Direct measurements of HOx radicals in the marine boundary layer: testing the current tropospheric chemistry mechanism

OH and HO(2) radicals, atmospheric detergents, and the reservoir thereof, play central roles in tropospheric chemistry. In spite of their importance, we had no choice but to trust their concentrations predicted by modeling studies based on known chemical processes. However, recent direct measurements of these radicals have enabled us to test and revise our knowledge of the processes by comparing the predicted and observed values of the radical concentrations. We developed a laser-induced fluorescence (LIF) instrument and successfully observed OH and HO(2) at three remote islands of Japan (Oki Island, Okinawa Island, and Rishiri Island). At Okinawa Island, the observed daytime level of HO(2) agreed closely with the model estimates, suggesting that the photochemistry at Okinawa is well described by the current chemistry mechanism. At Rishiri Island, in contrast, the observed daytime level of HO(2) was consistently much lower than the calculated values. We proposed that iodine chemistry, usually not incorporated into the mechanism, is at least partly responsible for the discrepancy in the results. At night, HO(2) was detected at levels greater than 1 pptv at all three islands, suggesting the presence of processes in the dark that produce radicals. We showed that ozone reactions with unsaturated hydrocarbons, including monoterpenes, could significantly contribute to radical production.     

Kinetic Studies of Heterogeneous Reaction of HO2 Radical by Dicarboxylic Acid Particles

The HO₂ uptake coefficients (γ) for organic submicron aerosol particles were measured using an aerosol flow tube coupled with a chemical conversion/laser‐induced fluorescence technique under ambient conditions (760 Torr and 296 ± 2 K) and different values of relative humidity (RH) (28% and 68%). Determined uptake coefficients for succinic, glutaric, adipic, and pimelic acid aerosol particles at 28% RH were 0.07 ± 0.02, 0.07 ± 0.03, 0.02 ± 0.01, and 0.06 ± 0.03, respectively, whereas the γ values for those particles at 68% RH were 0.18 ± 0.07, 0.15 ± 0.04, 0.06 ± 0.01, and 0.13 ± 0.04, respectively. An increase in γ with increasing RH was observed for all the dicarboxylic acids, suggesting a contribution by water amount in the particle, aqueous phase chemistry, and uptake of HO₂–H₂O. The anomalously low γ values for adipic acid are likely related to its high crystallization RH and thus provide a new clue that the water amount and/or RH have a significant influence on HO₂ uptake.     

Partially bio‐based tri‐ and hexaallyl monomers: Synthesis from naturally occurring myo‐inositol and polyaddition with dithiols

myo‐Inositol, a naturally occurring cyclic hexaol, was converted to 2,4,6‐tri‐O‐allyl‐myo‐inositol and 1,2,3,4,5,6‐hexa‐O‐allyl‐myo‐inositol. Polyaddition of the former product, a tri(allyl ether) bearing three hydroxyl groups, with dithiols yielded the corresponding networked polymers. Their glass transition temperatures (T_gs) were higher than those of networked polymers formed by the polyaddition of 1,3,5‐tri‐O‐methyl‐2,4,6‐tri‐O‐allyl‐myo‐inositol. This implied the reinforcement of the networks by hydrogen bonding between the hydroxyl groups. Polyaddition of the latter product, a hexa(allyl ether), with dithiols yielded the corresponding networked polymers with much higher T_gs than those of all of the aforementioned networked polymers. This implied that efficient use of the hexafunctional monomer leads to the formation of more densely crosslinked polymers. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 1524–1529     

Palladium‐Catalyzed Direct Thiolation of Aryl CH Bonds with Disulfides

A catalytic variant of the direct thiolation of arenes, bearing directing groups, with disulfides or thiols has been developed under palladium and copper co‐catalysis. Both sulfenyl moieties of the disulfide could be incorporated into the thiolated products, therefore, the reactions reached completion with only half an equivalent of disulfide, with respect to the starting arene. Experimental evidence suggested that the reaction proceeds through a Pd^II/Pd^IV mechanism.     

Magnetic relaxations of antiferromagnetic nanoparticles in magnetic fields

We reexamine anomalous magnetic relaxations of ferritin in magnetic fields, the presence of which has been regarded as evidence suggesting the existence of thermally assisted macroscopic quantum tunneling in antiferromagnetic nanoparticles. In the present study, relaxation curves of ferritin are examined using an approach that is free from assumptions regarding distributions of various parameters of polydispersive particles. The results are not anomalous. In other words, the relaxation is accelerated by the field, as expected for classical superparamagnetic fluctuations.     

High-Quality Protein Crystal Growth of Mouse Lipocalin-Type Prostaglandin D Synthase in Microgravity

Lipocalin-type prostaglandin (PG) D synthase (L-PGDS) catalyzes the isomerization of PGH(2) to PGD(2) and is involved in the regulation of pain and of nonrapid eye movement sleep and the differentiation of male genital organs and adipocytes, etc. L-PGDS is secreted into various body fluids and binds various lipophilic compounds with high affinities, acting also as an extracellular transporter. Mouse L-PGDS with a C65A mutation was previously crystallized with citrate or malonate as a precipitant, and the X-ray crystallographic structure was determined at 2.0 ? resolution. To obtain high-quality crystals, we tried, unsuccessfully, to crystallize the C65A mutant in microgravity under the same conditions used in the previous study. After further purifying the protein and changing the precipitant to polyethylene glycol (PEG) 8000, high-quality crystals were grown in microgravity. The precipitant solution was 40% (w/v) PEG 8000, 100 mM sodium chloride, and 100 mM HEPES-NaOH (pH 7.0). Crystals grew on board the International Space Station for 11 weeks in 2007, yielding single crystals of the wild-type L-PGDS and the C65A mutant, both of which diffracted at around 1.0 ? resolution. The crystal quality was markedly improved through the use of a high-viscosity precipitant solution in microgravity, in combination with the use of a highly purified protein.     

