Composition spread metal thin film fabrication technique based on ion beam sputter deposition

A composition spread metal thin film fabrication technique based on ion beam sputter deposition method was developed. The technique enables us to fabricate any desired part or a complete binary/ternary composition spread metal thin films onto a single substrate by sequentially sputtering different target materials. Composition spread metal thin films can be deposited directly on a dielectric film in patterned electrode shape for C-V and I-V measurements. The system could be especially useful in the search for new multi-component metal gate materials.     

Molecular programming of organogelators which can accept [60]fullerene by encapsulation

New porphyrin-based gelators bearing eight hydrogen-bond-forming amide groups at their periphery were synthesized. They acted as versatile gelators for aromatic solvents. SEM and TEM observations and X-ray crystallographic analysis established that they tend to aggregate into a two-dimensional sheet-like structure utilizing the intermolecular hydrogen-bonding interaction. In this structure the porphyrin-porphyrin π-π stacking interaction is not involved because of the energetically-predominant hydrogen-bonding interactions, keeping the space distance of 12.9 Å. Very interestingly, when C₆₀ was added, the morphology was transformed to a one-dimensional fibrous structure, which can enjoy a porphyrin-C₆₀-porphyrin interaction. This multicapsular structure having porphyrin-based compartments for hosting C₆₀ was further characterized by XRD, EPR of a Cu(II) analogue, and the theoretical calculation. Thus, this paper presents a new concept, ‘molecular recognition in gel’, which is effective for the weak host-guest interaction.     

Remarkable reactivities of the xanthone ketyl radical in the excited state compared with that in the ground state

The properties and reactivities of the xanthone (Xn) ketyl radical (XnH*) in the doublet excited state (XnH*(D1)) were examined by using two-color two-laser flash photolysis. The absorption and fluorescence of XnH*(D1) were observed for the first time. Several factors governing the deactivation processes of XnH*(D1) such as interaction and reaction with solvent molecules were discussed. The remarkable change of reactivity of XnH*(D1) compared with that in the ground state (XnH*(D0)) was indicated from the experimental results. The rapid halogen abstraction of XnH*(D1) from some halogen donors such as carbon tetrachloride (CCl4) was found to occur. The halogen abstraction occurred more efficiently in the polar solvents than in the nonpolar solvents. It is suggested that the polar solvents promote the spin distribution of XnH*(D1) of the phenyl ring favorable to the halogen abstraction.     

Photophysical properties of oligo(2,3-thienyleneethynylene)s

Photophysical properties of oligo(2,3-thienyleneethynylene)s (nTE, n denotes the number of thiophene rings, n = 2, 3) in benzene were investigated using steady-state, time-resolved fluorescence, and transient absorption spectroscopies. For 2TE, generation of the radiative S2 and nonradiative S1 states was confirmed. Upon excitation, the S2 state was initially generated and deactivated to the S1 state within 10 ps. The S1 state exhibited the transient absorption band at 470 nm, of which the lifetime was estimated to be 5.3 ns. In the case of 3TE, on the other hand, it was revealed that the radiative S1 state with a transient absorption peak at 650 nm was generated upon excitation. The T1 states of nTE were generated from the S1 states. The quantum yields were estimated to be 0.52 and 0.54 for 2TE and 3TE, respectively. Extremely fast reactions in the higher triplet excited state were indicated for both 2TE and 3TE.     

Binding of methyl orange and its homologs by powdered nylon 612: Peculiar temperature dependence on the binding

The ability of powdered Nylon 612 to bind methyl orange, ethyl orange, propyl orange, and butyl orange was investigated at 5, 15, 25 and 35°C in an aqueous solution. The amount of binding of the dye is much higher with this polyamide than with powdered Nylon 66 reported previously,¹ although the former polymer has fewer amide end groups. The Van't Hoff plots of the first binding constant for the binding of butyl orange and propyl orange by powdered Nylon 612 exhibit a bell-shaped curve, whereas the plots for methyl orange and ethyl orange do not. Maximal binding occurs at approximately 15°C for propyl orange and at about 25°C for butyl orange. This is the first instance where the peculiar temperature dependence of the binding constant has been found in the binding of propyl orange, whose hydrophobicity is less than that of butyl orange. These tendencies can be accounted for in terms of increased hydrophobic of butyl orange. These tendencies can be accounted for in terms of increased hydrophobic domains in powdered Nylon 612 and enhanced hydrophobic contributions in the binding process.     

Synthesis of optically active cobalt(salen) type complexes and their asymmetric reactivity toward propylene oxide

An optically active Co(I)(salen) type complex, lithium N,N′-bis(salicylaldehyde)-1(R), 2(R)-1,2-trans-cyclohexanediiminatocobalt(I), was prepared by reducing the Co^II complex, N,N′-bis(salicylaldehyde)-1(R),2(R)-1,2-trans-cyclohexanediiminatocobalt(II), with LiAlH₄. The structure of the Co^I complex was determined on the basis of the structure of the corresponding Co^II complex and was confirmed by usual physicochemical methods. Furthermore, characteristics of the absorption and circular dichroism(CD) spectra of the Co^I complex were compared with those of the reported structure of Na⁺[Co(I)(salen)]^?. Highly asymmetric selectivity was found in a resolution reaction of DL-propylene oxide by use of the above optically active lithium cobalt(I) complex as a catalyst.     

On the electronic character of localized singlet 2,2-dimethoxycyclopentane-1,3-diyl diradicals: substituent effects on the lifetime

Photodenitrogenation of the diazenes 4 affords exclusively the housanes 5 through intramolecular cyclization of the spectrally detected and characterized singlet diradicals 3. The lifetime of singlet diradical 3, determined by transient absorption measurements, depends on the Y and Z substituents at the para position of the phenyl ring and has the following order: Y, Z = OMe, OMe > OMe, CN > CN, CN > OMe, H > Cl, Cl approximately CN, H approximately Me, Me > H, H. This unprecedented substituent effect reveals stabilization of the singlet 2,2-dimethoxycyclopentane-1,3-diyl diradicals 3 through radical, zwitterionic, pi-bonding, and hyperconjugative structures.     

A New Convenient Synthesis of α-Arylpropionic Acid Esters and α-Arylpropionitriles

Various types of α-arylpropionic acid esters were effectively obtained by the coupling reaction of aryl Grignard reagents and α-bromopropionic acid esters in the presence of nickel catalysts. α-Arylpropionitriles, precursors of α-arylpropionic acids, were also synthesized by the reaction of α-methanesulfonyloxypropionitrile and arylcopper reagents prepared from equimolar amount of arylmagnesium halides and copper(I) bromide.     

Ammonium chiral borate salt catalyzed asymmetric Friedel-Crafts alkylation of indoles with α,β-disubstituted enals

In the presence of a catalytic amount of ammonium chiral borate salt, asymmetric Friedel-Crafts alkylation of indoles with α,β-disubstituted enals proceeded to give the corresponding 1,4-addition products with moderate enantioselectivities.