INOR 47

Within the current effort to understand and develop the organic functionalization of silicon surfaces, recent experiments have identified the radical chain reaction as a particularly promising route for controlled formation of such functionalized surfaces. Using periodic Density Functional Theory calculations, we theoretically study and characterize the basic steps of the radical chain reaction mechanism for different molecules reacting with the H-Si(111) surface. Molecular conjugation is found to play a crucial role in the viability of the reaction, by controlling the delocalization of the spin density at the reaction intermediate. [Takeuchi, et al J. Am. Chem. Soc. 2004, 126, 15890; Kanai, et al J. Chem. Phys. B 2005, 109, 18889.] Lastly, for the recently introduced optically activated functionalization of H-Si(111) [Eves et al. J. Am. Chem. Soc. 2004, 126, 14318; Sun et al. J. Am. Chem. Soc. 2005, 127, 2514], our study indicates that the most favorable mechanism is likely to be determined by kinetics rather than thermodynamics. [Kanai, et al J. Am. Chem. Soc. 2006, 128, 3892]