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The concept of Brønsted-Lowry acids and bases is long and widely recognized as the most reasonable theory to explain the behavior of H+ ions. Here, we report a Brønsted acid/base pair that does not follow this theory. Two heteronuclear metal complexes, in which Brønsted acid/base sites are sterically isolated, were synthesized and characterized. These sterically isolated sites exhibited anomalous behavior, wherein the H+ species encapsulated in the Brønsted acid site did not undergo a deprotonation reaction, and the corresponding protonation reaction at the Brønsted base site failed to proceed. As a result, two states that are in a relationship of a Brønsted acid-base pair stably exist over a wide pH range without any interconversion, generating a thermodynamically metastable state. Additionally, these two states exhibited distinct electron transfer abilities and reactivities. The system presented in this study is in sharp contrast with the traditional concept of Brønsted-Lowry acids and bases.

Electron transfers in multinuclear metal complexes are the origin of their unique functionalities both in natural and artificial systems. However, electron transfers in multinuclear metal complexes are generally complicated, and predicting and controlling these electron transfers is extremely difficult. Herein, we report the precise manipulation of the electron transfers in multinuclear metal complexes. The development of a rational synthetic strategy afforded a series of pentanuclear metal complexes composed of metal ions and 3,5-bis(2-pyridyl)pyrazole (Hbpp) as a platform to probe the phenomena. Electrochemical and spectroscopic investigations clarified the overall picture of the electron transfers in the pentanuclear complexes. In addition, unique electron transfer behaviours, in which the reduction of a metal centre occurs during the oxidation of the overall complex (reduction-upon-oxidation process), were discovered. We also elucidated the two dominant factors that determine the manner of the electron transfers. Our results provide comprehensive guidelines for interpreting the complicated electron transfers in multinuclear metal complexes.

While ortho-alkoxy aryl sulfoxides including various substituents were synthesized by Sharpless asymmetric oxidation reaction, we optimized the reaction conditions and screened better combination of starting materials to obtain high enantioselectivity. The result suggested new information that electron-withdrawing substituents on the aromatic ring have a strong influence upon enantioselectivity of the products. Also, several chiral ligands for Sharpless asymmetric oxidation reaction were evaluated to improve the enantioselectivity. High enantioselectivity of ortho-alkoxy aryl chiral sulfoxides have been achieved by Sharpless oxidation reaction using Ti(O-i-Pr)4 and diethyl tartrate under anhydrous condition. In particular, the enantioselctivity of products was influenced by electron-withdrawing substituents on the aromatic ring, such as nitro, ester and aldehyde groups.