Rare earth-rich cadmium compounds RE 4 TCd (T = Co, Ru, and Rh) with Gd4RhIn type structure

The rare earth-rich cadmium compounds RE ₄ TCd (RE = Y, La–Nd, Sm, and Gd–Tm, Lu; T = Co, Ru, and Rh) were prepared from the elements in sealed tantalum ampoules in an induction furnace. All samples were characterized by X-ray powder diffraction. The structures of Y₄RuCd (a = 1362.5(1) pm), La₄RuCd (a = 1415.9(1) pm), Gd₄RuCd (a = 1368.8(2) pm), La₄CoCd (a = 1417.9(4) pm), Gd₄CoCd (a = 1356.1(1) pm), and Gd₄RhCd (a = 1368.7(1) pm) were refined from single crystal X-ray diffractometer data. The RE ₄ TCd compounds crystallize with the cubic Gd₄RhIn type structure, space group F ${\bar 4}The rare earth-rich cadmium compounds RE ₄ TCd (RE = Y, La–Nd, Sm, and Gd–Tm, Lu; T = Co, Ru, and Rh) were prepared from the elements in sealed tantalum ampoules in an induction furnace. All samples were characterized by X-ray powder diffraction. The structures of Y₄RuCd (a = 1362.5(1) pm), La₄RuCd (a = 1415.9(1) pm), Gd₄RuCd (a = 1368.8(2) pm), La₄CoCd (a = 1417.9(4) pm), Gd₄CoCd (a = 1356.1(1) pm), and Gd₄RhCd (a = 1368.7(1) pm) were refined from single crystal X-ray diffractometer data. The RE ₄ TCd compounds crystallize with the cubic Gd₄RhIn type structure, space group F 3m. The transition metal atoms have tricapped trigonal prismatic rare earth coordination. The trigonal prisms are condensed via common edges, forming a rigid three-dimensional network with adamantane symmetry. Voids in these networks are filled by Cd₄ tetrahedra (304 pm Cd–Cd in Gd₄CoCd) and polyhedra of the RE1 atoms. The crystal chemical peculiarities are briefly discussed. Correspondence: Rainer P?ttgen, Institut für Anorganische und Analytische Chemie, Westf?lische Wilhelms-Universit?t Münster, Correnstrasse 30, 48149 Münster, Germany.     

“Small and beautiful” – The novel structures and phases of nano-oxides

Low-dimensional oxide nanostructures supported on well-defined metal surfaces raise scientific interest both on a fundamental level and for potential technological applications. These systems may be regarded as artificially created hybrid materials with novel emergent properties, supporting new concepts of geometrical structure, electronics and magnetism, complex phase diagrams and particular chemical reactivity. The coupling of the oxide nano-phase to the metal support surface by electronic and elastic interactions together with the low dimensionality aspects are at the origin of the particular behaviour of these hybrid structures. By way of prototypical examples, this Prospective article highlights some of the novel properties of nano-oxides and, as a side aspect, comments on the aesthetics of their structural motifs.     

Verdampfung von Kupfer(II)chlorid und Struktur des Dampfes untersucht mit UV./VIS.- und Raman-Spektroskopie

The vapour pressure of CuCl₂ and the dimerization of CuCl₂(g) have been investigated by optical spectroscopy in the range 420–650°C, p = 0.5-5 atm. The enthalpy of dimerization of CuCl₂(g) was determined by visible and by Raman spectroscopy and good agreement was found (?154 kJmol^?1 and ?143 kJmol^?1). CuCl₂(g) shows two totally symmetric Raman modes (373 and 127 cm^?1) indicating that, at least at elevated temperatures, CuCl₂(g) is not a linear molecule. The optical spectra of Cu₂Cl₄(g) and CuLCl₅(g) (L ? Ga, In) are very similar supporting a CuCl₃-chromophor in both cases. The formerly proposed structure of CuL₂Cl₈(g) (L ? Al, Ga) contains bridging and terminal chlorides, structural elements also present in Cu₂Cl₄(g). In agreement with the proposed structure v is identical in Cu₂Cl₄(g) and CuL₂Cl₈(g), while V is at lower energies (20–30 cm^?1) in CuL₂Cl₈(g) than in Cu₂Cl₄(g).     

Trapping of tin(II) and lead(II) homologues of carbon monoxide by a benzannulated lutidine-bridged bisstannylene

The reaction of the benzannulated bisstannylene ligand 2 with Sn O or Pb O generated in situ gave the pincer complexes 3 and 4. Both complexes have been characterized by X-ray diffraction and multinuclear NMR spectroscopy. A divalent state has been found by M?ssbauer spectroscopy for the tin atoms in complexes 3 and 4.     

