title: Double dative bond configuration: pyrimidine on Ge(100).
abstract: The adsorption of pyrimidine onto Ge(100) surfaces has been investigated using real-time scanning tunneling microscopy (STM), temperature-programmed desorption (TPD), and density-functional theory (DFT) calculations. Our results show that the adsorbed pyrimidine molecules are tilted about 40 degrees with respect to the Ge surface, and through a Lewis acid-base reaction form bridges between the down-Ge atoms of neighboring Ge dimer rows by double Ge-N dative bonding without loss of aromaticity. For coverages of pyrimidine up to 0.25 ML, a well-ordered c(4x2) structure results from states that appear in STM micrographs as oval-shaped protrusions, which correspond to pyrimidine molecules datively adsorbed on every other dimer. However, above 0.25 ML, the oval-shaped protrusions gradually change into brighter zigzag lines. At 0.50 ML, a p(2x2) structure results from the states that appear in STM as zigzag lines. The zigzag lines are formed by the attachment of pyrimidine molecules to the down-Ge atoms of every Ge dimer. However, the unstable p(2x2) structure eventually reconstructs into a c(4x2) structure due to steric hindrance between the adsorbed pyrimidine molecules after stopping the exposure of pyrimidine to the surface.
authors.affiliation: Department of Chemistry and School of Molecular Science, Korea Advanced Institute of Science and Technology, Daejeon 305-701, Republic of Korea.
authors.forename: Jun Young
authors.initials: JY
authors.lastname: Lee
authors.forename: Soon Jung
authors.initials: SJ
authors.lastname: Jung
authors.forename: Suklyun
authors.initials: S
authors.lastname: Hong
authors.forename: Sehun
authors.initials: S
authors.lastname: Kim
mesh_terms: D000327:Adsorption; D005857:Germanium / Q000737:chemistry*; D016252:Microscopy, Scanning Tunneling; D008956:Models, Chemical; D010316:Particle Size; D011743:Pyrimidines / Q000737:chemistry*; D012680:Sensitivity and Specificity; D013499:Surface Properties; D013696:Temperature
chemical_list: D011743:Pyrimidines; D005857:Germanium; C030986:pyrimidine