Self-Assembly of Luminescent Hexanuclear Lanthanide Salen Complexes

Four hexanuclear lanthanide salen complexes [Ln₆(L¹)₄(OH)₄(MeOH)₄]·2Cl·4MeOH (Ln = Nd (<b>1</b>), Tb (<b>2</b>)), [Eu₆(L²)₄(OH)₄(MeOH)₂(EtOH)₂(H₂O)₂]·2Cl·3EtOH·H₂O (<b>3</b>), and [Er₆(L²)₄(OH)₄(EtOH)₂(H₂O)₂]·2Cl·2EtOH·MeOH·H₂O (<b>4</b>) are formed from the reactions of LnCl₃·6H₂O and flexible Schiff base ligands H₂L¹ and H₂L² (H₂L¹ = <i>N</i>,<i>N</i>′-bis­(3-methoxysalicylidene)­(propylene-2-ol)-1,3-diamine, H₂L² = <i>N</i>,<i>N</i>′-bis­(salicylidene)­(propylene-2-ol)-1,3-diamine). The structures of <b>1</b>–<b>4</b> were determined by single crystal X-ray crystallographic studies, and their luminescence properties were determined

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

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

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

Low-Temperature Synthesis of Amorphous FeP₂ and Its Use as Anodes for Li Ion Batteries

The reaction of Fe­(N­(SiMe₃)₂)₃ with PH₃ in THF at 100 °C gives amorphous FeP₂ in high yield. As an anode material in a Li ion battery, this material shows remarkable performance toward electrochemical lithiation/delithation, with gravimetric discharge and charge capacities of 1258 and 766 mA h g^–1, respectively, translating to 61% reversibility on the first cycle and a discharge capacity of 906 mA h g^–1 after 10 cycles. This translates to 66% retention of the theoretical full conversion capacity of FeP₂ (1365 mA h g^–1)

Antioxidant Drug Tempol Promotes Functional Metabolic Changes in the Gut Microbiota

Recent studies have identified the important role of the gut microbiota in the pathogenesis and progression of obesity and related metabolic disorders. The antioxidant tempol was shown to prevent or reduce weight gain and modulate the gut microbiota community in mice; however, the mechanism by which tempol modulates weight gain/loss with respect to the host and gut microbiota has not been clearly established. Here we show that tempol (0, 1, 10, and 50 mg/kg p.o. for 5 days) decreased cecal bacterial fermentation and increased fecal energy excretion in a dose-dependent manner. Liver ¹H NMR-based metabolomics identified a dose-dependent decrease in glycogen and glucose, enhanced glucogenic and ketogenic activity (tyrosine and phenylalanine), and increased activation of the glycolysis pathway. Serum ¹H NMR-based metabolomics indicated that tempol promotes enhanced glucose catabolism. Hepatic gene expression was significantly altered as demonstrated by an increase in <i>Pepck</i> and <i>G6pase</i> and a decrease in <i>Hnf4a</i>, <i>ChREBP</i>, <i>Fabp1</i>, and <i>Cd36</i> mRNAs. No significant change in the liver and serum metabolomic profiles was observed in germ-free mice, thus establishing a significant role for the gut microbiota in mediating the beneficial metabolic effects of tempol. These results demonstrate that tempol modulates the gut microbial community and its function, resulting in reduced host energy availability and a significant shift in liver metabolism toward a more catabolic state