Adsorption and Reactivity of Pyridine Dicarboxylic Acid on Cu(111)

A detailed understanding of the reaction of a range of molecules on surfaces will be  key to developing targeted strategies for on-surface synthesis. Here, we studied the deprotonation and decarboxylation reactions of 3,5-pyridinedicarboxylic acid (PDC) on Cu(111) using synchrotron radiation photoelectron spectroscopy (SRPES), near-edge X-ray absorption fine structure (NEXAFS) spectroscopy, and density functional theory (DFT). PDC partially deprotonates upon deposition on Cu(111) at room temperature and adsorbs with the plane of its aromatic ring inclined at an average of ∼45° with respect to the surface. By heating to 100 °C, the deprotonation of the molecule increases. When the PDC is partially deprotonated the plane of its aromatic ring adopts a more upright orientation with respect to the surface. Additional heating to 160 °C causes complete deprotonation, upon which the molecule returns to a more planar molecular adsorption geometry. By examining both the N 1s core level and the NEXAFS results, we as...