New Triazoloquinoxaline Ligand and its Polymeric 1D Silver(I) complex Synthesis, Structure, and Antimicrobial activity

The organic ligand 4-Benzyl-1-(N,N-dimethylamino)-[1,2,4]triazolo[4,3a]quinoxaline 1 (L) and its polymeric silver(I) complex, [Ag2L(NO3)2]n (2), have been synthesized and characterized. The organic ligand 1 crystallizes in the triclinic space group P¯1. The unit cell contains two parallel-stacked molecules. The complex [Ag2L(NO3)2]n (2) crystallizes in the monoclinic space group P21/n. The structure contains two different silver(I) ions. Ag(2) is coordinated by three oxygens (involving two nitrate groups) and to a nitrogen of the triazole ring of 1. These ligands form a strongly distorted tetrahedral, nearly planar coordination sphere. Ag(1) has an approximately tetrahedral geometry. It is bonded to one oxygen of a nitrate anion and a nitrogen of two different L; this aspect giving rise to an infinite chain structure. A final bond to Ag(1) involves the carbon of a phenyl group. It is more weakly bonded to the phenyl carbons on either side of this, so that the Ag(1)-phenyl bonding has aspects of an Ag-allyl bond. Ag(1) and Ag(2) participate in bonding to a common nitrate anion and alternate, the two distinct modes of bridging between them lead to a zig-zag chain structure. In addition to spectroscopic studies, the biological activities of the ligand and of the complex were scanned over a wide range of Gram positive and Gram negative flesh- and bone-eating bacteria. The results are discussed in comparison with well-known antibiotics

Three-dimensional distribution of individual atoms in the channels of beryl

Abstract Single atom detection in nanoporous materials is a significant challenge, particularly due to their sensitivity to electron irradiation. Here, natural beryl (Be3Al2Si6O18) is used as a model system to quantitatively analyse the occupancy of its atomic channels. High-angle annular dark-field imaging in a scanning transmission electron microscope is employed, revealing the presence of Cs atoms within the channels. Through statistical analysis of atomic column intensities and comparison with a series of multislice simulations, we successfully pinpoint the three-dimensional positions of individual Cs atoms. Our findings indicate a non-uniform distribution of Cs atoms in the crystal. Importantly, by extracting both the crystal thickness and atomic positions from a single high-resolution micrograph, we effectively minimize the adverse effects of beam damage. This approach offers a promising pathway for accurately determining the three-dimensional distribution of dopant atoms in various porous materials, opening new possibilities for the study and application of these technologically important materials

Neutral “Cp-Free” Silyl-Lanthanide(II) Complexes: Synthesis, Structure, and Bonding Analysis

Complexes featuring lanthanide silicon bonds represent a research area still in its infancy. Herein, we report a series of Cp-free lanthanide (+II) complexes bearing σ-bonded silyl ligands. By reactions of LnI₂ (Ln = Yb, Eu, Sm) either with a 1,4-oligosilanyl dianion [K-Si­(SiMe₃)₂SiMe₂­SiMe₂Si­(SiMe₃)₂-K)] (<b>1</b>) or with <b>2</b> (Me₃Si)₃SiK (<b>3</b>) the corresponding neutral metallacyclopentasilanes ({Me₂Si­(Me₃Si)₂Si}₂)­Ln·(THF)₄ (Ln = Yb (<b>2a</b>), Eu (<b>2b</b>), Sm (<b>2c</b>)), or the disilylated complexes ({Me₃Si}₃Si)₂Ln·(THF)₃ (Ln = Yb (<b>4a</b>), Eu (<b>4b</b>), Sm (<b>4c</b>)), were selectively obtained. Complexes <b>2b</b>, <b>2c</b>, <b>4b</b>, and <b>4c</b> represent the first examples of structurally characterized Cp-free Eu and Sm complexes with silyl ligands. In both series, a linear correlation was observed between the Ln–Si bond lengths and the covalent radii of the corresponding lanthanide metals. Density functional theory calculations were also carried out for complexes <b>2a</b>–<b>c</b> and <b>4a</b>–<b>c</b> to elucidate the bonding situation between the Ln­(+II) centers and Si

Oligosilanylated Antimony Compounds

By reactions of magnesium oligosilanides with SbCl₃, a number of oligosilanylated antimony compounds were obtained. When oligosilanyl dianions were used, either the expected cyclic disilylated halostibine was obtained or alternatively the formation of a distibine was observed. Deliberate formation of the distibine from the disilylated halostibine was achieved by reductive coupling with C₈K. Computational studies of Sb–Sb bond energies, barriers of pyramidal inversion at Sb, and the conformational behavior of distibines provided insight for the understanding of the spectroscopic properties

Studying variability in human brain aging in a population-based German cohort – Rationale and design of 1000BRAINS

The ongoing 1000 brains study (1000BRAINS) is an epidemiological and neuroscientific investigation of structural and functional variability in the human brain during aging. The two recruitment sources are the 10-year follow-up cohort of the German Heinz Nixdorf Recall (HNR) Study, and the HNR MultiGeneration Study cohort, which comprises spouses and offspring of HNR subjects. The HNR is a longitudinal epidemiological investigation of cardiovascular risk factors, with a comprehensive collection of clinical, laboratory, socioeconomic, and environmental data from population-based subjects aged 45–75 years on inclusion. HNR subjects underwent detailed assessments in 2000, 2006, and 2011, and completed annual postal questionnaires on health status. 1000BRAINS accesses these HNR data and applies a separate protocol comprising: neuropsychological tests of attention, memory, executive functions and language; examination of motor skills; ratings of personality, life quality, mood and daily activities; analysis of laboratory and genetic data; and state-of-the-art magnetic resonance imaging (MRI, 3 Tesla) of the brain. The latter includes (i) 3D-T1- and 3D-T2-weighted scans for structural analyses and myelin mapping; (ii) three diffusion imaging sequences optimized for diffusion tensor imaging, high-angular resolution diffusion imaging for detailed fiber tracking and for diffusion kurtosis imaging; (iii) resting-state and task-based functional MRI; and (iv) fluid-attenuated inversion recovery and MR angiography for the detection of vascular lesions and the mapping of white matter lesions. The unique design of 1000BRAINS allows: (i) comprehensive investigation of various influences including genetics, environment and health status on variability in brain structure and function during aging; and (ii) identification of the impact of selected influencing factors on specific cognitive subsystems and their anatomical correlates