Ni(II)- and Co(II)-phosphine complex catalyzed carboncarbon bond formation between organic tellurides and grignard reagents

Treatment of alkenyl and aryl tellurides with Grignard reagents in the presence of NiCl₂(PPh₃)₂, NiCl₂(Ph₂PCH₂CH₂CH₂PPh₂), or CoCl₂(PPh₃)₂ as catalyst affords the cross-coupling products together with the homo-coupling products of the tellurides in good to moderate yields under mild conditions.     

In Situ Processing of Nano Crystalline Oxide Particles/Polymer Hybrid

Nano sized crystalline particles/polymer hybrids were synthesized form designed metal-organic precursors. The newly developed method is composed of the synthesis of organic matrix by polymerization and the in situ nucleation and growth of crystalline oxide particles in the organic matrix below 100°C. The design of metal-organic precursor modified with polymerizable ligand and the selection of reaction conditions does influence the size and crystallinity of ceramic particles in organic matrix. The nano-sized magnetic particle/polymer hybrid exhibits the interesting feature of superparamagnetism and quantum size effect. The crystalline particles of BaTiO₃/, PbTiO₃/, and KNbO₃/polymer hybrids behave to be dielectric and show the typical electro-rheological behavior.     

Optically active 1,2-bis(1-arylhydroxymethyl) ferrocene: a new, efficient chiral ligand for scandium-catalyzed asymmetric Diels-Alder reaction

[reaction: see text] The Sc(OTf)3/FERRODIOL (2) complex was prepared at -78 degrees C in CH2Cl2 in the presence of 2,6-lutidine and MS 4A. The chiral scandium Lewis acid-catalyzed asymmetric Diels-Alder reaction of cyclopentadiene (3) with 3-acyloxazolidin-2-ones (4) effectively produced the adduct (5) in a high yield with good selectivity, i.e., endo/exo = 90:10 up to 91% ee (endo).     

Development of Odorless Thiols and Sulfides and Their Applications to Organic Synthesis

Summary. Development of new odorless thiols (dodecanethiol, 4-n-heptylphenylmethanethiol, 4-trimethylsilylphenylmethanethiol, 4-trimethylsilylbenzenethiol) and an odorless sulfide (1-methylsulfanyldodecane) and their applications to dealkylation, Michael addition, Swern oxidation, and Corey-Kim oxidation are described.     

A large thermal hysteresis loop produced by a charge-transfer phase transition in a rubidium manganese hexacyanoferrate

In a rubidium manganese hexacyanoferrate, RbMn[Fe(CN)(6)], the magnetic susceptibility (chi(M)) decreased at 225 K (=T(1/2)decreasing) and abruptly increased at 300 K (=T(1/2)increasing) in the cooling and warming processes, respectively. X-ray photoelectron spectroscopy and infrared spectroscopy indicated that the high-temperature (HT) and low-temperature (LT) phases were composed of Mn(II)-NC-Fe(III) and Mn(III)-NC-Fe(II), respectively. A structural change from cubic (F43m, a = 10.533 A) to tetragonal (I4m2, a = b = 7.090 A, c = 10.520 A) accompanied the phase transition, and, on the basis of these results, the HT and LT phases were assigned to Mn(II)(t(2g)(3)e(g)(2), (6)A(1g); S = (5)/(2))-NC-Fe(III) (t(2g)(5), (2)T(2g); S = (1)/(2)) and Mn(III)(e(g)(2)b(2g)(1)a(1g)(1), (5)B(1g); S = 2)-NC-Fe(II) (b(2g)(2)e(g)(4), (1)A(1g); S = 0), respectively. This phenomenon is caused by a metal-to-metal charge transfer from Mn(II) to Fe(III) and a Jahn-Teller distortion of the produced Mn(III) ion. The reaction mechanism is discussed, considering the entropy difference between the HT and LT phases.     

Molar enthalpies of transfer of divalent transition metal lons and their chloro complexes from N,N-dimethylformamide to N,N-dimethylacetamide

The molar enthalpies of transfer _t H ^° of some divalent metal ions (M-Mn, Co, Ni and Zn) and their chloro complexes from N,N-dimethyl-for-mamide (DMF) to N,N-dimethylacetamide (DMA) have been determined using the tetraphenylarsonium-tetraphenylborate (TATB) assumption at 25°C. Although physicochemical properties of DMF and DMA as solvent are similar, the _t H ^°(M ²⁺) value increased significantly in the order Mnt H ^° values for the mono-and dichloro complexes showed also a strong metal dependence, while those for the triand tetrachloro complexes practically do not. These results can be reasonably explained in terms of steric hindrance upon solvation of the metal ions and complexes in DMA.     

Structural studies of the carbon monoxide complex of [NiFe]hydrogenase from Desulfovibrio vulgaris Miyazaki F: suggestion for the initial activation site for dihydrogen

The carbon monoxide complex of [NiFe]hydrogenase from Desulfovibrio vulgaris Miyazaki F has been characterized by X-ray crystallography and absorption and resonance Raman spectroscopy. Nine crystal structures of the [NiFe]hydrogenase in the CO-bound and CO-liberated forms were determined at 1.2-1.4 A resolution. The exogenously added CO was assigned to be bound to the Ni atom at the Ni-Fe active site. The CO was not replaced with H(2) in the dark at 100 K, but was liberated by illumination with a strong white light. The Ni-C distances and Ni-C-O angles were about 1.77 A and 160 degrees, respectively, except for one case (1.72 A and 135 degrees ), in which an additional electron density peak between the CO and Sgamma(Cys546) was recognized. Distinct changes were observed in the electron density distribution of the Ni and Sgamma(Cys546) atoms between the CO-bound and CO-liberated structures for all the crystals tested. The novel structural features found near the Ni and Sgamma(Cys546) atoms suggest that these two atoms at the Ni-Fe active site play a role during the initial H(2)-binding process. Anaerobic addition of CO to dithionite-reduced [NiFe]hydrogenase led to a new absorption band at about 470 nm ( approximately 3000 M(-1)cm(-1)). Resonance Raman spectra (excitation at 476.5 nm) of the CO complex revealed CO-isotope-sensitive bands at 375/393 and 430 cm(-1) (368 and 413 cm(-1) for (13)C(18)O). The frequencies and relative intensities of the CO-related Raman bands indicated that the exogenous CO is bound to the Ni atom with a bent Ni-C-O structure in solution, in agreement with the refined structure determined by X-ray crystallography.     

