Giant Porphyrin Wheels with Large Electronic Coupling as Models of Light‐Harvesting Photosynthetic Antenna

Hori, Takaaki; Aratani, Naoki; Takagi, Atsuko; Matsumoto, Takuya; Kawai, Tomoji; Yoon, Myung Hwan; Yoon, Zin Seok; Cho, Sung June; Kim, Dongho; Osuka, Atsuhiro

doi:10.1002/chem.200501373

Cited by 92 publications

(72 citation statements)

References 53 publications

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“…The STM images of C24ZB exhibited mostly ellipsoidal shapes, indicating its conformational flexibility of C24ZB as compared with rather uniform C12ZA (Figure 15b). 98 The averaged diameter of the STM images of C24ZB was 4570 ¡, which matched roughly with its estimated diameter (ca. 70 ¡).…”

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confidence: 66%

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Exploration of Giant Functional Porphyrin Arrays

Aratani

Osuka

2014

Bulletin of the Chemical Society of Japan

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Directly linked linear porphyrin arrays were synthesized and their photophysical properties depending on the length of the arrays were investigated. Ag(I)-promoted oxidative coupling of 5,15-diaryl Zn(II) porphyrins has proven to be effective for preparations of very long mesomeso-linked Zn(II) porphyrin arrays (Zn). A stepwise doubling strategy with strict purification at each doubling step allowed for preparation of gigantic but discrete linear arrays in an unprecedented manner. Large cyclic porphyrin wheels were also synthesized by final mesomeso coupling intramolecular cyclization. Crucial to this success are high reactivity and high regioselectivity of the Ag(I)-promoted oxidative coupling. Equally important are high solubilities of Zn despite their large molecular weights, which arise from their perpendicularly linked structures. Another advantage of this doubling strategy is a large difference in the molecular weights among reactants and products that increases as the reactant array becomes larger, allowing separation of coupling products by preparative GPC-HPLC. As an alternative protocol, Pd-catalyzed SuzukiMiyaura cross-coupling has been extensively used for synthesis of cyclic porphyrin arrays. This strategy gave novel linear and cyclic porphyrin arrays from β-borylated porphyrins that were prepared by Ir-catalyzed borylation of meso-free porphyrins. As an interesting example, a porphyrin nanotube consisting of four porphyrins doubly bridged by 2,6-pyridinylene spacers was synthesized and revealed to possess a C 60 -encapsulation capability. Exciton coupling, effective energy hopping, coherent length, and excitation energy transfer of mesomeso-linked linear and cyclic porphyrin arrays are discussed. STM and AFM detections of the large porphyrin arrays are also presented. We believe that these studies expand the range of organic molecules we can manipulate and open a door to a new area of nanoscaled and sub-microscaled functional porphyrin materials.

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confidence: 66%

“…98 We examined the intramolecular cyclization of the linear porphyrin 24-mer 24ZB to cyclic porphyrin C24ZB (Scheme 6). Under highly dilute conditions (1 © 10 ¹6 M), 24ZB was treated with 3.0 equivalents of AgPF 6 for 60 h at room temperature.…”

Section: M-phenylene-bridged Porphyrin Wheelsmentioning

confidence: 99%

Exploration of Giant Functional Porphyrin Arrays

Aratani

Osuka

2014

Bulletin of the Chemical Society of Japan

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“…We entered porphyrin chemistry with the aim to synthesize covalently linked organic constructs that can mimic the whole excitation energy transfer and electron transfer events of the photosynthetic reaction centers within a single molecular entity. 13 In the course of these studies, we fortunately encountered new reactions and structures, which drove us to change our research style from a well-designed, goal-orientated path to a flexible discovery-searching strategy to explore novel porphyrinoids. By following the flexible research style, we have explored mesomeso-linked Zn(II) porphyrin arrays, meso-aryl expanded porphyrins, transition-metal-catalyzed porphyrin modifications, and subporphyrins.…”

Section: A Brief Survey Of Our Efforts In the Exploration Of Novel Pomentioning

confidence: 99%

Subporphyrins: A Legitimate Ring-Contracted Porphyrin with Versatile Electronic and Optical Properties

