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This investigation explores optimum synthetic conditions for novel polymer-metal organic framework hybrid composites composed of Zr-terephthalate-based MOF UiO-66 and conductive polyaniline (PANI) nanofibers in an effort to optimize conductivity while minimizing MOF structural deformation. Successful syntheses of self-assembled PANI nanofibers in PANI@UiO-66 and PANI@UiO-66-NH2 composites were confirmed using scanning electron microscopy, infrared spectroscopy, and powder X-ray diffraction. The polymer-MOF composites show different bonding synergies to the PANI nanofibers depending on the organic linker used. Electronic properties of the post-synthetically modified PANI@UiO-66 and PANI@UiO-66-NH2 were investigated using UV–vis diffuse reflectance spectroscopy. Sheet resistivity of the self-assembled polymer-MOF composites was determined under an inert atmosphere at room temperature using four-point probe measurements to confirm tunable semiconductivity ranging from 40 to 2 mS/sq. Furthermore, the effects of aniline oxidation on the crystallinity and coordination of UiO-66 and UiO-66-NH2 were determined through analysis of these results.

Alzheimer's disease is a fatal neurological disorder affecting millions of people worldwide with an increasing patient population as average life expectancy increases. Accumulation of amyloid beta (Aβ) plaques is characteristic of the disease and has been the target of numerous failed clinical trials. In light of this, therapeutics that target mechanisms of neuronal death beyond Aβ aggregation are needed. One potential target is the formation of reactive oxygen species (ROS) that are created during an interaction between Aβ and copper ions. This work shows that ROS production can be slowed by disrupting the interaction between Aβ and copper using copper chelating compounds. We demonstrated that ROS are produced in the presence of Aβ and copper in solution by monitoring H2O2 production using a fluorescence-based assay, which increased when Cu2+ interacted with Aβ. In addition, we were able to show reduced ROS production, without exacerbating the aggregation of Aβ and in some cases alleviating it, by adding copper chelating ligands to the solution. Using cyclic voltammetry, we investigated how these different ligands influenced the electrochemical behavior of copper in solution revealing important insights into the mechanisms of ROS production and chemical interactions that result in decreased ROS rates.

The synthesis and characterization of N,N′-bis(2-pyridylmethyl)-trans-1,2-diaminocyclohexane-N,N′-diacetic acid (H2bpcd) cationic complexes of La(III), Nd(III), and Sm(III) are reported. The Ln(III)–bpcd2– complex ions, where bpcd2– stands for N,N′-bis(2-pyridylmethyl)-trans-1,2-diaminocyclohexane-N,N′-diacetate, were isolated as PF6– salts. These salts were characterized by elemental analysis, X-ray crystallography, IR, and 1H and 13C NMR spectroscopy. Binuclear [La2(bpcd)2(H2O)2]2+ crystallized from an aqueous solution in the monoclinic P21/c space group as a cocrystallate with Na2bpcd and NaPF6, nominally Na2.34[La1.22(C22H26N4O4)2(H2O)2][PF6]2·2H2O, with a = 11.3343(6) A, b = 17.7090(9) A, c = 15.0567(8) A, β = 110.632(3)°, and Z = 4 (Z′ = 2). La is eight-coordinate with distorted dodecahedral coordination geometry provided by a N4O4 donor atom set. In addition to four N atoms from the bpcd2– ligand, La’s coordination sphere includes O atoms from a water molecule and three acetate groups (one O atom f...

In the title compound, a CoIII center is coordinated by four N atoms and two O atoms, with the monodentate acetate groups of the ligand oriented trans with respect to each other, whereas the pyridine N atoms are coordinated in a cis configuration., The title compound [Co(C22H26N4O4)]PF6, commonly known as [Co(bpcd)]PF6, where bpcd2− is derived from the historical ligand name N,N′-bis­(2-pyridyl­meth­yl)-trans-1,2-di­amino­cyclo­hexane-N,N′-di­acetate, crystallized by slow evaporation of a saturated aceto­nitrile solution in air. The cation of the hexa­fluorido­phosphate salt has the CoIII atom in a distorted octa­hedral coordination geometry provided by an N4O2 donor atom set. The acetate groups, which are oriented trans with respect to each other, exhibit monodentate coordination whereas the pyridyl N atoms are coordinating in a cis configuration. The geometry of the cation is compared to the geometries of other di­amino di­acetate complexes with CoIII.

