Spectroscopic constants and potential energy surfaces for silanone (H2SiO), hydroxysilylene (HSiOH), the hydroxysilylene dimer, and the disilynyl radical (Si2H)

Abstract

Ab initio quantum mechanical methods were employed to study the spectroscopic constants and potential energy surfaces of H2SiO, HSiOH, the HSiOH dimer, and the Si2H radical. Consideration of the spectroscopic constants of silanone, cis- and trans-HSiOH and Si2H began with the TZ2P SCF level of theory. We predict a strongly bonded cis-HSiOH dimer. The structure of the cis-HSiOH dimer was optimized at the DZP SCF, DZP CISD, DZP+diff CISD and DZP MP2 levels. The hydrogen bond energy of the dimer is 14.8 kcal/mol at the DZP MP2 level and 12.0 kcal/mol at the DZP CCSD/DZP CISD level. The vibrational frequency of one Si–O bond stretch in the HSiOH dimer is 967 cm−1 at the DZP MP2 level, close to the 951 cm−1 and 986 cm−1 fundamentals observed experimentally for HxSiyOz aggregates. Therefore, it is possible that the HSiOH dimer has been observed in matrices. The potential energy surface of the Si2H radical was studied initially at the DZP CISD level. We found a bent Cs 2A″ Si2H structure which is 10.8 kcal/mol higher in energy than the C2v 2B1 structure. The C2v Si2H structures were optimized at the TZ2P (f,d) CCSD level. The 2B1 state is predicted to lie ΔE0=1.6 kcal/mol lower in energy than the 2A1 state of Si2H radical.