title: Relationship between incoherent excitation energy migration processes and molecular structures in zinc(II) porphyrin dendrimers.
abstract: Multiporphyrin dendrimers are among the most promising architectures to mimic the oxygenic light-harvesting complex because of their structural similarities and synthetic convenience. The overall geometries of dendrimers are determined by the core structure, the type of dendron, and the number of generations of interior repeating units. The rigid core and bulky volume of exterior porphyrin units in multiporphyrin dendrimers give rise to well-ordered three-dimensional structures. As the number of generations of interior repeating units increases, however, the overall structures of dendrimers become disordered and randomized due to the flexibility of the repeating units. To reveal the relationship between molecular structure and processes of excitation-energy migration in multiporphyrin dendrimers, we calculated the molecular structure and measured the time-resolved transient absorption and fluorescence anisotropy decays for various hexaarylbenzene-anchored polyester zinc(II) porphyrin dendrimers along with three types of porphyrin dendrons as references. We found that the congested two-branched type dendrimers exhibit more efficient energy migration processes than one- or three-branched type dendrimers because of multiple energy migration pathways, and the three-dimensional packing efficiency of dendrimers strongly depends on the type of dendrons.
authors.affiliation: National Creative Research Initiatives Center for Ultrafast Optical Characteristics Control and Department of Chemistry, Yonsei University, Seoul 120-749, Korea.
authors.forename: Sung
authors.initials: S
authors.lastname: Cho
authors.forename: Wei-Shi
authors.initials: WS
authors.lastname: Li
authors.forename: Min-Chul
authors.initials: MC
authors.lastname: Yoon
authors.forename: Tae Kyu
authors.initials: TK
authors.lastname: Ahn
authors.forename: Dong-Lin
authors.initials: DL
authors.lastname: Jiang
authors.forename: Jiwon
authors.initials: J
authors.lastname: Kim
authors.forename: Takuzo
authors.initials: T
authors.lastname: Aida
authors.forename: Dongho
authors.initials: D
authors.lastname: Kim
mesh_terms: D050091:Dendrimers / Q000737:chemistry*; D004735:Energy Transfer; D045342:Light-Harvesting Protein Complexes; D008665:Metalloporphyrins / Q000737:chemistry*; D018716:Molecular Mimicry; D015394:Molecular Structure
chemical_list: D050091:Dendrimers; D045342:Light-Harvesting Protein Complexes; D008665:Metalloporphyrins; C017802:zinc hematoporphyrin