Local structural analysis of In-doped Bi2Se3 topological insulator using X-ray fluorescence holography

We performed X-ray fluorescence holography measurements on an In-doped Bi₂Se₃ topological insulator and obtained an in-plane atomic image in the vicinity of In. We found that atomic images at the positions of the first nearest neighbors (NNs) are very weak whereas those at the positions of the second and the third NNs are relatively strong. On the basis of the fact that In is half of the atomic number of Bi, we attributed the origin of this feature to the clustering of the In atoms in the Bi plane. We calculated the intensity of the atomic images and confirmed that the formation of In cluster results in a decrease by 30% in the first NN atomic image intensity. However, the decrease in the magnitude is not enough to explain the experimental results, suggesting another contribution such as the lattice distortions. The effect of the lattice distortion on the atomic image intensity is discussed on the basis of the simulation including the positional fluctuation of In atoms.     

Dolbeault cohomology groups of compact pseudo-Kähler homogeneous manifolds

It is well known that a pseudo-Kähler structure is one of the natural generalizations of a Kähler structure. In this paper, we consider the Dolbeault cohomology groups of compact pseudo-Kähler homogeneous manifolds.     

Macroscopic Polarization Change of Mononuclear Valence Tautomeric Cobalt Complexes Through the Use of Enantiopure Ligand

The crystallization of a complex having electron transfer properties in a polar space group can induce the polarization switching of a crystal in a specific direction, which is attractive for the development of sensors, memory devices, and capacitors. Unfortunately, the probability of crystallization in a polar space group is usually low. Noticing that enantiopure compounds crystallize in Sohncke space groups, this paper reports a strategy for the molecular design of non-ferroelectric polarization switching crystals based on the use of intramolecular electron transfer and chirality. In addition, this paper describes the synthesis of a mononuclear valence tautomeric (VT) cobalt complex bearing an enantiopure ligand. The introduction of enantiomer enables the crystallization of the complex in the polar space group (P2₁). The polarization of the crystals along the b-axis direction is not canceled out and the VT transition is accompanied by a change in the macroscopic polarization of the polar crystal. Polarization switching via electron transfer is realized at around room temperature.     

A 116-Nuclear Metallosupramolecular Cage-of-Cage Showing Multistep Single-Crystal-to-Single-Crystal Transformation

Here a unique single-crystal-to-single-crystal (SCSC) transformation of a 116-nuclear Au^I₇₂Cd^II₄₀Na^I₄ cage-of-cage ( 2 _CdNa) is reported, which was created from a trigold(I) metalloligand with d -penicillamine by way of a 9-nuclear Au^I₆Cd^II₃ cage ( 1 ). Cage-of-cage 2 _CdNa is composed of 12 cages of 1 that are linked by 4 Cd²⁺ and 4 Na⁺ ions, with its surface being covered by 12 NO₃⁻ ions to form a discrete, spherical molecule with a diameter ca. 4.7 nm. In crystal 2 _CdNa, the cage-of-cage molecules are packed in a cubic lattice with a huge cell volume of ca. 4.5×10⁵ ų_, so as to have large interstices with diameters of more than 3 nm. Upon soaking crystals 2 _CdNa in aqueous Cu(NO₃)₂, all Cd²⁺ and Na⁺ were quickly exchanged by Cu²⁺ to produce an analogous Au^I₇₂Cu^II₄₄ cage-of-cage ( 2 _Cu) in a SCSC manner. Prolonged soaking led to the SCSC transformation to another supramolecular structure ( 2′ _Cu) consisting of 152-nuclear Au^I₇₂Cu^II₈₀ cage-of-cages that are alternately H-bonded with the Au^I₇₂Cu^II₄₄ cage-of-cages. 2′ _Cu showed the accommodation of MoO₄²⁻ and the conversion of MoO₄²⁻ to β-Mo₈O₂₆⁴⁻ in the crystal, with retention of single-crystallinity.     

