Mechanistic Insights into the Interface‐Directed Transformation of Thiols into Disulfides and Molecular Hydrogen by Visible‐Light Irradiation of Quantum Dots

Abstract

Quantum dots (QDs) offer new and versatile ways to harvest light energy. However, there are few examples involving the utilization of QDs in organic synthesis. Visible-light irradiation of CdSe QDs was found to result in virtually quantitative coupling of a variety of thiols to give disulfides and H2 without the need for sacrificial reagents or external oxidants. The addition of small amounts of nickel(II) salts dramatically improved the efficiency and conversion through facilitating the formation of hydrogen atoms, thereby leading to faster regeneration of the ground-state QDs. Mechanistic studies reveal that the coupling reaction occurs on the QD surfaces rather than in solution and offer a blueprint for how these QDs may be used in other photocatalytic applications. Because no sacrificial agent or oxidant is necessary and the catalyst is reusable, this method may be useful for the formation of disulfide bonds in proteins as well as in other systems sensitive to the presence of oxidants.

Schiff base complexes of Ni, Co, Cr, Cd and Zn supported on magnetic nanoparticles: As efficient and recyclable catalysts for the oxidation of sulfides and oxidative coupling of thiols

“…Therefore, many methods including different catalysts (homogeneous and heterogeneous catalysts) and various oxidants (e.g. metal oxidants, organic oxidant, peroxides, halogens, and air) have been used for the selective oxidation of organic sulfides and thiols [15][16][17][18][19][20][21][22][23][24][25]. Concerning the green oxidant, H 2 O 2 (with only H 2 O as a byproduct) in particular have received attention because of their environmental implications, readily available, high atom efficiency and lower costs involved than when using other oxidizing agents [26].…”

To Battle Surface Traps on CdSe/CdS Core/Shell Nanocrystals: Shell Isolation versus Surface Treatment

“…The CdSe/5CdS core/shell QDs was pre-treated with H 2 S. insufficient for isolation of the hole traps associated with the species removed by thiols, presumably the adsorbed H 2 S.It has been well established that thiol ligands on II-VI QDs could be photo-oxidized to disulfides 48,49. If it was the adsorbed H 2 S that acted as efficient hole traps to quench PL of the as-synthesized CdSe/CdS core/shell QDs in the current system, H 2 S might go through a similar photochemical reaction to become elemental sulfur,49,50 which would be an inert substance for the photo-generated excitons as discussed above. Consequently, PL QY of the QDs should gradually recover upon destruction of the adsorbed H 2 S. Results inFigure 2a…”

Schiff base complex of Cu immobilized on MCM-41 as reusable catalyst for efficient oxidative coupling of thiols and oxidation of sulfides using hydrogen peroxide

“…Coupling reactions such as oxidative coupling of thiols into corresponding disulfides and as well as oxidation of organic functional groups such as oxidation of sulfides into sulfoxides are useful transformations in the synthesis of new molecules, as well as for various medical, biological, materials, and nanotechnological applications [18][19][20]. In particular, some of biologically active sulfoxides play an important role as therapeutic agents such as antifungal, antibacterial, anti-ulcer, anti-atherosclerotic, antihypertensive and as well as psychotropics and vasodilators [21,22].…”

“…For these reasons, many methods have been developed over the years to find efficient these organic transformations [18][19][20][21][22][23][24][25][26][27][28][29][30][31][32]. For example, many methods have been reported in the presence of various catalysts and using different oxidant (e.g.…”