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.

Aggregation-Induced Energy Transfer in a Decanuclear Os(II)/Ru(II) Polypyridine Light-Harvesting Antenna Dendrimer

“…[25][26][27] Inter-dendrimer energy-transfer processes in self-assembled multidendrimer systems have never been reported, although in light-harvesting dendrimers, different energy-transfer patterns, called inter-wheel and intra-wheel energy transfer, have been described; in these, energy transfer takes place between chromophores belonging to the same branch (intra-wheel) or different branches (inter-wheel) of the dendrimers. 28 Similarly, intra-dendrimer energy-transfer processes that become active upon aggregation are also unknown. Indeed, inter-dendrimer energy transfer would be an interesting process, because it would resemble the energy migration processes occurring among various LH2 subunits-or LH2 and LH1 subunits-of the natural photosynthetic edifices, possibly following intra-dendrimer energy transfer, which would be analogous to energy migration processes within single LH2 or LH1 edifices.…”

Dendrimer/inorganic nanomaterial composites: Tailoring preparation, properties, functions, and applications of inorganic nanomaterials with dendritic architectures

“…By utilizing this unique feature, Aida, Jiang, Li et al have developed a series of multiporphyrin dendrimers, which possess a number of porphyrin units, all residing in the same layer of a dendritic scaffold [13,14]. These compounds served as models to study the energy migration and transfer processes in natural photosynthetic systems [15,16]. When these multiporphyrin dendrimers entrapped a layer of fullerene units via metal-ligand interactions, a concentric electron donating (D) and accepting (A) double layer structure formed [17].…”

Multiple‐Porphyrin Functionalized Hexabenzocoronenes

“…[22] Subsequently,t he compound class of porphyrin-HPBs expanded to al ibrary of extraordinary light-harvesting arrays. [22][23][24][25][26][27][28][29][30][31] Their oxidized derivatives, porphyrin-HBCs, [32][33][34][35][36][37][38][39][40][41] however,d id not evolve parallel to the discoveries of novel porphyrin HPBs, althought heir preparation seems to be the logical continuation of the HPB architectures.T he first directly linked porphyrin-HBC was reported in 2013, it was synthesized in an intramolecular oxidative cyclodehydrogenation reaction of the respective porphyrin-HPB. [33] The transformation, commonly known as "Scholl reaction", turns af lexible, nonconjugated HPB moiety into ap lanarized, aromatic HBC unit, which significantly influences the porphyrins'c haracteristics.…”