+ octahedral coordination, involving four different ligand types: a Dabco amine (twice), a monodentate carboxylate, a chelating carboxylate, and a water molecule. At 0.33 GPa/296 K and below 225 K/0.1 MPa a phase transition reduces the crystal symmetry from monoclinic to triclinic system and changes the conformation and orientation of linkers.

Metal‐Containing Pharmacophores in Molecularly Targeted Anticancer Therapies and Diagnostics

Molecularly targeted therapeutic agents make up an important class of oncology drugs that are used either alone, or in combination with classical cytotoxic agents, to combat many solid tumors and hematological cancers. Their targets in cancer cells are proteins that are encoded by oncogenes, which regulate cell growth, survival, and proliferation. These include a number of signal‐transducing and angiogenesis‐related kinases, hormone receptors, and certain cell‐surface antigens. Targeting of cancer cells harboring oncogenic molecular targets with precision medicines, while sparing the vast majority of normal healthy cells, has led to promising new treatments for cancer patients. Molecularly targeted therapeutic agents promise higher efficacy and weaker side effects than the traditional cytotoxic chemotherapies. Simple metal complexes and metal–organic hybrid agents have been the subjects of investigation for many years since the success of cisplatin in treating genitourinary cancers, but their applications in targeted therapies remain underexplored. In this review we highlight the development of metal‐based targeted cancer therapeutic agents with unique structures and functions. These strategies provide exciting opportunities for discovering new therapeutic and diagnostic agents for clinical uses.

ChemInform Abstract: Metal—Organic Hybrid Architectures Built from Functionalized Fullerenes and Metal Ions or Clusters

AbstractReview: 71 refs.

Systematic pH-specific synthesis and structure transformations in binary-ternary In(III) assemblies with hydroxycarboxylic DPOT and aliphatic-aromatic chelators

Driven by the need to generate hybrid In(III)-(O,N) luminescent materials containing appropriately configured organic ligands, binary-ternary In(III) metal-organic systems involving the multidentate organic ligand DPOT, ethylenediamine (en) and phenanthroline (phen) were investigated under pH-specific conditions. The arisen materials [In2(C11H13N2O9)2](CH6N3)4·7H2O(1), [In3(C11H13N2O9)2(C2H8N2)2](C2H9N2)·4H2O(2), [In2(C11H13N2O9)2](CH6N3)6(Cl)2·6H2O(3), and [In2(C11H13N2O9)(C12H8N2)2(Cl)(H2O)]·7.5H2O(4) were characterized by analytical, spectroscopic (FT-IR, 13C-MAS NMR, luminescence) techniques, TGA and X-ray crystallography. The binary materials 1 and 3 exhibit dinuclear alkoxido-bridged In2O2 cores, with the fully-deprotonated organic ligand spanning both centers. Introduction of bidentate ethylenediamine leads to ternary trinuclear species 2, whereas phen introduction in 4 leads to a dinuclear asymmetric assembly, incorporating a chloride ion and a water molecule. Chemical transformations among 1–4 provide mechanistic insight into the nature of chelators, dictating nuclearity, coordination, composition and lattice-specific luminescence. The collective physicochemical properties in 1–4 present well-defined 1D-3D structural architecture-dimensionality and spectroscopic property correlations, pointing out criteria based on which synthon design, custom architecture and photoactivity are interwoven into the future development of In(III)-containing metal-organic hybrid materials.

Two new crystal structures of two-dimensional lead(II) coordination polymers with flexible alicyclic carboxylate ligands

ABSTRACTTwo new coordination polymers with flexible alicyclic carboxylate ligands, generally formulated as [Pb(chda)]n (1, H2chda = 1,1′-cyclohexanediacetic acid) and [Pb(tmg)]n (2, H2tmg = 3,3′-tetramethyleneglutate), have been successfully synthesized through the liquid–liquid diffusion method. They represent the first main group of metal–organic hybrid compounds assembled from H2chda and H2tmg. Compound 1 crystallized in the non-centrosymmetric space group Pca21, whereas 2 adopts the centrosymmetric P2(1)/c space group. Their structure features one-dimensional infinite chains extended into two-dimensional layer framework. Interestingly, the lead atoms exhibit hemi- as well as holo-directed coordination geometry with coordination number seven in both compounds.

