π-Electron-system-layered polymer: through-space conjugation and properties as a single molecular wire

[2.2]Paracyclophane-based through-space conjugated oligomers and polymers were prepared, in which poly(p-arylene-ethynylene) (PAE) units were partially π-stacked and layered, and their properties in the ground state and excited state were investigated in detail. Electronic interactions among PAE units were effective through at least ten units in the ground state. Photoexcited energy transfer occurred from the stacked PAE units to the end-capping PAE moieties. The electrical conductivity of the polymers was estimated using the flash-photolysis time-resolved microwave conductivity (FP-TRMC) method and investigated together with time-dependent density functional theory (TD-DFT) calculations, showing that intramolecular charge carrier mobility through the stacked PAE units was a few tens of percentage larger than through the twisted PAE units.     

A Concise Route to 3-Hydroxy-4-Methoxy-5-Methylbenzaldehyde Derivative

3-Hydroxy-4-methoxy-5-methylbenzaldehyde derivative (1c) has been synthesized in 7 steps from 2,3-dihydroxytoluene (4). An isopropyl derivative has been used to protect a phenol during this transformation. The overall yield of 1c was 37%.     

Synthesis of biodegradable amphiphilic AB‐type diblock copolymers of lactide and depsipeptide with pendant reactive groups

The syntheses of amphiphilic AB‐type diblock copolymers composed of hydrophobic polylactide segment and hydrophilic polydepsipeptide segment with amino or carboxyl groups were performed. The protected cyclodepsipeptides cyclo[Glc‐Lys(Z)] and cyclo[Glc‐Asp(OBzl)] (where Glc is glycolic acid, Lys is lysine, Asp is aspartic acid, Z is benzyloxycarbonyl, and OBzl is benzyl) were first polymerized in tetrahydrofuran (THF) with potassium ethoxide as an initiator to obtain the corresponding protected polydepsipeptides. After the terminal hydroxyl groups of the protected polydepsipeptides were converted into the potassium alcoholates with K/naphthalene, L ‐lactide was polymerized in the presence of the corresponding polymeric alcoholates as macroinitiators in THF to obtain poly[Glc‐Lys(Z)]‐block‐poly(L ‐lactide) and poly[Glc‐Asp(OBzl)]‐block‐poly(L ‐lactide). Subsequent deprotection of Z and OBzl groups gave the objective amphiphiles poly(Glc‐Lys)‐block‐poly(L ‐lactide) and poly(Glc‐Asp)‐block‐poly(L ‐lactide), respectively. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 1218–1225, 2002     

Preparation of Polylactide Microspheres Having Positively or Negatively Charged Surfaces

The syntheses of polylactides (PLAs) with branched peptide end groups containing reactive (ionic) moieties such as amino or carboxyl groups are described and were used to prepare PLA‐based microspheres (MSs) with positively or negatively charged surfaces. Branched peptides with hydroxyl end groups and four protected amino or carboxyl groups, Boc₄‐K₃‐OH or Bn₄‐E₃‐OH, were synthesized, and the hydroxyl group converted to an alkoxide and was used as the initiation site for the ring‐opening polymerization of L ‐lactide. Subsequent deprotection gave PLAs end‐capped with branched peptides having four amino or carboxyl groups, respectively (K₃‐PLA and E₃‐PLA). K₃‐PLA and E₃‐PLA were converted to K₃⁴⁺‐PLA and E₃^4?‐PLA by acid or base treatment, respectively. MSs with charged surfaces were then prepared using K₃⁴⁺‐PLA or E₃^4?‐PLA as a surfactant [MS(K₃⁴⁺‐PLA) or MS(E₃^4?‐PLA)]. The ionic surface state of the MSs was confirmed by colloidal titration and zeta potential analysis.

SEM image of MSs: MS(K₃⁴⁺‐PLA).     

Readily Processable Hole‐Transporting Peropyrene Gels

The development of organic electronics requires scalable solution‐processing methods that enable the fabrication of electronic devices over large areas at low cost. The preparation of peropyrene gels constituted of 3D networks of entangled 1D ribbon‐like fibrils that extend over the μm scale are now reported. OFETs were easily fabricated by depositing the gels in the sol state over bottom‐gate bottom‐contact transistors and by allowing its gelation thereafter. Electrical characterisation of such field‐effect transistors shows a good balance between processability and performance with hole mobilities that are two orders of magnitude higher than those observed in thin films obtained from non‐gelating solvents under the same conditions.     

Liquid membrane transport of cytochrome c using a calix[6]arene carboxylic acid derivative as a carrier

The present study examined the liquid membrane transport of the cationic protein cytochrome c, using the macrocyclic compound calix[6]arene, which is a carboxylic acid derivative, as a carrier. The transport rate was governed by carrier concentration and the pH gradient between the feed and the receiving phases, as well as the salt concentration in the aqueous phases. Transport of cytochrome c was examined using a series of calix[n]arene carboxylic acid derivatives (n = 4, 6 and 8). Cytochrome c successfully permeated membranes in the presence of the calix[6]arene derivative. Liquid membrane separation of cytochrome c from a mixture of cationic proteins was demonstrated under optimal conditions. Cytochrome c was selectively extracted by the calix[6]arene carboxylic acid derivative and 77% of the extracted cytochrome c was recovered into the receiving phase. In this liquid membrane system, which discriminates between the number of lysine residues on the surface of proteins, cationic proteins with similar molecular weights and pIs were separated with macrocyclic compounds.     

Chemical states of dodecanethiolate-passivated Au nanoparticles: synchrotron-radiation photoelectron spectroscopy

We have carried out a photoemission study using synchrotron radiation of dodecanethiolate (DT)-passivated Au nanoparticles supported on the highly oriented pyrolytic graphite substrates. From detailed line-shape analyses of Au 4f core-level photoemission spectra of DT-passivated Au nanoparticles, it was found that Au 4f core-level spectra consist of two components. We attribute these components to the inner Au atoms and surface Au atoms bonded to surface dodecanethiolates. From these results, we discuss the chemical states of the present DT-passivated Au nanoparticles.