Dual Emission from Precious Metal-Free Luminophores Consisting of C,H, O,Si, and S/P at Room Temperature

Fluorescence–phosphorescence dual-emissive compounds are valuable tools for ratiometric luminescence sensing. Herein, it is reported that 2,5-bis(phenylsulfonyl)- and 2,5-bis[bis(4-methoxyphenyl)phosphinyl]-1,4-disiloxybenzenes exhibit dual emission with emission peaks that were easily identified without performing time-gated measurement. The disiloxybenzenes in powder simultaneously fluoresced and phosphoresced at 358–374 and 457–470 nm, respectively, under vacuum. The intensity ratios of the phosphorescence/fluorescence maxima of the disiloxybenzenes in powder and in a thin film of poly(methyl methacrylate) were sensitive to temperature and molecular oxygen, respectively. The plots of the relative intensity versus temperature or partial pressure of molecular oxygen were well fitted with calibration curves defined by an exponential approximation with excellent correlation coefficients R² (0.9708–0.9921), demonstrating the high potential of the disiloxybenzenes as precious metal-free probes applicable to ratiometric luminescence sensing.     

Formal total synthesis of fostriecin via 1,4-asymmetric induction using cobalt-alkyne complex

The synthesis of a protected dephosphofostriecin, and thereby a formal synthesis of fostriecin, has been accomplished. Two of the four chiral centers are controlled by an external chiral auxiliary and the other two are synthesized stereoselectively, one by a novel 1,4-asymmetric induction using cobalt-alkyne complex, and the other by 1,3-asymmetric induction.     

AlCl3-catalyzed tandem acetylation of hydroarylated [60]fullerenes

The AlCl3-catalyzed acetylation of 1,2-hydrophenylated [60]fullerenes, HC60-Ar, proceeded via a sequential manner involving the acetylation at the hydrogenated fullerene carbon, the following intramolecular cyclization with the adjacent aryl group, the facile loss of water, and the second acetylation of the generated indenylidene double bond. However, the similar reaction of the hydrobiphenylated analogue brought about the normal acetylation at the terminal aromatic ring prior to the same sequential reactions as did hydrophenylated fullerenes.     

Excellent chiralselectivity in sulfur-bridged CoIIIMCoIII (M = NiII and PdII) trinuclear complexes containing 1,2-cyclohexanediamine

The reaction of [Ni(aet)2] with [CoCl2(R,R-chxn)2]+ (aet = 2-aminoethanethiolate, R,R-chxn = 1R,2R-cyclohexanediamine) in water gave a CoIIINiIICoIII trinuclear complex, DeltaRRDeltaRR-[Ni(Co(aet)(2-)(R,R-chxn))2]4+ ([1a]4+), in which two cis(S)-[Co(aet)2(R,R-chxn)]+ units are linked by a central NiII ion through sulfur bridges. The two CoIII units in [1a]4+ uniformly adopt the Delta configuration, which is induced by the chirality of the terminal R,R-chxn ligands. The central NiII ion in [1a]4+ was replaced by a PdII ion to produce an analogous CoIIIPdIICoIII trinuclear complex, DeltaRRDeltaRR-[Pd(Co(aet)2(R,R-chxn))2]4+ ([2a]4+), with retention of the Delta configuration. When racemic R,R/S,S-chxn was employed instead of R,R-chxn, not only the chirality about two CoIII centers but also the chirality about two chxn ligands was unified in the S-bridged trinuclear structure, leading to the selective formation of a pair of enantiomers, DeltaRRDeltaRR/LambdaSSLambdaSS-[M(Co(aet)2(chxn))2]4+ (M = NiII ([1b]4+) and PdII ([2b]4+)). The stereochemical and spectroscopic features of these complexes are discussed on the basis of the electronic absorption, CD, and NMR spectroscopies, along with the crystal structures of [1a]4+ and [2a]4+.     

Biopolymer-Polysiloxane Double Network Aerogels

A new series of transparent aerogels of biopolymer-polysiloxane double networks is reported. Biopolymer aerogels have attracted much attention from green and sustainable aspects but suffered from strong hydrophilicity and difficulty to make homogeneous structures in nanoscale; these drawbacks are overcome by compositing with a polysiloxane network. Alginate-polymethylsilsesquioxane aerogel has high optical transparency, water repellency, comparable superinsulation property and improved bending flexibility compared to pure polymethylsilsesquioxane aerogel. The nanoscale homogeneity is realized by separating the crosslinking steps for two networks in a sequential protocol: condensation of siloxane bonds and metal-crosslinking of biopolymer. The crosslinking order, biopolymer-first or siloxane-first, and universality/limitation of biopolymer-crosslinker pairs are discussed to construct fundamental chemistry of double network systems for their further application potentials.