Selection of Adlayer Patterns of 1,3-Dithia Derivatives of Ferrocene by the Nature of the Solvent

Abstract

Ultrathin films of 2-ferrocenyl-1,3-dithiolane and 2-ferrocenyl-1,3-dithiane (Fcs), which are chemically inert at ambient conditions, are studied on the basal plane of highly oriented pyrolytic graphite (HOPG) using atomic force microscopy (AFM) and scanning tunneling microscopy (STM). Films are prepared by drop-casting using Fcs dissolved in different solvents. Films prepared from methanol and dichloromethane show structural polymorphs on HOPG, while those prepared from ethanol, acetone, and dimethylformamide show an exclusive selection of one of the polymorphs. The selection of growth patterns of Fcs shows interesting correlation to the bulk solubility of molecules in the corresponding solvents and the solvent boiling point. The growth of Fcs at the submonolayer coverage is templated by the surface symmetry, and the molecular level packing on the surface is understood using high-resolution AFM, STM, and the bulk crystal packing of the molecules.

Solvent‐ and Temperature‐Dependent Assembly in Monolayer Films of a Ferrocene‐Naphthyridine Hybrid on HOPG

“…The observation suggests that either high solubility of FcNP 2 and/or high boiling point of the solvents favor the formation of Phase‐I. As per our previous study, the selection of energetically favorable phase (assembly) on the surface depends on high boiling point of the solvent and or high solubility of the molecules in the solvent [17a] . If an equilibrium is established at the interface between “molecules on the surface” and “molecules dissolved in solvents” during the self‐assembly, then one expects the formation of an energetically favorable phase at the interface.…”

“…Thus, deposition of molecules form solvent with high boiling point or high solubility favors selection of energetically most stable phase on the surface. On the contrary, the low solubility of adsorbate molecules in the solvent and low boiling point (quick evaporation) rapidly increases the concentration of molecules at the interface and thus a non‐equilibrium phase is formed [17a] . Therefore, at this point, we tentatively conclude that at ambient conditions Phase‐I is energetically more favorable than Phase‐II.…”

Revealing the Limits of Intermolecular Interactions: Molecular Rings of Ferrocene Derivatives on Graphite Surface

“…The microscopic structure of these growths has been well understood in our previous report. 22 The relative percentage of 1D islands (∼65%) is higher with respect to that of 2D islands.…”

“…The molecules in 1D and 2D islands are stabilized by an edge-to-face (−C−H•••π) interaction. 22 The molecules in the 1D chain are stabilized through an edge-to-center (−C− H••• metal) interaction. 23−26 These arrangements are also known in metallocene assemblies on surfaces.…”

“…We have shown previously that 1D islands are energetically favorable compared to 2D islands. 22,23 Upon annealing, the relative abundance of 2D islands (∼35% at RT and ∼11% at 353 K) diminishes drastically compared to 1D islands (∼65% at RT and ∼64% at 353 K). In addition, it is observed that the remaining amount of 2D islands (indicated with orange lines; cf.…”