The 2-silaketenyl radical (HCSiO): Ground and first excited electronic states

Abstract

The ground and first excited electronic states of the 2-silaketenyl radical (HCSiO) have been studied systematically employing ab initio electronic structure theory. The ground (X̃2A″) state of HCSiO is found to have a trans-planar bent structure, while the first excited (Ã2A′) state possesses a linear equilibrium configuration. The X̃2A″ state of HCSiO is more distorted from linearity and is more polar than the ground state of HCCO. With our most reliable level of theory, cc-pVQZ CCSD(T), the classical X̃–Ã splitting was determined to be only 5.8kcal/mol (0.25eV, 2030cm−1). The ground state of HCSiO was found to be quite stable thermodynamically against the two dissociation reactions HCSiO(X̃2A″)→H(2S)+CSiO(X̃3Σ−) and HCSiO(X̃2A″)→CH(X̃2Π)+SiO(X̃1Σ+). HCSiO in its ground electronic state is predicted to lie 36.7kcal/mol above the HSiCO ground state. The structural and energetic features for the two lowest-lying states of HCSiO are closer to the corresponding states of HCCO than to those of HSiCO and HSiSiO. Due to its large dipole moment and the substantial infrared (IR) intensities of some of the vibrational modes, the HCSiO radical may be suitable for microwave and IR spectroscopic investigations.