Chen-Guang Wang¬1, Zhihai Cheng2,*, Xiaohui Qiu2,* and Wei Ji1,*
1Department of Physics and Beijing Key Laboratory of Optoelectronic Functional Materials & Micro-nano Devices, Renmin University of China, Beijing 100872, China
2Key Laboratory of Standardization and Measurement for Nanotechnology, Chinese Academy of Sciences, National Center for Nanoscience and Technology, Beijing 100190, China.
DOI:10.1016/j.cclet.2016.08.004 Publication Date: Sept. 3rd 2016
It has been demonstrate that intermolecular interaction, crucial in a plenty of chemical and physical processes, may vary in the presence of metal surface. However, such modification is yet to be quantitatively revealed. Here, we present a systematical density functional theory study on adsorbed bis(para-pyridyl)acetylene (BPPA) tetramer on Au(111) surface. We observed unusually high electron density between two head-to-head N atoms, an intermolecular “non-bonded” region, in adsorbed BPPA tetramer. This exceptional electron density originates from the wavefunction hybridization of the two compressed N lone-electron-pair states of two BPPA, as squeezed by a newly revealed N-Au-N three center bonding. Together with the minor contribution from N…H-C intermolecular hydrogen bonding, this three-center one shortens the N-N distance from over 4 Å to 3.30 Å and offers an attractive lateral interacting energy of 0.46 eV, effectively to a surface-confined in-plane pressure. The overlapped non-bonding wavefunction hybridization with N-Au-N three-center molecule-substrate bonding, as not been fully recognized in earlier studies, were manifested in non-contact Atomic Force Microscopy.