Construction of Quaternary Stereogenic Carbon Centers through Copper‐Catalyzed Enantioselective Allylic Alkylation of Azoles

Copper‐catalyzed enantioselective allylic alkylation of azoles with γ,γ‐disubstituted primary allylic phosphates was achieved using a new chiral N‐heterocyclic carbene ligand bearing a naphtholic hydroxy group. This reaction occurred with excellent branch regioselectivity and high enantioselectivity, thus forming a controlled all‐carbon quaternary stereogenic center at the position α to the heteroaromatic ring.     

HPLC determination of phenylpropanolamine in pharmaceutical OTC preparations

A convenient HPLC method to determine phenylpropanolamine (PPA) in addition to phenylephrine (PE) and chlorpheniramine (CPA) in commercially available over-the-counter (OTC) preparations has been developed. Sample solutions were prepared by dilution with water or methanol followed by filtration and direct injection into the HPLC system. The mobile phase was a mixture of methanol-acetonitrile-acetic acid (0.1 M)-triethylamine (20:20:60:0.6, v/v/v/v) containing sodium heptanesulfonate (0.5 mM) as an ion pair. The separation was achieved on a reversed-phase ODS column with detection wavelength set at 254 nm. The compounds showed good linearity in the range 2.5-1000 micro M with detection limits ranged from 0.13 to 0.48 micro M. PE, caffeine and CPA were well separated when present together with PPA. The method was applied to the determination of PPA in pharmaceutical preparations including hard and soft capsules.     

Preparation and multicolor electrochromic performance of a WO3/tris(2,2'-bipyridine)ruthenium(II)/polymer hybrid film

A tungsten trioxide (WO(3))/tris(2,2'-bipyridine)ruthenium(II) ([Ru(bpy)(3)](2+); bpy=2,2'-bipyridine)/poly(sodium 4-styrenesulfonate) (PSS) hybrid film was prepared by electrodeposition from a colloidal triad solution containing peroxotungstic acid (PTA), [Ru(bpy)(3)](2+), and PSS. A binary solution of [Ru(bpy)(3)](2+) and PTA (30 vol % ethanol in water) gradually gave an orange precipitate, possibly caused by the electrostatic interaction between the cationic [Ru(bpy)(3)](2+) and the anionic PTA. The addition of PSS to the binary PTA/[Ru(bpy)(3)](2+) solution remarkably suppressed this precipitation and caused a stable, colloidal triad solution to form. The spectrophotometric measurements and lifetime analyses of the photoluminescence from the excited [Ru(bpy)(3)](2+) ion in the colloidal triad solution suggested that the [Ru(bpy)(3)](2+) ion is partially shielded from electrostatic interaction with anionic PTA by the anionic PSS polymer chain. The formation of the colloidal triad made the ternary [Ru(bpy)(3)](2+)/PTA/PSS solution much more redox active. Consequently, the rate of electrodeposition of WO(3) from PTA increased appreciably by the formation of the colloidal triad, and fast electrodeposition is required for the unique preparation of this hybrid film. The absorption spectrum of the [Ru(bpy)(3)](2+) ion in the film was close to its spectrum in water, but the photoexcited state of the [Ru(bpy)(3)](2+) ion was found to be quenched completely by the presence of WO(3) in the hybrid film. The cyclic voltammogram (CV) of the hybrid film suggested that the [Ru(bpy)(3)](2+) ion performs as it is adsorbed onto WO(3) during the electrochemical oxidation. An ohmic contact between the [Ru(bpy)(3)](2+) ion and the WO(3) surface could allow the electrochemical reaction of adsorbed [Ru(bpy)(3)](2+). The composition of the hybrid film, analyzed by electron probe microanalysis (EPMA), suggested that the positive charge of the [Ru(bpy)(3)](2+) ion could be neutralized by partially reduced WO(3)(-) ions, in addition to Cl(-) and PSS units, based on the charge balance in the film. The electrostatic interaction between the WO(3)(-) ion and the [Ru(bpy)(3)](2+) ion might be responsible for forming the electron transfer channel that causes the complete quenching of the photoexcited [Ru(bpy)(3)](2+) ion, as well as the formation of the ohmic contact between the [Ru(bpy)(3)](2+) ion and WO(3). A multicolor electrochromic performance of the WO(3)/[Ru(bpy)(3)](2+)/PSS hybrid film was observed, in which transmittances at 459 and 800 nm could be changed, either individually or at once, by the selection of a potential switch. Fast responses, of within a few seconds, to these potential switches were exhibited by the electrochromic hybrid film.     

Forward and backward extractions of cytochrome c using reverse micellar system of sucrose fatty acid ester

The effects of solvent, pH, and ionic strength on the reverse micellar extraction of cytochrome c have been examined, when sucrose fatty acid esters were employed as surfactants of reverse micelles. The transparent and stable reverse micellar organic phase was formed, when the mixture of isooctane and n-butanol (7:3 v/v) was used as the bulk organic phase. The high forward extraction ratio was obtained under mild alkaline and low ionic strength conditions, while the high backward extraction ratio was obtained for acidic pH values or at high ionic strength. The activity of cytochrome c recovered from the reverse micellar phase was sufficiently retained.     