Long‐Lived Phosphorescence: Strongly Enhanced Long‐Lived Persistent Room Temperature Phosphorescence Based on the Formation of Metal–Organic Hybrids (Advanced Optical Materials 6/2016)

Long‐Lived Phosphorescence: Strongly Enhanced Long‐Lived Persistent Room Temperature Phosphorescence Based on the Formation of Metal–Organic Hybrids (Advanced Optical Materials 6/2016)

Nucleation and Growth of Ordered Arrays of Silver Nanoparticles on Peptide Nanofibers: Hybrid Nanostructures with Antimicrobial Properties.

Silver nanoparticles have been of great interest as plasmonic substrates for sensing and imaging, catalysts, or antimicrobial systems. Their physical properties are strongly dependent on parameters that remain challenging to control such as size, chemical composition, and spatial distribution. We report here on supramolecular assemblies of a novel peptide amphiphile containing aldehyde functionality in order to reduce silver ions and subsequently nucleate silver metal nanoparticles in water. This system spontaneously generates monodisperse silver particles at fairly regular distances along the length of the filamentous organic assemblies. The metal–organic hybrid structures exhibited antimicrobial activity and significantly less toxicity toward eukaryotic cells. Metallized organic nanofibers of the type described here offer the possibility to create hydrogels, which integrate the useful functions of silver nanoparticles with controllable metallic content.

Facile Synthesis of Au or Ag Nanoparticles-Embedded Hollow Carbon Microspheres from Metal-Organic Framework Hybrids and Their Efficient Catalytic Activities.

Au or Ag nanoparticles-embedded hollow carbon spheres, which display outstanding catalytic activity and excellent recyclability, are prepared by a one-step pyrolysis of metal-organic framework (MOF) hybrids consisting of polystyrene cores and MOF shells loaded with noble metal ions (polystyrene@ZIF-8/M(n+) ; M(n+) = Au(3+) or Ag(+) ).

Methanol-Influenced Assembly of Metal–Organic Hybrid Compounds Based on Propane-1,3-diamine Ligands and [XCl4]2– (X = Zn, Hg)

The authors designed two flexible ligand molecules, namely, (N1,N1,N3,N3-tetrakis(4-methylbenzyl)propane-1,3-diamine) (L1) and (N1,N1,N3,N3-tetrabenzylpropane-1,3-diamine) (L2), with (CH2)3 alkyl chains attached to the two N atoms. The ligands are double protonated and can react with tetrachloride metal dianion [XCl4]2– (X = Zn, Hg) in the presence of methanol solvent, leading to a series of new inclusion complexes, (CH3OH)2 ⊂ [L1]2H+· [ZnCl4]2–(crystal 1), (CH3OH)0.5 ⊂ [L2]2H+·[HgCl4]2 (crystal 2), and CH3OH ⊂ {[L2]2H+}0.5· {[ZnCl4]2–}0.5 (crystal 3). The molar ratios of methanol and ligand are 2:1, 1:2, and 2:1 in the three crystals, respectively. The structures were characterized by NMR and single-crystal X-ray diffractions. The effect of guest methanol molecules on the formation of supramolecular assemblies was discussed. The ligand can adopt different molecular arrangements as so to suit for the demands of same guest species. From the structural view point, we showed the relationship between the diversity of inclusion hosts and conformational flexibility of ligand.

Strongly Enhanced Long‐Lived Persistent Room Temperature Phosphorescence Based on the Formation of Metal–Organic Hybrids

Molecule‐based solid‐state materials with room temperature phosphorescence (RTP) are playing an increasingly important role in developing optical sensors, security systems, and biological imaging. However, molecular systems involving long‐lived persistent RTP are still rare to date, which has limited the efficiently luminescent recognition and identification. Herein, it is illustrated that the RTP properties of molecular phosphors can be highly enhanced based on coordination interaction with common metal (such as Zn2+). These molecule–metal hybrids present tunable afterglow phosphorescence by adjusting metal species and stacking fashions of molecular units, with the longest RTP lifetime of 1.3 s. Such long‐lived persistent emission decay is higher than most of currently reported molecule‐based and molecule–metal solid‐state RTP systems. Moreover, the reversible phosphorescence transformation under different pH and heat conditions can be further switched and recycled. This work therefore offers a cost‐effective and facile way to achieve high‐performance RTP metal‐organic hybrid materials, which could serve as promising candidates for noble‐metal‐free and rare‐earth‐free phosphors in illumination and sensor applications.

