Effects of Block Length in Copolymers Based on Regioregular Oligothiophenes Linked With Electron‐Accepting Units

Copolymers with an alternating structure of regioregular oligo(3‐hexylthiophene) (O3HT) with different lengths and 2,5‐dibutyl‐3,6‐di(thiophen‐2‐yl)pyrrolo[3,4‐c]pyrrole‐1,4(2H,5H)‐dione (DPP) were synthesized through Stille coupling reaction. The light absorption of the copolymers can be rationally tuned to have a broad spectrum across the visible region by adjusting the length of O3HT. Organic solar cells fabricated with the copolymers and PCBM showed a broad photoresponse and a comparable efficiency to that of poly(3‐hexylthiophene) (P3HT):PCBM cells. The external quantum efficiency and fluorescence spectra suggested that the intrachain energy transfer from the O3HT block to the vicinity of the DPP unit could limit the photovoltaic performance of the copolymers.     

In silico design, synthesis and evaluation of 3'-O-benzylated analogs of salacinol, a potent α-glucosidase inhibitor isolated from an Ayurvedic traditional medicine "Salacia"

With the aid of an in silico method, α-glucosidase inhibitors with far more potent activities than salacinol (1), a potent natural α-glucosidase inhibitor isolated from an Ayurvedic traditional medicine Salacia reticulata, have been developed.     

Enantio- and diastereoselective hetero-Diels-Alder reactions between 2-aza-3-silyloxy-1,3-butadienes and aldehydes catalyzed by chiral dirhodium(II) carboxamidates

The first catalytic asymmetric hetero-Diels-Alder reaction between 2-aza-3-silyloxy-1,3-butadienes and aldehydes is described. With dirhodium(II) tetrakis[N-benzene-fused-phthaloyl-(S)-piperidinonate], Rh(2)(S-BPTPI)(4), the cycloaddition reaction proceeded exclusively in an endo mode to give all-cis-substituted 1,3-oxazinan-4-ones in high yields with up to 98% ee.     

A facile one-step hydrothermal synthesis of rhombohedral CuFeO2 crystals with antivirus property

The rhombohedral-like CuFeO(2) crystals are synthesized via a facile hydrothermal route by using propionaldehyde as a reducing agent. The obtained CuFeO(2) crystals show promising efficiency in the inactivation of bacteriophage Qβ.     

Umpolung of fluoroform by cf bond activation: direct difluoromethylation of lithium enolates

Double agent: The direct α-difluoromethylation of lithium enolates using an umpolung form of fluoroform as a difluoromethyl carbocation equivalent leads to an all-carbon quaternary center. Late transition metals are not necessary and the reaction involves activation of inert C?F bonds with subsequent C?C bond formation.     

A catalytic asymmetric Ugi-type reaction with acyclic azomethine imines

An unconventional Ugi: A catalytic asymmetric Ugi-type reaction can be realized by use of N'-alkylbenzohydrazide, instead of a conventional amine, in the presence of an axially chiral dicarboxylic acid. The reaction proceeds through a key acyclic azomethine imine intermediate, which has recently emerged as a promising electrophile in asymmetric catalysis.     

Photocatalytic reduction of nitrite to dinitrogen in aqueous suspensions of metal-loaded titanium(IV) oxide in the presence of a hole scavenger: an ensemble effect of silver and palladium co-catalysts

Nitrite (NO(2)(-)) was photocatalytically reduced to dinitrogen (N(2)) in an aqueous suspension of two kinds of titanium(iv) oxide particles loaded with palladium and silver (Pd-TiO(2) and Ag-TiO(2)) at pH 8 under irradiation of UV light in the presence of sodium oxalate as a hole scavenger. The two metal-loaded TiO(2) photocatalysts had different roles in conversion of NO(2)(-) to N(2) and worked in an effective ensemble without conflict: (1) Pd-TiO(2) induced photocatalytic disproportionation of NO(2)(-) to N(2) and nitrate (NO(3)(-)) and (2) Ag-TiO(2) selectively reduced the thus-formed NO(3)(-) back to NO(2)(-) (partially to N(2)) with oxalate acting as a hole scavenger. When Pd-TiO(2) was used alone for NO(3)(-) reduction in the presence of sodium oxalate, Pd-TiO(2) induced fruitless photocatalytic decomposition of oxalate to carbon dioxide and dihydrogen. The presence of Ag-TiO(2) suppressed the fruitless decomposition of oxalate by Pd-TiO(2) because Ag-TiO(2) continuously provided NO(2)(-) in the reaction system using oxalate as a hole scavenger and Pd-TiO(2) therefore only worked as a photocatalyst for disproportionation of NO(2)(-) to N(2) and NO(3)(-) as it did when used alone.     

Furanose ring conformations in a 1′-alkynyl C-nucleoside and the dinucleotide

A large-scale synthesis was carried out for alkynyl C-nucleotide oligomers in order to clarify the structural details of the artificial DNA. A liquid-phase synthesis by means of phosphoramidite methodology enabled us to handle ～0.1 g of the DNA oligomers possessing a pseudouracil derivative (T*) as a non-natural nucleobase. ¹H NMR measurements in aqueous media were carried out for the oligomers, succeeded in the accurate assignments of the protons accompanying with determination of the coupling constants (J values). These J values revealed that average conformation of the alkynylribose rings in the DNA was substantially biased toward the S-type conformers (²T₁/E₁/^OT₁). X-ray crystal analysis of the non-natural nucleoside also supported the S-type conformation (²E/²T₁) as seen in natural B-DNA.     

Biogenous iron oxide-immobilized palladium catalyst for the solvent-free Suzuki–Miyaura coupling reaction

Iron oxide produced by iron-oxidizing bacteria, Leptothrix ochracea, (biogenous iron oxide: BIO) was used as a support for immobilized palladium catalysts with organic cross-linkers. Palladium immobilized on BIO bearing imidazolium chloride delivered the desired biaryl products in sufficient yields in the Suzuki–Miyaura coupling reactions under solvent-free conditions and could be reused several times without significant loss of catalytic activity. It is shown that BIO can be exploited as a useful support for immobilization of palladium and the BIO-immobilized palladium catalyst effectively promotes the solvent-free Suzuki–Miyaura coupling reactions.     

Controlling the Electronic States and Physical Properties of MMX-Type Diplatinum-Iodide Chain Complexes via Binary Countercations

MMX-type quasi-one-dimensional iodide-bridged dinuclear Pt complexes (MMX chains) with binary countercations show a new alternating charge-polarization + charge-density-wave (ACP+CDW) electronic state and reversible switching of the electronic states and physical properties upon dehydration and rehydration process. By comparing several MMX chains with various binary countercations with previous chains, we found that the short backbone of the aliphatic diammonium ion was indispensable for realizing the ACP+CDW state because it induces a 2-fold periodicity along the chain axis via twisting of the ligands. Moreover, the reversibility of the changes in the structure and electrical conductivity upon dehydration and rehydration depend on the length of aliphatic diammonium ion. Short diammonium ions support a robust framework, which undergoes reversible structural changes. On the other hand, long and bent aliphatic diammonium ions weaken the framework, which causes partial degradation of the crystal and a decrease in the electrical conductivity when the structure changes. However, the decrease in the activation energy of the electrical conductivity after the dehydration process is independent of the robustness of the complex, indicating that the orbital overlap in MMX chains with binary countercations increases upon dehydration. Controllable electronic states and physical properties provide a platform for designing the multifunctional materials based on MMX chains.