Uniform π‐System Alignment in Thin Films of Template‐Grown Dicarbonitrile‐Oligophenyls

Abstract

The ordering and conformational properties of dicarbonitrile‐para‐oligophenyls are studied with complementary methods, namely X‐ray structure analysis, low‐temperature scanning tunneling microscopy, and near‐edge X‐ray absorption fine‐structure spectroscopy. The packing of the functionalized variants differs from their technologically interesting para‐oligophenyl counterparts, both in the bulk crystal phase and in thin films grown by organic molecular beam epitaxy (OMBE) under ultra‐high vacuum conditions on the Ag(111) surface. In the crystal phase, the conformation depends on the number n of phenyl rings, exhibiting an intriguing screw‐like structure in the case of n = 4 at room temperature as well as at 180 K. For OMBE‐grown thin films, the whole series acquires the same type of conformation, characterized by alternately twisted phenyl rings, similar to the pure oligophenyl species. However, for all tested molecules, the orientation of the molecular reference plane is uniform within the entire film and coincides with the surface plane. This contrasts with the herringbone ordering adopted by the phenyl backbones without the carbonitrile groups. Our results demonstrate how the functionalization of moieties with extended conjugated electron systems can help to improve the structural homogeneity in technologically relevant organic thin films.

Two-Orbital Kondo Screening in a Self-Assembled Metal–Organic Complex

“…The higher intensity observed on one side of the molecules is ascribed to the tilt of the phenyl rings with respect to the surface and to each other. 25,28,29 Notice that very similar results have been obtained for Fe atoms buried by NC-Ph 5 -CN molecules (see Supporting Information).…”

On‐Surface Formation of Cumulene by Dehalogenative Homocoupling of Alkenyl gem‐Dibromides

“…As shown in Figure 3a and 3b, both cumulene products adopt flat-lying geometries on Au(111) except the slight tilt of the benzene rings with respect to each other, 43,44 and the cumulene group adopts for both cases a linear geometry. The average molecular heights are measured to be 3.1 Å from the DFT models.…”

“…To further verify the formation of the cumulene group,we performed further DFT calculations to construct the relevant structural models of both trans-and cis-cumulene products on Au(111), and calculated the corresponding charge densities. As shown in Figure 3a and 3b,both cumulene products adopt flat-lying geometries on Au(111) except the slight tilt of the benzene rings with respect to each other, [44,45] and the cumulene group adopts for both cases al inear geometry. Theaverage molecular heights are measured to be 3.1 from the DFT models.I th as been previously stated that the intramolecular contrast resolved by nc-AFM can be modeled by considering the charge density of the targeted molecules, because the atomic contrast is ac onsequence of Pauli repulsion.…”

Device-Compatible Chiroptical Surfaces through Self-Assembly of Enantiopure Allenes

“…A fitting of the leading edge of the experimental spectra with Voigt peaks ( Figure S12a) and comparison of the peak intensities to theoretical curves 49 indicates an average adsorption angle a of the pyridine moiety between 50° and 60° (between the normal of the ring plane and the surface normal, Figure S12b), clearly ruling out a flat adsorption geometry as the dominant configuration. On the other hand, the consistent anchoring via the thiol groups rules out a random orientation of the pyridine rings 50 . Thus, even though the quality of the film is inferior to what has been achieved with simple alkene-SAMs, the combined X-ray spectroscopic data evidence the formation of a monolayerthin CF-2 upstanding chiral architecture and indicate a preferential average inclination of the molecular backbone of approximately 30° (Figure 2f, for more detail see the SI), in accordance with the ellipsometry experiments.…”