Spin Catalysis over Conductive Solids: Enhancing the Rate of Model C−C Bond Cracking over Carbon Nanoparticles

Abstract

The concept of catalysis over a spin‐conductive mediator is investigated with quantum‐chemical calculations. Specifically, homolytic C−C bond cleavage in ethane over small edge‐oxidized half‐metallic carbon clusters in the presence of a methyl radical was considered with the complete active space self‐consistent field method. The methyl radical (spin catalyst) and carbon cluster (mediator) are found to share a common electronic orbital containing the radical unpaired electron, allowing nascent radicals emerging from ethane dissociation to interact with the spin catalyst through the carbon electronic system. This could result in spin flip, affording formation of a triplet radical pair not prone to recombination and thus resulting in the acceleration of the reaction rate. This demonstrates that new pathways may open up in controlled catalytic processes by allowing normally spin‐forbidden reactions and not necessarily lowering activation barriers in the traditional sense of catalysis.

Alcohol imination catalyzed by carbon nanostructures synthesized by C(sp2)-C(sp3) free radical coupling

“…Since the first report of spin catalysis in 1994, 21 it has been found that many spin carriers can serve as spin catalysts, which makes it possible to overcome spin conservation rules in basic chemical reactions, thus increasing the possibility of chemical reaction success. 22 , 23 , 24 There are two important mechanisms of spin catalysis: (1) Exchange (nonmagnetic) interactions of electron spins, and (2) dipole-dipole interactions of electron spins through their magnetic dipoles. 23 Carbon, being abundantly available, is a very promising candidate for constructing carbon-based materials that can act as metal-free catalysts with different electronic states and molecular structures.…”

“…Stable carbon-centered neutral radicals, including open-shell graphene as a gigantic π-conjugated aromatic hydrocarbon 25 , 26 , 27 that has the spin states of a multielectron system, 28 can function as spin catalysts by allowing spin-flip processes during a reaction. 24 Here, we report the use of a free radical C(sp 2 )-C(sp 3 ) coupling reaction to synthesize two-dimensional (2D) carbon nanosheets and three-dimensional (3D) carbon organic framework (COF) nanostructures with high electron spin densities. These materials can be applied as spin catalysts in a direct imine synthesis via aerobic oxidative coupling of an alcohol (benzyl alcohol) and an amine (benzylamine or aniline).…”