A Mononuclear CoII Coordination Complex Locked in a Confined Space and Acting as an Electrochemical Water‐Oxidation Catalyst: A “Ship‐in‐a‐Bottle” Approach

AbstractPreparing efficient and robust water oxidation catalyst (WOC) with inexpensive materials remains a crucial challenge in artificial photosynthesis and for renewable energy. Existing heterogeneous WOCs are mostly metal oxides/hydroxides immobilized on solid supports. Herein we report a newly synthesized and structurally characterized metal–organic hybrid compound [{Co3(μ3‐OH)(BTB)2(dpe)2} {Co(H2O)4(DMF)2}0.5]n⋅n H2O (Co‐WOC‐1) as an effective and stable water‐oxidation electrocatalyst in an alkaline medium. In the crystal structure of Co‐WOC‐1, a mononuclear CoII complex {Co(H2O)4(DMF)2}2+ is encapsulated in the void space of a 3D framework structure and this translationally rigid complex cation is responsible for a remarkable electrocatalytic WO activity, with a catalytic turnover frequency (TOF) of 0.05 s−1 at an overpotential of 390 mV (vs. NHE) in 0.1 m KOH along with prolonged stability. This host–guest system can be described as a “ship‐in‐a‐bottle”, and is a new class of heterogeneous WOC.

A Mononuclear Co(II) Coordination Complex Locked in a Confined Space and Acting as an Electrochemical Water-Oxidation Catalyst: A "Ship-in-a-Bottle" Approach.

Preparing efficient and robust water oxidation catalyst (WOC) with inexpensive materials remains a crucial challenge in artificial photosynthesis and for renewable energy. Existing heterogeneous WOCs are mostly metal oxides/hydroxides immobilized on solid supports. Herein we report a newly synthesized and structurally characterized metal-organic hybrid compound [{Co3 (μ3 -OH)(BTB)2(dpe)2} {Co(H2O)4(DMF)2}0.5]n ⋅n H2O(Co-WOC-1) as an effective and stable water-oxidation electrocatalyst in an alkaline medium. In the crystal structure of Co-WOC-1, a mononuclear Co(II) complex {Co(H2O)4(DMF)2}(2+) is encapsulated in the void space of a 3D framework structure and this translationally rigid complex cation is responsible for a remarkable electrocatalytic WO activity, with a catalytic turnover frequency (TOF) of 0.05 s(-1) at an overpotential of 390 mV (vs. NHE) in 0.1 m KOH along with prolonged stability. This host-guest system can be described as a "ship-in-a-bottle", and is a new class of heterogeneous WOC.

Elaboration of metal organic framework hybrid materials with hierarchical porosity by electrochemical deposition–dissolution

Rationally designed hierarchical macro-/microporous HKUST-1 electrodes were prepared via an electrochemical deposition–dissolution technique with the motivation to overcome diffusion limitations that typically occur for conventional microporous MOFs. A colloidal crystal of silica spheres was prepared by the Langmuir–Blodgett (LB) technique. Using this crystal as a template, macroporous copper electrodes with a controlled number of pore layers were prepared via electrodeposition. After the removal of the template, the synthesis of HKUST-1 was performed via partial anodic dissolution of the copper surface in the presence of an organic linker, leading to the deposition of HKUST-1 on the electrode surface with the designed macroporous structure. The macroporous Cu electrodes do not only behave as structural templates but are also the Cu source for the formation of MOFs. The applied potential and deposition time allow the characteristics of the porous layer to be fine-tuned. The developed synthesis is rapid, occurs under mild conditions and therefore opens up various potential applications including catalysis, separation and sensing based on these hierarchical materials.

ALD/MLD processes for Mn and Co based hybrid thin films.

Here we report the growth of novel transition metal-organic thin-film materials consisting of manganese or cobalt as the metal component and terephthalate as the rigid organic backbone. The hybrid thin films are deposited by the currently strongly emerging atomic/molecular layer deposition (ALD/MLD) technique using the combination of a metal β-diketonate, i.e. Mn(thd)3, Co(acac)3 or Co(thd)2, and terephthalic acid (1,4-benzenedicarboxylic acid) as precursors. All the processes yield homogeneous and notably smooth amorphous metal-terephthalate hybrid thin films with growth rates of 1-2 Å per cycle. The films are stable towards humidity and withstand high temperatures up to 300 or 400 °C under an oxidative or a reductive atmosphere. The films are characterized with XRR, AFM, GIXRD, XPS and FTIR techniques.

