Visible‐Light‐Induced Photoredox Catalysis with a Tetracerium‐Containing Silicotungstate

Abstract

The development of visible-light-induced photocatalysts for chemoselective functional group transformations has received considerable attention. Polyoxometalates (POMs) are potential materials for efficient photocatalysts because their properties can be precisely tuned by changing their constituent elements and structures and by the introduction of additional metal cations. Furthermore, they are thermally and oxidatively more stable than the frequently utilized organometallic complexes. The visible-light-responsive tetranuclear cerium(III)-containing silicotungstate TBA 6 [{Ce(H 2 O)} 2 {Ce(CH 3 CN)} 2 -(m 4 -O)(g-SiW 10 O 36 ) 2 ] (CePOM; TBA = tetra-n-butylammonium) has now been synthesized; when CePOM was irradiated with visible light (l > 400 nm), a unique intramolecular Ce III -to-POM(W VI ) charge transfer was observed. With CePOM, the photocatalytic oxidative dehydrogenation of primary and secondary amines as well as the a-cyanation of tertiary amines smoothly proceeded in the presence of O 2 (1 atm) as the sole oxidant.

Giant Ln 30 -Cluster-Embedded Polyoxotungstate Nanoclusters with Exceptional Proton-Conducting and Luminescent Properties

“…Diverse magnetic and electronic properties of 4f lanthanide (Ln) ions have rendered the Ln-containing polyoxotungstates (POTs) a prime target in new polyoxometalates (POMs) material synthesis over the past 20 years. [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18] Of particular interest is the creation of POTs with a high number of Ln centers or high-nuclearity Ln-O clusters because of their extraordinary structural features and attractive electronic, optical, and magnetic properties (e.g., large uniaxial anisotropy parameter, multiple configurations, and high-spin ground state) relevant to appealing applications in many fields such as single-molecule magnets, photoelectric molecular materials, and high-density information storage. [12][13][14] However, the discovery of such POTs proves challenging and is usually by trial and error because their syntheses involve remarkably complex assembly processes and are hard to predict or design.…”

Synthesis, Characterization, Electrochemistry, Photoluminescence and Magnetic Properties of a Dinuclear Erbium(III)-Containing Monolacunary Dawson-Type Tungstophosphate: [{Er(H2O)(CH3COO)(P2W17O61)}2]16−

“…Until now, there are only a few reports on the sandwich-type Ln-POM family, where lanthanide metal centers (Ln III nuclearity ≥ 2) are sandwiched between two lacunary POM ligands [ 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 , 23 , 24 , 25 , 26 ]. Lanthanide-containing POM assemblies have demonstrated outstanding properties in various fields of research such as molecular magnetism [ 27 ], imaging [ 28 ], photoluminescence [ 29 ], catalysis [ 30 , 31 ] and electrochemistry [ 32 ]. Magnetic POMs have attracted an increasing interest after the discovery of the first POM-based single molecule magnet (SMM) [ErW 10 O 36 ] 9– [ 33 ].…”

“…Some of the important intrinsic properties of POM clusters are their thermal and hydrolytic stability, tunability of acid and redox properties and high solubility in a variety of solvents, which make them promising catalysts for different chemical processes. The Ln-POMs have exhibited noteworthy catalytic performances in various chemical processes [ 30 , 31 , 32 ]. The photochemistry of Ln-POMs is also of great interest; POM ligands usually act as light harvesting antennae in photoluminescent lanthanopolyoxotungstate species, which sensitize Ln III centers (such as Sm III , Eu III , Tb III and Dy III ) by absorbing incident light and then transferring this excitation to Ln III ions through an energy transfer process [ 29 , 35 ].…”

Self-Assembly of Nanoscale Lanthanoid-Containing Selenotungstates: Synthesis, Structures, and Magnetic Studies

“…8 are famous for their largely arisen lacunary BBs 12 (e.g., [A-α-SiW 9 O 34 ] 10− , [γ-GeW 10 O 36 ] 8− , [P 2 W 12 O 48 ] 14− ), in which vacancies on their shells can be replaced by simple metal centers or may support the assemblies of larger metal moieties, to be utilized as discrete "secondary BBs" (short for SBUs) for the construction of growingly diverse higher-nuclearity mixed-metal POMs. By virtue of the flexible coordination numbers and high oxophilicity of 4f metal ions, the related lanthanoid (Ln)containing POTs have been attracting great consideration on the principles of topology, size, and functionality, 16−27 typical assemblies include complex architectures (i.e., tetramer, 20 decamer, 21 and dodecamer 22−24 ), a Ce-sandwich-type silicotungstate with photoredox catalysis, 25 a tetrahedral 3d−4f single-molecule magnet (SMM), 26 tungstate proton conduction framework, 27 etc., as such, the integrated cationic 4f metal linkers endow POTs with not only structural diversities but also promising magnetic, catalytic, and optic properties. 16−27 Selenotungstates, as an essential subfamily of POTs, have attracted immense concern in recent years.…”