Self-assembly of flexible supramolecular metallacyclic ensembles: structures and adsorption properties of their nanoporous crystalline frameworks

The syntheses, structures, and N2 adsorption properties of six new supramolecular metallacycles are reported. Flexible ditopic linkers, 1-4, with systematically varied lengths and conformational degrees of freedom were synthesized utilizing ester linkages. They were used in combination with (dppp)M(OTf)2, where M = Pt(II) and Pd(II), and cis-(Me3P)2Pt(OTf)2 to form flexible supramolecular metallacycles 5-10 in 88-98% isolated yields. Their structures were characterized via multinuclear NMR and X-ray crystallography. The metallacycles stack to form porous structures in the crystalline state. The pore dimensions depend on both the phosphorus ligands attached to the metals and the flexible linkers. Adsorption studies on the porous materials show that 5a, 6, 8, and 9 held 11.7, 16.5, 5.7, and 6.8 cm3/g STP of N2 at 77 K, respectively. A guest-exchange study with nitromethane and toluene reveals that the nanopore in 5 is flexible, a property which was transferred from the linker to the supramolecular structure in the solid state.     

Organotrichlorogermane synthesis by the reaction of elemental germanium, tetrachlorogermane and organic chloride via dichlorogermylene intermediate

Organotrichlorogermanes were synthesized by the reaction of elemental germanium, tetrachlorogermane and organic chlorides, methyl, propyl, isopropyl and allyl chlorides. Dichlorogermylene formed by the reaction of elemental germanium with tetrachlorogermane was the reaction intermediate, which was inserted into the carbon-chlorine bond of the organic chloride to give organotrichlorogermane. When isopropyl or allyl chloride was used as an organic chloride, organotrichlorogermane was formed also in the absence of tetrachlorogermane. These chlorides were converted to hydrogen chloride, which subsequently reacted with elemental germanium to give the dichlorogermylene intermediate. The reaction of elemental germanium, tetrachlorogermane and organic chlorides provides a simple and easy method for synthesizing organotrichlorogermanes, and all the raw materials are easily available.     

Distributed computing and NMR constraint-based high-resolution structure determination: applied for bioactive Peptide endothelin-1 to determine C-terminal folding

Distributed computing has been implemented to the solution structure determination of endothelin-1 to evaluate efficiency of the method for NMR constraint-based structure calculations. A key target of the investigation was determination of the C-terminal folding of the peptide, which had been dispersed in previous studies of NMR, despite its pharmacological significances. With use of tens of thousands of random initial structures to explore the conformational space comprehensively, we determined high-resolution structures with good convergences of C-terminal as well as previously defined N-terminal structures. The previous studies had missed the C-terminal convergence because of initial structure dependencies trapped in localized folding of the N-terminal region, which are strongly constricted by two disulfide bonds.     

Concise synthesis of anti-HIV-1 active (+)-inophyllum B and (+)-calanolide A by application of (-)-quinine-catalyzed intramolecular oxo-Michael addition

(-)-Quinine-catalyzed intramolecular oxo-Michael addition (IMA) of 7-hydroxy-5-methoxy-8-tigloylcoumarins was developed for the enantioselective construction of 2,3-dimethyl-4-chromanone systems in the context of the asymmetric synthesis of anti-HIV-1 active Calophyllum coumarins. Combination of the IMA and MgI(2)-assisted demethylation of the 5-methoxy group along with isomerization of the formed chromanone systems as key steps successfully led to the concise synthesis of (+)-inophyllum B and (+)-calanolide A, possible candidates for AIDS drugs. Further examination of the asymmetric IMA with cinchona alkaloids lacking a methoxy group on the quinoline skeleton suggested the influence of the methoxy substituent on stereoselectivity at the stereogenic centers of the chromanone systems.     

