Photoactive Metal–Organic Framework for the Reduction of Aryl Halides by the Synergistic Effect of Consecutive Photoinduced Electron-Transfer and Hydrogen-Atom-Transfer Processes

Abstract

Consecutive photoinduced electron transfer (ConPET) has advantages on overcoming the current energetic limitation of visible-light photoredox catalysis for utilizing the energies of two photons in one catalytic cycle. A heterogeneous approach for radical chain reduction of various aryl bromides and chlorides without adding any cocatalyst is introduced by incorporating polyoxometalates (POMs) and amine catalysts into a naphthalenediimide (NDI)-based polymer. CoW-DPNDI–PYI exhibits high activity in the photocatalytic reduction of aryl halides by the synergistic effects of ConPET and hydrogen-atom-transfer (HAT) processes and an enzyme-mimicking CO2 cycloaddition reaction. The ConPET process with N,N′-bis­(4-pyridylmethyl)­naphthalenediimide (DPNDI) facilitates effective solar energy conversion. POMs and amine catalysts, as efficient HAT catalysts and electron donors, improve the generation of the ConPET process. The success of this work demonstrates the great application of the synergistic effects of ConPET and HAT processes in heterogeneous photocatalysis C–H arylation.

Hole-Mediated PhotoRedox Catalysis: Tris(p-Substituted)biarylaminium Radical Cations as Tunable, Precomplexing and Potent Photooxidants

“…Nevertheless, in the absence of an applied potential for the optimized synthesis of 3gb, only a 12% yield of 3gb was observed. The detection of small amounts of product in the aforementioned control reactions corroborates a conPET-type mechanism (13)(14)(15)(16)(17) where photoexcitation of TpBPA or TCBPA leads to SET reduction of protons or trace O2 (reactions were bubbled by N2 for 5 min during preparation and sealed; no further strict precautions were taken) to generate the corresponding TPA .+ . In any case however, the very substantial yield differences when applied potential is present or absent confirm the pivotal role of the TPA .+ s and that e-PRC is the main product-forming pathway in both reactions.…”

“…Multiple-photon-accumulating strategies such as consecutive photoelectron transfer (conPET) (13)(14)(15)(16)(17) and triplet-triplet annihilation upconversion (TTA-UC), (18)(19)(20) have represented an elegant means to achieve powerful SET reductions, but their use in oxidations has so far been elusive. However, these techniques place limiting requirements on reactions, such as the requirement in conPET for both ground and radical ion states to be visible-light active.…”

Excitation of Radical Anions of Naphthalene Diimides in Consecutive‐ and Electro‐Photocatalysis**

“…ET from excited NDI radical anions have been reported by laser flash photolysis experiments [37] and more recently, a conPET mechanism have been proposed with an NDI photocatalyst as part of a complex Metal-Organic Framework heterogeneous catalyst. [38] Therefore, synthesis of all NDIs started from commercially available naphthalene-1,4,5,8-tetracarboxylic acid dianhydride (NDA) and the corresponding amine using the reported procedure (see section S.2 in SI for details). We decided to study a family of simple naphthalene diimides with different substitutions (NDI1-5, Figure 2).…”

Consecutive Photocatalysis vs Electro-Photocatalysis. Excitation of Radical Anions of Naphthalene Diimides.

“…Particularly, its use in a conPET approach and electro-photocatalysis would broad the applicability of these privileged structures used in other catalysis such as ion-π catalysis and applications in supramolecular chemistry, sensors, host−guest complexes for molecular switching devices, ion-channels, intercalations with DNA for medicinal applications, etc. 32 ET form excited NDI radical anions have been reported in laser flash photolysis experiments 33 and more recently, a conPET mechanism have been proposed with a NDI photocatalyst as part of a complex Metal-Organic Framework heterogeneous catalyst 34 although ET to aryl halides was successful, a constructive approach has not been explored and only dehalogenation was reported. The same material was probed in other catalytic activities and an important reaction of oxiranes with CO 2 was accomplished with good results, showing the potential of this core in the construction of polyfunctional catalyst.…”