Ab‐Initio study of Helium‐small carbon cage systems

The traditional method for opening the electron shells of noble gas atoms involves a strong electronegative atom or group. However, this approach is limited to only heavy noble‐gas atoms, such as Kr and Xe. In this paper, we performed accurate calculations of He@C₈H₈ and He@C10H16 and showed the possibility of opening the electron shell of a light noble‐gas atom. © 2012 Wiley Periodicals, Inc.     

The Redox‐Neutral Approach to C?H Functionalization

The direct functionalization of C? H bonds is an attractive strategy in organic synthesis. Although several advances have been made in this area, the selective activation of inert sp³ C? H bonds remains a daunting challenge. Recently, a new type of sp³ C? H activation mode through internal hydride transfer has demonstrated the potential to activate remote sp³ C? H linkages in an atom‐economic manner. This Minireview attempts to classify recent advances in this area including the transition to non‐activated sp³ C? H bonds and asymmetric hydride transfers.     

Mechanistic Aspects of Gas‐Phase Hydrogen‐Atom Transfer from Methane to [CO].+ and [SiO].+: Why Do They Differ?

The reactivity of the two diatomic congeneric systems [CO]^.+ and [SiO]^.+ towards methane has been investigated by means of mass spectrometry and quantum‐chemical calculations. While [CO]^.+ gives rise to three different reaction channels, [SiO]^.+ reacts only by hydrogen‐atom transfer (HAT) from methane under thermal conditions. A theoretical analysis of the respective HAT processes reveals two distinctly different mechanistic pathways for [CO]^.+ and [SiO]^.+, and a comparison to the higher metal oxides of Group 14 emphasizes the particular role of carbon as a second‐row p element.     

Boric acid in aqueous micellar medium: an effective and recyclable catalytic system for the synthesis of aryl-7,8-dihydro[1,2,4]triazolo[4,3-a]pyrimidine-6-carbonitriles

A simple, green, and efficient protocol is reported for the preparation of aryl-7,8-dihydro[1,2,4]triazolo[4,3-a]-pyrimidine-6-carbonitriles through one-pot multi component reaction using substituted aromatic aldehydes, malononitrile, and 3-amino[1,2,4]triazole. The reaction is catalyzed by boric acid in aqueous micellar condition. Present protocol incorporates environmentally non-hazardous reaction condition, easy work-up, and use of recyclable catalytic system with associated benefits like excellent yield (84–96%) and shorter reaction time (20 min). Proposed methodology offers rapid access to substituted aryl-7,8-dihydro[1,2,4]triazolo[4,3-a]pyrimidine-6-carbonitriles with high atom-economy and catalytic efficiency.     

Adaptive lambda square dynamics simulation: An efficient conformational sampling method for biomolecules

A novel, efficient sampling method for biomolecules is proposed. The partial multicanonical molecular dynamics (McMD) was recently developed as a method that improved generalized ensemble (GE) methods to focus sampling only on a part of a system (GEPS); however, it was not tested well. We found that partial McMD did not work well for polylysine decapeptide and gave significantly worse sampling efficiency than a conventional GE. Herein, we elucidate the fundamental reason for this and propose a novel GEPS, adaptive lambda square dynamics (ALSD), which can resolve the problem faced when using partial McMD. We demonstrate that ALSD greatly increases the sampling efficiency over a conventional GE. We believe that ALSD is an effective method and is applicable to the conformational sampling of larger and more complicated biomolecule systems. © 2013 Wiley Periodicals, Inc.     

Recent Progress on Transition Metal Catalyst Separation and Recycling in ATRP

Atom transfer radical polymerization (ATRP) is a versatile and robust tool to synthesize a wide spectrum of monomers with various designable structures. However, it usually needs large amounts of transition metal as the catalyst to mediate the equilibrium between the dormant and propagating species. Unfortunately, the catalyst residue may contaminate or color the resultant polymers, which limits its application, especially in biomedical and electronic materials. How to efficiently and economically remove or reduce the catalyst residue from its products is a challenging and encouraging task. Herein, recent advances in catalyst separation and recycling are highlighted with a focus on (1) highly active ppm level transition metal or metal free catalyzed ATRP; (2) post‐purification method; (3) various soluble, insoluble, immobilized/soluble, and reversible supported catalyst systems; and (4) liquid‐liquid biphasic catalyzed systems, especially thermo‐regulated catalysis systems.

