Supramolecular clusters and chains of 2,6-dimethylpyridine on Cu(110): Observation of dynamic configuration change with real-space surface science techniques and DFT calculations

Abstract

The adsorption of 2,6-dimethylpyridine (2,6-DMP) on Cu(110) has been studied using low temperature scanning tunneling microscopy (LT-STM), time-of-flight electron stimulated desorption ion angular distribution (TOF-ESDIAD), and density functional theory (DFT) calculations. At low temperatures (T<~150K), the 2,6-DMP adsorbs in a flat configuration on Cu(110) producing clusters and extended domains via weak hydrogen bonding (C—H···N) with the molecular symmetry axis aligned along the <001> surface direction. At near-saturation coverage, a c(6×2) long-range ordered structure was observed. Upon annealing to T=200K, the 2,6-DMP molecules adopt an upright configuration with their pyridine ring plane oriented parallel to the <11̅0> azimuth. These upright 2,6-DMP molecules produce extended molecular chains where the repulsive interactions between the molecular chains give rise to coverage-dependent interchain distances. At near-saturation coverage, a 1260 surface structure is observed for the upright configuration. The DFT calculations suggest that the Cu adatom plays an important role in the adsorption configuration change of the 2,6-DMP molecule.