Emiko Koyama

Odd–even effect and metal induced structural convergence in self-assembled monolayers of bipyridine derivatives

Scanning tunneling microscopy (STM) observations reveal that bipyridine derivatives which exhibit various two-dimensional structures due to the odd-even chain length effect are converged into a lamellar structure upon metal coordination.

Photoinduced crystal-to-liquid phase transitions of azobenzene derivatives and their application in photolithography processes through a solid-liquid patterning.

The direct and reversible transformation of matter between the solid and liquid phases by light at constant temperature is of great interest because of its potential applications in various manufacturing settings. We report a simple molecular design strategy for the phase transitions: azobenzenes having para-dialkoxy groups with a methyl group at the meta-position. The photolithography processes were demonstrated using the azobenzene as a photoresist in a single process combining development and etching of a copper substrate.

Bipyridine derivatives at a solid/liquid interface: effects of the number and length of peripheral alkyl chains.

Bipyridine derivatives (bpys) with various number and length of peripheral alkyl chains (with carbon numbers of n = 11-17) were synthesized, and their self-assembled monolayers were observed by scanning tunneling microscopy (STM) at a 1-phenyloctane/highly oriented pyrolytic graphite (HOPG) interface. The effects of the number, the substitution position, and the length of alkyl chains on the two-dimensional structures were systematically studied. Bpys substituted by a single alkyl chain in the p-position on each side adopted an almost linear form with zigzag-type alignment of the pi-conjugated unit, whereas, in the case of m-substitution, the bpys showed Z-shaped morphology with interdigitated alkyl chains. In both cases, no odd-even alkyl chain length effects were observed. The bpys with double alkyl chains at m- and p-positions displayed odd-even alkyl chain effects, suggesting that the formation of two-dimensional structure is dominated by the interactions between alkyl chains. Bpys with triple alkyl chains at o-, m-, and p-positions also showed odd-even alkyl chain effects, but only for the higher number of carbon atoms in the alkyl chain unit (n = 14-17). These results indicate that concerted intermolecular interactions of the alkyl chain unit introduce the odd-even chain length effect on the self-assembled two-dimensional structure. After coordination of PdCl(2), odd-even effects were quenched, and bpys were converged into the same lamellar structure, in which the molecules are almost linear. All the structural differences due to the odd-even alkyl chain length effect were explained in terms of intermolecular and molecule-substrate interactions.

A novel synthesis of bis(benzoxazole) derivatives via tandem Claisen rearrangement

Abstract The one-pot thermal reaction of 1,3-bis( o -acylamino phenyloxy)-2-methylene propane derivatives gave either the bis(benzoxazole) derivatives or the benzodihydrofuran derivatives via tandem Claisen rearrangement in good yields. The reaction courses strongly depend upon the reaction conditions such as the solvent or the substituent of the carbamoyl moiety. The resulting bis(benzoxazole) derivative having a 2-aromatic substituent emits blue fluorescence and has almost the same fluorescence quantum yield as the model mono(benzoxazole) compound.

Innovative platform for transmission localized surface plasmon transducers and its application in detecting heavy metal Pd(II).

Transmission localized surface plasmon resonance (T-LSPR) transducers based on the characteristic surface plasmon absorption band of Au island films have become increasingly attractive. The first and main bottleneck hampering the development of T-LSPR sensors is instability, manifested as change in the surface plasmon absorbance band following immersion in organic solvents and aqueous solutions. In this paper, we innovate the platform for T-LSPR transducer by using remarkably stable and highly adhesive Au/Al(2)O(3) nanocomposite film. Isolated Au nanoparticles embedded in dielectric matrix Al(2)O(3) were prepared by a simple one-step radio frequency magnetron cosputtering technique. The obtained nanocomposite film is exceedingly stable during immersion in solvents, drying, and binding of different molecules; it successfully passes the adhesive tape test and sonication treatment. The superior stability and adhesion, obtained without the use of any intermediate adhesion layer or protective overlayer, is attributed to (1) the Au nanoparticles embedment and Al(2)O(3) rim formation during the sputtering process and (2) the resistance of element Al in matrix to the nucleophilic attack by the solvent molecules. Given this success, we believe that the Au/Al(2)O(3) nanocomposite film holds promise as an innovative sensing platform in T-LSPR detection technology, as demonstrated here for the Pd(II) sensing process with excellent sensitivity and low detection limit.

[3]Rotaxane synthesized via covalent bond formation can recognize cations forming a sandwich structure

A novel [3]rotaxane composed of two 25-membered crownophanes and one axle molecule having two anthryl end groups was successfully synthesized via covalent bond formation followed by aminolysis, and can incorporate caesium ion into the space between the two macrocycles as a 1 : 1 sandwich-type complex, whereas it makes a 1 : 2 complex with lithium ion.

Reversed micellar fibres in organic media as a new model of the parallel-chain β-sheet structure of peptides

In aggregates of tripeptide-containing amphiphiles, the tripeptide groups possess a parallel-chain β-sheet structure not only in water but also in CCl4, in which the amphiphiles form a reversed micellar fibre structure.

Synthesis of Novel Bis(benzoxazole) Derivatives by Tandem Claisen Rearrangement and Their Fluorescence Behavior

Novel bis(benzoxazole) derivatives were easily synthesized from isobutenyl bis(amide−ether)s by tandem Claisen rearrangement and subsequent intramolecular cyclization of the amide−phenol intermediates. The yields of the bis(benzoxazole)s depended on whether the reaction was carried out with or without solvent, as well as on the substituents on the aryl group and the carbonyl group. The solvent effect was dramatic. No significant difference in the overall reaction rate constant with variation of the substituents on the carbonyl group was observed, but the nature of the aryl group on the ether had a large effect on the tandem Claisen rearrangement. The corresponding amide−phenol derivatives were confirmed as intermediates in this rearrangement. The fluorescence quantum yields of the obtained bis(benzoxazole)s were high, but the yields were lower than those of the corresponding monobenzoxazoles. (© Wiley-VCH Verlag GmbH, 69451 Weinheim, Germany, 2002)

Metallation of bipyridine derivatives substituted at meta position by alkyl chains: effects on the 2D structures

Bipyridine derivatives (bpys) substituted by alkyl chains at meta position were observed by scanning tunnelling microscopy at a highly oriented pyrolytic graphite–1-phenyloctane interface. In those molecules, the alkyl chains were interdigitated, and the π-conjugated bipyridine core parts were aligned side by side. Metal coordination should induce 2D structural transformations due to the alteration of intermolecular interactions. The bpy platinum complexes were aligned in a straight fashion, in which the alkyl chains were interdigitated. The molecular arrangements were quite different from those of free bpy. In contrast, there was no structural change in the case of palladium complexes, suggesting the decoordination of the ligand from the metal. The equilibrium of metallation/demetallation affected the 2D structure, and should be taken into account for the nanoarchitecture design on the basis of the intermolecular interactions.

Conductance Changes of Conjugated 2,2

Phenylene ethynylene dithiol derivatives containing a bipyridine ligand along the conjugated system were introduced between nanogap electrodes, and significant conductance changes of the bridging molecules were observed upon complexation with Pd(II).