Crosslinked Redox‐Responsive Micelles Based on Lipoic Acid‐Derived Amphiphiles for Enhanced siRNA Delivery

Successful application of gene silencing approaches critically depends on systems that are able to safely and efficiently deliver genetic material such as small interfering RNA (siRNA). Due to their beneficial well‐defined dendritic nanostructure, self‐assembling dendrimers are emerging as promising nanovectors for siRNA delivery. However, these kinds of vectors are plagued with stability issues, especially when considered for in vivo applications. Therefore, in the present study, disulfide‐based temporarily fixed micelles are developed that can degrade upon reductive conditions, and thus lead to efficient cargo release. In detail, lipoic acid‐derived crosslinked micelles are synthesized based on small polymerizable dendritic amphiphiles. Particularly, one candidate out of this series is able to efficiently release siRNA due to its redox‐responsive biodegradable profile when exposed to simulated intracellular environments. As a result, the reduction‐triggered disassembly leads to potent gene silencing. In contrast, noncrosslinkable, structurally related constructs fails under the tested assay conditions, thereby confirming the applied rational design approach and demonstrating its large potential for future in vivo applications.

     

Trivalent‐Intermediate Valent Cerium Ordering in CeRuSn – A Static Intermediate Valent Cerium Compound with a Superstructure of the CeCoAl Type

New equiatomic stannide CeRuSn was synthesized from the elements by arc‐melting. CeRuSn was investigated by X‐ray powder and single crystal diffraction: C2/m, a = 1156.1(4), b = 475.9(2) and c = 1023.3(4) pm, β = 102.89(3)°, wR2 = 0.0466, 1229 F² values and 38 variables. CeRuSn adopts a superstructure of the monoclinic CeCoAl type through a doubling of the subcell c axis. In the superstructure two crystallographically independent cerium sites occur. Based on the interatomic distances the two sites can be assigned to trivalent Ce2 and intermediate valent Ce1. This trivalent‐intermediate valent cerium ordering is underlined by magnetic susceptibility measurements χ_m(T): below 150 K χ_m, measured with decreasing temperature, follows a Curie‐Weiss law χ_m = C_m/(T–θ_p) giving C_m = 0.38 emuK/mol as Curie constant per CeRuSn mol; a value showing that only half of the cerium atoms are trivalent in CeRuSn (C_m = 0.807 emuK/mol for one free Ce³⁺ ion). A remarkable feature of the CeRuSn structure are the short Ce1–Ru1 (233 pm) and Ce1–Ru2 (246 pm) distances. The crystal chemistry of CeRuSn is discussed on the basis of a group‐subgroup scheme.     

The molecular orientation of para-sexiphenyl on Cu(110) and Cu(110) p(2x1)O.

Controlling the molecular growth of organic semiconductors is an important issue to optimize the performance of organic devices. Conjugated molecules, used as building blocks, have an anisotropic shape and also anisotropic physical properties like charge transport or luminescence. The main challenge is to grow highly crystalline layers with molecules of defined orientation. The higher the crystallinity, the closer these properties reach their full intrinsic potential, while the orientation determines the physical properties of the film. Herein we show that the molecular orientation and growth can be steered by the surface chemistry, which tunes the molecule-substrate interaction. In addition, the oxygen reconstruction of the surface, demonstrates the flexibility of the organic molecules to adopt a given surface corrugation and their unique possibility to release stress by tilting.     

Structure and Properties of EuZnGa

New ternary gallide EuZnGa was synthesized by reaction of the elements in a sealed tantalum tube at 1320 K and subsequent annealing at 970 K for seven days. EuZnGa was investigated by X‐ray diffraction on both powders and single crystals. Its structure was refined from single crystal diffractometer data: KHg₂ type, space group Imma, a = 461.7(2), b = 761.4(3), c = 777.0(3) pm, R = 0.041 for 486 structure factors and 13 variables. The zinc and gallium atoms statistically occupy the mercury position of the KHg₂ type of structure. No long‐range ordering between the zinc and gallium atoms could be detected from the X‐ray data. Magnetic susceptibility measurements show Curie‐Weiss behavior above 50 K with a magnetic moment of μ_exp = 7.86(5) μ_B/Eu and θ = 17(2) K, suggesting divalent europium. Low‐field, low‐temperature susceptibility measurements indicate cluster glass behavior (mictomagnetism) with a freezing temperature of 24(2) K. Magnetization measurements show a magnetic moment of 4.9(1) μ_B/Eu at 2 K and a magnetic flux density of 5.5 T. Electrical resistivity data indicate metallic behavior. ¹⁵¹Eu Mössbauer spectroscopic measurements show onset of magnetic hyperfine splitting at ≤ 17.0 K. Down to the temperature of 4.2 K the spectra reflect magnetic relaxation effects suggesting the presence of a substantial extent of disordering. This observation is consistent with the cluster glass behavior as evident from the magnetic susceptibility data and may be a consequence of the presence of multiple local Eu sites as expected from the statistical Zn and Ga distribution over the corresponding sites in the KHg₂ structure.