Encapsulation of a Quinhydrone Cofactor in the Inner Pocket of Cobalt Triangular Prisms: Combined Light‐Driven Reduction of Protons and Hydrogenation of Nitrobenzene

Zhao, Liang; Wei, Jianwei; Zhang, Jing; He, Cheng; Duan, Chunying

doi:10.1002/ange.201707676

Cited by 14 publications

(4 citation statements)

References 43 publications

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“…In view of the interest regarding developing host−guest systems mimicking natural photosynthesis systems, the localization of bioinspired cofactors into the pocket and of the photosensitizer outside the pocket was postulated as an alternatively way to construct artificial systems. 44…”

Section: Discussionmentioning

confidence: 99%

Photochemical Properties of Host–Guest Supramolecular Systems with Structurally Confined Metal–Organic Capsules

Zhao

et al. 2018

Acc. Chem. Res.

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144

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Inspired by natural photosynthesis, researchers have designed symmetric metal–organic hosts with large inner pockets that are spontaneously generated through preorganized ligands and functionalized metallocorners to construct dye-containing host–guest systems. The abundant noncovalent interaction sites in the pockets of the hosts facilitated substrate–catalyst interactions for possible enrichment, fixation, and activation of substrates/reagents, providing special electron transfer pathways for regio- or stereoselectively photocatalytic chemical transformations. In this Account, we focus our attention on metal–organic hosts that contain photoactive or redox-active units to evaluate electron transfer and charge separation between host and guest units in these supramolecular systems and elucidate the related photoinduced chemical reactions controlled by these electron transfer processes within the structurally confined pockets of these interesting metal–organic hosts. We have been engaged in developing methods to isolate a series of chromophores for charge separation in supramolecular systems, incorporating organic dyes as photosensitizers in metal–organic hosts with electron acceptor/donor guests is a promising way to enable typical enzyme-like photocatalytic transformations within a confined microenvironment. Related to these inter- and intramolecular photoinduced electron transfer (PET) processes, the formation of host–guest supramolecular systems to fix and isolate the donor–acceptor pair with a short through-space distance provided a new PET pathway to stabilize the charge-separated ion pair. Highly efficient photosynthetic systems can be obtained when charge transfer to electron donors/acceptors occurs faster than the charge recombination. This Account starts with a brief summary of the potential approaches for constructing photoactive metal–organic hosts through the incorporation of dye molecules within ligand backbones or as a part of the metal nodes of the architecture. Following the methodological summary is a discussion on the mechanisms governing the photoinduced charge separation and electron transfer pathways within the dye-incorporated metal–organic hosts. We also searched for strategies for constructing photoactive supramolecular systems through encapsulating dye molecules within the inner space of redox-active hosts. The photochemistry of these systems demonstrated the following advantages due to the structural confinement: avoiding excited state quenching caused by other chemical species, including aggregated dyes, stabilizing the radical intermediate and tuning the absorption or emission of the guest through electron/energy transfer pathways. The photoinduced dye to redox-active host electron transfer is a new and efficient pathway that is meaningful for chemists to realize and understand many important enzymatic processes and to reveal the secrets of a substance and energy metabolism in biological systems. The confined interactions between the host and the guest have shown fascinating effects of ...

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Section: Discussionmentioning

confidence: 99%

Photochemical Properties of Host–Guest Supramolecular Systems with Structurally Confined Metal–Organic Capsules

Zhao

et al. 2018

Acc. Chem. Res.

