The Unexpected Helical Supramolecular Assembly of a Simple Achiral Acetamide Tecton Generates Selective Water Channels

Achiral 2-hydroxy-N-(diphenylmethyl)acetamide (HNDPA) crystallizes in the P6₁ chiral space group as a hydrate, building up permeable chiral crystalline helical water channels. The crystallization-driven chiral self-resolution process is highly robust, with the same air-stable crystalline form readily obtained under a variety of conditions. Interestingly, the HNDPA supramolecular helix inner pore is filled by a helical water wire. The whole edifice is mainly stabilized by robust hydrogen bonds involving the HNDPA amide bonds and CH^…π interactions between the HNDPA phenyl groups. The crystalline structure shows breathing behavior, with completely reversible release and re-uptake of water inside the chiral channel under ambient conditions. Importantly, the HNDPA channel is able to transport water very efficiently and selectively under biomimetic conditions. With a permeability per channel of 3.3 million water molecules per second in large unilamellar vesicles (LUV) and total selectivity against NaCl, the HNDPA channel is a very promising functional nanomaterial for future applications.     

Theoretical investigation of the uranyl ion sorption on the rutile TiO2(110) face

Canister integrity and radionuclide retention is of first importance for assessing the long-term safety of nuclear waste stored in engineered geologic depositories. Uranyl ion sorption on the TiO(2) rutile (110) face is investigated using periodic density functional theory (DFT) calculations. From experimental observations, only two uranyl surface complexes are observed and characterized. When the pH increases (from 1.5 to 4.5), the relative ratios of these two surface complexes are modified. From a crystallographic point of view, three sorption sites can be considered and have been studied with different protonation states of the surface to account for very acidic and low acidic conditions. The two surface complexes experimentally observed were calculated as the most stable ones, while the evolution of their sorption energies agrees with experimental data.     

Synthesis and reactivity of [penta(4-halogenophenyl)cyclopentadienyl][hydrotris(indazolyl)borato]ruthenium(II) complexes: rotation-induced Fosbury flop in an organometallic molecular turnstile

The preparation of ruthenium(II) complexes coordinated to a penta(4-halogeno)phenylcyclopentadienyl ligand and to the hydrotris(indazolyl)borate ligand are detailed. Our strategy involves first the coordination of the penta(4-bromo)phenylcyclopentadienyl ligand by reaction with the ruthenium-carbonyl cluster followed by the coordination of the tripodal ligand. The pentabrominated precursor was successfully converted to the pentaiodinated derivative by using the Klapars-Buchwald methodology, applied for the first time on organometallic substrates. Cross-coupling reactions were performed on both pentabromo and pentaiodo complexes to introduce in a single step the five peripheric ferrocenyl fragments required to obtain a potential molecular motor. The two ligands present in the ruthenium complexes undergo a correlated rotation that was established both experimentally by NMR experiments and an X-ray diffraction study, and theoretically by DFT calculations. The potential-energy curve obtained by DFT revealed the energy barrier of the gearing mechanism to be only 4.5 kcal mol(-1). These sterically highly constrained complexes can be regarded as organometallic molecular turnstiles.     

Titelbild: Enantiospecific C?H Activation Using Ruthenium Nanocatalysts (Angew. Chem. 36/2015)

The activation of C H bonds has revolutionized modern synthetic chemistry. However, no general strategy for enantiospecific C H activation has been developed to date. We herein report an enantiospecific C H activation reaction followed by deuterium incorporation at stereogenic centers. Mechanistic studies suggest that the selectivity for the α‐position of the directing heteroatom results from a four‐membered dimetallacycle as the key intermediate. This work paves the way to novel molecular chemistry on nanoparticles.     

