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In situ temperature-dependent crystal structure of lead-free ferroelectric perovskite Ba0.798Ca0.202Zr0.006Ti0.994O3 single crystal was characterized using x-ray diffraction from 170 to 380 K. Three phases were identified at different temperatures of 170, 220, and 298 K, revealing rhombohedral (R3m), orthorhombic (Pmm2), and tetragonal (P4mm) crystal structures, respectively. The change in the bond length and its distortion are reported for both AO12 and BO6 polyhedrons, allowing for the estimation of the spontaneous polarization. The Debye–Waller factor is reported as a function of temperature for A and B-sites. Density-functional theory calculations on the tetragonal phase were performed to obtain information on the distribution of the Ca ions, the local atomic displacements, and the ideal value of the spontaneous polarization of a defect-free crystal at 0 K. We find that Ca prefers to arrange in columnar 2D plates oriented along the tetragonal axis. The Ca ions avoid being next neighbors of Zr; however, the specific arrangement of Ca has only a minor impact on the spontaneous polarization. [ABSTRACT FROM AUTHOR]

Only one (trans(O5)-Na[Rh(ED3AP)]∙3H2O) of possible two isomers was synthesized and characterized by single crystal X-ray analysis, IR and UV–Vis spectroscopy. Computational analysis of both isomers was performed with three levels of theory (B3LYP/TZV, BP86/TZV, OPBE/TZV), which gave consistent results. The more stable isomer by total energy and ligand field stabilization energy (LFSE) was trans(O5) which appeared in synthesis. The calculation of excited state energies complied with UV–Vis spectra, especially with OPBE functional. The results of excited state energy pointed out the differences among isomers in means of a splitting pattern of 1T2g excited state term. Both isomers have a strongly delocalized structure, according to the natural bonding orbital (NBO) analysis. NBO analysis shows that the trans(O5) isomer is more stable than trans(O5O6) for approx. 87 kJ/mol. Therefore, only the trans(O5) isomer is present in the reaction mixture.

The new hydrazine 5H-dibenzo[b,f]azepin-5-amine (2) reacts with P- and Si-electrophiles via deprotonation to afford P(III)-, P(V)-, and TMS-hydrazides 3–8 and with carbonyl electrophiles via acid-free condensation to the N-substituted hydrazones 9–12 that are potential N-alkene ligands. While β-ketohydrazone 9 and α-dihydrazone 10 react with [Mes(Cu)]4, [Cu(NCCCH3)4]2PF6, and FeCl2(THF)1.5 to afford complexes devoid of alkene interaction, [Cu(OTf)]2·C6H6 reacts with the α-keto hydrazone 11 or with N,N dimethyl-hydrazone 12 to form the neutral dimeric Cu(I) complex 18 with bridging Cu(I)–alkene interactions or the tetrahedral cationic complex 19 in which 12 binds as a bidentate hydrazone-alkene ligand, respectively. The surprising stability of the alkene coordination in complexes 18 and 19 prevents substitutions with, e.g., PPh3. [ABSTRACT FROM AUTHOR]

The genuine trivalent uranium complex, K[UIII(mesBAP)4], employing four bidentate bis(2,4,6‐trimethylbenzoyl)phosphide (mesBAP) chelating ligands, is reported and obtained by the reduction of the literature‐known tetravalent analog [UIV(mesBAP)4]. Hence, the bis(acyl)phosphide mesBAP ligand allowed to establish a fully reversible redox couple with uranium in the oxidation states +III and +IV. In both complexes [U(mesBAP)4]0/−, the uranium ions are coordinated to four mesBAP ligands in a square antiprismatic geometry. All new compounds have been characterized by single‐crystal XRD analysis, 1H and 31P NMR, and UV/Vis/NIR electronic absorption spectroscopy, as well as SQUID magnetization and electrochemical measurements, and CW X‐band EPR in the case of the trivalent complex. [ABSTRACT FROM AUTHOR]

Separation and reuse of the catalytically active metal complexes are persistent issues in homogeneous catalysis. Supported Ionic Liquid Phase (SILP) catalysts, where the catalytic center is dissolved in a thin film of a stable ionic liquid, deposited on a solid support, present a promising alternative. However, the dissolution of the metal center in the film leaves little control over its position and its activity. We present here four novel, task‐specific ionic liquids [FPhnImHR]I (n=1, 2; R=PEG2, C12H25), designed to self‐assemble on a silica surface without any covalent bonding and offering a metal binding site in a controlled distance to the support. Advanced multinuclear solid‐state NMR spectroscopic techniques under Magic Angle Spinning, complemented by molecular dynamics (MD) simulations, allow us to determine their molecular conformation when deposited inside SBA‐15 as a model silica support. We provide here conceptual proof for a rational design of ionic liquids self‐assembling into thin films, opening an avenue for a second, improved generation of SILP catalysts. [ABSTRACT FROM AUTHOR]

Alkene planar chirality is introduced in the 'privileged' P-alkene phosphoramidite ligand 1. The resulting diastereomeric ligands (pR,R)-5 and (pS,R)-5 form optically pure complexes of Rh(I) and Pd(II), which catalyze conjugate additions of boron C-nucleophiles to enones and allylic alkylations, respectively. In the Rh-catalyzed reaction, the planar chirality of the alkene exerts absolute enantiocontrol over the potent BINOL auxiliary. [ABSTRACT FROM AUTHOR]

Compound [(3-H2PA)(HCh)]·2H2O (1) represents a novel example of an ionic co-crystal that undergoes regioselectively a triple photoreaction to form a rare multivalent tetramolecular zwitterion (2) with a pentacyclic ladderane-like core in high yield. Molecular docking and molecular dynamics show that this molecule can bind well to the interface between the spike protein of SARS-CoV-2 and the cell surface receptor ACE2 with which it forms a complex to facilitate infection. At the same time, it could theoretically decrease viral replication. [ABSTRACT FROM AUTHOR]

The selective activation of C–C bonds holds vast promise for catalysis. So far, research has been primarily directed at rhodium and nickel under harsh reaction conditions. Herein, we report C–C insertion reactions of a 12-electron palladium(0) surrogate stabilized by a cyclic(alkyl)(amino) carbene (CAAC) ligand. Benzonitrile (1), biphenylene (2), benzocyclobutenone (3), and naphtho[b]cyclopropene (4) were studied. These substrates allow elucidation of the effect of ring strain as well as hybridization encompassing sp3, sp2 and sp hybridized carbon atoms. All reactions proceed quantitatively at or below room temperature. This work therefore outlines perspectives for mild C–C bond functionalization catalysis. [ABSTRACT FROM AUTHOR]

Depleted uranium is a mildly radioactive waste product that is stockpiled worldwide. The chemical reactivity of uranium complexes is well documented, including the stoichiometric activation of small molecules of biological [...]