The synthesis and characterization of N,N'-bis(2-pyridylmethyl)-trans-1,2-diaminocyclohexane-N,N'-diacetic acid (H

Global environmental and economic impact from carbon emission has sparked abundant interest in the development of renewable photocatalytic based energy sources. In the continued search for new and versatile photocatalytic materials, metal organic frameworks (MOFs) have emerged as highly promising prospects, consisting of metal ions or metal ion clusters bridged by organic linkers to form a porous 3-dimensional array. Attributes of MOFs include ease of tunability coupled with well defined surface areas and structural alignment. UiO-66, a Zr-bdc MOF, was chosen as the photocatalytic center for this study due to its unprecedented chemical and thermal stability while still lacking effective valence-conduction band alignment for visible light absorption or efficient charge transport. To address the latter, a conductive organic polymer [polyaniline (PANI)] was grown in-situ to produce a novel heterogeneous composite film. Pre-functionalized UiO-66-NH2 was also conceived for more direct interaction within the framework. Major effects in both electronic and structural properties were observed for both unfunctionalized and amine functionalized PANI@MOF composites. Structural attributes were determined using infrared spectroscopy, scanning electron microscopy and energy dispersive X-ray spectroscopy. Electronic properties were determined using four-point probe measurements, and diffuse reflectance UV-Vis Spectroscopy.

The Amyloid β peptide (Aβ-42) can be expressed through cleavage of a precursor protein (APP) during post-translational modification as a result of oxidative stress in the brain. Once expressed, the peptide will readily form binding interactions with free metal ions, particularly Cu2+, initiating a series of redox reactions that result in the production of Reactive Oxygen Species (ROS) and amyloid plaques within the brain. This process has been implicated as the major contributing factor in neurodegeneration in Alzheimer’s patients. An increasingly promising area of study in the treatment of AD is to disrupt this pathway using metal ion chelation, which can serve as a form of therapeutic treatment. The work presented herein focuses on different copper coordination compounds and their redox activity using various ligands such as glycine, beta alanine, phenylalanine, 2,2’-bipyridine (bipy), 2,2’-thiodipyridine (DPS), 2,2’-dipyridylamine (DPA), and 1,10-phenanthroline-2-thiopyridine (TPP). Utilizing Cyclic Voltammetry to monitor redox activity, the more stable ligand complexes resulted in a more quasi-reversible cyclic voltammogram, allowing for potential redox cycling between Cu2+ and Cu+ at the Aβ-42 active site. The CV results correlated well with hydroxyl radical trapping experiments that measured the rate of hydroxyl radical production in each complex, and a relationship between redox activity and hydroxyl radical production was observed. With the Aβ-42 peptide, these coordination complexes were analyzed using Atomic Force Microscopy (AFM) to correlate the rate of fibril formation to plaque formation. These results provide valuable insight into ligand design characteristics important for the development of potential therapeutic treatments that slow AD progression.

Economic distress resulting from global dependence on diminishing fossil fuels that adversely impact the environment has led to increased interest in alternative green energy technologies. The photoelectrochemical cell (PEC), provides an attractive green energy solution that incorporates semiconductor materials capable of absorbing visible light to power the splitting of water and create H2 gas, a clean fuel source. PEC systems today, however, are not yet commercially viable due to a lack in efficiency, stability and cost effectiveness. Therefore, the goal of this work is to create a novel, low price semiconducting material to be used as an electrode in a PEC system. This will be accomplished by incorporating the zirconium based Metal Organic Framework (MOF) UiO-66 into a celllulostic network to create a flexible, semiconducting material. The UiO-66 MOF offers a combination of defect sites on the Zr metal cluster and an aromatic linker allowing for light absorption coupled with efficient charge transport. Unfortunately, UiO-66 absorbs in the UV region (2% of sunlight), but its high stability and conjugated organic ligands make it ideal for photosensitization. Simple post synthetic modifications (PSM) can be done to improve light harvesting and electron transport capabilities within the cellulose network. Modifications incorporated in this work include the use of polyaniline crosslinkers as well as metal nanoparticle doping. Conductivity of each material was characterized using a four point probe and measuring current response to applied stepwise voltage. PEC performance was determined by illuminating cell with light and measuring voltage, current and product evolution. Overall, this work provides a foundational design of low cost working electrodes for use in PEC systems, that can lead to future modifications to optimize cell performance.