     

Tuning Deazaflavins Towards Highly Potent Reducing Photocatalysts Guided by Mechanistic Understanding – Enhancement of the Key Step by the Internal Heavy Atom Effect

Deazaflavins are well suited for reductive chemistry acting via a consecutive photo-induced electron transfer, in which their triplet state and semiquinone – the latter is formed from the former after electron transfer from a sacrificial electron donor – are key intermediates. Guided by mechanistic investigations aiming to increase intersystem crossing by the internal heavy atom effect and optimising the concentration conditions to avoid unproductive excited singlet reactions, we synthesised 5-aryldeazaflavins with Br or Cl substituents on different structural positions via a three-component reaction. Bromination of the deazaisoalloxazine core leads to almost 100 % triplet yield but causes photo-instability and enhances unproductive side reactions. Bromine on the 5-phenyl group in ortho position does not affect the photostability, increases the triplet yield, and allows its efficient usage in the photocatalytic dehalogenation of bromo- and chloroarenes with electron-donating methoxy and alkyl groups even under aerobic conditions. Reductive powers comparable to lithium are achieved.     

Highly Efficient Oxygen Reduction Reaction Fe-N-C Cathode in Long-durable Direct Glycol Fuel Cells

The oxygen reduction reaction in direct glycol fuel cells heavily relies on noble metal-based electrocatalysts. In this work, novel Pt group metal-free catalysts based on porous Fe-N-C materials are successfully synthesized as catalysts with high activity and durability for the cathode oxygen reduction reaction (ORR). Through the encapsulation of NH₄SCN salt, the surface elements and pore structure of the catalyst are effectively changed, and the active sites of Fe effectively are increased. The half-wave potential of the best Fe-N-C catalyst was –0.02 V vs. Hg/HgO in an alkaline environment. The porous Fe-N-C catalyst possesses a large specific surface area(1158 m²/g) and shows good activity and tolerance to glycol. The direct glycol fuel cell with the Fe-N-C cathode achieved a maximum power density of 62.2 mW/cm² with 4 mol/L KOH and 4 mol/L glycol solution at 25 °C and maintained discharge for more than 250 h at a 50 A/cm² current density.     

Atom-economic Approach to the Synthesis of α-(Hetero)aryl-substituted Furan Derivatives from Biomass

An atom-economic ring construction approach to the synthesis of α-(hetero)arylfurans based on renewable furanic platform chemicals has been developed. Corresponding compounds have been prepared in good to excellent yields via [2+2+2] and [4+2] cycloaddition reactions using metal-catalyzed or photoredox protocols. Easily available HMF-based 2-hydroxymethyl-5-ethynylfuran and 2-hydroxymethyl-5-cyanofuran were used as starting materials. A synthetic route with an improved carbon economy factor has been implemented to achieve sustainability aim. The possible application of arylfurans as molecular conductors has been investigated by DFT calculations, which revealed excellent charge transfer properties. As a future perspective, integration of biomass processing strategy into manufacturing of molecular electronics was pointed out to achieve the aim of sustainability.     

On the potentiality of a cluster-beam source to produce free-standing one-dimensional and two-dimensional FeAg nanostructures: mechanisms underlying their shape genesis

Controlling the morphology and composition of one-dimensional (1D) and two-dimensional (2D) assemblies of matter is essential to design and create nanostructures with exceptional material properties, for applications ranging from nanoelectronics to nanomedicine. Within this latter, a great interest is placed on assembling magnetoplasmonic nanostructures to enable multimodal biosensing and bioimaging for early diagnosis and prognosis of diseases. To date, the synthesis of such complex nanostructures is mostly relying on wet chemistry and templates. Herein, we employed a templateless physical method to generate FeAg-based anisotropic nanostructures, using a modified cluster source. Under tuned experimental conditions, we demonstrated the successful magnetic-assisted assembly of Fe nanoclusters (Fe NCs), to form stable and permanent branched Fe nanorods (Fe NRs), core@shell Fe@Ag-NRs, Fe nanosheets (Fe NSs), and Fe/Ag-NSs. This assembly is driven by the need to reduce their magnetic interaction energy on one hand and their overall surface energy on the other hand. When NCs and NRs are magnetically brought into intimate contact, they undergo a coalescence process, through the interfacial diffusion of the surface atoms, resulting in the formation of 1D and 2D nanostructures. For Fe@Ag NRs, the advantage conferred by the Ag shell is to protect Fe NRs from oxidation and prevent them from aggregation at the same time. The observed contrast reversal in Scanning Electron Microscopy (SEM) images of Fe NRs and Fe NSs is discussed.