Decatungstate‐Photocatalyzed Acylation of Single‐Walled Carbon Nanotubes

Abstract

Although the functionalization and modification of single‐walled carbon nanotubes (SWCNTs) has been advanced for two decades, their chemical transformation via catalytic processes has yet to be explored and further facilitate their industrial utility. Here, the decatungstate‐photocatalyzed acylation is described of semiconducting (7,6)SWCNTs and the scope of the reaction is investigated by employing alkyl, aromatic, and organometallic aldehydes. The success of the methodology is confirmed by diverse spectroscopic, thermal, microscopy imaging, and redox techniques. The developed catalytic process for the functionalization of SWCNTs is environmetal friendly, since the catalyst and unreacted aldehydes can be recovered and reused, while the modified SWCNTs can be easily isolated and purified by membrane filtration. It is believed that the current findings will open new avenues for the catalytic functionalization of SWCNTs and the approach is intended to extend for modifying 2D nanomaterials.

Sustainable Photocatalytic Acylation of Transition Metal Dichalcogenides with Atom Economy

“…[10] Similarly, for SWCNTs, the valence band and conduction band have appropriate interposed energies (−4.90 and −3.88 eV, respectively), [14] therefore a similar correlation with the energy levels of W 10 O 32 −4 and W 10 O 32 −5 •H + is achieved, effectively driving the reaction. [11] Considering the aforementioned discussion and in an analogous fashion, the semiconducting properties of TMDs make them ideal candidates for the expansion of this methodology and transfer of this knowledge to 2D nanomaterials. This fact gives rise to the introduction of a catalytic methodology in the quiver of chemical transformations available for the modification of 2D nanomaterials in general.…”

“…[ 9 ] Following its catalytic role in organic synthesis, decatungstate anion was later utilized for the chemical modification of nanomaterials, specifically for the direct photocatalytic acylation of C 60 , a 0D carbon nanomaterial [ 10 ] and recently single‐walled carbon nanotubes (SWCNTs) a 1D carbon nanomaterial, with the use of aldehydes. [ 11 ] In both cases, a new C─C bond is formed between the carbonyl's C atom of an aldehyde and a C atom of carbon nanomaterial's lattice. Decatungstate W 10 O 32 −4 catalytic activity is attributed to the HOMO (Highest Occupied Molecular Orbital), which has an energy level as low as −7.13 eV and, once photoexcited, can therefore accept a H atom, through hydrogen atom transfer, from various functional groups, based on their hydrogen atom dissociation energy, yielding W 10 O 32 −5 •H + .…”

“…[ 10 ] Similarly, for SWCNTs, the valence band and conduction band have appropriate interposed energies (−4.90 and −3.88 eV, respectively), [ 14 ] therefore a similar correlation with the energy levels of W 10 O 32 −4 and W 10 O 32 −5 •H + is achieved, effectively driving the reaction. [ 11 ]…”

Decatungstate‐Photocatalyzed Diastereoselective Dearomative Hydroalkylation of Indoles

“…[10] In that respect, our group recently reported the catalytic hydroacylation of indoles leading to diverse trans-2-acylindolines with great yields and diastereoselectivities. [11] We focused on tetrabutylammonium decatungstate (TBADT, 3) [12,13] -an easily available photoexcitable polyoxometalate (POM) based on Earth's crust abun-dant tungsten -to effectively promote the formation of acyl radicals from aldehydes through hydrogen abstractions. [11] Building on this previous work and our long term interest in photocatalysis, [14] our goal was to establish a novel C2-alkylation of indoles (Scheme 1F).…”