Advances in the Engineering of Near Infrared Emitting Liquid Crystals and Copolymers, Extended Porous Frameworks, Theranostic Tools and Molecular Junctions Using Tailored Re6 Cluster Building Blocks

International audienceAt the occasion of the fiftieth birthday of the introduction of the term 'metal atom cluster' by F. A. Cotton in inorganic chemistry, it is the good time to make a review on the advances in the engineering of molecular assemblies and nanomaterials based on octahedral Re6 metal atom clusters. The latter exhibit unique intrinsic structural and physicochemical properties (orthogonal disposition of metallic sites that can be selectively functionalized, photoluminescence, redox, generation of singlet oxygen) that make them relevant building blocks for the structuration at the nanometric scale and functionalization of hybrid organic-inorganic materials and supramolecular frameworks. After synthesis by solid state chemistry techniques at high temperature, inorganic precursors built up on face-capped [(Re6Yi8)Ya6] cluster units (Y = chalcogen and/or halogen) can be functionalized via solution chemistry techniques or organic melts to form [(Re6Yi8)La6] (L = CN, OH, various organic ligands...). This work reports advances in the synthesis of [(Re6Yi8)Ya6] and [(Re6Yi8)La6] cluster units as well as on their use in the elaboration of supramolecular frameworks, nanoparticles, hybrid nanomaterials (co-polymers and liquid crystals) and active molecular junctions

Strict baselines for Covid-19 forecasting and ML perspective for USA and Russia

Currently, the evolution of Covid-19 allows researchers to gather the datasets accumulated over 2 years and to use them in predictive analysis. In turn, this makes it possible to assess the efficiency potential of more complex predictive models, including neural networks with different forecast horizons. In this paper, we present the results of a consistent comparative study of different types of methods for predicting the dynamics of the spread of Covid-19 based on regional data for two countries: the United States and Russia. We used well-known statistical methods (e.g., Exponential Smoothing), a "tomorrow-as-today" approach, as well as a set of classic machine learning models trained on data from individual regions. Along with them, a neural network model based on Long short-term memory (LSTM) layers was considered, the training samples of which aggregate data from all regions of two countries: the United States and Russia. Efficiency evaluation was carried out using cross-validation according to the MAPE metric. It is shown that for complicated periods characterized by a large increase in the number of confirmed daily cases, the best results are shown by the LSTM model trained on all regions of both countries, showing an average Mean Absolute Percentage Error (MAPE) of 18%, 30%, 37% for Russia and 31%, 41%, 50% for US for predictions at forecast horizons of 14, 28, and 42 days, respectively

Mssbauer study of Се2Fe17 compound in different magnetic states

Mssbauer spectra of two samples of the Ce2Fe17 compound have been analyzed and hyperfine parameters, compared. The samples were subjected to different preparation techniques and display different magnetic properties. It is established that to well fit the Mssbauer spectra of these samples, an appropriate model should be used that takes into account an additional subspectrum differing in hyperfine parameters from the subspectra employed in conventional models. It is shown that in the ferromagnetic state, the samples contain local regions with an antiferromagnetic order, the volume fraction of which, being different for two samples, increases on approaching the temperature of ferro-to-antiferromagnet transition

Molecular evolution of cyclin proteins in animals and fungi

<p>Abstract</p> <p>Background</p> <p>The passage through the cell cycle is controlled by complexes of cyclins, the regulatory units, with cyclin-dependent kinases, the catalytic units. It is also known that cyclins form several families, which differ considerably in primary structure from one eukaryotic organism to another. Despite these lines of evidence, the relationship between the evolution of cyclins and their function is an open issue. Here we present the results of our study on the molecular evolution of A-, B-, D-, E-type cyclin proteins in animals and fungi.</p> <p>Results</p> <p>We constructed phylogenetic trees for these proteins, their ancestral sequences and analyzed patterns of amino acid replacements. The analysis of infrequently fixed atypical amino acid replacements in cyclins evidenced that accelerated evolution proceeded predominantly during paralog duplication or after it in animals and fungi and that it was related to aromorphic changes in animals. It was shown also that evolutionary flexibility of cyclin function may be provided by consequential reorganization of regions on protein surface remote from CDK binding sites in animal and fungal cyclins and by functional differentiation of paralogous cyclins formed in animal evolution.</p> <p>Conclusions</p> <p>The results suggested that changes in the number and/or nature of cyclin-binding proteins may underlie the evolutionary role of the alterations in the molecular structure of cyclins and their involvement in diverse molecular-genetic events.</p

Stabilization of interpenetrating cluster-based frameworks promoted by N-HX hydrogen bonds synthesis, structures and properties of {[Cd(NH3)(4)](3)[Re3Mo3Se8(CN)(6)]}X (X = Cl, Br and I)

