Highly Effective Photocatalytic Radical Reactions Triggered by a Photoactive Metal–Organic Framework

Abstract

On account of their inherent reactive properties, radical reactions play an important role in organic syntheses. The booming photochemistry provides a feasible approach to trigger the generation of radical intermediates in organic reaction processes. Thus, developing effective photocatalysts becomes the key step in radical reactions. In this work, the triphenylamine moiety with photoactivity is successfully embedded in a highly porous and stable metal–organic framework (MOF), and the obtained MOF, namely, Zr-TCA, naturally displays a photoactive property derived from the triphenylamine-based ligand. In photocatalytic studies, the triphenylamine-based Zr-TCA not only exhibits a high catalytic activity on the aerobic oxidation of sulfides via the generation of the superoxide radical anion (O2 •–) under light irradiation but also shows good efficiency in the trifluoromethylation of arenes and heteroarenes by the formation of the trifluoromethyl radical (CF3 •) as an intermediate. Moreover, the high performance of Zr-TCA can be well maintained over a wide range of substrates in these radical reactions, and the recycled Zr-TCA still retains its excellent photocatalytic activity. The high recyclability and catalytic efficiency to various substrates make the constructed triphenylamine-based Zr-TCA a promising photocatalyst in diverse radical reactions.

Alkaline Earth Metal–Organic Frameworks Based on Tetratopic Anthraquinone-Based Linkers: Synthesis, Characterization, and Photochemical Applications

“…The activation of dioxygen may be promoted by the diphenylamine units as recently shown for a Zr-based containing similar organic strut. 22 However, in this system, only the formation of the radical O 2 − was observed, which supports the participation of the anthraquinone core of H 4 L, since 1 O 2 was indicated.…”

“…Finally, the use of t BuOH did not lead to a strong suppression of the conversion, suggesting that hydroxyl radicals do not play a decisive role in the mechanism. The activation of dioxygen may be promoted by the diphenylamine units as recently shown for a Zr-based containing similar organic strut . However, in this system, only the formation of the radical O 2 – was observed, which supports the participation of the anthraquinone core of H 4 L, since 1 O 2 was indicated.…”

Unveiling the Synthetic Potential of 1,3,5-Tri(10H-phenothiazin-10-yl)benzene-Based Optoelectronic Material: A Metal-Free and Recyclable Photocatalyst for Sequential Functionalization of C(sp2)–H Bonds

“…Particularly, almost quantitative NMR yield (99%) was obtained for the formation of oxindole 3a in acetonitrile, which proceeded via cascade trifluoromethylation/cyclization. Importantly, this protocol is highly selective as the competitive processes such as atom transfer radical addition (ATRA) of alkenes , and direct C–H trifluoromethylation of arenes , were inhibited completely. Further optimization of bases revealed that NaHCO 3 was optimal in which 3a was furnished in 92% isolated yield (entries 6–10, Table ).…”

“…The photogenerated electrons reduce CF 3 SO 2 Cl (−0.18 V vs SCE) to form the CF 3 radical accompanied with sulfur dioxide and the chloride ion (Figures S6 and S7). − The electrophilic CF 3 radical then adds to the terminal olefin of 1a , which induces a subsequent cyclization to afford B ( 1a → A → B ). Finally, single-electron oxidation of unstable arene radical species ( B ) by photoexcited holes yields trifluoromethylated oxindole 3a after the release of a proton.…”

Dual-Ligand-Oriented Design of Noncentrosymmetric Complexes with Nonlinear-Optical Activity

“…1 belongs to the monoclinic P 2 1 space group, with the asymmetric unit consisting of two crystallographically independent Ni II ions, two N-containing tipa ligands, two fully deprotonated p-bdc 2– ligands, and four coordinated and one free H 2 O molecules (Table and Figure S1a). Each Ni 2+ ion is connected by three N atoms from distinct tipa ligands as well as three O atoms from one p-bdc 2– and two coordinated H 2 O molecules. − All of the Ni–N and Ni–O distances are in the reasonable ranges (Table S3). Bond-valence-sum (BVS) calculations give values of 2.06 and 2.16 for Ni atoms, which are consistent with the expected valence.…”