Synthesis of furan-substituted aza-BODIPYs having near-infrared emission

Development of near-infrared-emissive aza-boron dipyrromethene (aza-BODIPY) derivatives having furanyl groups is reported. From the optical measurements, it was clearly indicated that the emission bands were presented in the longer wavelength region than those of the conventional aza-BODIPYs. The emission bands with the peaks at 730 nm and 758 nm were observed from the bis- and tetra-substituted furanyl aza-BODIPYs with similar extents of emission efficiencies, respectively. According to the computer calculations, it was proposed that molecular planarity could be enhanced in the case of the furan groups. As a result, band-gap energy could be lowered comparing to those of the conventional benzene and thiophene-substituted aza-BODIPYs.     

Principles of Aggregation-Induced Emission: Design of Deactivation Pathways for Advanced AIEgens and Applications

Twenty years ago, the concept of aggregation-induced emission (AIE) was proposed, and this unique luminescent property has attracted scientific interest ever since. However, AIE denominates only the phenomenon, while the details of its underlying guiding principles remain to be elucidated. This minireview discusses the basic principles of AIE based on our previous mechanistic study of the photophysical behavior of 9,10-bis(N,N-dialkylamino)anthracene ( BDAA ) and the corresponding mechanistic analysis by quantum chemical calculations. BDAA comprises an anthracene core and small electron donors, which allows the quantum chemical aspects of AIE to be discussed. The key factor for AIE is the control over the non-radiative decay (deactivation) pathway, which can be visualized by considering the conical intersection (CI) on a potential energy surface. Controlling the conical intersection (CI) on the potential energy surface enables the separate formation of fluorescent (CI:high) and non-fluorescent (CI:low) molecules [control of conical intersection accessibility ( CCIA )]. The novelty and originality of AIE in the field of photochemistry lies in the creation of functionality by design and in the active control over deactivation pathways. Moreover, we provide a new design strategy for AIE luminogens (AIEgens) and discuss selected examples.     

Crystal field effect on X-ray magnetic circular dichroism spectra at the L<Subscript>2,3</Subscript> absorption edges of mixed-valence Ce and Yb compounds in high magnetic fields

A theoretical study is presented, with an extended single impurity Anderson model, for the crystal field effect on the X-ray magnetic circular dichroism (XMCD) spectra at L_2,3 edges of mixed-valence Ce and Yb compounds in high magnetic fields. The crystal field acting on the 4f electrons is assumed to have cubic symmetry. Due to the competition among the effects of crystal field, mixed valency, and external magnetic field, the magnetic-field-dependence of XMCD spectra exhibits a variety of features; for instance, the branching ratio, R(L₂/L₃), of L₂ and L₃ XMCD intensities of Ce compounds can take R(L₂/L₃) > 1.0 and <1.0, and that of Yb compounds can take R(L₂/L₃) > 0 and <0. It is shown that the magnetic-field-dependence of the total XMCD intensity I(L₂ + L₃) is proportional to the magnetization curve, but that of R(L₂/L₃) gives more precise information on the ground state wavefunction in magnetic fields. A new and useful method to correlate the XMCD spectra, the 4f magnetization and the ground state wavefunction is proposed and used to discuss the relation between I(L₂ + L₃) and the magnetization curve and that between R(L₂/L₃) and the ground state wavefunction.     

Effective methods for the measurement of CsI cluster ions using MALDI‐MS with suitable solvent combinations and additives

A method to measure CsI cluster ions ((CsI)_nCs⁺, (CsI)_nI^?) from CsI samples in matrix‐assisted laser desorption/ionization mass spectrometry (MALDI‐MS) was developed with a 2‐[(2E)‐3‐(4‐tert‐butylphenyl)‐2‐methylprop‐2‐enylidene] malononitrile (DCTB) matrix and additives. Solvent combinations in which the CsI and DCTB solutions were miscible were effective in detecting CsI cluster ions at a mass range of over m/z 2000 and are associated with a characteristic spread of DCTB within the CsI/DCTB mixture. The addition of saccharides or sugar alcohols to the CsI/DCTB mixture improved the DCTB distribution and widened the mass distribution of CsI cluster ions up to m/z 10 000 in the linear mode. Copyright © 2014 John Wiley & Sons, Ltd.     

PhI(OAc)2‐Mediated Radical Trifluoromethylation of Vinyl Azides with Me3SiCF3

The fluorine‐containing organic motif is becoming privileged in pharmaceuticals, agrochemicals, and functional materials, owing to its unique properties such as electron‐withdrawing character, metabolic stability, and lipophilicity. Described herein is the PhI(OAc)₂‐mediated radical trifluoromethylation of vinyl azides with Me₃SiCF₃ to efficiently generate α‐trifluoromethyl azines. The resulting α‐trifluoromethyl azines were successfully transformed to valuable fluorine‐containing molecules such as α‐trifluoromethyl ketones, β‐trifluoromethyl amines, 5‐fluoropyrazoles, and trifluoroethyl isoquinolines.     

