title: Structural factors determining photophysical properties of directly linked zinc(II) porphyrin dimers: linking position, dihedral angle, and linkage length.
abstract: We have investigated the relationship between the photophysical properties and structures of a series of directly linked zinc(II) porphyrin dimers (mmZ2, mbZ2, and bbZ2) using time-resolved spectroscopic measurements and theoretical calculations. Their unique characters such as CT nature and torsional motion are caused by interporphyrin interactions and steric effects, respectively, which can be fully understood in terms of three structural factors: linking position, dihedral angle, and linkage length. The orthogonal geometry and heterolinking of mmZ2 and mbZ2 induce the localized MOs and electron unbalance in the constituent porphyrin units, respectively, and consequently lead to distinct CT characters in spite of their different origin. On the other hand, a small interporphyrin steric hindrance in bbZ2 makes a torsional motion possible around the direct beta-beta' linkage in the excited state, which is correlated with the solvent dependence of the fast S(1) fluorescence decay component. On the basis of this work, we can gain further insight into the effect of individual structural factors on the photophysical properties, which provides a firm basis for further understanding of the photophysical properties mainly determined by the structural factors in multiporphyrin systems.
authors.affiliation: Spectroscopy Laboratory for Functional pi-Electronic Systems and Department of Chemistry, Yonsei University, Seoul 120-749, Korea.
authors.forename: Sung
authors.initials: S
authors.lastname: Cho
authors.forename: Min-Chul
authors.initials: MC
authors.lastname: Yoon
authors.forename: Jong Min
authors.initials: JM
authors.lastname: Lim
authors.forename: Pyosang
authors.initials: P
authors.lastname: Kim
authors.forename: Naoki
authors.initials: N
authors.lastname: Aratani
authors.forename: Yasuyuki
authors.initials: Y
authors.lastname: Nakamura
authors.forename: Toshiaki
authors.initials: T
authors.lastname: Ikeda
authors.forename: Atsuhiro
authors.initials: A
authors.lastname: Osuka
authors.forename: Dongho
authors.initials: D
authors.lastname: Kim