Reaction of indium ate complexes with allylic compounds. Controlling SN2/SN2′ selectivity by solvents

Vinyl and methylindium ate complexes (indates) were prepared and both the tendency of immigration and regioselectivity toward cinnamyl bromide were investigated. The vinyl group was more preferably transferred than the Me group, giving a regioisomeric mixture of S_N2 and S_N2′ products. The ratio of S_N2/S_N2′ selectivity can be controlled by solvents; in the presence of polar solvents, such as N-butylpyrrolidone (NBP) and THF, the S_N2′ product was mainly obtained, whereas the S_N2 product was selectively prepared in solutions containing hexane. The vinylindium compound, generated by the reaction of allylic-type diindium reagents with imine, was also converted to the corresponding vinyl indate, which was allowed to react with allyl chloride to give a three-component coupling product.     

Kinetic study of the γ radiolysis of polyethylene

A kinetic study was made of the formation of hydrogen and trans-vinylene unsaturation in the radiolysis of polyethylene induced by γ rays with a dose rate of 6.35 × 10⁵ rad/hr at 30–100°C in vacuo. The rates of the formation of hydrogen and trans-vinylene unsaturation were described by the zero-order formation kinetics with respect to each concentration combined with the first-order disappearance. The apparent rate constant for the formation of hydrogen increased gradually with rising irradiation temperature to give the activation energy of 0.6 kcal/mole. On the other hand, those for the disappearance of hydrogen and the formation and disappearance of trans-vinylene unsaturation were almost independent of temperature. The G values for crosslinking and main-chain scission were obtained from the gel data by using the Charlesby-Pinner equation, and the activation energy of 1.5 kcal/mole was given for both of them. On the basis of these results the reactions induced by γ rays in solid polyethylene were discussed.     

Modular Synthesis of Polybenzo[b]silole Compounds for Hole‐Blocking Material in Phosphorescent Organic Light Emitting Diodes

A diversity‐oriented synthetic strategy allowed us to design a series of conjugated molecules containing multiple benzosilole units that can be utilized as efficient hole‐blocking materials for phosphorescent organic light emitting diodes (OLEDs). Some of these compounds showed a performance surpassing that of the current standard, bathocuproine. The new compounds were easily synthesized in a modular fashion from a previously reported 3‐stannyl benzosilole building unit. Studies on the properties of these compounds in solution and in the solid state indicate that they possess high electron affinity, high ionization potential, and form stable amorphous films that show high electron‐drift mobility. The correlation between their molecular properties and the efficiency of the OLED device performance is also investigated.     

Naphtho[2,1-b:6,5-b']difuran: a versatile motif available for solution-processed single-crystal organic field-effect transistors with high hole mobility

We here report naphtho[2,1-b:6,5-b']difuran derivatives as new p-type semiconductors that achieve hole mobilities of up to 3.6 cm(2) V(-1) s(-1) along with high I(on)/I(off) ratios in solution-processed single-crystal organic field-effect transistors. These features originate from the dense crystal packing and the resulting large intermolecular π-orbital overlap as well as from the small reorganization energy, all of which originate from the small radius of an oxygen atom.     

Development of an energy‐domain 57Fe‐Mössbauer spectrometer using synchrotron radiation and its application to ultrahigh‐pressure studies with a diamond anvil cell

An energy‐domain ⁵⁷Fe‐Mössbauer spectrometer using synchrotron radiation (SR) with a diamond anvil cell (DAC) has been developed for ultrahigh‐pressure measurements. The main optical system consists of a single‐line pure nuclear Bragg reflection from an oscillating ⁵⁷FeBO₃ single crystal near the Néel temperature and an X‐ray focusing device. The developed spectrometer can filter the Doppler‐shifted single‐line ⁵⁷Fe‐Mössbauer radiation with a narrow bandwidth of neV order from a broadband SR source. The focused incident X‐rays make it easy to measure a small specimen in the DAC. The present paper introduces the design and performance of the SR ⁵⁷Fe‐Mössbauer spectrometer and its demonstrative applications including the newly discovered result of a pressure‐induced magnetic phase transition of polycrystalline ⁵⁷Fe₃BO₆ and an unknown high‐pressure phase of Gd⁵⁷Fe₂ alloy placed in a DAC under high pressures up to 302 GPa. The achievement of Mössbauer spectroscopy in the multimegabar range is of particular interest to researchers studying the nature of the Earth's core.     

Characterization of alkyl monolayer covalently bonded to Si(111) and soft-landing of vanadium-benzene sandwich clusters onto the alkyl monolayer substrate

A hexadecyl monolayer covalently attached to Si(111) surfaces (C₁₆–Si(111)) was prepared at 200 ^○C from 1-hexadecene. Formation of the monolayer was characterized by water contact angle measurement, attenuated total reflection infrared (ATR-IR) spectroscopy, and X-ray photoelectron spectroscopy (XPS). Gas phase synthesized vanadium (V)-benzene (Bz) 1:2 (VBz₂) sandwich clusters were size-selectively deposited onto the C₁₆–Si(111) substrate thus prepared and an oxidized Si substrate. Investigation of the resultant clusters was implemented by thermal desorption spectroscopy (TDS). About 30 K increase in threshold desorption temperature of the landed clusters was observed on going from the oxidized Si to the C₁₆–Si(111) substrate, a result indicating that the clusters are more strongly bound to the C₁₆–Si(111) than to the oxidized Si. This result was explained by the penetration of the landed clusters into the hexadecyl monolayer.     

Oxidation-active flavin models: oxidation of alpha-hydroxy acids by benzo-dipteridine bearing metal-binding site in the presence of divalent metal ion and base in organic solvents.

The oxidizing ability of benzo-dipteridine bearing a bipyridin-6-ylmethyl moiety (4) was found to be increased with Zn(2+) by approximately 10(3)-fold for sulfite addition in MeOH and approximately 10(2)-fold for oxidation of an NADH model in MeCN. It was found for the first time that 4 is able to oxidize alpha-hydroxy acids to alpha-keto acids in the presence of a divalent metal ion such as Zn(2+), Co(2+), and Ni(2+) and an amine base in MeCN or t-BuOH, whereas benzo-dipteridine having a bipyridin-5-ylmethyl moiety (3) is unable to oxidize them under the same conditions. The oxidation reaction was kinetically investigated including the kinetic isotope effect for deuterated mandelic acids (k(H)/k(D) = 2.1-3.7) and the Hammett plots for substituted mandelic acids (V-shaped plots). In the reaction of alpha-substituted alpha-hydroxy acids such as alpha-methyl mandelic and benzylic acids with 4, novel oxidative decarboxylation was found to take place, giving acetophenone and benzophenone, respectively. The oxidation mechanism for mandelic acid was proposed to proceed via a ternary complex of 4.Zn(2+).PhCH(OH)CO(2)(-), in which alpha-oxyanion of mandelate attacks C(4a)-position of 4 to form an adduct followed by 1,2-elimination to afford benzoyl formate and 2e-reduced 4. The roles of the metal ion were proposed as follows; (i) activation of 4, (ii) substrate-binding site, and (iii) activation of the bound alpha-hydroxy acid by lowering pK(a)'s of alpha-OH and alpha-CH. This is a first example that a flavin model oxidizes alpha-hydroxy acids in the presence of a metal ion.