Masashi Uebe

Synthesis and Characterization of 6,13-Diamino-Substituted Pentacenes

A series of 6,13-diamino-substituted pentacenes 1 a-d has been prepared and characterized as a new class of pentacene derivatives with strong donor ability and enhanced solubility in common organic solvents. The spectroelectrochemical and DFT studies revealed that the two-electron oxidation process was accompanied by the substantial structural change into a butterfly-like conformation of the pentacene moiety. More importantly, the extent of deformation from the planar pentacene moiety in the dications of 6,13-diaminopentacene is tunable by varying the N-substituents.

Mesityl‐Substituted Acene Radical Cations: Decent Stability Comparable to Their Neutral States under Ambient Light and Air

Anthracene, tetracene, and pentacene, with moderately bulky mesityl substituents revealed that their photochemical stability in solution under ambient light and air conditions is comparable to that of the corresponding neutral state, thus indicating the possibility of persistent acene radical cations.

9,10-Diaminoanthracenes Revisited: The Influence of N-Substituents on Their Electronic States

The electronic and molecular structures of 9,10-diamino-substituted anthracenes with different N-substituents have been re-examined. In particular, different N-substituents influence both the electronic and molecular structures of the oxidized species of 9,10-diaminoanthracenes. The anthrylene moiety of 9,10-bis(N,N-di(p-anisyl)amino)anthracene retains its planarity during the course of two successive one-electron oxidations, whereas 9,10-bis(N,N-dimethylamino)anthracene and 9,10-bis(N-p-anisyl-N-methylamino)anthracene undergo a substantial structural change to a butterfly-like structure through a two-electron oxidation process. The structural changes observed for the oxidized states are ascribed to significant differences in the frontier molecular orbitals of the above-mentioned three kinds of 9,10-diaminoanthracenes due to different extents of mixing between the amine-localized and anthrylene-localized orbitals.

Isolable Triradical Trication of Hexaaza[16]paracyclophane with Embedded 9,10-Anthrylenes: A Frustrated Three-Spin System

A new derivative of hexaaza[16]paracyclophane in which p-phenylenes are alternately replaced by 9,10-anthrylenes was prepared to investigate the impact on overall π-conjugation as well as conformational change of the macrocycle. The charge and spin distribution for one-electron and three-electron oxidation of the macrocycle was elucidated by means of electrochemical, spectroelectrochemical, EPR spectroscopic, and SQUID magnetometric methods. In particular, the triradical trication was successfully isolated as an air-stable salt, and moreover, its structure was disclosed by X-ray analysis. The triradical trication was characterized as a spin-frustrated three-spin system with the antiferromagnetic exchange interaction (J/kB ≃ - 74 K).

5,12-Diaminotetracenes: The Impact of Orbital Interactions between the Acene π System and Amino Groups on Their Electronic States

5,12-Diamino-substituted tetracenes with various N-substituents have been prepared, and their molecular structural changes upon oxidation have been evaluated in association with their electronic structures. The N-substituents influence both the electronic and molecular structures of the oxidized species of 5,12-diaminotetracenes. The tetracene moiety of 5,12-bis(N,N-dianisylamino)tetracene retained its planarity during the course of two successive one-electron oxidations, whereas 5,12-bis(N,N-dimethylamino)tetracene and 5,12-bis(N-anisyl-N-methylamino)tetracene underwent substantial structural changes into butterfly like structures through a simultaneous two-electron oxidation process. The molecular structures in the oxidized states were closely related to the nature of the highest occupied orbitals, which were characterized by the extent of mixing between the fragment orbitals for the teracene moiety and the substituted amino groups in 5,12-diaminotetracenes. As a consequence, the present work revealed that the extent of folding deformation of the acene moiety in the oxidized diaminoacenes could be fine-tuned by varying the N-substituents.

Diazadibora[1.1.1.1]m,p,m,p‐cyclophanes: Ambipolar Conjugated Macrocycles with Different B–π–N Embedded Patterns

Are different B(boron)-π-N(nitrogen) embedded patterns to bring about significant different (opto)electronic properties for the same macrocyclic molecular backbone? A series of B-π-N-embedded alternate-meta-para-linked cyclophanes 1-3 have been prepared and characterized as a new class of ambipolar π-conjugated B-π-N macrocycles. The answer to the opening question is yes. These macrocycles revealed the intramolecular charge transfer in the oxidized states and the intriguing photophysical proprerties in accordance with the embedded patterns, suggesting the electronic structures are tunable by introducing multiple B-π-N moieties.