Phase Transitions of Naphthalene-2,3-carbonitride Steered by Solvent Effects and Metal Ion Concentration Variation

The delicate regulation of structural phase transition can provide advanced approaches for fabricating desired and well-organized nanoarchitectures on surfaces. Introduction of metal ions into pure organic systems can facilitate the phase transition from hydrogen-bonded structures to metal-organic structures by coordinating with organic molecules. However, it remains a challenge to attain a phase transition dominated by variable metal coordination configurations through adjustment of the metal ion concentration. Herein, we report the phase transitions of naphthalene-2,3-carbonitride (2,3-DCN) molecules on highly oriented pyrolytic graphite (HOPG) under varying solvents and Cu²⁺ ion concentrations. By integrating data from scanning tunneling microscopy imaging and density functional theory calculations, it is demonstrated that phase transitions of 2,3-DCN occur through forming diverse coordination configurations where Cu²⁺ ions can coordinate with 2,3-DCN and 1-nonanoic acid or Cl^- ions to form different ligand components with a coordination number of 4 when varying the molar ratios of 2,3-DCN to Cu²⁺ ion in the 1-nonanoic acid solvent. However, in the case of 1-heptanoic acid as a solvent, the self-assembly structure of 2,3-DCN only changes via the alteration of hydrogen bonding sites and Cu²⁺ ions do not coordinate with 2,3-DCN molecules. These findings provide valuable insights into the coordination behavior of metal ions in different solvents.