Structure Switching and Modulation of the Magnetic Properties in Diarylethene‐Bridged Metallosupramolecular Compounds by Controlled Coordination‐Driven Self‐Assembly

We report three self‐assembled iron complexes that comprised an anti‐parallel open form (o‐ L _anti), a parallel open form (o‐ L _syn), and a closed form (c‐ L ) of diarylethene conformers. Under kinetic control, Fe^II₂(o‐ L _anti)₃ was isolated, which exhibited a dinuclear structure with diamagnetic properties. Under light‐irradiation control, Fe^II₂(c‐ L )₃ was prepared and exhibited paramagnetism and spin‐crossover behaviour. Under thermodynamic control and in the presence of indispensable [Fe^III(Tp*)(CN)₃]^?, Fe^II₂(o‐ L _anti)₃ and Fe^II₂(c‐ L )₃ transformed into tetranuclear Fe^III₂Fe^II₂(o‐ L _syn)₂, which exhibited complete spin‐crossover behaviour at T_1/2=353 K.     

Enantioselective Diels-Alder reaction of α-(acylthio)acroleins: a new entry to sulfur-containing chiral quaternary carbons

A catalytic and enantioselective Diels-Alder reaction of α-(carbamoylthio)acroleins induced by an organoammonium salt of chiral triamine is described. α-(Carbamoylthio)acroleins are designed and synthesized as new sulfur-containing dienophiles for the first time. The Diels-Alder reaction affords chiral tertiary thiol precursors with up to 91% ee.     

High-volume production of single and compound emulsions in a microfluidic parallelization arrangement coupled with coaxial annular world-to-chip interfaces

This study describes a microfluidic platform with coaxial annular world-to-chip interfaces for high-throughput production of single and compound emulsion droplets, having controlled sizes and internal compositions. The production module consists of two distinct elements: a planar square chip on which many copies of a microfluidic droplet generator (MFDG) are arranged circularly, and a cubic supporting module with coaxial annular channels for supplying fluids evenly to the inlets of the mounted chip, assembled from blocks with cylinders and holes. Three-dimensional flow was simulated to evaluate the distribution of flow velocity in the coaxial multiple annular channels. By coupling a 1.5 cm × 1.5 cm microfluidic chip with parallelized 144 MFDGs and a supporting module with two annular channels, for example, we could produce simple oil-in-water (O/W) emulsion droplets having a mean diameter of 90.7 μm and a coefficient of variation (CV) of 2.2% at a throughput of 180.0 mL h(-1). Furthermore, we successfully demonstrated high-throughput production of Janus droplets, double emulsions and triple emulsions, by coupling 1.5 cm × 1.5 cm - 4.5 cm × 4.5 cm microfluidic chips with parallelized 32-128 MFDGs of various geometries and supporting modules with 3-4 annular channels.     

Kinetics of the radical scavenging activity of β-carotene-related compounds

To clarify the non-enzymatic radical-scavenging activity of β-carotene-related compounds and other polyenes, we used differential scanning calorimetry to study the kinetics of radical polymerization of methyl methacrylate (MMA) by 2,2′-azobisisobutyronitrile (AIBN) or benzoyl peroxide (BPO) in the absence or presence of polyenes under nearly anaerobic conditions at 70°C, and analyzed the results with an SAR approach. The polyenes studied were all-trans retinol, retinol palmitate, calciferol, β-carotene and lycopene. Polyenes produced a small induction period. The stoichiometric factor (n) (i.e. the number of radicals trapped by each inhibitor molecule) of polyenes was close to 0. Tetraterpenes (β-carotene, lycopene) suppressed significantly more of the initial rate of polymerization (R ^inh) than did diterpenes (retinol, retinol palmitate). The inhibition rate constants (k ^inh) for the reaction of β-carotene with AIBN-or BPO-derived radicals were determined to be 1.2–1.6?×?10⁵ l?/?mol?s, similar to published values. A linear relationship between k ^inh and the kinetic chain length (KCL) for polyenes was observed; as k ^inh increased, KCL decreased. KCL also decreased significantly as the number of conjugated double bonds in the polyenes increased. Polyenes, particularly β-carotene and lycopene, acted as interceptors of growing poly-MMA radicals.