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144

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“…This shows that ATP effectively competes with 1 for binding in the pocket, and as such, the catalyst properties can be controlled by using this as a cofactor. 40 From a mechanistic viewpoint, the encapsulation of a substrate in a pocket forces the active sites to be in close proximity to the substrate, enabling efficient hydrogenation in the pocket and gave the oxidation state of the active sites (NAD + mimics) (Figure S23). 41 Under illumination, the oxidation state NAD + mimics were regenerated via photoinduced electron transfer from electron donors outside the flask (Figures 5 and S18).…”

Section: Journal Of the American Chemical Societymentioning

confidence: 99%

Metal–Organic Capsules with NADH Mimics as Switchable Selectivity Regulators for Photocatalytic Transfer Hydrogenation

Wei

Zhao

et al. 2019

J. Am. Chem. Soc.

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Switchable selective hydrogenation among the groups in multifunctional compounds is challenging because selective hydrogenation is of great interest in the synthesis of fine chemicals and pharmaceuticals as a result of the importance of key intermediates. Herein, we report a new approach to highly selectively (>99%) reducing CX (X = O, N) over the thermodynamically more favorable nitro groups locating the substrate in a metal−organic capsule containing NADH active sites. Within the capsule, the NADH active sites reduce the double bonds via a typical 2e − hydride transfer hydrogenation, and the formed excited-state NAD + mimics oxidize the reductant via two consecutive 1e − processes to regenerate the NADH active sites under illumination. Outside the capsule, nitro groups are highly selectively reduced through a typical 1e − hydrogenation. By combining photoinduced 1e − transfer regeneration outside the cage, both 1e − and 2e − hydrogenation can be switched controllably by varying the concentrations of the substrates and the redox potential of electron donors. This promising alternative approach, which could proceed under mild reaction conditions and use easy-to-handle hydrogen donors with enhanced high selectivity toward different groups, is based on the localization and differentiation of the 2e − and 1e − hydrogenation pathways inside and outside the capsules, provides a deep comprehension of photocatalytic microscopic reaction processes, and will allow the design and optimization of catalysts. We demonstrate the advantage of this method over typical hydrogenation that involves specific activation via well-modified catalytic sites and present results on the high, well-controlled, and switchable selectivity for the hydrogenation of a variety of substituted and bifunctional aldehydes, ketones, and imines.

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“…Exploring highly efficient catalysts for the hydrogenation of nitroarenes to anilines is of significance because the functionalized anilines and their derivatives are key chemical intermediates for the manufacture of pharmaceutical, agrochemical, and pigment industries [1][2][3]. Compared with metal nanoparticle (MNP) catalysts, the supported MNPs catalysts can avoid the MNPs aggregation and offer improved performance in catalytic reduction of various nitroaromatics [4][5][6]. Especially, the development of highly selective, earth-abundant, atom-efficient and recyclable catalysts has been attracting much interest in order to meet the substantially industrial requirements owing to the high-cost and limited availability of noble metals [3,4,7].…”

Section: Introductionmentioning

confidence: 99%

“…Compared with metal nanoparticle (MNP) catalysts, the supported MNPs catalysts can avoid the MNPs aggregation and offer improved performance in catalytic reduction of various nitroaromatics [4][5][6]. Especially, the development of highly selective, earth-abundant, atom-efficient and recyclable catalysts has been attracting much interest in order to meet the substantially industrial requirements owing to the high-cost and limited availability of noble metals [3,4,7].…”

Section: Introductionmentioning

confidence: 99%

Ag/Ag2O confined visible-light driven catalyst for highly efficient selective hydrogenation of nitroarenes in pure water medium at room temperature

Yin

Xie

Cao

et al. 2020

Chemical Engineering Journal

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Encapsulation of a Quinhydrone Cofactor in the Inner Pocket of Cobalt Triangular Prisms: Combined Light‐Driven Reduction of Protons and Hydrogenation of Nitrobenzene

Cited by 14 publications

References 43 publications

Photochemical Properties of Host–Guest Supramolecular Systems with Structurally Confined Metal–Organic Capsules

Photochemical Properties of Host–Guest Supramolecular Systems with Structurally Confined Metal–Organic Capsules

Metal–Organic Capsules with NADH Mimics as Switchable Selectivity Regulators for Photocatalytic Transfer Hydrogenation

Ag/Ag2O confined visible-light driven catalyst for highly efficient selective hydrogenation of nitroarenes in pure water medium at room temperature

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