The growing demand for cost-effective clean water solutions has resulted in increased interests in advanced adsorbent materials capable of remediating a wide variety of pollutants. The work presented here focuses on the development of two spherical cellulosic nanoporous materials utilizing different copper-based particles. The copper-based Metal-Organic Framework, MOF-199 (HKUST-1), was incorporated into a cellulose acetate slurry and polymerized into nanoporous beads. The MOF-cellulose beads exhibit an increased number of binding sites that allow for adsorption driven primarily through intraparticle diffusion. Additionally, the MOF-199 framework within the beads acts as a template for post-synthetic modification, which yields a novel nanoporous material containing reduced copper particles capable of enhanced dye remediation. Incorporation of the MOF and reduced copper have been validated by microscopic imaging of the surface and characterized using infrared spectroscopy and thermogravimetric analysis. The presence of copper in both materials allows for a “self-cleaning material” capable of inhibiting the growth of the Gram-negative bacterium Escherichia coli. Further post-synthetic modifications to both the polymer and MOF-199 framework allow for the potential to create advanced adsorbent materials capable of remediating a broader range of pollutants including organic compounds and toxic metal ions.

As the complexity of three-dimensional large-scale integration (3D-LSI) circuits increases, copper (Cu) Chemical Mechanical planarization (CMP) has emerged as a critical step in the fabrication of semiconductor wafers attaining global planarization. Through-silicon Via (TSV) CMP incorporates elimination of deposited excess trench overburden above a silicon wafer at a high removal rate, thus allowing additional layers to be added for substantial 3D-LSI circuit architecture. Enhancing the planarity of the substrate as a result of undesired topography removal is controlled through optimization of slurry composition. In traditional slurries, a synergistic chemical interaction between a corrosion inhibitor and a complexing agent removes irregularities from the surface while at high downforce. To optimize slurry interaction and promote film formation at the interface, a suite of additives incorporating both properties of the slurry are being developed. More specifically, the functionalization of a supramolecular structure enables removal rate to rely heavily on surface chemistry due to its polymeric nature while simultaneously preserving surface uniformity. The introduction of substituents with high-binding affinity for Cu into the slurry such as heterocyclic pyridines, amino, and carboxyl groups directly correlate to a higher removal rate. Preliminary results have shown a correlation between the molecular structure of the complexing and inhibiting agents and their effect on film formation. Adding a system that integrates simultaneous chelation and passivation to the slurry via the supramolecular complex will directly impact the planarity and therefore alter the removal mechanism. This work employs electrochemical surface analysis such as open-circuit potential (OCP) to monitor film formation kinetics and results have shown a direct correlation to CMP parameters.

Alzheimer’s patients are found to have high concentrations of Amyloid-Beta peptide (Aβ-42), an overexpressed 42 amino acid sequence, along with a high concentration of copper ions in the brain. The Aβ-42 peptide results from the cleavage of a precursor protein (APP) and aggregates to form beta sheets during post-translational modification due to oxidative stress. Free metal ions, particularly Cu2+, initiate this oxidative stress by binding to the 14th Histidine residue in the primary structure of Aβ-42 and undergoing a single electron-transfer reduction to Cu+. This redox activity ultimately generates reactive oxygen species (ROS) through Fenton Decomposition to produce hydroxyl radicals within the brain. ROS initiate the progressive transitive states of Aβ-42 from fibril to oligomer to finally aggregate plaque formation, which causes cellular degeneration. The work presented here specifically focuses on the copper redox activity in the biological pathway leading to Alzheimer’s disease. The redox activity of copper at the active site is monitored and correlated to the degree of Aβ-42 fibrillization and aggregation, which is examined using Atomic Force Microscopy (AFM). Evaluating the copper-mediated toxicity will allow for a better understanding of the electrochemical process that initiates ROS and ultimately leads to Aβ-42 plaque formation.

