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.

Cesium lead halide (CsPbX3) perovskites, having stood out for solar cell applications, are now garnering attention in the field of photocatalysis as well. With a fundamental challenge in photocatalysis of...

The ultrathin films of 2-ferrocenyl-1,3-dithiolane (FcS 2 C 3 ) and 2-ferrocenyl-1,3-dithiane (FcS 2 C 4 ) dropcasted from toluene on highly oriented pyrolytic graphite (HOPG) surface are investigated using atomic force microscopy (AFM). Two types of growth polymorphs have been observed, which are distinctly different based on their nature of growth and the molecular level packing. We have developed a new type of temperature-dependent desorption experiment named "microscopic thermal desorption analysis" (MTDA) for understanding the adsorption energetics related to the observed growth polymorphs on the surface. Using MTDA, we have calculated the adsorption energies of growth polymorphs of both molecules and further revealed that their formation requires an activation energy. The subtle relation between the adsorption energies and activation energies of growth polymorphs account for their average abundance on the surface. The experimental observations are further supported by density functional theory (DFT) calculations.

Funding information Visveswaraya PhD SchemeA new class of ferrocenyl surfactants based on covalent linkage between amino acids or peptides and ferrocene was designed. Accordingly, five ferrocenyl amphiphiles, FcS1-5, were synthesized, and their aggregation behaviors in aqueous solutions were studied. Compared to the other surfactants containing ferrocenyl units, FcS have a relatively smaller size and low molecular weight and are easy to synthesize. The influences of the number of carboxylic acid head groups and the number of Fc group in the hydrophobic tail, on the stability and aggregation behavior of these amphiphiles in aqueous medium, were explored to deduce the structure property relationships. A combination of fluorescence and dynamic light scattering techniques was used to elucidate the behavior of these molecules. A good agreement between the results obtained using different techniques was observed.

Efficient charge extraction in lead halide perovskite nanocrystals is frequently sought-after and probed using various probe molecules. Often ignored, the chemical bonding of the molecules to the perovskite’s surface, as dictated by the terminal anchoring functional group, can have implications on the excited-state interactions between perovskite nanocrystals and the charge-shuttling molecules. Considering the remarkability of the recent work on ferrocene-based molecules in allowing charge transfer in perovskite nanocrystals, we have employed ferrocene molecule functionalized with various functional groups to understand the binding and charge-transfer process at the interface of the perovskite nanocrystal and the redox relay molecule. We evidenced that the charge transfer enhanced with enhancement in binding, as validated by the association constant evaluated as high as 1.71 × 107 M–1. In particular, the −COOH and −NMe2 functional groups led to the efficient quenching of photoluminescence (PL) emission and a decrease in photoluminescence lifetime than the other functional group analogues, showing their feasibility in charge transfer studies. More importantly, the −NMe2 functional group indicated passivation of the defects on the perovskite surface, attributed to the interaction between the lone pair of nitrogen and the undercoordinated surface Pb2+ cations. This was also evident in the transient absorption spectra, where the excited-state interaction could be analyzed better. This work opens avenues for exploring anchoring moieties in facilitating charge transfer across the perovskite interface, thus impacting its photocatalytic applications.

We report the formation of discrete molecular rings/spirals of small molecules (1,3-dithia derivatives of ferrocene) on a highly oriented pyrolytic graphite (HOPG) surface. On the basis of microscopy and theoretical calculations, molecular level arrangement within the molecular rings is understood. The molecular rings show a limiting inner diameter, and we interpret it to be related to the critical intermolecular interaction limit. This limiting value of the inner diameter is surprisingly correlated with that observed for molecular rings/disks of a few reported molecules. The correlation reveals that molecular rings formed typically by weak van der Waals interactions should always show a limiting inner diameter and should be independent of molecular structure, size, and chemical nature.

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