Pyridine and pyridine carboxylic acids as guests in a bidimensional hydrogen bond structure analyzed by scanning tunneling microscopy

2-Mercaptopyrimidine (2MPy) forms a stable two-dimensional network on Au(1 1 1). The 2MPy dimeric structure forms chains separated by narrow channels that can trap a variety of molecules such as oligopyridines and arenes. In this work, the 2MPy structure was used to intercalate pyridine and its acid derivatives, specifically, picolinic acid, dipicolinic acid, niconitic acid and isonicotinic acid. Pyridine and the pyridine carboxylic acids were intercalated into the thiol structure in a 2:1 stoichiometry. The STM contrast of the carboxylic group varies with its position on the pyridine ring and with the tunneling parameters employed to acquire the images.