title: Two-dimensionally extended porphyrin tapes: synthesis and shape-dependent two-photon absorption properties.
abstract: We report the synthesis and characterization of L- and T-shaped porphyrin tapes as extensible structural motifs of two-dimensionally extended porphyrin tapes. The two-photon absorption (TPA) cross-section values (sigma((2))) for L- and T-shaped porphyrin tapes as well as those for linear trimeric and tetrameric porphyrin tapes were measured by an open-aperture Z-scan method at 2300 nm, a wavelength at which the one-photon absorption contribution is either zero or almost negligible. Under these conditions, the sigma((2)) values for the linear porphyrin tape trimer and tetramer were determined to be 18 500 and 41 200 GM, respectively. The sigma((2)) value for the L-shaped trimer was determined to be 8700 GM, which is only half that of the linear trimer, whereas the sigma((2)) value for the T-shaped tetramer was measured to be 35 700 GM. These results clearly indicate the dependence of the TPA cross-section on the molecular shape, which underscores the importance of directionality in the pi-conjugation pathway for the enhancement of TPA cross- section.
authors.affiliation: Department of Chemistry, Graduate School of Science, Kyoto University, Sakyo-ku, Kyoto 606-8502, Japan.
authors.forename: Yasuyuki
authors.initials: Y
authors.lastname: Nakamura
authors.forename: So Young
authors.initials: SY
authors.lastname: Jang
authors.forename: Takayuki
authors.initials: T
authors.lastname: Tanaka
authors.forename: Naoki
authors.initials: N
authors.lastname: Aratani
authors.forename: Jong Min
authors.initials: JM
authors.lastname: Lim
authors.forename: Kil Suk
authors.initials: KS
authors.lastname: Kim
authors.forename: Dongho
authors.initials: D
authors.lastname: Kim
authors.forename: Atsuhiro
authors.initials: A
authors.lastname: Osuka