Structures, relative stability and dissociation of [Si,N,C,O]2+ isomers

Abstract

Fifteen isomers of [Si,N,C,O] 2+ system are obtained at UB3LYP/6-311G(d) and UCCSD(T)/6-311+G(2df) (single-point) levels. The analyses are made for predicting the structures of optimized isomers, while ionic fragments with lower energies are suggested. The calculated results indicate that linear isomer SiNCO 2+ ( ) is thermodynamically the most stable species in [Si,N,C,O] Π 2 2+ system, followed by linear SiOCN 2+ ( Π 2 ), SiCNO 2+ ( Π 2 ), and SiC(NO) ( 2 A″ ) with NCO three-membered ring. The order of stability of several kinetically stable isomers is SiNCO 2 ＞ SiCNO 2+ ( )＞SiOCN). The obtained results by analyzing the isomerizations and ionic fragment patterns show that the signal peaks of [Si,N,C,O] 2+ are attributed to the contribution of linear SiNCO 2+ species, which is metastable and can dissociate to the ionic fragments in the mass spectrometry experiments.