Sensitized luminescence properties of dinuclear lanthanide macrocyclic complexes bearing a benzophenone antenna

Dinuclear lanthanide (Ln=Tb³⁺ or Eu³⁺) complexes (Ln₂L2) of two octadentate macrocyclic polyaminopolycarboxylic ligands connected through a benzophenone (BP) moiety (L2) have been synthesized. Sensitized luminescence properties of Ln₂L2 in water have been studied in comparison to those of BP-conjugated mononuclear Ln complexes (LnL1). The luminescence intensity of Tb₂L2 is lower than that of TbL1 because of lower triplet quantum yield of the BP moiety. In contrast, Eu₂L2 shows higher intensity than EuL1. For both Eu complexes, energy level of triplet excited-state BP (³BP*) is only 3 kJ mol⁻¹ higher than that of ⁵D₂ excited-state of Eu³⁺. The ⁵D₂ state formed by a triplet-energy transfer (TET) from ³BP* is therefore deactivated by a back energy transfer (BET) to the ground-state BP, resulting in low luminescence intensity of EuL1. In contrast, within Eu₂L2, TET from ³BP* to ⁵D₀ state of two Eu³⁺ ions is accelerated, thus leading to higher luminescence intensity. Another notable feature of Eu₂L2 is the luminescence quantum yield independent of its concentration. In contrast, for EuL1 system, an intermolecular BET occurs from ⁵D₂ state of Eu³⁺ to the ground-state BP conjugated to another EuL1 complex, resulting in a yield decrease with the concentration increase.     

Hybrid molecular material exhibiting single-molecule magnet behavior and molecular conductivity

Two unique materials based on Mn4 single-molecule magnet (SMM) clusters (ST=9) and integer or non-integer average valent platinum maleonitriledithiolate (mnt2-) complexes, [{MnII2MnIII2(hmp)6(MeCN)2}{Pt(mnt)2}2][Pt(mnt)2]2.2MeCN (1) and [{MnII2MnIII2(hmp)6(MeCN)2}{Pt(mnt)2}4][Pt(mnt)2]2 (2), were synthesized by the material diffusion method and electrochemical oxidation, respectively (hmp-=2-hydroxymethylpyridinate). 1 and 2 are comprised of four and six [Pt(mnt)2]n- units, respectively, in addition to a common MnII2MnIII2 double-cuboidal unit, [MnII2MnIII2(hmp)6(MeCN)2]4+ (hereinafter [Mn4]4+). Among the [Pt(mnt)2]n- units, two units in 1 and four units in 2 are coordinated with the [Mn4]4+ unit, forming a 1D chain of {-[Mn4]-[Pt(mnt)2]2-} for 1 and a discrete subunit of {[Pt(mnt)2]2-[Mn4]-[Pt(mnt)2]2} for 2. The other two [Pt(mnt)2]n- units, occupying void space of the packing, form a stacking column with the coordinating [Pt(mnt)2]n- units, finally constructing hybrid frames of aggregates consisting of [Mn4]4+ units and [Pt(mnt)2]n- units. Electronic conductivity measurements revealed that 1 is an insulator and 2 is a semiconductor with sigma=0.22 S.cm(-1) at room temperature and an activation energy of 136 meV. Detailed magnetic measurements proved that the [Mn4]4+ units in 1 and 2 behave as SMMs with an ST=9 ground state at low temperatures. There is no significant interaction between [Mn4]4+ units and [Pt(mnt)2]n- units, but interactions between localized spins of [Pt(mnt)2]n- were detected even in 2 at low temperatures where the conductivity is electronically insulated. 2 is the first example of a hybridized material exhibiting SMM behavior and electronic conductivity.     

Ruthenium-catalyzed [1,n]-metallotropic shift (n = 3, 5) of alkynyl carbene complex intermediates

The ruthenium-catalyzed isomerization of diynes and triynes involving propargyl carboxylate moieties affords dienynes and dienediynes, respectively. The [1,n]-metallotropic shift (n = 3, 5) (carbene walk) of in situ generated alkynyl carbene complexes has been proposed for the catalytic isomerization reaction.     

Photo‐Electrochemical C−H Bond Activation of Cyclohexane Using a WO3 Photoanode and Visible Light

The photo‐electrochemical C?H bond activation of cyclohexane to produce cyclohexanol and cyclohexanone (KA oil) with high partial oxidation selectivity (99 %) and high current utilization ratio (76 %) was achieved in air at room temperature at atmospheric pressure. The production rate of KA oil was accelerated by applying a bias. The incident photon to current efficiencies at 365 and 420 nm were 57 % and 24 %, respectively.