Polymeric Materials for the Separation of <i>f</i>‑Elements Utilizing Carbamoylmethylphosphine Oxide Chelating Ligands

The ability of carbamoylmethylphosphine oxide (CMPO) ligands to selectively chelate actinides has been shown to be enhanced by preorganizing the ligands on molecular scaffolds. To increase the preorganization, a new polymeric material with a polyoxanorbornene backbone and CMPO ligand pendant groups has been synthesized, and the ability of the material to selectively extract actinides utilizing a biphasic extraction strategy has been tested. In liquid–liquid extractions of <i>f</i>-block metals from acidic aqueous media into an organic solution containing chelating materials, the polymeric material exhibited a significantly higher ability to extract Th⁴⁺ ions than the monomer, with an order of magnitude greater affinity for the polymeric material in most cases. Due to the unique properties of polymeric materials versus small molecules, additional questions arose as to the effect of molecular weight on extraction efficiency. Extraction and separation efficiencies varied for materials of differing molecular weights, with the largest molecular weight polymer extracting near quantitative amounts of thorium ions, and the smaller molecular weight polymers showing separation factors for Th⁴⁺ ions over Ce³⁺, La³⁺, and Eu³⁺ ions ranging from 124 to 328

Polymeric Materials for the Separation of <i>f</i>‑Elements Utilizing Carbamoylmethylphosphine Oxide Chelating Ligands

The ability of carbamoylmethylphosphine oxide (CMPO) ligands to selectively chelate actinides has been shown to be enhanced by preorganizing the ligands on molecular scaffolds. To increase the preorganization, a new polymeric material with a polyoxanorbornene backbone and CMPO ligand pendant groups has been synthesized, and the ability of the material to selectively extract actinides utilizing a biphasic extraction strategy has been tested. In liquid–liquid extractions of <i>f</i>-block metals from acidic aqueous media into an organic solution containing chelating materials, the polymeric material exhibited a significantly higher ability to extract Th⁴⁺ ions than the monomer, with an order of magnitude greater affinity for the polymeric material in most cases. Due to the unique properties of polymeric materials versus small molecules, additional questions arose as to the effect of molecular weight on extraction efficiency. Extraction and separation efficiencies varied for materials of differing molecular weights, with the largest molecular weight polymer extracting near quantitative amounts of thorium ions, and the smaller molecular weight polymers showing separation factors for Th⁴⁺ ions over Ce³⁺, La³⁺, and Eu³⁺ ions ranging from 124 to 328

Understanding the Effect of Metal Centers on Charge Transport and Delocalization in Conducting Metallopolymers

A series of conducting polymers, formed from an electropolymerizable Schiff-base ligand, <i><i>N</i>,<i>N</i></i>′-((2,2′-dimethyl)­propyl)­bis­(2-thiophenyl)­salcylidenimine, and the corresponding metal complexes (i.e., Ni­(II), Cu­(II), V­(IV)O, Co­(II), and Zn­(II)) have been prepared, characterized, and studied in detail. Our successful synthesis of the ligand polymer helps to make a direct comparison between the properties of metal-free conducting polymers and the corresponding metallopolymers. This enables the role of metal centers in these Schiff-base conducting metallopolymers (CMPs) in particular, and in Wolf type III CMPs in general, to be unambiguously elucidated. Vis–NIR absorption spectroelectrochemical studies show that longer distances for charge delocalization were found in the CMPs when compared to the metal-free counterpart, an indication of the contribution of the metal centers in extending the effective conjugation length of these electroactive polymers. The systematic use of both redox-active and redox-inactive first row transition metals helps to better understand the nature of charge transport and the specific role of the metal centers in these systems. Cyclic voltammetry and <i>in situ</i> conductivity show superior charge transport in the CMPs compared to the ligand polymer, especially in systems containing redox-active metal centers with redox potentials higher than, but similar to, that of the conjugated organic backbone. Our results indicate that inner-sphere charge transport within the organic backbone, which is serving as a hopping station, is the dominant mechanism of conductivity enhancement and favorable for efficient charge transport in Schiff-base CMPs

Electrochemical Modification of Indium Tin Oxide Using Di(4-nitrophenyl) Iodonium Tetrafluoroborate

Optoelectronic applications often rely on indium tin oxide (ITO) as a transparent electrode material. Improvements in the performance of such devices as photovoltaics and light-emitting diodes often requires robust, controllable modification of the ITO surface to enhance interfacial charge transfer properties. In this work, modifier films were deposited onto ITO by the electrochemical reduction of di­(4-nitrophenyl) iodonium tetrafluoroborate (DNP), allowing for control over surface functionalization. The surface coverage could be tuned from submonolayer to multilayer coverage by either varying the DNP concentration or the number of cyclic voltammetry (CV) grafting scans. Modification of ITO with 0.8 mM DNP resulted in near-monolayer surface coverage (4.95 × 10¹⁴ molecules/cm²). X-ray photoelectron spectroscopy (XPS) analysis confirmed the presence of 4-nitrophenyl (NO₂Ph) moieties on the ITO surface through the detection of a NO₂ nitrogen signal at 405.6 eV after grafting. Further XPS evidence suggests that the NO₂Ph radicals do not bond to the surface indium or tin sites, consistent with modification occurring either through bonding to surface hydroxyl groups or through strong physisorption on ITO. CV in the presence of an electroactive probe and electrochemical impedance spectroscopy (EIS) were used to investigate the electronic effects that modification via DNP has on ITO. Even at submonolayer coverage, the insulating organic films can reduce the current response to ferrocene oxidation and reduction by more than 25% and increase the charge transfer resistance by a factor of 10

