Double dative bond configuration: pyrimidine on Ge(100).
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.
Lee
Jun Young
JY
Department of Chemistry and School of Molecular Science, Korea Advanced Institute of Science and Technology, Daejeon 305-701, Republic of Korea.
Jung
Soon Jung
SJ
Hong
Suklyun
S
Kim
Sehun
S
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
D011743:Pyrimidines; D005857:Germanium; C030986:pyrimidine