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     

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.     

Imaging of enzyme activity by scanning electrochemical microscope equipped with a feedback control for substrate-probe distance

The enzymatic activity of diaphorase (Dp) immobilized on a solid substrate was characterized using a scanning electrochemical microscope (SECM) with shear force feedback to control the substrate-probe distance. The shear force between the substrate and the probe was monitored with a tuning fork-type quartz crystal and used as the feedback control to set the microelectrode probe close to the substrate surface. The sensitivity and the contrast of the SECM image were improved in the constant distance mode (distance, 50 nm) with the shear force feedback compared to the image in the constant height mode without the feedback. By using this system, the SECM and topographic images of the immobilized diaphorase were simultaneously measured. The microelectrode tip used in this study was ground aslant like a syringe needle in order to obtain the shaper topographic images. This shape was also effective for avoiding the interference during the diffusion of the enzyme substrates.     

Dynamic anisotropy and heterogeneity of polystyrene thin films as studied by inelastic neutron scattering

We studied the dynamic anisotropy and heterogeniety of polystyrene thin films in glassy state with inelastic neutorn scattering. Adjusting the scattering vector to the directions parallel and perpendicular to the film surface, we observed the elastic scattering intensities as a function of temperature. It was found for the 200 A film that the elastic intesity decreased with increasing temperature more rapidly in the perpendicular direction than in the pararell direction, showing the higher mobility in the perpendicular direction. However, such dynamical anisotropy was not observed in the 1000 A film. The decrease in the mobility was observed with the film thickness in both the directions. These results were explained in terms of an interface hard layer. We also evelauated the dynamical heterogeniety from the non-Gaussian parameter A0, which increased with decreasing the film thickness, showing the increase in the dynamical heterogeneity. Assuming a simple bi-layer model consisting of the interface hard layer and the bulk-like layer, we analyzed the thickness dependence of the non-Gaussian parameter A0 and the mean square displacement (u2) to find that the hard layer has a thickness of approximately 130 A and a mean square displacement of approximately 0.018 A2 at 230 K.     

Extended studies of the automated odor-sensing system based on plural semiconductor gas sensors with computerized pattern recognition techniques

The odor-sensing system reported earlier is used to measure odors of 47 compounds. Three computerized pattern recognition techniques, the k-NN, simplex and potential function methods, are applied to the data set for the prediction of the odors of the corresponding compounds. The best prediction results (80.9%) were obtained by means of the potential function method.     

Lower critical solution temperature type of phase separation in aqueous mixture of polyelectrolytes

Phase separation behavior in aqueous mixture of different polyelectorolytes having like charges has been investigated as functions of concentration and charge density. When the charge densities of both polyelectorolytes were equally high, the compatibility between different polyelectorolytes was relatively good and the phase separation behavior was a normal upper critical solution temperature (UCST) type. With decreasing the charge density of one polyelectorolyte keeping the charge density of another polyelectrolyte unchanged, the compatibility between different polyelectorolytes became poorer. When the charge density of one polyelectorolyte was lowered below a certain value, the phase separation behavior suddenly changed from the UCST type to a lower critical solution temperature (LCST) type.     

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.     

Light scattering and dielectric relaxation studies of glass forming liquids

Extended Abstract: Glass forming organic liquids and polymers exhibit long range density fluctuations with correlation length ξ in the range of 10–300 nm at temperatures above T_g (1 - 6). This follows from dynamic and static light scattering experiments revealing some unexpected features, which cannot be explained on the basis of conventional liquid state theories: (i) In static light scattering the intensity I(q → 0) is no longer proportional to the isothermal compressibility, (ii) This excess scattering I_exc shows a strong q-dependence (q = (4π/Λ.)sin(θ/2)) corresponding to a correlation length ξ in the above mentioned range, (iii) The Landau-Placzek ratio I_Rayleigh/2I_Brillouin is much too high compared with the results of light scattering theories, (iv) In photon correlation spectroscopy a new ultraslow hydrodynamic mode (Γ ˜ q²) is detected with relaxation rates Γ about 10⁻⁶ to 10⁻⁹ lower than those of the α-process at a given temperature. In order to explain these observations, a two-state fluid model is proposed, which starts from the coexistence of “liquid-like” and “aperiodic solid-like” regions within the liquids. Such ideas have been discussed many times before, so for example A.R. Ubbelohde (7) speculates about “anticrystalline” clusters in liquids. Molecular dynamics simulations of atomic liquids showed that long range orientational fluctuations appear upon supercooling (8). A preferred icosahedral ordering is observed (9) and the number of icosahedral clusters increases with decreasing temperature (10). In connection with the interpretation of the dynamics of supercooled liquids different “two-state” models have been proposed (11 - 15). For the explanation of the light scattering results we propose that the molecules in the different dynamic states (“liquid” or “solid”) aggregate during annealing of the liquid at temperatures above T_g. Experiments showed that the equilibration times can be rather long (3 - 5), but nevertheless the liquids exhibiting long range density fluctuations are in the state of lowest free energy. We claim that our observations are the first experimental proof of the existence of such different dynamic states, which have been discussed many times before. The extended secondary clusters can also be detected by ultra small angle X-ray scattering.     

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.     

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.