Engineering the proton conductivity of metal–organic hybrid materials by varying the coordination mode of the ligand

We report the adjustment of proton conductivity by varying the coordination mode of a ligand.

Poly[diaquo(1,10-phenanthroline-κ2N1:N10)(μ2-sulphato-κ2O:O′)copper(ii)]: hydrothermal synthesis, crystal structure and magnetic properties

Of late, hydrothermal synthesis has gained much interest in the synthesis of metal–organic hybrid complexes with fascinating architectures and topologies.

Surprising coordination for low-valent actinides resembling uranyl(vi) in thorium(iv) organic hybrid layered and framework structures based on a graphene-like (6,3) sheet topology.

Three thorium(iv)-based metal-organic hybrid compounds with 2D layered and 3D framework structures exhibiting graphene-like (6,3) sheet topologies were prepared with linkers with threefold symmetry. These compounds contain rare and relatively anisotropic coordination environments for low-valent actinides that are similar to those often observed for high-valent actinide ions.

Magnetic coupling in a hybrid Mn(ii) acetylene dicarboxylate.

The design of ligands that mediate through-bond long range super-exchange in metal-organic hybrid materials would expand chemical space beyond the commonly observed short range, low temperature magnetic ordering. Here we examine acetylene dicarboxylate as a potential ligand that could install long range magnetic ordering due to its spatially continuous frontier orbitals. Using a known Mn(ii)-containing coordination polymer we compute and measure the electronic structure and magnetic ordering. In this case, the latter is weak owing to the sub-optimal ligand coordination geometry, with a critical temperature of 2.5 K.

Organics on oxidic metal surfaces: a first-principles DFT study of PMDA and ODA fragments on the pristine and mildly oxidized surfaces of Cu(111).

Metal-organic hybrid materials are ubiquitous and a fundamental understanding of the hybrid-interface is key for the development of these hybrid material systems. In this work, using first-principles density-functional theory (including van der Waals (vdW) corrections), we study the fundamental physico-chemical properties of the molecular fragments of pyromellitic dianhydride oxydianiline (PMDA-ODA) on pristine Cu(111), as well as oxidic p4:O/Cu(111) in order to investigate the effect of mild oxidation of the metal substrate on PMDA-ODA adsorption. Firstly, we report the most favorable adsorption geometries amongst the various surface models and correlate the adsorption behavior with the electronic structure of the molecular fragments and the substrate layer. PMDA adsorbs weakly on both the clean and mildly oxidized copper surface via vdW forces while ODA adsorbs much stronger with a significant charge transfer between the substrates. Here, the oxidic layer is found to reduce the adsorption strength of both fragments and in particular, the ODA molecule interacts with the substrate via additional hydrogen bonding. Finally, our simulated scanning tunneling microscopy (STM) images suggest possible orientations of PMDA and ODA on clean and oxidic Cu surfaces to guide future experiments.

Tuning the microstructures of decavanadate-based supramolecular hybrids via regularly changing the spacers of bis(triazole) ligands

With tuning the ligands from bte, btp, btb to bth, four new decavanadate-based metal–organic hybrid compounds, [Zn(bte)(H2O)4][Zn2(bte)(H2O)10](V10O28)·8H2O, [Zn2(btp)4(H2O)6](H2V10O28)·4H2O, [Zn(H2O)6][Zn2(btb)2V10O28(H2O)6]·4H2O, and [Zn2(bth)(H2O)10](H2V10O28)·6H2O (bte=1,2-bis(1,2,4-triazol-1-yl)ethane, btp=1,3-bis(1,2,4-triazol-1-y1)propane, btb=1,4-bis(1,2,4-triazol-1-y1)butane, bth=1,6-bis(1,2,4-triazol-1-y1)hexane), have been synthesized under conventional conditions. The four compounds represent the first examples of decavanadate-based metal–organic hybrids constructed by Zn–bis(triazole) complexes. Their structural analyses show that the four compounds possess different Zn–bis(triazole) structural motifs and various finally structures, which verifies that regular changing the spacers of ligands is an effective strategy to tuning the structures of polyoxometalate-based hybrids. Also, the electrochemical studies show that the compounds have good electrocatalytic activities towards oxidation of nitrite molecules ascribed to V-centers.