Self-assembly of isonicotinic acid molecules into supramolecular films on Ag (111)

Self assembly processes of isonicotinic acid (INA) molecules into supramolecular structures on Ag (111) surface are studied with UHV-STM, XPS, and IR spectroscopy. INA molecule contains both a ring nitrogen and carboxyl tail, which lead to a tape-like molecular solid.~At room temperature, INA~molecules organize into 2D islands that exceed~100 nm on Ag (111), demonstrating 2D H-bonding interactions. A series of carboxy O-H\textbullet \textbullet \textbullet N hydrogen bonds assemble INA molecules into linear chains, while~weaker hydrogen bonds between carbonyl O and aromatic~H link the chains sideways into ordered 2D structures. Different orientational domains are observed and the domain walls (carboxyl-carboxyl coupling)~establish the molecular dipole direction. XPS spectroscopy corroborates the H-bonding interactions, while IR spectroscopy was used to assess INA molecular orientation with respect to the surface plane.