Potential energy surface survey towards prediction of a new radical [H ₂,Si,C,N]

While the cyanomethyl radical CH₂CN has been detected in space and extensively studied, the silicon-analogue [H₂,Si,C,N] is still unknown even in laboratory and has never been studied in spite of experimental expectation. Here, we present a detailed theoretical investigation on the doublet [H_2,Si,C,N] potential energy surfaces including 21 minimum isomers and 44 interconversion transition states at the Gaussian-3//B3LYP/6- 31G(d) and CSB-QB3 levels. The former three low-lying isomers within 10 kcal/mol are bent H₂Si^•-C≡N| 1 (0.0 kcal/mol), linear H₂CNSi 3 (0.8) with resonating structures H₂C=N=Si| ^• ↔ H₂C^•=N=Si| and bent H ₂Si^•N≡C| 2 (6.5), for which high conversion barriers exist between them. Additionally, five isomers HCNSiH 7 (26.6), H ₂NCSi 5 (30.6), H₂CSiN 4 (58.5), HCSiNH 10a (63.5) and 10b (60.1) each have considerable barriers. Interesting features such as the intra-and inter-donor-acceptor bonding, the cumulenic silicon-bonding and silylene are revealed. Future experimental characterization and astrophysical detection of the eight [H₂,Si,C,N] isomers, especially the former three low-lying species 1, 3 and 2, are strongly recommended. The accurate spectroscopic data at the QCISD/6-311G(d,p) level are provided.