Takuya Nishioka

Intracomplex electron transfer in a hydrogen-bonded calixarene-porphyrin conjugate: tweezers for a quinone

Abstract The synthesis and characterization of a new supramolecular assembly I , wherein photoinduced electron transfer through non-covalent interactions may be probed, is reported. Ensemble I is based on supramolecular contacts between the phenolic hydroxyl groups of a calix[4]arene-substituted Zn(II) metalloporphyrin photodonor 1a and the carbonyl groups of a benzoquinone acceptor 6 . Ensemble I is formed with a K a of 70±10 dm 3 mol −1 in CDCl 3 as judged by 1 H NMR spectroscopic analysis. Upon irradiation of the porphyrin subunit of I at 400xa0nm, a photoinduced intramolecular electron transfer from the Zn(II) metalloporphyrin to the benzoquinone occurs with a rate constant of 3.3×10 10 s −1 . Two phenolic hydroxyl groups of the calix[4]arene serve not only as tweezers to capture the benzoquinone by two-point hydrogen bonding fixation, but also as useful building blocks in the construction of non-covalent donor–acceptor electron transfer model systems.

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

Synthesis of 5-formyl-17-nitrocalix[4]arenes in the 1,3-alternate conformation

Three 1,3-alternate-5-formyl-17-nitrocalix[4]arenes (4, 5, 7) bearing two propoxyl groups at one side (at 25 and 27 positions) and two benzyloxyl or propoxyl groups at the other side were synthesized.

No scrambling in the synthesis of meso -substituted porphyrins from one dipyrromethane and aryl aldehydes

The cross-condensation of dipyrromethane 1 and aryl aldehydes in the presence of trichloroacetic acid in CH2 Cl2 afforded non-scrambled products in good yields for the first time.