Tsutomu Miyashi

First stable tetracyanodiphenoquinodimethane with a completely planar geometry: Preparation, X-ray structure, and highly conductive complexes of bis[1,2,5]thiadiazolo-TCNDQ

The titled tetracyanodiphenoquinodimethane (TCNDQ) derivative was newly designed and prepared as a novel component for highly conductive organic materials. Introduction of 1,2,5-thiadiazole rings into the TCNDQ skeleton leads to large stabilization in the neutral state. X-ray analysis has revealed their structural details which suggest that interatomic interactions (Cue5f8H…N, S…N) play an important role in determining the molecular and crystal structure. The novel electron acceptor shows strong electron affinity comparable with that of TCNQ, and gave highly conductive charge-transfer (CT) complexes and an anion radical salt.

Dynamic Redox Systems: Toward the Realization of Unimolecular Memory

“Dynamic redox systems” is the name given to a certain class of compounds that can be reversibly converted into the corresponding charged species upon electron transfer (ET) but accompanied by drastic structural changes and/or covalent bond making/breaking. Although transformation between the neutral and charged species proceeds quantitatively in most cases, their electrochemical processes are irreversible owing to the chemical reactions followed by ET. This situation endows the “dynamic redox pairs” with very high bistability, which is a prerequisite in order to construct the molecular response systems.

Dibenzotetrathiafulvalenes inserted with cycloalkanes and their tricyclic valence isomers: reversible C–C bond making/breaking upon electron transfer

The title TTF derivatives and their tricyclic valence isomers afford the same bicyclic dications upon two-electron oxidation, and the resulting dications regenerate either one or the other of the two isomers selectively upon reduction.

CHARGE-TRANSFER EXCITATION OF ELECTRON DONOR-ACCEPTOR COMPLEXES OF ARYLCYCLOPROPANES

Electron-transfer (ET) reactions of mono- and ndi-arylcyclopropanes 1 and 2 have been investigated by employing ncharge-transfer (CT) excitation of their electron donor–acceptor n(EDA) complexes with tetracyanoethylene (TCNE) or p-chloranil n(CA). For the TCNE complexes, no reaction is observed following nphotoexcitation within their CT bands. Picosecond absorption nspectroscopic experiments with phenylcyclopropane 1a and n1,1-diphenylcyclopropane 2a reveal that the photogenerated ion radical npairs [1a˙+, TCNE˙-] and n[2a˙+, TCNE˙-] are too nshort-lived to undergo chemical reaction. For the CA complexes, net nchemical change is observed in the CT excitation of the 2a–CA ncomplex though the efficiency is very low. The other narylcyclopropane–CA complexes are found to be unreactive. Factors nconcerned with the reactivity of 1 and 2 upon their CT-excitation are ndiscussed.