| Budget Amount *help |
¥3,700,000 (Direct Cost: ¥3,700,000)
Fiscal Year 2006: ¥500,000 (Direct Cost: ¥500,000)
Fiscal Year 2005: ¥700,000 (Direct Cost: ¥700,000)
Fiscal Year 2004: ¥2,500,000 (Direct Cost: ¥2,500,000)
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| Research Abstract |
TTF is a good candidate as a building block for supramolecular systems as macrocycles, cyclophanes, catenanes, denderimers, and polymers. We designed new donor molecules that show new functions such as reproducible conductivity with electrical switching ability responded to the external stimuli. Incorporation of donor units into [3.3]paracyclophane bridges to make perpendicular orientation among donor units and aromatic rings in a cyclophane molecule results a charge transfer process with through-bond or through-space interaction. We synthesized orthogonalized cyclophanes (1, 2) linked with two 1,3-dithiol-2-ylidene (DT) or (2-methylidene-1,3-dithiolo[4,5-d])tetrathiafulvalene (DT-TTF) units as π-donors to cyclophane trimethylene bridges. Electronic spectra of 1 and 2 show broad absorption band in the 400-600 nm region, centered at ca. 450 nm (ε~150), which points weak intramolecular charge transfer interaction. Furthermore, in the cases of 3, the broad absorption band reveals 20nm lon
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ger than those of 1 and 2. This suggests long-range charge transfer interaction between 1,3-dithiol-2-ylidene and dicyanoethylidene units via cyclophane benzene rings. Cyclic voltammmogram of 1 shows five oxidation waves characteristic for DT-TTF moieties, in which the first, second, and third waves were reversible processes; the fourth one was quasi-reversible, the fifth and sixth ones were irreversible. This suggests that there are interactions of DT-TTF units through benzene rings of cyclophane. The first redox potential of 1 was appeared at ca. 0.1 V lower than that of 2, and the ΔE(=E_2-E_1) value for 1 was ca. 0.1 V which was smaller than that of 2. This fact suggests that the on-site Coulombic repulsion in their dication states is reduced by delocalization of two positive charges in the DT-TTF units and interaction between DT-TTF ones.
In conclusion, we report synthesis of cyclophanes (1, 2, 3) linked orthogonally with two donor units or a donor and acceptor one. Compounds 1, 2, and 3 are the unique examples of donor or donor-acceptor systems with weak intramolecular charge transfer properties. Furthermore another approach for new donor-acceptor molecular systems is combination of trinitrofluorene acceptor as stronger acceptor or DT-TTF as stronger donor. Less
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