title: Donor/Acceptor Properties of Aromatic Molecules in Complex Metal-Molecule Interfaces.
abstract: We present a comparative study, combining density functional theory with scanning tunneling microscopy/spectroscopy, of two aromatic molecules bonded with a variable number of Cu adatom(s) on a Cu(111) surface. The two molecules, 1,3,5-tris(pyridyl)benzene (TPyB) and 1,3,5-tris(4-radical-phenyl)benzene (TPB), possess the same aromatic backbone but bond weakly versus strongly to Cu with different terminal groups, respectively. We find that TPyB and TPB exhibit, respectively, small versus large charge transfers between the surface and the molecule; this contrast results in opposite shifts in the calculated density of states distributions and thus explains the opposite STS peak shifts observed in our experiments. The two molecules exhibit weak donor versus strong acceptor characters. This work provides a fundamental understanding, on a single-molecule level, of the principle that selecting specific functional groups can effectively and intentionally modify the molecular electronic properties in a wider class of molecule-metal interfaces.
authors.affiliation: Institute of Computational and Theoretical Studies & Department of Physics, Hong Kong Baptist University , Hong Kong, China.
authors.forename: Yan-Ling
authors.identifier: 0000-0001-5840-9149
authors.initials: YL
authors.lastname: Zhao
authors.affiliation: Department of Physics, The Hong Kong University of Science and Technology , Hong Kong, China.
authors.forename: Weihua
authors.identifier: 0000-0002-2269-1952
authors.initials: W
authors.lastname: Wang
authors.affiliation: Institute of Computational and Theoretical Studies & Department of Physics, Hong Kong Baptist University , Hong Kong, China.
authors.forename: Fei
authors.initials: F
authors.lastname: Qi
authors.affiliation: Department of Physics and Materials Science, City University of Hong Kong , Hong Kong, China.
authors.forename: Jian-Fu
authors.initials: JF
authors.lastname: Li
authors.affiliation: Department of Physics, The Hong Kong University of Science and Technology , Hong Kong, China.
authors.forename: Guowen
authors.initials: G
authors.lastname: Kuang
authors.affiliation: Department of Physics and Materials Science, City University of Hong Kong , Hong Kong, China.
authors.forename: Rui-Qin
authors.identifier: 0000-0001-6897-4010
authors.initials: RQ
authors.lastname: Zhang
authors.affiliation: Department of Physics, The Hong Kong University of Science and Technology , Hong Kong, China.
authors.forename: Nian
authors.initials: N
authors.lastname: Lin
authors.affiliation: Institute of Computational and Theoretical Studies & Department of Physics, Hong Kong Baptist University , Hong Kong, China.
authors.forename: Michel A
authors.identifier: 0000-0002-8898-6921
authors.initials: MA
authors.lastname: Van Hove