期刊
JOURNAL OF CHEMICAL PHYSICS
卷 129, 期 21, 页码 -出版社
AMER INST PHYSICS
DOI: 10.1063/1.3021291
关键词
adsorption; annealing; copper; dissociation; molecular configurations; organic compounds; scanning tunnelling microscopy; self-assembly; XANES; X-ray photoelectron spectra
资金
- Canada Foundation of Innovation (CFI)
- National Science and Engineering research Council of Canada (NSERC)
- British Columbia Knowledge Development Fund (BCKDF)
- Swiss National Science Foundation (NSF-CH)
- German Academic Exchange Service (DAAD)
- BCSI
- BMBF [05ES3XBA/5]
We present a combined scanning tunneling microscopy (STM), near-edge x-ray-absorption fine-structure, and x-ray photoemission spectroscopy (XPS) study on the bonding and ordering of tetrapyridyl-porphyrin molecules on the Cu(111) surface in the 300-500 K temperature range. Following deposition at 300 K the molecules are adsorbed with a pronounced conformational adaptation of the anchored species featuring a saddle-shaped macrocycle and terminal groups pointing toward the substrate. Upon moderate annealing supramolecular chains evolve that are stabilized by metal-ligand interactions between the mesopyridyl substituents and copper adatoms resulting in twofold copper coordination. Annealing to temperatures exceeding 450 K strongly alters the molecular appearance in high-resolution STM data. This modification was also induced by controlled voltage pulses and related to a deprotonation of the molecule by XPS. Under appropriate conditions a novel binding motif leads to honeycomb structures coexisting with the chain segments. The conformation withstands annealing without large modification.
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