Takashi Arimura

A non-covalent assembly for electron transfer based on a calixarene–porphyrin conjugate: tweezers for a quinone

The synthesis and characterization of a new supramolecular assembly, a calix[4]arene substituted Zn(II) metalloporphyrin 4 and benzoquinone 6, wherein photoinduced electron transfer through non-covalent interactions may be probed, is reported.

Inclusion Properties of a New Metallo-Porphyrin Dimer Derived from a Calix[4]arene: Tweezers for C 70

For the selective binding of the fullerence C 70 , we report here on the inclusion properties of a novel metallo-porphyrin dimer 1 which entails the functionalization of the basic supramolecular frame of a calix[4]arene. First, the electrochemical property of 1 was evaluated by a voltammetric method. The redox potential for reduction is m 0.46 V vs. Fc/Fc + , and those for the first and second oxidation are 0.14 V and 0.32 V vs. Fc/Fc + , respectively. These results show two porphyrin moieties of 1 are essentially unperturbed each other. Second, the selectivity factor of C 70 for 1 is remarkably large as compared with competing C 60 , because evidence for the formation of the complex came from 1 H NMR and fluorescence spectroscopic studies. In any event, the present work shows two porphyrin groups of 1 serve as tweezers to capture C 70 by two-point fixation. porphyrin supramolecular chemistry fullerene redox potential tweezers calixarene

Intracomplex electron transfer in a hydrogen-bonded calixarene–porphyrin system

Photoinduced electron transfer in a non-covalent assembly based on supramolecular contacts between the phenolic hydroxy groups of a calix[4]arene-substituted ZnII metalloporphyrin photodonor and the carbonyl groups of a benzoquinone acceptor (Ka= 40 ± 3.6 dm3 mol–1) in CDCl3 occurs with a rate constant of (8.0 ± 0.2)× 108 s–1.

Anisotropic Self-Oscillating Reaction in Liquid Crystalline Nanosheet Hydrogels

Anisotropic chemical wave propagation of self-oscillating Belousov-Zhabotinsky (BZ) reaction was demonstrated in the poly( N-isopropylacrylamide) gel films embedded with macroscopically aligned liquid crystalline inorganic nanosheets. Although the average propagation rate of chemical wave v̅ was 3.56 mm min-1 in the gels without nanosheets, the propagation was retarded in the gels with 1 wt % of nanosheets: [Formula: see text] = 1.89 mm min-1 and [Formula: see text] = 1.33 mm min-1 along the direction parallel and perpendicular to the nanosheet planes, respectively. Thus, the wave propagation is anisotropic with the anisotropy ratio [Formula: see text] = 1.42 in these gels and the periodic patterns formed by the BZ reaction were concentric ellipses, different from circles seen in isotropic gels. Furthermore, the propagation rate and degree of anisotropy were controllable by nanosheet concentration. These phenomena can be explained that the diffusion of molecules inside the gel is effectively hindered along the direction perpendicular to the nanosheet planes due to the very large aspect ratio of the aligned nanosheets. The present systems will be applicable for anisotropic self-oscillating soft actuators with one-dimensional motions as well as for ideal model system of BZ reactions.

Electrochemically Switchable Molecular-Tweezers

Synthetic receptors possessing two complexing chromophores connected by a single spacer are referred to as molecular tweezers. We report an electrochemically triggered molecular tweezers, which is a calix[4]arene-bis-porphyrin conjugate, that acts as a proof-of-concept demonstration system showing an electro-statically induced approach to guest release. The electrochemical behavior represents that 1,4-diazabicyclo[2.2.2]octane (DABCO) is released from the complex formed between calix[4]arene-bis-porphyrin conjugate and DABCO, just after cooperative two-oxidation occurs at 0.41 V.

Detection of Fluorinated Compounds Using Quartz Crystal Microbalance Coated with Plasma Polymerized Styrene Derivatives

Abstract We report preliminary results of the detection of fluorinated compounds using a quartz crystal microbalance coated with plasma-polymerized styrene (pp-St) and pentafluorostyrene (pp-PFSt). The sorption of fluorinated compounds on pp-PFSt is 1.2–4.8 times larger than that of these compounds on pp-St.