Site-Selective Supramolecular Complexation Activates Catalytic Ethane Oxidation by a Nitrido-Bridged Iron Porphyrinoid Dimer

Development of supramolecular methods to further activate a highly reactive intermediate is a fascinating strategy to create novel potent catalysts for activation of inert chemicals. Herein, a supramolecular approach to enhance the oxidizing ability of a high-valent oxo species of a nitrido-bridged iron porphyrinoid dimer that is a known potent molecular catalyst for light alkane oxidation is reported. For this purpose, a nitrido-bridged dinuclear iron complex of porphyrin-phthalocyanine heterodimer 3 ⁵⁺, which is connected through a fourfold rotaxane, was prepared. Heterodimer 3 ⁵⁺ catalyzed ethane oxidation in the presence of H₂O₂ at a relatively low temperature. The site-selective complexation of 3 ⁵⁺ with an additional anionic porphyrin (TPPS⁴⁻) through π–π stacking and electrostatic interactions afforded a stable 1:1 complex. It was demonstrated that the supramolecular post-synthetic modification of 3 ⁵⁺ enhances its catalytic activity efficiently. Moreover, supramolecular conjugates achieved higher catalytic ethane oxidation activity than nitrido-bridged iron phthalocyanine dimer, which is the most potent iron-oxo-based molecular catalyst for light-alkane oxidation reported so far. Electrochemical measurements proved that the electronic perturbation from TPPS⁴⁻ to 3 ⁵⁺ enhanced the catalytic activity.     

Femtosecond laser-induced stimulation of a single neuron in a neuronal network

We demonstrated the stimulation of neurons at a single-cell level in cultured neuronal network by a focused femtosecond laser. When the femtosecond laser was focused on a neuron loaded with a fluorescent calcium indicator, the fluorescence intensity immediately increased at the laser spot, suggesting that intracellular Ca²⁺ increases in the neuronal cell due to the femtosecond laser irradiation. The probability of Ca²⁺ elevation at the laser spot depended on the average laser power, irradiation time, and position of the focal point along the optical axis, indicating that the femtosecond laser activates neurons because of multiphoton absorption. Moreover, after laser irradiation of a single neuron cultured on multielectrode arrays, the evoked electrical activity of the neurons was demonstrated by electrophysiological systems, which concluded that the focused femtosecond laser could achieve stimulating a single neuron in a neuronal network with high spatial and temporal resolution.     

DFT calculations for Au adsorption onto a reduced TiO2 (110) surface with the coexistence of Cl

Residual chlorines, which originate from HAuCl₄, enhance the aggregation of gold (Au) nanoparticles and clusters, preventing the generation of highly active supported Au catalysts. However, the detailed mechanism of residual-chlorine-promoted aggregation of Au is unknown. Herein to investigate this mechanism, density functional theory (DFT) calculations of Au and Cl adsorption onto a reduced rutile TiO₂ (110) surface were performed using a generalised gradient approximation Perdew, Burke, and Ernzerhof formula (GGA–PBE) functional and plane-wave basis. Although both Au and Cl atoms prefer to mono-absorb onto oxygen defect sites, Cl atoms have a stronger absorption onto a reduced TiO₂ (110) surface, abbreviated as rTiO₂ (110) in the following, than Au atoms. Additionally, co-adsorption of a Cl atom and a Au atom or Au nanorod onto a rTiO₂ surface was investigated; Cl adsorption onto an oxygen defect site weakens the interaction between a Au atom or Au nanorod and rTiO₂ (110) surface. The calculation results suggest that the depletion of interaction between Au and rTiO₂ surface is due to strong interaction between Cl atoms at oxygen defect sites and neighbouring bridging oxygen (O^B) atoms.     

Syntheses and Crystal Structures of Ruthenium Complexes of 1,4,8,11-Tetraazacyclotetradecane, Tris(2-aminoethyl)amine (tren), and Bis(2-aminoethyl)(iminomethyl)amine. A Microporous Layered Structure Consisting of {[K(tren)](2)[RuCl(6)]}(n)()(n)()(-) and {(H(5)O(2))(4)[RuCl(6)]}(n)()(n)()(+)

