The University of Osaka · Materials Science
Professor Yasukazu Hirao's research lab specializes in the design, synthesis, and characterization of advanced organic electronic materials with unique electronic structures, particularly focusing on multi-radical and polycationic systems. The lab investigates intramolecular spin transfer, intervalence charge transfer, and biradicaloid character in conjugated and through-space conjugated systems, often employing electrochemical, spectroelectrochemical, and ESR techniques to probe electronic coupling and spin delocalization. A key research direction involves the development of dendritic oligoarylamine architectures and twisted or strained π-systems to access high-spin states and unusual electronic properties. The lab also explores proton-coupled electron transfer (PCET) processes through hydrogen-bonded complexes, linking molecular structure to reactivity and dynamics in redox processes.
Figures are computed from collected data and may differ slightly.
The intervalence (IV) states of the monocationic states of the star-shaped nonaamine (3) and the triamine (2) as the branched unit in 3 have been examined by electrochemical, spectroelectrochemical, and temperature-dependent ESR spectroscopy. The oligoarylamines 2 and 3 were synthesized by using the successive palladium-catalyzed amination reaction. The redox property of 3 was basically the same as that of 2. However, there exist small potential differences between the first three one-electron o
A through-space conjugated multi-phenalenyl triradical 1 a has been prepared and characterized. Partial occupancy of doubly degenerate molecular orbitals in 1 a leads to Jahn-Teller distortion, creating a molecular skeleton in which C<sub>2v</sub> doublet states are lower in energy than undistorted D<sub>3h</sub> doublet and quartet states. Triradical 1 a exists in an acute form in the solution state, whereas it adopts a preferred obtuse form in the solid state. The results of the investigation
Intriguing electronic properties were observed for the radical cation 1+ of a spiro-fused bis(triarylamine). In a new example of intramolecular spin transfer (IST) in organic intervalence systems connected by a non-π-conjugated bridging unit, the as-prepared radical cation 1+ exhibited thermally activated IST. Furthermore, it was found that 1+ decomposes slowly to the tri-p-anisylamine radical cation. Supporting information for this article is available on the WWW under http://www.wiley-vch.de/c
A new dendritic oligoarylamine, N,N,N',N',N",N"-hexakis[4-(di-4-anisylamino)phenyl]- 1,3,5-benzenetriamine (BTA) 2, which contains a 1,3,5-benzenetriamine molecular unit as an potential precursor of a high-spin molecule and three oligoarylamine moieties as spin-carrying units surrounding the core BTA, has been prepared by the sequential palladium-catalyzed amination reactions. The redox property has been investigated by cyclic voltammetry, and the highly charged states up to the hexacation are a
A compound with a highly twisted C═C bond in the intermediate bond dissociation region was isolated, and its biradicaloid nature was experimentally demonstrated. A bianthrone derivative substituted with long-chain alkoxy groups was synthesized, and its twisted conformer was assembled into crystals through hydrophobic intermolecular interactions of the introduced alkoxy chains. X-ray crystallography revealed that the C═C bond connecting the two anthrone rings has a long bond length (1.429 Å) and
A hydrogen-bonded complex was successfully isolated as crystals from the anthranol/anthroxyl pair in the self-exchange proton-coupled electron transfer (PCET) reaction. The anthroxyl radical was stabilized by the introduction of a 9-anthryl group at the carbon atom at the 10-position. The hydrogen-bonded complex with anthranol self-assembled by π-π stacking to form a one-dimensional chain in the crystal. The conformation around the hydrogen bond was similar to that of the theoretically predicted
The twisted form of bianthrone is known as a metastable state provided by a photo-induced or thermal-induced isomerization of the folded form, and thus prevents the isolation and the detailed analysis of its electronic structure. In this study, an unsymmetrical bianthrone (2), consisting of the electron-withdrawing anthrone and electron-donating acridane, have been synthesized and shown to exhibit a solvent-polarity-dependent isomerization reaction between the folded and twisted isomers. With in
A novel π-extended trinaphtho[3.3.3]propellane (TNP) derivative was prepared and through-space electronic communication in its radical cation species was characterized by electrochemical and spectroscopic methods. Cyclic voltammetry and UV/Vis-NIR titrations suggested weak electronic communication among the three aromatic rings. Variable-temperature ESR measurements of the radical cation showed a drastic change in the spectra in the range of 230-180 K, indicating hopping-type spin delocalization
Views Icon Views Article contents Figures & tables Video Audio Supplementary Data Peer Review Share Icon Share Twitter Facebook Reddit LinkedIn Tools Icon Tools Reprints and Permissions Cite Icon Cite Search Site Citation Yasukazu Hirao, Akihito Konishi, Kouzou Matsumoto, Hiroyuki Kurata, Takashi Kubo; Synthesis and electronic structure of bisanthene: A small molecular-sized graphene with zigzag edges. AIP Conf. Proc. 10 December 2012; 1504 (1): 863–866. https://doi.org/10.1063/1.4771831 Downloa
The designed and synthesized tetramethoxy-substituted bianthrone exists as an equilibrium mixture of the folded and twisted conformers in solution. The introduction of methoxy groups into the 3,3',6,6'-positions of bianthrone reduces the energy difference between the conformers and results in a bistable system. The survey of its equilibrium constant based on the optical absorption and variable temperature quantitative NMR spectroscopic studies in various solvents revealed that the equilibration
The synthesis of phenalenyl-endcapped [5]cumulene as a cumulene-based singlet biradical and the spin correlation changes of one-dimensional aggregates are described. The high propensity for self-aggregation of phenalenyl rings and the introduction of bulky substituents into the appropriate positions led to the formation of a one-dimensional chain assembly. Single-crystal X-ray structural analysis indicated that the bond length alternation of the cumulene chain increased with decreasing temperatu
Faszinierende elektronische Eigenschaften wurden für das Radikalkation 1+ eines spiro-verknüpften Bis(triarylamins) nachgewiesen. Frisch präpariertes 1+ geht einen thermisch aktivierten intramolekularen Spintransfer (IST) ein und ist ein neuartiges Beispiel für IST in organischen Intervalenzsystemen ohne π-konjugierte Brücke. Weiter wurde gefunden, dass sich 1+ langsam zum Tri-p-anisylamin-Radikalkation zersetzt. Supporting information for this article is available on the WWW under http://www.wi
The 3-fold interpenetration of the β-quartz-type hydrogen-bonded organic framework (HOF) from the dication salts of tetrakis(4-pyridyl)methane develops a host–guest system featuring flexibility and durability in accordance with the state change of guest molecules. Water molecules are incorporated into HOF and form a one-dimensional helical-shaped molecular chain in nanopores. X-ray crystallographic analysis and the dielectric dispersion in the impedance measurements revealed that guest water mol
Abstract The intramolecular spin–spin interaction in the highly oxidized species of a star‐shaped oligoarylamine, namely hexakis{4‐[bis( p ‐methoxyphenyl)amino]phenyl}benzene ( 1 ), in which six diphenylamine units are introduced as redox‐active sites into a central hexaphenylbenzene core, has been investigated by EPR spectroscopy. The hexacation‐rich sample was prepared by chemical oxidation with 7.5 equivalents. of [bis(trifluoroacetoxy)iodo]benzene (PIFA) in the presence of 10 vol.‐% trifluor
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