Tuning of Intramolecular π-π Overlap Mode of Tetrathiafulvalene Bisannulated Macrocycles in the Open-Shell Electronic State

Akutagawa, Tomoyuki; Abe, Y.; Hasegawa, Tatsuo; Nakamura, Takayoshi; Inabe, Tamotsu; Christensen, Christian A.; Becher, Jan

doi:10.1246/cl.2000.132

Cited by 14 publications

(8 citation statements)

References 5 publications

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“…The fact that only one wave for the two-electron oxidation generating the diradicals ( 3a ) 2+ and ( 4a ) 2+ is observed in the voltammograms of 3a and 4a ( E 1 ‘ ≤ E 1 ) reflects that the formation of π-dimers is favored relative to the formation of MV complexes. The ability of bis-TTFs containing flexible linkers to form intramolecular π-dimers was earlier observed in the crystal structures of divalent cation salts of 2,3-cyclized bis-TTF macrocycles containing S(CH 2 CH 2 O) n CH 2 CH 2 S ( n = 1, 2) bridges . Moreover, spectroelectrochemical experiments in solution have revealed intramolecular aggregation of TTF radical cations in a (TTF) 21 -glycol dendrimer in which flexible polyether spacers allow TTFs in close spatial contact to interact …”

Section: Resultsmentioning

confidence: 79%

Multiple-Bridged Bis-Tetrathiafulvalenes: New Synthetic Protocols and Spectroelectrochemical Investigations

et al. 2000

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Synthetic strategies for preparing dimeric tetrathiafulvalenes (TTFs) linked by either one, two, or four bridges have been developed. In particular, we report efficient few-step protocols for the preparation of face-to-face overlapped quadruple-bridged bis-TTFs. The ready interconversion of cis and trans TTFs in the presence of catalytic amounts of acid was implemented in one synthetic protocol as a way to control the isomeric outcome. The compounds were characterized by NMR spectroscopy, mass spectrometry, and elemental analysis. Moreover, the X-ray crystal structure of the macrocycle 4b is presented and compared to semiempirical (PM3) geometry optimizations. Cyclic voltammetry and spectroelectrochemistry were used to describe the interactions established between two TTF units upon oxidation, that is, their ability to form mixed-valence complexes and π-dimers either intra- or intermolecularly. The length, flexibility, and number of bridging units in a bis-TTF, as well as the specific TTF positions being connected, determine the extent of these interactions. Thus, rigid linkers enhance the formation of intermolecular mixed-valence complexes. For 4b, the absorption spectrum of this mixed-valence state of TTF in solution has been recorded for the first time. Finally, preliminary complexation experiments with different electron-deficient molecules are described.

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Section: Resultsmentioning

confidence: 79%

Multiple-Bridged Bis-Tetrathiafulvalenes: New Synthetic Protocols and Spectroelectrochemical Investigations

et al. 2000

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“…Note that the alkyl chains are omitted for clarity. The electronic states of the TTF units and F 4 -TCNQ molecules in the nanowire, as well as the (2)(F 4 -TCNQ) 2 crystal, are in a fully charged transferred state, as seen by comparing the IR spectra with that of a reported complex (33) and (1a)(F 4 -TCNQ) 2 (34).…”

Section: Resultsmentioning

confidence: 94%

Formation of oriented molecular nanowires on mica surface

Akutagawa

Ohta

Hasegawa

et al. 2002

Proc. Natl. Acad. Sci. U.S.A.

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Molecular ''nanowire'' structures composed of the charge transfer complex of a bis-tetrathiafulvalene substituted macrocycle and tetrafluorotetracyanoquinodimethane were constructed on mica substrates by employing the Langmuir-Blodgett technique. The nanowires transferred from a dilute aqueous potassium chloride subphase had typical dimensions of 2.5 nm ؋ 50 nm ؋ 1 m. The nanowires are oriented to specific directions, corresponding to the directions of the potassium-ion array on the mica surface having sixfold symmetry. Such correlation between the nanowires and the substrate surface was also observed when a dilute aqueous rubidium chloride subphase was used. On the other hand, the correlation completely disappeared when the subphase contained divalent cations, indicating that the molecular nanowires orient by recognizing the monocation array on the mica surface. The nanowires formed by the vertical dipping method coexist with the monolayers. Only nanowire structures are, however, observed when we apply the horizontal lifting method. Based on the crystal structure of a related complex, a possible structure of the nanowires is presented. The conductivity of the nanowires was estimated to be of the order of 10 ؊3 S⅐cm ؊1 . The nanowires formed specific (regular) structures such as T-shape junctions, suggesting their use in construction of future molecular nanoscale devices.

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Section: 2 Cyclophanes and Macrocycles With A Double Linkage115mentioning

confidence: 99%

“…Recently, many macrocyclic bis-TTFs with a variety of spacers, such as alkyl chains, dialkylpyridine, dialkylbiphenyl, dialkylbutadiyne, and crown ether, have been studied. Crown ethers 149a , b containing two TTF units were prepared, and the crystal structures of the divalent cations and the CT complexes were described . These X-ray analyses suggest that 149a 2+ takes a Z-type intramolecular π-dimer structural conformation and the magnitude of intramolecular π−π overlap depends on the ring size of the macrocycles.…”

Section: 2 Cyclophanes and Macrocycles With A Double Linkage115mentioning

confidence: 99%