Franck-Condon Dominated Cheistry. Dissociations of Silicon-Centered Radicals Prepared by Femtosecond Reduction of Their Cations in the Gas Phase

Article abstract of DOI:10.1021/j100042a019

The dimethylhydroxysilyl radical, (CH3)2Si^.OH, (1) is generated in the gas phase by collisional neutralization of its cation 1⁺.Radical 1 undergoes extensive dissociation by C-Si bond cleavage depending on the internal energy of the precursor ion 1⁺.A small fraction of stable 1 is obtained from vibrationally excited 1⁺.Significant fractions of stable deuterio analogues of 1, (CD3)2Si^.OH and (CH3)2Si^.OD, are formed from their corresponding gas-phase cations.Stable CH3SiOH molecules and H2Si^.OH, ^., and (CH3)3Si^. radicals are also formed by collisional neutralization of their cations.Collisional reionization of gas-phase 2-silapropan-2-one results in extensive dissociation of its cation radical.MP4(SDTQ)/6-31+G(d) calculations predict large Franck-Condon effects in the veritcal reduction of 1⁺ that deposits up to 229 kJ mol^-1 in the radical formed.Isodesmic and charge-transfer reactions are used to estimate the heat of formation of 1 as -254 kJ mol^-1, and its adiabatic ionization energy as 6.25 eV.The dissociation energies of the O-H and C-Si bonds in 1 are calculated as 166 and 195 kJ mol^-1, respectively.