Noncovalently Linked Metallacarboranes on Functionalized Magnetic Nanoparticles as Highly Efficient, Robust, and Reusable Photocatalysts in Aqueous Medium

Abstract

A successful homogeneous photoredox catalyst has been fruitfully heterogenized on magnetic nanoparticles (MNPs) coated with a silica layer, keeping intact its homogeneous catalytic properties but gaining others due to the easy magnetic separation and recyclability. The amine-terminated magnetic silica nanoparticles linked noncovalently to H­[3,3′-Co­(1,2-C2B9H11)2]− (H­[1]), termed MSNPs-NH2@H­[1], are highly stable and do not produce any leakage of the photoredox catalyst H­[1] in water. The magnetite MNPs were coated with SiO2 to provide colloidal stability and silanol groups to be tethered to amine-containing units. These were the MSNPs-NH2 on which was anchored, in water, the cobaltabis­(dicarbollide) complex H­[1] to obtain MSNPs-NH2@H­[1]. Both MSNPs-NH2 and MSNPs-NH2@H­[1] were evaluated to study the morphology, characterization, and colloidal stability of the MNPs produced. The heterogeneous MSNP-NH2@H­[1] system was studied for the photooxidation of alcohols, such as 1-phenylethanol, 1-hexanol, 1,6-hexanediol, or cyclohexanol among others, using catalyst loads of 0.1 and 0.01 mol %. Surfactants were introduced to prevent the aggregation of MNPs, and cetyl trimethyl ammonium chloride was chosen as a surfactant. This provided adequate stability, without hampering quick magnetic separation. The results proved that the catalysis could be speeded up if aggregation was prevented. The recyclability of the catalytic system was demonstrated by performing 12 runs of the MSNPs-NH2@H­[1] system, each one without loss of selectivity and yield. The cobaltabis­(dicarbollide) catalyst supported on silica-coated magnetite nanoparticles has proven to be a robust, efficient, and easily reusable system for the photooxidation of alcohols in water, resulting in a green and sustainable heterogeneous catalytic system.

Molecular and supported ruthenium complexes as photoredox oxidation catalysts in water

“…Few examples involving only a photocatalyst have been carried out. [16][17][18][19][20] The most studied ruthenium complexes have been [Ru(bpy) 3 ] 2+ 21,22 and derivatives 23,24 as photocatalysts; however, very few ruthenium aqua complexes have been tested both as a photosensitizer and a catalyst in the oxidation of organic substrates in water. 25 From the perspective of sustainability and industrial applicability, the grafting of homogeneous catalysts on solid supports with a high surface is a good approach.…”

“…Few examples involving only a photocatalyst have been carried out. 16–20 The most studied ruthenium complexes have been [Ru(bpy) 3 ] 2+ 21,22 and derivatives 23,24 as photocatalysts; however, very few ruthenium aqua complexes have been tested both as a photosensitizer and a catalyst in the oxidation of organic substrates in water. 25…”

Ex Vivo and In Vivo Evaluation of Dodecaborate-Based Clusters Encapsulated in Ferumoxytol Nanoparticles

“…At a dose of 20 mg/kg, 1 @FMX localized in tissues ranging from 0 to 65 μg of B per gram of tissue, suggesting that encapsulation of dodecaborate-based compounds in a polymer matrix can potentially have favorable effects on the biodistribution results. More broadly, this work suggests the potential importance of noncovalent interaction between boron clusters and polymers stemming from nonelectrostatic interactions and points to new avenues for creating hybrid boron-cluster-based nanomaterials without covalent attachment. − …”

Aqueous Persistent Noncovalent Ion-Pair Cooperative Coupling in a Ruthenium Cobaltabis(dicarbollide) System as a Highly Efficient Photoredox Oxidation Catalyst

“…A high performance of Na­[1] in the photooxidation of alcohols is observed, using a catalyst load of 0.01 mol % and reaching TON = 10000, in some cases . We have also supported the cobaltabis­(dicarbollide) catalyst on silica-coated magnetite nanoparticles . This system has proven to be a green and sustainable heterogeneous catalytic system, highly efficient and easily reusable for the photooxidation of alcohols in water.…”

“…33 We have also supported the cobaltabis(dicarbollide) catalyst on silica-coated magnetite nanoparticles. 34 This system has proven to be a green and sustainable heterogeneous catalytic system, highly efficient and easily reusable for the photooxidation of alcohols in water. In general, the SET processes carry out the transformation of a limited number of substrates, and in some cases undesirable byproducts are generated.…”