Jun Zhang1,*, Pengcheng Chen1,*, Bingkai Yuan1, Wei Ji2,†, Zhihai Cheng1,†, Xiaohui Qiu1,†
1Key Laboratory of Standardization and Measurement for Nanotechnology, Chinese Academy of Sciences, National Center for Nanoscience and Technology, Beijing 100190, China.
2Department of Physics, Renmin University of China, Beijing 100872, China.
* These authors contributed equally to this work.
DOI:10.1126/science.1242603 Publication Date: Published Online September 26 2013
We report a real-space visualization of the formation of hydrogen bonding in 8-hydroxyquiline (8-hq) molecular assemblies on a Cu(111) substrate using noncontact atomic force microscopy (NC-AFM). The atomically resolved molecular structures enable a precise determination of the characteristics of hydrogen bonding networks, including the bonding sites, orientations, and lengths. The observation of bond contrast was interpreted by ab initio density functional calculations, which indicated the electron density contribution from the hybridized electronic state of the hydrogen bond. Intermolecular coordination between the dehydrogenated 8-hq and Cu adatoms was also revealed by the submolecular resolution AFM characterization. The direct identification of local bonding configurations by NC-AFM would facilitate detailed investigations of intermolecular interactions in complex molecules with multiple active sites.