International audienceControl of covalent coordination polymer structures using non-covalent interactions is a promising way for obtaining functional materials by self-assembly in solution. Here we report the crucial role of halide anions in the formation of interpenetrating frameworks based on cyanometalate clusters. It was found that the interaction of [Re3Mo3Se8(CN)(6)](5-) cluster anions and Cd2+ cations in aqueous ammonia led to the formation of the 1D polymeric compound {[Cd(NH3)(5)](2)[Cd(NH3)(4)](3)[Re3Mo3Se8(CN)(6)](2)}5H(2)O (1). Compound 1 is unstable outside the mother liquor due to the rapid loss of NH3 and H2O molecules. Addition of KX (X = Cl, Br, I) to the reaction mixture led to selective formation of 3D framework compounds {[Cd(NH3)(4)](3)[Re3Mo3Se8(CN)(6)]}X (2-4 for X = Cl, Br, I, respectively) stabilized by N-HX hydrogen bonding. Compounds 2-4 demonstrate high thermal stability as well as reversible loss of ammonia and reversible oxidation in the solid state

Hexacyano octahedral metallic clusters as versatile building blocks in the design of extended polymeric framework and clustomesogens

International audienceUsing self-assembling processes to generate hybrid organic inorganic materials allows the control of their structuration at the nanometric scale. We describe in this work the synthesis, liquid crystal and photo-physical properties of [M6Qi8(CN)a6]n- (M = Mo, Re; Qi = Br, Se; n = 2, 3 or 4) cluster anionic units containing clustomesogens. A new and efficient synthetic route was developed to synthesize the [Mo6Bri8(CN)a6]2- building block that is stable in water solution and that could be crystallized as the porous [trans-Cd(H2O)2][Mo6Bri8(CN)a6]. Hybrids were obtained by a metathesis reaction with a specifically designed organic cation. Their self-assembling abilities can be tailored by playing with the charge of the inorganic building blocks going from a nematogenic behaviour, which is particularly rare for ionic mesomorphic material, to the formation of layered structures. The intrinsic properties (luminescence or magnetism) of transition metal clusters are well retained in the hybrid matrices. The nanostructuration of the material influences its ability to emit light despite the isotropy of the emissive nanocluster. Finally, we demonstrate that the magnetic [Re6Se8CN6]3- can be reduced into the luminescent [Re6Se8CN6]4- upon heating at 150 [degree]C. These hybrid materials show promising prospects in the field of luminescent material

Mssbauer study of Се2Fe17 compound in different magnetic states

Mssbauer spectra of two samples of the Ce2Fe17 compound have been analyzed and hyperfine parameters, compared. The samples were subjected to different preparation techniques and display different magnetic properties. It is established that to well fit the Mssbauer spectra of these samples, an appropriate model should be used that takes into account an additional subspectrum differing in hyperfine parameters from the subspectra employed in conventional models. It is shown that in the ferromagnetic state, the samples contain local regions with an antiferromagnetic order, the volume fraction of which, being different for two samples, increases on approaching the temperature of ferro-to-antiferromagnet transition

Hydrogen bonded networks based on hexarhenium(III) chalcocyanide cluster complexes structural and photophysical characterization

International audienceTwo series of isostructural compounds resulting from the combination of the four-fold hydrogen bond donors bisamidinium cations, namely 1-2H(+) and 2-2H(+), and the anionic chalcocyanide clusters of general formula [Re(6)Qi8(CN)a6](4-) are presented (Q = S or Se; where i and a denote inner and apical position, respectively). 1-2H(+) is built upon two imidazolium groups linked together by a -(CH2)(2)- alkyl chain. 2-2H(+) is built upon two hydroxyamidinium groups linked together via a phenyl group and, in consequence, it exhibits a planar geometry. This ionic association leads to either two or three-dimensional hydrogen-bonded networks in the solid state, as confirmed by X-ray crystallographic analysis. The solid-state structures arise from the recognition between the pendant C[triple bond]N ligands of the cluster cores and the amidinium H-bond donors. The luminescence properties of the compounds are investigated in the solid state by means of steady-state and time-resolved techniques. Results are discussed and compared with those measured for the parent Cs-4[Re(6)Si8(CN)a6] and Cs-4[Re(6)Sei8(CN)a6] species. The H-bonded networks display featureless deep-red emission bands centered at (em) = 722 and 737 nm and average excited-state lifetimes ranging between 11.5 and 14.8 s, in accordance with the triplet nature of the radiative process. These photoluminescence properties are similar to the Cs+ homologues and are attributed to the [Re(6)Qi8](2+) emitting core