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Phenothiazine-bridged cyclic porphyrin dimers as high-affinity hosts for fullerenes and linear array of C60 in self-assembled porphyrin nanotube.

Authors
  • Sakaguchi, Ken-ichi
  • Kamimura, Takuya
  • Uno, Hidemitsu
  • Mori, Shigeki
  • Ozako, Shuwa
  • Nobukuni, Hirofumi
  • Ishida, Masatoshi
  • Tani, Fumito
Type
Published Article
Journal
The Journal of Organic Chemistry
Publisher
American Chemical Society
Publication Date
Apr 04, 2014
Volume
79
Issue
7
Pages
2980–2992
Identifiers
DOI: 10.1021/jo500034f
PMID: 24597606
Source
Medline
License
Unknown

Abstract

Free-bases and a nickel(II) complex of phenothiazine-bridged cyclic porphyrin dimers bearing self-assembling 4-pyridyl groups (M2-Ptz-CPDPy(OCn); M = H2 or Ni, OCn = OC6 or OC3) at opposite meso-positions have been prepared as host molecules for fullerenes. The free-base dimer (H4-Ptz-CPDPy(OC6)) includes fullerenes with remarkably high association constants such as 3.9 ± 0.7 × 10(6) M(-1) for C60 and 7.4 ± 0.8 × 10(7) M(-1) for C70 in toluene. This C60 affinity is the highest value ever among reported receptors composed of free-base porphyrins. The nickel dimer (Ni2-Ptz-CPDPy(OC6)) also shows high affinities for C60 (1.3 ± 0.2 × 10(6) M(-1)) and C70 (over 10(7) M(-1)). In the crystal structure of the inclusion complex of C60 within H4-Ptz-CPDpy(OC3), the C60 molecule is located just above the centers of the porphyrins. The two porphyrin planes are almost parallel to each other and the center-to-center distance (12.454 Å) is close to the optimal separation (∼12.5 Å) for C60 inclusion. The cyclic porphyrin dimer forms a nanotube through its self-assembly induced by C-H···N hydrogen bonds between porphyrin β-CH groups and pyridyl nitrogens as well as π-π interactions of the pyridyl groups. The C60 molecules are linearly arranged in the inner channel of this nanotube.

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