The synthesis of N,N'-bis(2-pyridylmethyl)-trans-1,2-diaminocyclohexane-N,N'-diacetic acid (H2bpcd) and its complexation of Ga(III) and Co(III) are reported. H2bpcd and the metal-bpcd(2-) complexes, isolated as hexafluorophosphate salts, were characterized by elemental analysis, X-ray crystallography, IR spectroscopy, and (1)H and (13)C NMR spectroscopy. [Ga(bpcd)]PF6, [Ga(C22H26N4O4)]PF6, crystallized in the orthorhombic space group Ibca, with a = 13.8975(7) Å, b = 15.0872(7) Å, c = 22.2418(10) Å, and Z = 8. Ga is coordinated in a distorted octahedral geometry provided by a N4O2 donor atom set with trans-monodentate acetate groups and cis-2-pyridylmethyl N atoms, i.e., the trans-O,O isomer. The diamagnetic [Co(bpcd)]PF6, [Co(C22H26N4O4)]PF6, also crystallized from solution in the Ibca space group as the trans-O,O isomer. The (1)H and (13)C assignments for H2bpcd and metal-bpcd(2-) complexes were made on the basis of 2D COSY and HSQC experiments, which were used to differentiate among three possible isomers, i.e., one cis (C1 symmetry) and two trans (C2 symmetry). NMR results indicate that the [Ga(bpcd)](+), [Co(bpcd)](+), and cis-O,O, cis-Npy,Npy-[Ga(bppd)](+) cations, where bppd(2-) stands for bis(2-pyridylmethyl)-1,3-diaminopropane diacetate, are present in solution as isomers with the same symmetry as observed in the solid state. The crystallographic data and the dramatic shift that occurs in the position of the cis/trans isomerization equilibria for the [Ga(bpad)](+) cations simply by increasing the number of bridging CH2 groups in the ligand's diamine backbone represent a unique opportunity to assess the accuracy of modern computational methods. The performance of several local density functionals using a pseudopotential-based SDD basis set was compared with the more rigorous HF and MP2 ab initio calculations. The SVWN5 and SV5LYP functionals provide significantly better Ga-O and Ga-N distances than the HF method or the nonlocal BLYP functional. However, to provide proper isomerization energies the pseudopotential-DFT calculations must be augmented by MP2 single-point energies and calculations of solvation free energies.

A higher yield synthesis of N,N'-bis(2-pyridylmethyl)-1,3-diaminopropane-N,N'-diacetic acid (H2bppd) and its complexation of trivalent metal ions (Al(III), Ga(III), In(III)) and selected lanthanides (Ln(III)) are reported. H2bppd and the metal-bppd(2-) complexes, isolated as hexafluorophosphate salts, were characterized by elemental analysis, mass spectrometry, IR, and (1)H and (13)C NMR spectroscopy. [Ga(bppd)]PF6, [Ga(C19H22N4O4)]PF6, was crystallized as colorless needles by slow evaporation from anhydrous methanol; its molecular structure was solved by direct X-ray crystallography methods. The compound crystallized in the monoclinic space group P21/c, with a = 9.6134(2) Å, b = 20.2505(4) Å, c = 11.6483(3) Å, β = 97.520(1)(o), and Z = 4. Ga is coordinated in a distorted octahedral geometry provided by a N4O2 donor atom set with cis-monodentate acetate groups and cis-2-pyridylmethyl N atoms. Quantum mechanical calculations were performed for the three possible geometric isomers of a pseudo-octahedral metal-bppd(2-) complex with five different metal ions. The results indicate, that in aqueous solution, the stability of the trans-O,O isomer is similar to that of the cis-O,O; cis-Npy,Npy isomer but is greater than that of the trans-Npy,Npy isomer. Calculations for a six-coordinate La(III)-bppd(2-) complex converge to a structure with a very large Npy-La-Npy bond angle (146.4°), a high metal charge (2.28 au), and a high solvation free energy (-79.4 kcal/mol). The most stable geometric arrangement for bppd(2-) around the larger La(III) is best described as an open nestlike structure with space available for additional ligands. IR spectroscopy was used to investigate the nature of the H2bppd-metal complexes isolated in the solid state and the binding modes of the carboxylate functionalities. The spectra indicate that fully deprotonated [M(bppd)](+) complexes as well as partially protonated complexes [M(Hbppd)Cl](+) were isolated. The (1)H and (13)C assignments for H2bppd and metal-bppd(2-) complexes were made on the basis of 2D COSY, NOESY, and (1)H-(13)C HSQC experiments, which were used to differentiate among the cis (C1 symmetry) and the two trans (C2 symmetry) isomers.

In the title compound, [Co(C19H22N4O4)]PF6·0.064CH3CN, commonly known as [Co(bppd)]PF6·0.064CH3CN, where bppd represents the historical ligand name N,N'-bis(2-pyridylmethyl)-1,3-diaminopropane-N,N'-diacetate, the Co(III) atom is coordinated in a distorted octa-hedral geometry with an N4O2 donor atom set. The acetate O atoms, which exhibit monodentate coordination, are oriented in a trans configuration with respect to each other, whereas the pyridyl N atoms are coordinated in a cis configuration. The compound crystallizes with two crystallographically unique cations and two anions per asymmetric unit along with a disordered, partially occupied (occupancy = 0.128) aceto-nitrile solvent mol-ecule. Crystals of the title complex were found to be twinned by pseudomerohedry with a 180° rotation around [10-1] and a refined contribution of 90.5 (3)% of the major twin component.