STM study of the conformation and reaction of long-chain haloalkanes at Si(111)-7 x 7

Scanning tunneling microscopy (STM) has been used to study the adsorption of 1-fluoro-, 1-chloro-, and 1-bromo-substituted C(12) alkanes at the Si(111)-7 x 7 surface, at temperatures from 300 to 500 K. We report self-assembly of these physisorbed adsorbates, C(12)H(25)X, to form approximately circular corrals, (C(12)H(25)X)(2), with charge transfer to a corralled adatom in each case (cf. Dobrin et al. Surf. Sci. 2006, 600, L43). The corrals comprised pairs of semicircular horizontal long-chain molecules stable to approximately 100 degrees C. At > or =150 degrees C, the corrals desorbed or reacted locally to imprint a halogen atom, X-Si, and an adjacent alkane residue, R-Si. The corral height profiles, together with the location of the imprinted X-Si resulting from thermal or electron-induced surface reaction, led to a picture of the molecular configurations in these haloalkane corrals, (C(12)H(25)X)(2), X = F, Cl, Br, and the dichloro corrals, 1,12-dichlorododecane, (ClC(12)H(24)Cl)(2).