Supramolecular Photocatalysis by Utilizing the Host–Guest Charge‐Transfer Interaction: Visible‐Light‐Induced Generation of Triplet Anthracenes for [4+2] Cycloaddition Reactions

Uchikura, Tatsuhiro; Oshima, Mari; Kawasaki, Minami; Takahashi, Kohei; Iwasawa, Nobuharu

doi:10.1002/anie.201916732

Cited by 35 publications

(34 citation statements)

References 77 publications

(11 reference statements)

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“…Numerous examples for receptors with optical read‐out, photoswitchable self‐assemblies and light‐controlled molecular machines have been reported [3] . Recently, photo‐redox chemistry started to take advantage of the supramolecular organization of organic or metal‐based chromophores into functional systems, for example, for catalytic oxidation of alcohols [4] or cycloadditions to anthracenes [5] . Dye‐based assemblies have further been studied for bio‐imaging [6] and medicinal applications such as photodynamic therapy [7]…”

Section: Figurementioning

confidence: 99%

Coal‐Tar Dye‐based Coordination Cages and Helicates

et al. 2021

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A strategy to implement four members of the classic coal‐tar dye family, Michler's ketone, methylene blue, rhodamine B, and crystal violet, into [Pd2L4] self‐assemblies is introduced. Chromophores were incorporated into bis‐monodentate ligands using piperazine linkers that allow to retain the auxochromic dialkyl amine functionalities required for intense colors deep in the visible spectrum. Upon palladium coordination, ligands with pyridine donors form lantern‐shaped dinuclear cages while quinoline donors lead to strongly twisted [Pd2L4] helicates in solution. In one case, single crystal X‐ray diffraction revealed rearrangement to a [Pd3L6] ring structure in the solid state. For nine examined derivatives, showing colors from yellow to deep violet, CD spectroscopy discloses different degrees of chiral induction by an enantiomerically pure guest. Ion mobility mass spectrometry allows to distinguish two binding modes. Self‐assemblies based on this new ligand class promise application in chiroptical recognition, photo‐redox catalysis and optical materials.

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Section: Figurementioning

confidence: 99%

Coal‐Tar Dye‐based Coordination Cages and Helicates

et al. 2021

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“…On the other hand, the host-guest complex benefits from the well-defined structure, considerable solubility and adequate dynamicity to ensure the contact of the triplet state guest with other reactants, thus facilitating energy transfer and electron transfer. [41][42][43][44][45][46][47][48][49][50][51][52][53][54] To this end, N,Ndimethyl 2,5-bis(4-pyridinium)thiazolo [5,4-d]thiazole diiodide (MPT), an efficient fluorochrome with acceptor-donoracceptor structure, was designed. [55] As shown in Scheme 1, it self-assembled into supramolecular dimer in the cavity of cucurbit [8]uril (CB [8]) in a parallel and staggered conformation.…”

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confidence: 99%

Transforming a Fluorochrome to an Efficient Photocatalyst for Oxidative Hydroxylation: A Supramolecular Dimerization Strategy Based on Host‐Enhanced Charge Transfer

Tang

et al. 2021

Angew Chem Int Ed

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The development of non‐covalent synthetic strategy to fabricate efficient photocatalysts is of great importance in theranostic and organic materials. Herein, a fluorochrome N,N′‐dimethyl 2,5‐bis(4‐pyridinium)thiazolo[5,4‐d]thiazolediiodide (MPT) was transformed into an efficient photocatalyst through supramolecular dimerization in the cavity of cucurbit[8]uril (CB[8]). The host‐enhanced charge transfer interaction within the supramolecular dimer 2MPT‐CB[8] dramatically promoted intersystem crossing to produce triplet. In addition, the staggered conformation of 2MPT‐CB[8] facilitated the energy transfer and electron transfer of the triplet. As a result, 2MPT‐CB[8] could serve as a high‐efficiency photocatalyst for the oxidative hydroxylation of arylboronic acids. This supramolecular dimerization strategy enriches the supramolecular engineering of functional π‐systems. It is anticipated that this strategy can be extended to fabricate various π‐systems with tailor‐made functions.

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“…In 2020, an elegant supramolecular photocatalytic system via charge-transfer excitation of a host-guest complex was described by Iwasawa's group for the [4 + 2] cycloaddition reaction of anthracenes 91. [68] In particular, this supramolecular system which includes as host the macrocyclic boronic ester [2 + 2]BTH-F decorated with electron-deficient difluorobenzothiazole moieties, can generate the triplet state of guest molecule and thus, promoting the photocycloaddition of anthracenes with several dienes and alkenes in high yields. In detail, DFT calculations suggest that under visible light irradiation, the anthracene@[2 + 2]BTH-F complex undergoes charge-transfer excitation to induce a charge-separated singlet state (Scheme 52).…”

Section: [4 + 2] Cycloaddition Crafting Six Membered Ringsmentioning

confidence: 99%

Recent Visible Light and Metal Free Strategies in [2+2] and [4+2] Photocycloadditions

2021

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When aiming to synthesize molecules with elevated molecular complexity starting from relatively simple starting materials, photochemical transformations represent an open avenue to circumvent analogous multistep procedures. Specifically, lightmediated cycloadditions remain as powerful tools to generate new bonds begotten from non-very intuitive disconnections, that alternative thermal protocols would not offer. In response to the current trend in both industrial and academic research pointing towards green and sustainable processes, several strategies that meet these requirements are currently available in the literature. This Minireview summarizes [2 + 2] and [4 + 2] photocycloadditions that do not require the use of metal photocatalysts by means of alternative strategies. It is segmented according to the cycloaddition type in order to give the reader a friendly approach and we primarily focus on the most recent developments in the field carried out using visible light, a general overview of the mechanism in each case is offered as well.

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Supramolecular Photocatalysis by Utilizing the Host–Guest Charge‐Transfer Interaction: Visible‐Light‐Induced Generation of Triplet Anthracenes for [4+2] Cycloaddition Reactions

Cited by 35 publications

References 77 publications

Coal‐Tar Dye‐based Coordination Cages and Helicates

Coal‐Tar Dye‐based Coordination Cages and Helicates

Transforming a Fluorochrome to an Efficient Photocatalyst for Oxidative Hydroxylation: A Supramolecular Dimerization Strategy Based on Host‐Enhanced Charge Transfer

Recent Visible Light and Metal Free Strategies in [2+2] and [4+2] Photocycloadditions

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