Conducting Molecular Nanomagnet of DyIII with Partially Charged TCNQ Radicals

artículo científicoBifunctional electrically conducting single-molecule magnets are highly promising platforms for non-volatile memory devices and quantum computing applications. The development of these molecular materials, however, has largely been hindered by the lack of straightforward synthetic methods. Herein we demonstrate a facile and modular approach for the realization of bifunctional materials that does not require electrochemical or chemical oxidation to obtain partially charged organic radicals. Magnetic and electrical conductivity studies reveal that the Dy(III) compound exhibits slow relaxation of the magnetization between 5.0-8.0 K and semiconducting behavior over the range 180-350 K. DC magnetic fields suppress the quantum tunneling of the magnetization and affect the spin-canted antiferromagnetic interactions.U.S. Department of Energy

Relaxation Dynamics of Identical Trigonal Bipyramidal Cobalt Molecules with Different Local Symmetries and Packing Arrangements: Magnetostructural Correlations and ab inito Calculations

A family of isostructural, mononuclear CoII complexes with distorted trigonal bipyramidal coordination environments is reported. The degree of distortion as well as the overall symmetry of the molecules varies among the members of the series. Different experimental procedures resulted in the isolation of solvomorphs (pseudopolymorphs with different solvent content) for some of the family members. Importantly, their disparate packing arrangements lead to very different dynamic magnetic behavior. The results of magnetostructural correlations and ab initio calculations reveal that the deciding factor for SMM behavior is not the degree of distortion which, a priori, would be expected to be the case, but rather the interactions between neighboring molecules in the solid state.Department of Energy, Basic Energy Sciences, Materials Sciences Division Robert A. Welch Foundation for financial support Ciencia y Tecnología del Distrito Federal (ICyTDF) Spanish Ministerio de Economía y Competitivida

Strong Ferromagnetic Exchange Coupling Mediated by a Bridging Tetrazine Radical in a Dinuclear Nickel Complex.

The radical bridged compound [(Ni- (TPMA))2-μ-bmtz•−](BF4)3·3CH3CN (bmtz = 3,6-bis- (2′-pyrimidyl)-1,2,4,5-tetrazine, TPMA = tris(2- pyridylmethyl)amine) exhibits strong ferromagnetic exchange between the S = 1 NiII centers and the bridging S = 1/2 bmtz radical with J = 96 ± 5 cm−1 (−2JNi‑radSNiSrad). DFT calculations support the existence of strong ferromagnetic exchange.Department of Energy Office of Science Graduate Fellowship, Instituto de Ciencia y Tecnología del Distrito Federal (ICyTDF) National Science Foundation (CHE-1310574) and the Robert A. Welch Foundation (A-1449)

An unexpected twist to the activation of IKKβ:TAK1 primes IKKβ for activation by autophosphorylation

IKKβ {IκB [inhibitor of NF-κB (nuclear factor κB)] kinase β} is required to activate the transcription factor NF-κB, but how IKKβ itself is activated in vivo is still unclear. It was found to require phosphorylation by one or more ‘upstream’ protein kinases in some reports, but by autophosphorylation in others. In the present study, we resolve this contro-versy by demonstrating that the activation of IKKβ induced by IL-1 (interleukin-1) or TNF (tumour necrosis factor) in embryonic fibroblasts, or by ligands that activate Toll-like receptors in macrophages, requires two distinct phosphorylation events: first, the TAK1 [TGFβ (transforming growth factor β)-activated kinase-1]-catalysed phosphorylation of Ser(177) and, secondly, the IKKβ-catalysed autophosphorylation of Ser(181). The phosphorylation of Ser(177) by TAK1 is a priming event required for the subsequent autophosphorylation of Ser(181), which enables IKKβ to phosphorylate exogenous substrates. We also provide genetic evidence which indicates that the IL-1-stimulated, LUBAC (linear ubiquitin chain assembly complex)-catalysed formation of linear ubiquitin chains and their interaction with the NEMO (NF-κB essential modulator) component of the canonical IKK complex permits the TAK1-catalysed priming phosphorylation of IKKβ at Ser(177) and IKKα at Ser(176). These findings may be of general significance for the activation of other protein kinases

Disorder and diffuse scattering in single-chirality (TaSe4_4)2_2I crystals

The quasi-one-dimensional chiral compound (TaSe$_4$)$_2$I has been extensively studied as a prime example of a topological Weyl semimetal. Upon crossing its phase transition temperature $T_\textrm{CDW}$ $\approx$ 263 K, (TaSe$_4$)$_2$I exhibits incommensurate charge density wave (CDW) modulations described by the well-defined propagation vector $\sim$(0.05, 0.05, 0.11), oblique to the TaSe$_4$ chains. Although optical and transport properties greatly depend on chirality, there is no systematic report about chiral domain size for (TaSe$_4$)$_2$I. In this study, our single-crystal scattering refinements reveal a bulk iodine deficiency, and Flack parameter measurements on multiple crystals demonstrate that separate (TaSe$_4$)$_2$I crystals have uniform handedness, supported by direct imaging and helicity dependent THz emission spectroscopy. Our single-crystal X-ray scattering and calculated diffraction patterns identify multiple diffuse features and create a real-space picture of the temperature-dependent (TaSe$_4$)$_2$I crystal structure. The short-range diffuse features are present at room temperature and decrease in intensity as the CDW modulation develops. These transverse displacements, along with electron pinning from the iodine deficiency, help explain why (TaSe$_4$)$_2$I behaves as an electronic semiconductor at temperatures above and below $T_\textrm{CDW}$, despite a metallic band structure calculated from density functional theory of the ideal structure.Comment: 24 pages, 20 figures, 3 table

Maternal behaviours and adult offspring behavioural deficits are predicted by maternal TNFα concentration in a rat model of neurodevelopmental disorders

Exposure to inflammatory stressors during fetal development is a major risk factor for neurodevelopmental disorders (NDDs) in adult offspring. Maternal immune activation (MIA), induced by infection, causes an acute increase in pro-inflammatory cytokines which can increase the risk for NDDs directly by inducing placental and fetal brain inflammation, or indirectly through affecting maternal care behaviours thereby affecting postnatal brain development. Which of these two potential mechanisms dominates in increasing offspring risk for NDDs remains unclear. Here, we show that acute systemic maternal inflammation induced by the viral mimetic polyinosinic:polycytidylic acid (poly I:C) on gestational day 15 of rat pregnancy affects offspring and maternal behaviour, offspring cognition, and expression of NDD-relevant genes in the offspring brain. Dams exposed to poly I:C elicited an acute increase in the pro-inflammatory cytokine tumour necrosis factor (TNF; referred to here as TNFα), which predicted disruption of key maternal care behaviours. Offspring of poly I:C-treated dams showed early behavioural and adult cognitive deficits correlated to the maternal TNFα response, but, importantly, not with altered maternal care. We also found interacting effects of sex and treatment on GABAergic gene expression and DNA methylation in these offspring in a brain region-specific manner, including increased parvalbumin expression in the female adolescent frontal cortex. We conclude that the MIA-induced elevation of TNFα in the maternal compartment affects fetal neurodevelopment leading to altered offspring behaviour and cognition. Our results suggest that a focus on prenatal pathways affecting fetal neurodevelopment would provide greater insights into the mechanisms underpinning the TNFα-mediated genesis of altered offspring behaviour and cognition following maternal inflammation