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We studied the adsorption and reaction behavior of the ionic liquid (IL) 1,3-dimethylimidazolium bis[(trifluoromethyl)sulfonyl]imide ([C1C1Im][Tf2N]) on Cu(111) using non-contact atomic force microscopy (nc-AFM), scanning tunneling microscopy (STM), and angle-resolved X-ray photoelectron spectroscopy (ARXPS) in ultrahigh vacuum as a function of temperature, supported by density-functional theory (DFT) calculations. Our nc-AFM results for sub-monolayer IL films show that at 200 K, the IL self-assembles into highly ordered islands, with cations and anions arranged next to each other in a checkerboard–type phase. After extended annealing at 300 K, the structure transforms first to a hexagonal phase and then to a porous honeycomb phase. Simultaneously, many small, disordered islands are formed. Complementary ARXPS reveals no IL desorption until 300 K. However, a significant fraction of the IL is converted to a new species as deduced from new, strongly shifted peaks that develop in the XP spectra at around 275 K and grow with annealing time at 300 K. We correlate the remaining unshifted peaks to the ordered phases observed in nc-AFM and the shifted peaks to decomposition products, which appear as disordered islands in nc-AFM and STM. Upon further heating to 360 K, about 50% of the anions or their decomposition products desorb from the surface, while cation-related fragments mostly remain on the surface. From DFT, we obtain additional information on the structure of the ordered phases and the interaction of the IL with the substrate.

We have studied the adsorption, wetting, growth, and thermal evolution of the protic IL diethylmethylammonium trifluoromethanesulfonate ([dema][TfO]) on Au(111) and Ag(111). Ultrathin films were deposited at room temperature (RT) and at 90 K, and were characterized in situ by angle-resolved X-ray photoelectron spectroscopy. For both surfaces, we observe that independent of temperature, initially, a closed 2D wetting layer forms. While the film thickness does not increase past this wetting layer at RT, at 200 K and below, "moderate" 3D island growth occurs on top of the wetting layer. Upon heating, on Au(111), the [dema][TfO] multilayers desorb at 292 K, leaving an intact [dema][TfO] wetting layer, which desorbs intact at 348 K. The behavior on Ag(111) is much more complex. Upon heating [dema][TfO] deposited at 90 K, the [dema]+ cations deprotonate in two steps at 185 and 305 K, yielding H[TfO] and volatile [dema]0. At 355 K, the formed H[TfO] wetting layer partly desorbs (∼50%) and partly decomposes to form an F-containing surface species, which is stable up to 570 K.

We investigated the adsorption, surface enrichment, ion exchange, and on‐surface metathesis of ultrathin mixed IL films on Ag(111). We stepwise deposited 0.5 ML of the protic IL diethylmethylammonium trifluoromethanesulfonate ([dema][TfO]) and 1.0 ML of the aprotic IL 1‐methyl‐3‐octylimidazolium hexafluorophosphate ([C8C1Im][PF6]) at around 90 K. Thereafter, the resulting layered frozen film was heated to 550 K, and the thermally induced phenomena were monitored in situ by angle‐resolved X‐ray photoelectron spectroscopy. Between 135 and 200 K, [TfO]− anions at the Ag(111) surface are exchanged by [PF6]− anions and enriched together with [C8C1Im]+ cations at the IL/vacuum interface. Upon further heating, [dema][PF6] and [OMIm][PF6] desorb selectively at ∼235 and ∼380 K, respectively. Hereby, a wetting layer of pure [C8C1Im][TfO] is formed by on‐surface metathesis at the IL/metal interface, which completely desorbs at ∼480 K. For comparison, ion enrichment at the vacuum/IL interface was also studied in macroscopic IL mixtures, where no influence of the solid support is expected.

We study the interaction and metalation reaction of a free base 5,10,15,20‐terakis(4‐cyanophenyl)porphyrin (2HTCNPP) with post‐deposited Zn atoms and the targeted reaction product Zn‐5,10,15,20‐terakis(4‐cyanophenyl)porphyrin (ZnTCNPP) on a Ag(111) surface. The investigations are performed with scanning tunneling microscopy at room temperature after Zn deposition and subsequent heating. The goal is to obtain further insights in the metalation reaction and the influence of the cyanogroups on this reaction. The interaction of 2HTCNPP with post‐deposited Zn leads to the formation of three different 2D ordered island types that coexist on the surface. All contain a new species with a bright appearance, which increases with the amount of post‐deposited Zn. We attribute this to metastable SAT (“sitting atop”) complexes formed by Zn and the macrocycle, that is, an intermediate in the metalation reaction to ZnTCNPP, which occurs upon heating to 500 K. Interestingly, the activation barrier for the successive reaction of the SAT complex to the metalated ZnTCNPP species can also be overcome by a voltage pulse applied to the STM tip., Metalation with zinc: Post‐deposition of Zn onto 2HTCNPP leads to the formation of a SAT complex, which reacts to ZnTCNPP upon heating or application of a voltage pulse.

The adsorption behavior and the mobility of 2H‐Tetranaphthylporphyrin (2HTNP) on Cu(111) was investigated by scanning tunneling microscopy (STM) at room temperature (RT). The molecules adsorb, like the structurally related 2HTPP, in the “inverted” structure with the naphthyl plane restricted to an orientation parallel to the Cu surface. The orientation of the four naphthyl groups yields altogether 16 possible conformations. Due to the existence of rotamer pairs, 10 different appearances are expected on the surface, and all of them are identified by STM at RT. Most interestingly, the orientation of the naphthyl groups significantly influences the diffusion behavior of the molecules on Cu(111). We identify three different groups of conformers, which are either immobile, medium or fast diffusing at RT. The mobility seems to decrease with increasing size of the footprint of the conformers on the surface., Mobile or not? 2H‐Tetranaphthylporphyrin adsorbs as ten different conformers on Cu(111) at RT. The orientation of the naphthyl groups controls the diffusion behaviour of the molecules, from immobile to medium and fast.

In light of the increasing interest in organic-organic multicomponent heterostructures on metals, this molecular-scale study investigates prototypical composite systems of ultrathin porphyrin and ionic liquid (IL) films on metallic supports under well-defined ultra-high vacuum conditions. By means of angle-resolved X-ray photoelectron spectroscopy, we investigated the adsorption, stability and thermal exchange of the resulting films after sequential physical vapor deposition of the free-base porphyrin 5,10,15,20-tetraphenyl-porphyrin, 2H-TPP, and the IL 1-methyl-3-octylimidazolium hexafluorophosphate, [C8C1Im][PF6], on Ag(111) and Au(111). 2H-TPP shows 2D growth up to two closed molecular layers on Ag(111) and Au(111), and 3D island growth for thicker films. IL films on top of a monolayer of 2H-TPP exhibit Stranski-Krastanov-like growth and are stable up to 385 K. The 2H-TPP layer leads to a destabilization of the IL films compared to the IL in direct contact with the bare metals by inhibiting the specific adsorption of the ions to the metal surfaces. When the porphyrin is deposited on top of [C8C1Im][PF6] at low temperature, the 2H-TPP molecules adsorb on top of the IL film at first, but replace the IL at the IL/metal interfaces upon heating above 240 K. This exchange process is most likely driven by the higher adsorption energy of 2H-TPP on the Ag(111) and Au(111) surfaces, as compared to the IL. The behavior observed on Ag(111) and Au(111) is identical. The results are highly relevant for the stability of porphyrin/IL-based thin film catalyst systems and molecular devices, and more generally, stacked organic multilayer architectures.