Dynamics and thermal stability of surface-confined metal-organic chains

Understanding the dynamics and thermal stability of metallosupramolecular chains on surfaces is of relevance for the development of molecular connectors in nanoelectronics or other fields. Here we present a combined study using temperature-controlled STM and Monte Carlo simulations to explore the behavior of metal-organic porphyrin chains on Cu(111) based on two-fold pyridyl-Cu-pyridyl coordination motifs. We monitor their behavior in the 180-360 K range, revealing three thermal regimes: i) flexibility up to 240 K, ii) diffusion of chain fragments and partial dissociation into a fluid phase for T > 240 K, and iii) full dissolution with temperatures exceeding ~ 320 K. The experimentally estimated reaction enthalpy of the metal-organic bonding is ~ 0.6 eV. Monte Carlo simulations reproduce qualitatively our STM observations and reveal the preference for linear and extended supramolecular chains with reduced substrate temperatures.