Osuka

Tsurumaki

Tanaka

2011

Bulletin of the Chemical Society of Japan

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After a brief survey of our efforts in the development of novel porphyrinoids that include mesomeso-linked porphyrin arrays, meso-aryl expanded porphyrins, and transition-metal-catalyzed functionalizations of porphyrins, a particular focus in this account is placed on the chemistry of subporphyrins that has been explored in our group. Subporphyrin is a legitimate ring-contracted porphyrin consisting of three pyrrolic subunits domed in a C 3 symmetric bowl shape. While subporphyrins are simple and small macrocycles and possess a key position in porphyrin chemistry, they had been elusive until our first synthesis of tribenzosubporphines in 2006. Shortly after, synthetic protocols of mesoaryl-substituted subporphyrins were developed to produce various subporphyrins with versatile electronic properties that can be widely tuned by meso-aryl substituents. Raney nickel reduction was used to prepare meso-alkyl-substituted subporphyrins from meso-thienyl-substituted subporphyrins. Subchlorins and subbacteriochlorins were prepared respectively by the reduction of subporphyrins with p-tosylhydrazide and Raney nickel. While subporphyrins and subchlorins share conjugated 14³-electronic circuits, subbacteriochlorins have a rare [13]diazaannulene circuit maintained through the lone-pair electrons of the nitrogen atom. The aromaticity decreases in the order of subporphyrin > subchlorin > subbacteriochlorin, as indicated from 1 H-and 11 B NMR spectra and nuclear independent chemical shift (NICS) calculations. Despite these progresses, the chemistry of subporphyrins is still in the infant stage with many untouched aspects and further improvements in synthetic yields are highly desirable for the developments of the chemistry of subporphyrins as well as their applications in diverse fields. A Brief Survey of Our Efforts in the Exploration of Novel PorphyrinoidsIn the last three decades, we have been involved in the exploration of novel porphyrinoids with intriguing structures, electronic and optical properties, and functions. We entered porphyrin chemistry with the aim to synthesize covalently linked organic constructs that can mimic the whole excitation energy transfer and electron transfer events of the photosynthetic reaction centers within a single molecular entity. 13 In the course of these studies, we fortunately encountered new reactions and structures, which drove us to change our research style from a well-designed, goal-orientated path to a flexible discovery-searching strategy to explore novel porphyrinoids. By following the flexible research style, we have explored mesomeso-linked Zn(II) porphyrin arrays, meso-aryl expanded porphyrins, transition-metal-catalyzed porphyrin modifications, and subporphyrins. After a brief survey of the former three topics, a particular focus is placed on the chemistry of subporphyrins that are legitimate ring-contracted porphyrins. As described below, subporphyrins are a new class of functional molecules, particularly in view of their highly tunable electronic and optical properties.

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“…Two types of a series of extremely large yet discrete cyclic porphyrin wheels were also prepared to explore EET processes. The directly meso-meso linked porphyrin dimer Z2 and tetramer Z4 are bridged by m-phenylene spacers, respectively, to form cyclic structures C N ZA (N = 10, 12, 16, 18, 24 and 32) and C N ZB (N = 24; scheme 4) [15,16].…”

Section: Cyclic Porphyrin Arraysmentioning

confidence: 99%

Excitation energy migration processes in various multi-porphyrin assemblies

Yang

Kim

2012

Phil. Trans. R. Soc. A.

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The electronic interactions and excitation energy transfer (EET) processes of a variety of multi-porphyrin arrays with linear, cyclic and box architectures have been explored. Directly meso-meso linked linear arrays (Z N ) exhibit strong excitonic coupling with an exciton coherence length of approximately 6 porphyrin units, while fused linear arrays (T N ) exhibit extensive p-conjugation over the whole array. The excitonic coherence length in directly linked cyclic porphyrin rings (CZ N ) was determined to be approximately 2.7 porphyrin units by simultaneous analysis of fluorescence intensities and lifetimes at the single-molecule level. By performing transient absorption (TA) and TA anisotropy decay measurements, the EET rates in m-phenylene linked cyclic porphyrin wheels C12ZA and C24ZB were determined to be 4 and 36 ps −1 , respectively. With increasing the size of C N ZA, the EET efficiencies decrease owing to the structural distortions that produce considerable non-radiative decay pathways. Finally, the EET rates of self-assembled porphyrin boxes consisting of directly linked diporphyrins, B1A, B2A and B3A, are 48, 98 and 361 ps −1 , respectively. The EET rates of porphyrin boxes consisting of alkynylenebridged diporphyrins, B2B and B4B, depend on the conformation of building blocks (planar or orthogonal) rather than the length of alkynylene linkers.

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Giant Porphyrin Wheels with Large Electronic Coupling as Models of Light‐Harvesting Photosynthetic Antenna

Cited by 92 publications

References 53 publications

Exploration of Giant Functional Porphyrin Arrays

Exploration of Giant Functional Porphyrin Arrays

Subporphyrins: A Legitimate Ring-Contracted Porphyrin with Versatile Electronic and Optical Properties

Excitation energy migration processes in various multi-porphyrin assemblies

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