Gas-phase synthesis of the bicyclic silicon tricarbide molecule (c-SiC₃) as a precursor to silicon carbide nanoparticles in space

Silicon–carbon bond couplings represent a fundamental foundation for bottom-up molecular mass growth processes of silicon carbide grains in extraterrestrial environments. Yet, the elementary reaction mechanisms affording the gas-phase preparation of simple silicon- and carbon-containing molecules, which act as central molecular building blocks of silicon carbide grains, remain largely unexplored. Herein, we reveal the barrierless gas-phase preparation of the bicyclic silicon tricarbide molecule (c-SiC₃, X¹A₁) and its linear isomer (l-SiC₃, X³Σ⁻) as prototype silicon carbide grain precursors via the bimolecular reaction between tricarbon (C₃, X¹Σ_g⁺) and silylidyne (SiH, X²Π) under single-collision conditions. With the detection of c-SiC₃ and l-SiC₃ in the circumstellar envelope of the carbon star IRC+10216, the title reaction offers an entrance point for the exotic silicon chemistry in deep space thus bringing us closer to an understanding of how silicon and carbon chemistries can be coupled in our galaxy.