A new method for modelling spectator chemical groups in ab initio calculations: effective group potentials

 A new method for an increased numerical efficiency of ab initio calculations is proposed. It is based on the assumption that in most cases chemical properties of functional groups in molecules are mainly controlled by a few electrons. This statement allows one to distinguish between two classes of nuclei and electrons: active and inactive ones. The effective group potential (EGP) method presupposes that the effect of inactive electrons in a functional chemical group can be described by a pseudopotential, in the same way that core electrons are replaced by effective core potentials in atoms. It is shown that EGPs are able to predict chemical and structural features of the active part of a molecule and at a fraction of the ordinary computational cost. The preliminary results reported here concern the determination of EGPs for ammonia, the methyl radical and the cyclopendadienyl ligand, which represent different types of bonding. Received: 15 September 1999 / Accepted: 3 February 2000 / Published online: 2 May 2000     

Nitroanilinomethanephosphonates derived from ferrocene and nitrobenzaldehyde

A series of new aminophosphonates derived from ferrocene and nitrobenzene were synthesized. They were characterized by means of the ¹H and ³¹P NMR spectroscopy as well as by their elemental analysis. Synthesis of esters was carried out without solvent as refluxing of the reagents in toluene or in acetonitrile gave no results. © 2003 Wiley Periodicals, Inc. Heteroatom Chem 14:144–148, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.10128     

The unusual stereochemical behavior in the addition of phosphites to N‐1‐naphthyl terephthalic and isophthalic Schiff bases

The reaction of N‐α‐naphthylimines of terephthalic and isophthalic aldehydes with dialkyl and diaryl phosphites gave corresponding N‐α‐naphthylamino‐phosphonates in fair yields. An unusual stereochemical behavior was observed and the explanation for such a phenomenon was suggested. © 2001 John Wiley & Sons, Inc. Heteroatom Chem 12:27–32, 2001     

Cubic aluminum silicides RE8Ru12Al49Si9(Al(x)Si12-x) (RE = Pr, Sm) from liquid aluminum. Empty (Si,Al)12 cuboctahedral clusters and assignment of the Al/Si distribution with neutron diffraction.

Two new quaternary aluminum silicides, RE8Ru12Al49Si9(Al(x)Si12-x) (x approximately 4; RE = Pr, Sm), have been synthesized from Sm (or Sm2O3), Pr, Ru, and Si in molten aluminum between 800 and 1000 degrees C in sealed fused silica tubes. Both compounds form black shiny crystals that are stable in air and NaOH. The Nd analog is also stable. The compounds crystallize in a new structural type. The structure, determined by single-crystal X-ray diffraction, is cubic, space group Pm3m with Z = 1, and has lattice parameters of a = 11.510(1) A for Sm8Ru12Al49Si9(Al(x)Si12-x) and a = 11.553(2) A for Pr8Ru12Al49Si9(Al(x)Si12-x) (x approximately 4). The structure consists of octahedral units of AlSi6, at the cell center, Si2Ru4Al8 clusters, at each face center, SiAl8 cubes, at the middle of the cell edges, and unique (Al,Si)12 cuboctohedral clusters, at the cell corners. These different structural units are connected to each other either by shared atoms, Al-Al bonds, or Al-Ru bonds. The rare earth metal atoms fill the space between various structural units. The Al/Si distribution was verified by single-crystal neutron diffraction studies conducted on Pr8Ru12Al49Si9(Al(x)Si12-x). Sm8Ru12Al49Si9(Al(x)Si12-x) and Pr8Ru12Al49Si9(Al(x)Si12-x) show ferromagnetic ordering at Tc approximately 10 and approximately 20 K, respectively. A charge of 3+ can be assigned to the rare earth atoms while the Ru atoms are diamagnetic.     

Ln2Al3Si2 (Ln=Ho,Er, Tm): New Silicides from Molten Aluminum—Determination of the Al/Si Distribution with Neutron Crystallography and Metamagnetic Transitions

Highly metallic compounds with a quasi‐one‐dimensional structure, the new ternary compounds Ln₂Al₃Si₂ (Ln=Ho, Er, Tm) are synthesized in molten aluminum from lanthanoid and silicon as reagents. Their structures show a formally [Al₃Si₂]⁶⁻ framework that contains infinite Al zigzag chains and Si−Si dimers and accommodates rows of Ln³⁺ ions in parallel tunnels. The compounds exhibit metamagnetic transitions at high magnetic fields.