Charge carrier transport in high purity perylene single crystal studied by time-of-flight measurements and through field effect transistor characteristics

Electronic transport has been studied by measuring the characteristics of field effect transistors using high purity perylene and the results have been compared with those from time-of-flight measurements. The purity of the material has been monitored by carrier trapping time and delayed fluorescence lifetime. Three types of field effect transistors have been studied: (1) thin film transistor, (2) transistor prepared by placing a single crystal flake on a substrate and (3) transistor fabricated on a single crystal by depositing electrodes and insulating layer onto it. Compared to thin film transistors prepared by evaporating perylene onto a SiO₂/Si substrate, higher mobility values were obtained with transistors using single crystals, but the electrical characteristics of the transistors were far from ideal: large threshold gate voltage observed in the second class of FETs indicated that a high density of traps are present at the interface between the organics and the insulator. A transistor of the third class showed that it functioned indeed as a FET with a reasonably high mobility, but the operation was not stable enough to allow reliable measurements. Much remains to be improved in the design and construction of a perylene FET before the potentiality of the material is fully developed. Also, it remains to be explored to what extent the bulk purity and the molecular order at the organics/insulator interface influence the transport of the charge carriers in an organic FET.     

Porous Colloidal Hydrogels Formed by Coordination-Driven Self-Assembly of Charged Metal-Organic Polyhedra

Introduction of porosity into supramolecular gels endows soft materials with functionalities for molecular encapsulation, release, separation and conversion. Metal-organic polyhedra (MOPs), discrete coordination cages containing an internal cavity, have recently been employed as building blocks to construct polymeric gel networks with potential porosity. However, most of the materials can only be synthesized in organic solvents, and the examples of porous, MOP-based hydrogels are scarce. Here, we demonstrate the fabrication of porous hydrogels based on [Rh₂(OH-bdc)₂]₁₂, a rhodium-based MOP containing hydroxyl groups on its periphery (OH-bdc=5-hydroxy-1,3-benzenedicarboxylate). By simply deprotonating [Rh₂(OH-bdc)₂]₁₂ with the base NaOH, the supramolecular polymerization between MOPs and organic linkers can be induced in the aqueous solution, leading to the kinetically controllable formation of hydrogels with hierarchical colloidal networks. When heating the deprotonated MOP, Na_x[Rh₂₄(O-bdc)_x(OH-bdc)_24-x], to induce gelation, the MOP was found to partially decompose, affecting the mechanical property of the resulting gels. By applying a post-synthetic deprotonation strategy, we show that the deprotonation degree of the MOP can be altered after the gel formation without serious decomposition of the MOPs. Gas sorption measurements confirmed the permanent porosity of the corresponding aerogels obtained from these MOP-based hydrogels, showing potentials for applications in gas sorption and catalysis.     

The effects of O-substituents of hexahomotrioxacalix[3]arene on potentiometric discrimination between dopamine and biological organic/inorganic cations

As an interesting type of molecular recognition at a membrane surface, the tri-O-acetic acid ester (host 2) of hexahomotrioxacalix[3]arene, when incorporated into poly(vinyl chloride) (PVC) liquid membranes, displays a high potentiometric selectivity for dopamine over, not only other catecholamines (noradrenaline, adrenaline), but also quaternary ammonium guests (tetramethylammonium, choline, and acetylcholine) and inorganic cations (Na+, K+, NH4+). Interestingly, changes in membrane potential based on the host-guest complexation of host 2 that were observed dopamine/inorganic cation selectivity were not displayed by the related hosts 3 and 4, which contain amide substituents. This paper describes our efforts to separately estimate the two factors contributing to the dopamine selectivities, i.e., the guest lipophilicity factor and the host-guest complexation factor, in an attempt to understand the effects of the O-substituents of these hosts. The potentiometric experiments showed that, although the guests had roughly equal lipophilicity, the electromotive force (EMF) response for dopamine by host 2 was excellent. Furthermore, host 2 displayed ca. a 20-fold stronger complexation for dopamine, compared to noradrenaline, adrenaline, K+, and NH4+ cations. These results indicate that the high potentiometric selectivity of the ion-selective electrode for dopamine mainly reflect, not the guest lipophilicity factor but the host-guest complexation factor. On the other hand, host 3 displayed ca. a 3000-fold stronger binding to Na+ than dopamine, thus explaining the reasons for the lower dopamine-selectivities of host 3 compared to host 2. It is interesting to note that the high potentiometric selectivities for dopamine were displayed by not only host 2 but also host 5, regardless of the simple structure of the O-substituents.     

Boron-doped diamond as a new heating element for internal-resistive heated diamond-anvil cell

We have developed an internal-resistive heated diamond-anvil cell (IHDAC) with a new resistance heater – boron-doped diamond (BDD) – along with an optimized design of the cell assembly, including a composite gasket. Our proposed technique is capable of heating a silicate/oxide material with (1) long-term stability (>1?h at 2500?K) and (2) uniform radial temperature distribution (±35?K at 2500?K across a 40-µm area), which are clear advantages over the conventional laser-heated and internal-heated DACs. In addition, the achieved temperature in this study was greater than 3500?K, which mostly covers the possible geotherm of the entire lower mantle. In situ X-ray diffraction (XRD) measurement and ex situ chemical analyses confirmed that weak XRD intensity from the BDD heater and chemical inertness (no boron diffusion into silicate samples). This newly developed IHDAC with a BDD heater can be used to determine the phase diagrams of mantle materials with high precision and be used in lower-mantle petrology.     

Formal [4+2] Reaction between 1,3‐Diynes and Pyrroles: Gold(I)‐Catalyzed Indole Synthesis by Double Hydroarylation

Indole synthesis by a gold(I)‐catalyzed intermolecular formal [4+2] reaction between 1,3‐diynes and pyrroles has been developed. This reaction involves the hydroarylation of 1,3‐diynes with pyrroles followed by an intramolecular hydroarylation to give the 4,7‐disubstituted indoles. This reaction can also be applied to the synthesis of carbazoles when indoles are used as the nucleophiles instead of pyrroles.