Sunlight‐Driven Hydrogen Peroxide Production from Water and Molecular Oxygen by Metal‐Free Photocatalysts

Design of green, safe, and sustainable process for the synthesis of hydrogen peroxide (H₂O₂) is a very important subject. Early reported processes, however, require hydrogen (H₂) and palladium‐based catalysts. Herein we propose a photocatalytic process for H₂O₂ synthesis driven by metal‐free catalysts with earth‐abundant water and molecular oxygen (O₂) as resources under sunlight irradiation (λ>400 nm). We use graphitic carbon nitride (g‐C₃N₄) containing electron‐deficient aromatic diimide units as catalysts. Incorporating the diimide units positively shifts the valence‐band potential of the catalysts, while maintaining sufficient conduction‐band potential for O₂ reduction. Visible light irradiation of the catalysts in pure water with O₂ successfully produces H₂O₂ by oxidation of water by the photoformed valence‐band holes and selective two‐electron reduction of O₂ by the conduction band electrons.     

Theory of XMCD spectra at the L2,3 absorption edges of mixed valence Ce and Yb compounds in high magnetic fields

We examine the structure of aggregates formed due to DNA interaction with dipalmitoylphosphatidylcholine (DPPC) in presence of Ca²⁺ and Zn²⁺ using small-angle synchrotron X-ray diffraction (SAXD) and neutron scattering (SANS). SAXD shows structural heterogeneity as a function of the cation concentration and temperature: At low cation concentration (∼1 mM), aggregates show two DPPC phases, one with a lateral segregation of DNA and cation, while higher cation concentration improves the DNA packing and the condensed lamellar phase is observed in DNA+DPPC+20mMion²⁺ aggregates. The SANS detected the dissolution of the condensed lamellar phase into unilamellar DPPC+Zn²⁺ vesicles due to gel ↦ liquid-crystal phase transition in DNA+DPPC+20mM Zn²⁺ aggregates with the short fragmented salmon sperm DNA.     

Muon science in J-PARC

The intensity of proton accelerator has attained to the order to mega-watt, and several MW-class proton accelerators start to operate in the world. J-PARC is a complex of three accelerators, and generates a variety of secondary beams, i.e. muon beam, neutron beam, meson beam and neutrino beam. The muon facility is established in order to provide a pulsed muon beam for various experimental programs. The first muon beam is transported to the experimental area in September 2008. Although the accelerator is still under commissioning, and the beam power doesn’t reach the design value of 1 MW yet, the world strongest pulsed muon beam will be provided shortly. In this paper, we review the muon beam line in J-PARC, and discuss evolved scientific programs.     

Heat capacities of the electron acceptor 7,7,8,8-tetracyano- quinodimethane (TCNQ) and its radical-ion salt NH4(TCNQ) showing spin-Peierls transition

Heat capacities of the electron acceptor 7,7,8,8-tetracyanoquinodimethane (TCNQ) and its radical-ion salt NH₄-TCNQ have been measured at temperatures in the 12-350 K range by adiabatic calorimetry. A λ-type heat capacity anomaly arising from a spin-Peierls (SP) transition was found at 301.3 K in NH₄-TCNQ. The enthalpy and entropy of transition are Δ_trsH=(667±7) J mol⁻¹ and Δ_trsS=(2.19±0.02) J K⁻¹ mol⁻¹, respectively. The SP transition is characterized by a cooperative coupling between the spin and the phonon systems. By assuming a uniform one-dimensional antiferromagnetic (AF) Heisenberg chains consisting of quantum spin (S=1/2) in the high-temperature phase and an alternating AF nonuniform chains in the low-temperature phase, we estimated the magnetic contribution to the entropy as Δ_trsS_mag=0.61 J K⁻¹ mol⁻¹ and the lattice contribution as Δ_trsS_lat=1.58 J K⁻¹ mol⁻¹. Although the total magnetic entropy expected for the present compound is R ln 2 (=5.76 J K⁻¹ mol⁻¹), a majority of the magnetic entropy (∼4.6 J K⁻¹ mol⁻¹) persists in the high-temperature phase as a short-range-order effect. The present thermodynamic investigation quantitatively revealed the roles played by the spin and the phonon at the SP transition. Standard thermodynamic functions of both compounds have also been determined.     

Synthesis of 2,6-di(1,8-naphthyridin-2-yl)pyridines functionalized at the 4-position: Building blocks for suitable metal complex-based dyes

This study reports the synthesis of a methoxy-substituted 2,6-di(1,8-naphthyridin-2-yl)pyridine using Friedländer methodology. The functionalization at the 4-carbon of the methoxy-substituted derivative was confirmed by X-ray structural analysis. Finally, the methyl ether protecting group was cleaved to obtain 2,6-di(1,8-naphthyridin-2-yl)pyridine-4-ol. Using the compounds, coordination behavior to ruthenium(II) center was also examined.