Relationship between third-order nonlinear optical properties and magnetic interactions in open-shell systems: a new paradigm for nonlinear optics

Although most third-order nonlinear optical (NLO) materials are closed-shell singlet systems, this Letter theoretically shows that the third-order NLO properties are drastically enhanced in symmetric open-shell diradical systems with intermediate diradical character and further reveals that this enhancement is associated with the ferromagnetic and antiferromagnetic interactions. This new paradigm opens up a promising area for designing new third-order NLO materials.     

Lewis acid-catalyzed conjugate addition-cyclization reactions of ethenetricarboxylates with substituted propargyl alcohols: stereoselectivity in the efficient one-pot synthesis of methylenetetrahydrofurans

Oxygen-containing heterocyclic systems are important structures in organic chemistry because of their presence in many biologically active compounds. In this work, a Lewis acid-catalyzed cyclization of ethenetricarboxylate derivatives 1 with substituted propargyl alcohols to give methylenetetrahydrofurans was investigated. Reaction of 1 and gamma-silicon-substituted propargyl alcohols 4 with ZnBr2 at 80-110 degrees C led to (Z)-silicon-substituted products stereoselectively. Reaction of 1 and gamma-ester-substituted propargyl alcohol 7 in the presence of various Lewis acids gave ester-substituted methylenetetrahydrofurans stereoselectively. Interesting Lewis acid dependency on stereoselectivity for the reaction of 7 was found. Reaction of alpha-substituted propargyl alcohols also gave cyclized products.     

Development of a highly specific rhodamine-based fluorescence probe for hypochlorous acid and its application to real-time imaging of phagocytosis

The tetramethylrhodamine (TMR) fluorophore is a useful platform for fluorescence probes, being applicable, for example, to biological investigations utilizing fluorescence microscopy, owing to its excellent photochemical properties in aqueous media. We have developed new TMR derivatives that show different dependences of their behavior upon the environment. Among them, HMTMR showed unique characteristics, and its putative spirocyclic structure was confirmed by X-ray crystallography. Utilizing this discovery, we have established a strategy to modulate the fluorescence of TMR by regulating the spirocyclization, and we have obtained a new fluorescence probe that can detect hypochlorous acid specifically. This probe, HySOx, can work in 99.9% aqueous solution at pH 7.4 and was confirmed to be able to detect hypochlorous acid being generated inside phagosomes in real time. HySOx is tolerant to autoxidation and photobleaching under bioimaging conditions. Regulation of the spirocyclization of rhodamines, as we describe here, provides a new approach to the rational development of novel fluorescence probes.     

Recent advances in reactions between arynes and organosulfur compounds

The recent progress made on transformations involving the reactions between aryne intermediates and organosulfur compounds has been reviewed. A wide variety of aromatic organosulfurs are now synthesizable by generating arynes in the presence of organosulfur compounds. Organosulfurs have distinctive reactivities with arynes, which depend on the sulfur atom’s valence state, that is, S(II), S(IV), and S(VI), as well as the presence or absence of other intra- or intermolecular reactive moieties. These novel transformations have enabled the diversity-oriented synthesis of unique aromatic organosulfurs that were once difficult to prepare by the conventional methods, paving the way for the development of molecules that are beneficial across numerous disciplines, including pharmaceutical science and materials science.     

Development of modulating permanent magnet sextupole lens for focusing of pulsed cold neutrons

Modulating permanent magnet sextupole lens (PMSx) for focusing pulsed cold neutrons is under development. The synchronized modulation of its field gradient suppresses the chromatic aberration which arises from the Time Of Flight method. The strength of the magnetic field, the torque, and the rise of temperature during its operation are studied on a fabricated prototype. Experiments on focusing pulsed very cold neutrons (VCN) at ILL (Institute of Laue Langevin, France) were carried out and VCN with around λ=40 Å were focused by the PMSx at a focal length of about 0.5 m. The experimental results are presented in conjunction with the principle of the neutron focusing and the modulating method of the focal strength of permanent magnet lens with the double ring structure.     

Origin of the enhancement of the second hyperpolarizability of singlet diradical systems with intermediate diradical character

The origin of the diradical character dependence of the second hyperpolarizability (gamma) of neutral singlet diradical systems is clarified based on the perturbation formula of gamma using the simplest diradical molecular model with different diradical characters, i.e., H2 under bond dissociation. The enhancement of gamma in the intermediate diradical character region turns out to originate from the increasing magnitude of the transition moment between the first and second excited states and the decrease of that between the ground and first excited states, respectively, with the increase in diradical character. This feature confirms that open-shell singlet conjugated molecules with intermediate diradical characters constitute a new class of third-order nonlinear optical systems, whose gamma values can be controlled by the diradical character in addition to the conjugation length.     

Synthesis of a coumarin compound from phenanthrene by a TiO2-photocatalyzed reaction

Phenanthrene was converted into a coumarin compound by a TiO2-photocatalyzed reaction in an acetonitrile solution containing 8 wt% water and molecular oxygen in 45% yield.     

Cross-Coupling of Aryllithiums with Aryl and Vinyl Halides in Flow Microreactors

The use of Pd catalysts that contained a carbene ligand, such as PEPPSI-SIPr, speeded up the Murahashi coupling of ArLi with ArBr, by enabling its integration with the Br/Li exchange of ArBr with BuLi in flow. Space integration realized the rapid cross-coupling of two different ArBr substrates. However, the cross-coupling reaction with vinyl halides could not be achieved under similar conditions. Pd(OAc)₂ was an effective catalyst, and the space integration of the Br/Li exchange of ArBr with BuLi and the Murahashi coupling with vinyl halides was successfully achieved.     

Hydrolysis of aromatic polyurethane in water under high pressure of CO2

We have demonstrated a hydrolysis reaction of polyurethane (PU) under high pressure of carbon dioxide (CO₂) in water. We employed the PU sample, poly(methylene bis‐(1,4‐phenylene)hexamethylene dicarbamate), denoted as M‐PU, which was synthesized from 4,4′‐diphenyl methane diisocyanate and 1,4‐butane diol (BD). The optimum hydrolysis reaction condition was 190 °C under CO₂ pressures over 4.1 MPa in water medium, and 93% hydrolysis of M‐PU was achieved. After the reaction, the water‐soluble parts were obtained, and isolated by column chromatography. The isolated products were 4,4′‐methylenedianiline (MDA) and 1,4‐butane diol (BD), which were components of repeating unit of M‐PU. In addition, the hydrolysis reaction gave no byproduct. This hydrolysis under high pressure of CO₂ with water is a reaction by which M‐PU is selectively hydrolyzed into MDA and BD by cleaving urethane linkage. Moreover, the resulting hydrolyzed products were easily obtained by evaporation of aqueous layer after the reaction, indicating an efficient chemical recycling of PU was achieved. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 2004–2010