The second method for the synthesis of cis-[Ru(III)Cl(2)(cyclam)]Cl (1) (cyclam = 1,4,8,11-tetraazacyclotetradecane), with use of cis-Ru(II)Cl(2)(DMSO)(4) (DMSO = dimethyl sulfoxide) as a starting complex, is reported together with the synthesis of [Ru(II)(cyclam)(bpy)](BF(4))(2).H(2)O (2) (bpy = 2,2'-bipyridine) from 1. The syntheses of Ru complexes of tris(2-aminoethyl)amine (tren) are also reported. A reaction between K(3)[Ru(III)(ox)(3)] (ox = oxalate) and tren affords fac-[Ru(III)Cl(3)(trenH)]Cl.(1)/(2)H(2)O (3) (trenH = bis(2-aminoethyl)(2-ammonioethyl)amine = monoprotonated tren) and (H(5)O(2))(2)[K(tren)][Ru(III)Cl(6)] (4) as major products and gives fac-[Ru(III)Cl(ox)(trenH)]Cl.(3)/(2)H(2)O (5) in very low reproducibility. A reaction between 3 and bpy affords [Ru(II)(baia)(bpy)](BF(4))(2) (6) (baia = bis(2-aminoethyl)(iminomethyl)amine), in which tren undergoes a selective dehydrogenation into baia. The crystal structures of 2-6 have been determined by X-ray diffraction, and their structural features are discussed in detail. Crystallographic data are as follows: 2, RuF(8)ON(6)C(20)B(2)H(34), monoclinic, space group P2(1)/c with a = 12.448(3) ?, b = 13.200(7) ?, c = 17.973(4) ?, beta = 104.28(2) degrees, V = 2862(2) ?(3), and Z = 4; 3, RuCl(4)O(0.5)N(4)C(6)H(20), monoclinic, space group P2(1)/a with a = 13.731(2) ?, b = 14.319(4) ?, c = 13.949(2) ?, beta = 90.77(1) degrees, V = 2742(1) ?(3), and Z = 8; 4, RuKCl(6)O(4)N(4)C(6)H(28), trigonal, space group R&thremacr; with a = 10.254(4), c = 35.03(1) ?, V = 3190(2) ?(3), and Z = 6; 5, RuCl(2)O(5.5)N(4)C(8)H(22), triclinic, space group P&onemacr; with a = 10.336(2) ?, b = 14.835(2) ?, c = 10.234(1) ?, alpha = 90.28(1) degrees, beta = 90.99(1) degrees, gamma = 92.07(1) degrees, V = 1567.9(4) ?(3), and Z = 4; 6, RuF(8)N(6)C(16)B(2)H(24), monoclinic, space group P2(1)/c, a = 10.779(2) ?, b = 14.416(3) ?, c = 14.190(2) ?, beta = 93.75(2) degrees, V = 2200.3(7) ?(3), and Z = 4. Compound 4 possesses a very unique layered structure made up of both anionic and cationic slabs, {[K(tren)](2)[Ru(III)Cl(6)]}(n)()(n)()(-) and {(H(5)O(2))(4)[Ru(III)Cl(6)]}(n)()(n)()(+) (n = infinity), in which both sheets {[K(tren)](2)}(n)()(2)(n)()(+) and {(H(5)O(2))(4)}(n)()(4)(n)()(+) offer cylindrical pores that are occupied with the [Ru(III)Cl(6)](3)(-) anions. The presence of a C=N double bond of baia in 6 is judged from the C-N distance of 1.28(2) ?. It is suggested that the structural restraint enhanced by the attachment of alkylene chelates at the nitrogen donors of amines results in either the mislocation or misdirection of the donors, leading to the elongation of the Ru-N(amine) distances and to the weakening of their trans influence. Such structural strain is also discussed as related to the spectroscopic and electrochemical properties of the cis-[Ru(II)L(4)(bpy)](2+) complexes (L(4) = (NH(3))(4), (ethylenediamine)(2), and cyclam).     

Skeletal Ni Catalysts Prepared from Amorphous Ni–Zr Alloys: Enhanced Catalytic Performance for Hydrogen Generation from Ammonia Borane

Skeletal Ni catalysts were prepared from Ni–Zr alloys, which possess different chemical composition and atomic arrangements, by a combination of thermal treatment and treatment with aqueous HF. Hydrogen generation from ammonia borane over the skeletal Ni catalysts proceeded efficiently, whereas the amorphous Ni–Zr alloy was inactive. Skeletal Ni prepared from amorphous Ni₃₀Zr₇₀ alloy had a higher catalytic activity than that prepared from amorphous Ni₄₀Zr₆₀ and Ni₅₀Zr₅₀ alloys. The atomic arrangement of the Ni–Zr alloy also strongly affected the surface structure and catalytic activities. Thermal treatment of the amorphous Ni–Zr alloys at a temperature slightly lower than the crystallization temperature led to an increase of the number of surface‐exposed Ni atoms and an enhancement of the catalytic activities for hydrogen generation from ammonia borane. The skeletal Ni catalysts also showed excellent durability and recyclability.     

DFT studies of the characteristics of Pd−Pt core-shell clusters

It is reported that Pd?Pt core-shell type nanoclusters in which the inner atoms of the Pd cluster are substituted by Pt significantly enhance the catalytic activity for cycloocatdiene hydrogenation. In order to discuss the electronic states of core-shell clusters, DFT calculations were carried out for Pd₁₃, Pt₁₃, Pt/Pd₁₂, Pd/Pt₁₂ Pd₃₈ and Pd₆/Pt₃₂ clusters. From these calculations, it was found that the charge transfer between the core atoms and the shell atoms played an important role for the modification of the electronic state of the surface atoms in them.     

Guerbet reaction of primary alcohols leading to beta-alkylated dimer alcohols catalyzed by iridium complexes

[IrCl(cod)]2 and [Cp*IrCl2]2 complexes catalyzed efficiently the Guerbet reaction of primary alcohols to beta-alkylated dimer alcohols in good yields. For instance, the reaction of 1-butanol in the presence of [Cp*IrCl2]2 (1 mol %), t-BuOK (40 mol %), and 1,7-octadiene (10 mol %) produced 2-ethyl-1-hexanol in 93% yield. Various primary alcohols undergo the Guerbet reaction under the influence of Ir complexes to give the corresponding dimer alcohols in good yields. This method provides an alternative direct route to beta-alkylated primary alcohols which are prepared by aldol condensation of aldehydes followed by hydrogenation.     

Synthesis and characterization of thiochromone S,S-dioxides as new photolabile protecting groups

3-Arylthiochromone derivatives were synthesized as new photolabile protecting groups, in which the photoreactivity was switchable based on oxidation of the sulfur atom (sulfide and sulfone); the protected substrates , released the corresponding alcohols, amines or carbonxylic acids almost quantitatively under UV-light in neutral condition and the photoproduct showed high fluorescence intensity.     

Superconductivity of doped Ar@C60

The synthesis of a mg amount of pure argon containing fullerene allowed the synthesis of the first endohedral superconductors with critical temperatures lower than expected, an indication of the strong influence of the argon atom on the C60 cage.