title: Phenothiazine-bridged cyclic porphyrin dimers as high-affinity hosts for fullerenes and linear array of C60 in self-assembled porphyrin nanotube.
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.
authors.affiliation: Institute for Materials Chemistry and Engineering, Kyushu University , 6-10-1 Hakozaki, Higashi-ku, Fukuoka 812-8581, Japan.
authors.forename: Ken-ichi
authors.initials: K
authors.lastname: Sakaguchi
authors.forename: Takuya
authors.initials: T
authors.lastname: Kamimura
authors.forename: Hidemitsu
authors.initials: H
authors.lastname: Uno
authors.forename: Shigeki
authors.initials: S
authors.lastname: Mori
authors.forename: Shuwa
authors.initials: S
authors.lastname: Ozako
authors.forename: Hirofumi
authors.initials: H
authors.lastname: Nobukuni
authors.forename: Masatoshi
authors.initials: M
authors.lastname: Ishida
authors.forename: Fumito
authors.initials: F
authors.lastname: Tani