Single-step synthesis of ternary metal chalcogenides (sf-CuInS2 and sf-CuInSe2) stripped off the organic cover and their use as a catalyst for symmetric Glaser–Hay coupling reactions

Abstract

Generally, inorganic nano/microparticles produced by chemical routes are covered by organic surfactants or polymers to control their agglomeration during their synthesis. However, these surfactants and polymers negatively affect their catalytic activity because these molecules mask the surface. This work presents the synthesis of surfactant-free CuInS₂ and CuInSe₂ (sf-CuInS₂ and sf-CuInSe₂) nano/microparticles through simple reactions without surfactant or polymer coatings using LiBH₄ under a thermodynamically favourable condition. These reactions are rare observations of a single-step process to produce ternary metal chalcogenides without any template assistance. We have also demonstrated efficient catalysis by sf-CuInS₂ nanoparticles in the coupling reaction of substituted phenylacetylenes. We tested it as catalysts in dimerizing 1,3-diyne derivatives while using 8-diazabicyclo[5.4.0]undec-7-ene (DBU) as the base. These Glassar–Hay coupling reactions are conducted at room temperature in acetonitrile (4–7 h, depending on the substrate) using 10 mg of sf-CuInS₂. The maximum yield obtained in these reactions is 97%, while the catalyst is reusable for five cycles with little difference in its ability to catalyse. The effectiveness of the catalyst is credited to the availability of a free catalytic surface.