J-aggregation and its characterization in Langmuir-Blodgett films of merocyanine dyes

Langmuir-Blodgett (LB) films are constructed by successively transferring monomolecular layers formed at the air-water interface onto solid substrates. One of the advantages of the LB technique in fabricating molecular aggregates lies in the fact that it can employ various kinds of molecules by mixing them at the air-water interface. The mixed system may exhibit new properties that are not observed for individual components. This method would be useful, for example, in the studies of the formation and control of the J-aggregates of functional dyes that attract attention both in science and technology. In this paper, I review this subject mainly based on our recent results in merocyanines. LB films of merocyanine dyes, mixed with arachidic acid (C(20)), exhibit J-aggregate formation and have been serving as typical systems in revealing the physical and structural aspects of nanosized molecular aggregates constructed as monolayers. In the case of LB films of a merocyanine dye having benzothiazole as donor nucleus (abbreviated as DS), electron spin resonance (ESR) spectroscopy has been successful in determining the characteristic in-plane orientation of dye molecules with respect to the dipping direction, which led to the discovery of the flow orientation effect during the dipping process of LB films as the origin of optical dichroism often observed in LB films. In this article, after an introduction of ESR spectroscopy, three major topics on the merocyanine J-aggregation and its characterization in mixed films are discussed. The first topic is the observation and control of the size of J-aggregates in the dilution limit of dyes in arachidic acid matrix for a methyl-substituted DS (6-Me-DS). Dependence of atomic force microscopy (AFM) patterns on the molar ratio allows the identification of dye domains. J-band optical peak analysis based on the Kuhn's extended dipole model, supplemented by a novel application of femtosecond pump-probe optical spectroscopy, yields the size of the J-aggregates of 10(3). The second topic is the control of the J-band peak wavelengths by mixing two different kinds of dye molecules. The first case is the mixture of a J-forming 6-Me-DS and non-J-forming merocyanine analog, DO with benzo-oxazole instead of benzothiazole of DS. The second case is the mixture of both J-forming dyes but with different J-band peak positions, 6-Me-DS and another analog of 5-Cl-DS. The optical peak shifts depending on the molar mixing ratio will be presented. The last topic is related to the elucidation of electronic states of dye molecules in the J-aggregates. Light-induced ESR (LESR) of DS films with stable isotope ((15)N or (13)C)-substituted dyes provide clear evidence for the photoinduced charge transfer by the detection of hyperfine structures. Moreover, infrared (IR) spectroscopy of (13)C-enriched dye identifies the IR absorption peak of the relevant carbon in the chromophore. The results give evidence for the enhanced intramolecular charge transfer of dyes in the J-aggregates compared with an isolated merocyanine composed of donor and acceptor moiety. Lastly, the Cl attachment in 5-Cl-DS leads to a significant enhancement of the nitrogen hyperfine coupling in the LESR spectra. These examples and others demonstrate the potential of LB films of merocyanines in the studies of the nanosized molecular aggregates in monolayer assemblies.     

Orientation control of perovskite thin films on glass substrates by the application of a seed layer prepared from oxide nanosheets

Orientation control of perovskite compounds was investigated by the application of a seed layer prepared from oxide nanosheets. An aqueous suspension of oxide nanosheets was prepared by the exfoliation of a layered compound of KCa₂Nb₃O₁₀ oxide grains. A seed layer composed of (TBA)Ca₂Nb₃O₁₀ nanosheets (TBA = tetrabutylammonium) was formed on a glass substrate by simply dip coating it in the suspension. Two kinds of perovskite compounds, LaNiO₃ (LNO) and Pb(Zr,Ti)O₃ (PZT) with a preferred orientation of (00l) were successfully grown on this seeded glass substrate. In this study, the relation between lattice mismatch and electrical properties is investigated. A large, oriented PZT film with a size of 5 ×4 cm shows an improved P-E hysteresis behavior by use of this orientation control.     

Asymmetric Diels–Alder reactions in supercritical carbon dioxide catalyzed by rare earth complexes

The rare earth(III) salt catalysed asymmetric Diels–Alder reaction of cyclopentadiene with a chiral dienophile in supercritical carbon dioxide (scCO₂) proceeded rapidly to give the adduct with a higher diastereoselectivity than that in dichloromethane; Yb(ClO₄)₃ gave the endo adduct with value up to 77% de at 40°C, 8 MPa. The chiral rare earth diketonate catalyzed hetero Diels–Alder reaction of the Danishefsky's diene with benzaldehyde gave a higher yield and an enantioselectivity in scCO₂ than that in dichloromethane. Scandium/pybox 8a complex catalysed asymmetric Diels–Alder reaction of 3-crotonoyl-2-oxazolidinone with cyclopentadiene in the presence of MS4A proceeded smoothly in scCO₂ to give the endo adduct 10 in a good yield with up to 88% ee.