Doctor of Science

No

Organic Chemistry

0000-0002-9166-2127

00years00months

Aromatic diimide compounds such as naphthalene diimide (NDI) and perylene diimide (PDI) have attracted much attention as electron acceptors, n-type semiconductors, chromophores in visible region and building blocks of supramolecular architectures. Besides NDI and PDI, tetracene diimide (TDI) is also expected to exhibit intriguing electronic and photophysical properties since TDI possesses linearly extended π-conjugated system. However, there have been only limited TDI derivatives reported in a few papers. Herein, we have designed a further π-extended TDI by fusing azulene as a 10π-conjugating unit. Azulene is a unique molecule, which has a dipole moment of about 1.08 D along the C2-C6 axis to afford electron-donating five-membered ring and electron-withdrawing seven-membered ring. Hence, bonding of five-membered ring of azulene to a diimide core is anticipated to realize effective donor-acceptor interaction and π-extension, leading to a smaller HOMO-LUMO gap and characteristic photophysical and electronic properties. TA-fused TDI exhibited four reversible one-electron reduction processes at –0.77, –1.08, –1.97, –2.12 V versus the Fc/Fc+ with a remarkable small HOMO-LUMO gap (0.96 eV). Absorption spectrum of TA-fused TDI exhibited intense absorption bands at 343, 410, 426, 600, 651 nm derived from TDI skeleton, and a broad low-energy band centered at 946 nm. The edge of the lowest-energy absorption band reached ca. 1400 nm corresponding to the energy gap of 0.89 eV, which is in good agreement with the electrochemical HOMO-LUMO gap. The Two-photon absorption (TPA) cross-section of TA-fused TDI was determined to be σ(2) = 2140 GM at 950 nm (1 GM = 10-50 cm4 s photon-1 molecule-1). The electron mobility of a thin film of TA-fused TDI prepared on an ITO /glass substrate was revealed to be μ = 1.7×10–4 cm2 V–1 s–1 by space charge limited current (SCLC) method.

Construction of functionalized nano space surrounded by large pai-electronic systems.
We have studied the supramolecular structures and photoelectronic properties of inclusion complexes of cyclic porphyrin dimers (M2-CPDPy, M=Ni, 2H) and fullerenes (C60, C70, PCBM ([6,6]-Phenyl-C61-butyric acid methyl ester) and Li+@C60). The porphyrin dimers have self-assembling 4-pyridyl groups at the meso positions and include fullerenes in their cavities with high affinities (Kassoc. ≈ 105 M-1). In crystals, C60⊂Ni2-CPDPy and PCBM⊂Ni2-CPDPy afford self-assembled porphyrin nanotubes containing the linear arrays of fullerene molecules. These self-assemblies are induced mainly by the non-classical hydrogen bonds between pyridyl nitrogens and porphyin β C-H groups. On the other hand, in the crystals of C60⊂H4-CPDPy and C70⊂H4-CPDPy, the included fullerene molecules show zigzag chains through van der Waals contacts with each other. Due to these well-ordered arrays of C60, both crystals of C60⊂Ni2-CPDPy and C60⊂H4-CPDPy have high charge mobilities (Σμ > 0.1 cm2V-1s-1). C60⊂H4-CPDPy shows photoinduced electron transfer from the porphyrin moieties to C60 and photovoltaic activity with IPCEmax=17 % in photoelectrochemical cells. Moreover, the inclusion complexes of lithium ion encapsulated C60 (Li+@C60) and M2-CPDPy exhibit photoinduced charge separation with very long lifetimes reaching submillisecond order.

Modeling study for cytochrome P450 by the use of synthetic heme complex to elucidate the oxygen activation mechanism of this enzyme family.

Research Interests

• Synthesis and photoelectronic properties of novel polycyclic pi-electron compounds
  keyword : pai-electron system, polycyclic,aromaticity
  2013.04～2027.03Synthesis and evaluation of functional compounds and supramolecular assemblies composed of porphyrins, phthalocyanines and fullerene.
• Synthesis and evaluation of functional organic compounds and supramolecular assemblies including porphyrins, phthalocyanines and fullerenes
  keyword : porphyrin, phthalocyanine,fullerene,energy transfer,self-assembly,supramolecule, pai-electron system, electron transfer
  2002.04～2027.03Synthesis and evaluation of functional compounds and supramolecular assemblies composed of porphyrins, phthalocyanines and fullerene.
• modeling of cytochrome P450
  keyword : porphyrin,catalyst,oxygen,oxidation,metalloenzyme,heme,P450,model,metal complex,
  1986.04～2007.12Modeling study to elucidate the mechanism of oxygen activation of cytochrome P450 by the use of synthetic heme complexes.

Academic Activities Awards

• An Azulene-Based Chiral Helicene and Its Air-Stable Cation Radical
• Supramolecular Structures of Inclusion Complexes of C70 and Cyclic Porphyrin Dimers

Educational Activities