A Thiophene-Containing Conductive Metallopolymer Using an Fe(II) Bis(terpyridine) Core for Electrochromic Materials

Three Fe­(II) bis­(terpyridine)-based complexes with thiophene (Fe­(L1)₂), bithiophene (Fe­(L2)₂), and 3,4-ethylenedioxythiophene (Fe­(L3)₂) side chains were designed and synthesized for the purpose of providing two terminal active sites for electrochemical polymerization. The corresponding metallopolymers (poly-Fe­(L<i>n</i>)₂, <i>n</i> = 2 or 3) were synthesized on indium tin oxide (ITO)-coated glass substrates via oxidative electropolymerization of the thiophene-substituted monomers and characterized using electrochemistry, X-ray photoelectron spectroscopy, UV–vis spectroscopy, and atomic force microscopy. The film poly-Fe­(L2)₂ was further studied for electrochromic (EC) color-switching properties and fabricated into a solid-state EC device. Poly-Fe­(L2)₂ films exhibit an intense MLCT absorption band at 596 nm (ε = 4.7 × 10⁴ M^–1 cm^–1) in the UV–vis spectra without any applied voltage. Upon application of low potentials (between 1.1 and 0.4 V vs Fc⁺/Fc), the obtained electropolymerized film exhibited great contrast with a change of transmittance percentage (Δ<i>T</i>%) of 40% and a high coloration efficiency of 3823 cm² C^–1 with a switching time of 1 s. The film demonstrates commonplace stability and reversibility with a 10% loss in peak current intensity after 200 cyclic voltammetry cycles and almost no loss in change of transmittance (Δ<i>T</i>%) after 900 potential switches between 1.1 and 0.4 V (vs Fc⁺/Fc) with a time interval of 0.75 s. The electropolymerization of Fe­(L2)₂ provides convenient and controllable film fabrication. Electrochromic behavior was also achieved in a solid-state device composed of a poly-Fe­(L2)₂ film and a polymer-supported electrolyte sandwiched between two ITO-coated glass electrodes

Copper Selective Polymeric Extractant Synthesized by Ring-Opening Metathesis Polymerization

Novel polymers bearing pendant picolinic acid functionalities have been synthesized by ring-opening metathesis polymerization (ROMP) for applications in separations-based purification protocols. These polymers and their corresponding monomer were shown to be selective for Cu²⁺ over a variety of other divalent metal cations as inferred from pH dependent studies carried out under both liquid–liquid and solid–liquid extraction conditions. The polymer system of this study also showed high selectivity for Cu²⁺ over Ni²⁺ in mock protocols that could be relevant to the purification of Cu radioisotopes. Separation factors as high as 290 were achieved for extractions from solutions containing a 100-fold excess of Ni²⁺ relative to Cu²⁺

Episodic, transient systemic acidosis delays evolution of the malignant phenotype: Possible mechanism for cancer prevention by increased physical activity

Background: The transition from premalignant to invasive tumour growth is a prolonged multistep process governed by phenotypic adaptation to changing microenvironmental selection pressures. Cancer prevention strategies are required to interrupt or delay somatic evolution of the malignant invasive phenotype. Empirical studies have consistently demonstrated that increased physical activity is highly effective in reducing the risk of breast cancer but the mechanism is unknown. Results: Here we propose the hypothesis that exercise-induced transient systemic acidosis will alter the in situ tumour microenvironment and delay tumour adaptation to regional hypoxia and acidosis in the later stages of carcinogenesis. We test this hypothesis using a hybrid cellular automaton approach. This model has been previously applied to somatic evolution on epithelial surfaces and demonstrated three phases of somatic evolution, with cancer cells escaping in turn from the constraints of limited space, nutrient supply and waste removal. In this paper we extend the model to test our hypothesis that transient systemic acidosis is sufficient to arrest, or at least delay, transition from in situ to invasive cancer. Conclusions: Model simulations demonstrate that repeated episodes of transient systemic acidosis will interrupt critical evolutionary steps in the later stages of carcinogenesis resulting in substantial delay in the evolution to the invasive phenotype. Our results suggest transient systemic acidosis may mediate the observed reduction in cancer risk associated with increased physical activity

Anion-Dependent Self-Assembly of Near-Infrared Luminescent 24- and 32-Metal Cd–Ln Complexes with Drum-like Architectures

Two series of 4d–4f clusters [Ln₈Cd₂₄L₁₂­(OAc)₄₈] and [Ln₆Cd₁₈L₉Cl₈₍₁₀₎­(OAc)₂₈₍₂₆₎] (Ln = Nd, Gd, Er, and Yb) with novel drum-like structures were prepared using a flexible Schiff base ligand. Their NIR luminescence properties were determined

Anion-Dependent Self-Assembly of Near-Infrared Luminescent 24- and 32-Metal Cd–Ln Complexes with Drum-like Architectures

Two series of 4d–4f clusters [Ln₈Cd₂₄L₁₂­(OAc)₄₈] and [Ln₆Cd₁₈L₉Cl₈₍₁₀₎­(OAc)₂₈₍₂₆₎] (Ln = Nd, Gd, Er, and Yb) with novel drum-like structures were prepared using a flexible Schiff base ligand. Their NIR luminescence properties were determined