Highly Ordered 2D Hydrogen‐Bonded Structures of a Tetralactam Macrocycle on the Au(111) Surface

Abstract

Monolayers of a tetralactam macrocycle, which are commonly used as building blocks in the synthesis of rotaxanes or catenanes, are deposited on a Au(111) surface by using vapor deposition. Due to self‐organization, 2D highly ordered supramolecular networks form. From scanning tunneling microscopy (STM) and concomitant density‐function theory calculations, two structurally different phases are found. In both phases, pairs of hydrogen bonds between the amide groups of next‐neighbor macrocycles are responsible for the structural arrangement of the macrocycles. The structure of both phases differs from that of bulk lattice planes, which reveals that the Au(111) surface acts as a template for the growth of the specific 2D structures. These networks of tetralactam macrocycles possibly open a route to study mechanical interlocking processes or guest/host interactions of the molecules in further detail by using STM.

Conformational Flexibility of Tetralactam Macrocycles and Their Intermolecular Hydrogen‐Bonding Patterns in the Solid State

“…X-ray-quality crystals [9] of TLMs 4 + and 5 (Scheme 1) were obtained in different ways: 4 + was crystallized by slow evaporation of CDCl 3 , whereas needlelike crystals of 5 were obtained through gradient vacuum sublimation at 1 10 À5 mbar and a sublimation temperature of 600-630 K. [10] For comparison, we include the previously published crystal structures of 1, [11] 2, [12] and 3. [13] Note that TLM 3 is an exceptional case, because two different conformers (3 A and 3 B) coexist in the crystal structure in a 1:2 ratio.…”

“…The solid-state structure of 2 thus nicely supports the structural model that was based on the STM images and theoretical calculations of TLM trimers. [10] Variations of this pattern have been observed by STM: Two different types of domains have been observed in the monolayer of 5, one in which infinite ladders of macrocycles cover the surface and one in which trimers of 5 exist with the same H-bonding pattern as that found in the crystal of 2. [10] In contrast to 2, the 2-in-2-out conformation of 3 (3 B) coexists in a 2:1 ratio with the corresponding all-in conformation (3 A) [18] in the solid state.…”

“…[10] Variations of this pattern have been observed by STM: Two different types of domains have been observed in the monolayer of 5, one in which infinite ladders of macrocycles cover the surface and one in which trimers of 5 exist with the same H-bonding pattern as that found in the crystal of 2. [10] In contrast to 2, the 2-in-2-out conformation of 3 (3 B) coexists in a 2:1 ratio with the corresponding all-in conformation (3 A) [18] in the solid state. This results in a quite different hydrogen-bonding pattern: The two conformers are interconnected by intermolecular NÀH···O=C bonds between all of the A out protons of 3 B and all of the A in oxygen atoms of 3 A.…”

Two-Dimensional Nanotemplates as Surface Cues for the Controlled Assembly of Organic Molecules

“…For this network, the driving force to adsorption was the The non-planar tetralactam macrocycle (TLM) shown in Fig. 43 was able to form 2D highly ordered supramolecular networks [106]. It contains four amide groups, which are involved in hydrogen bonds.…”

“…After deposition, two ordered phases (α and β) were found at the surface. The α phase is believed to be the most thermodynamically stable one since it prevails at RT, whereas the β phase prevails after annealing at 400 K. The monolayers decompose if [106]. © (2007) Wiley a tunneling current higher than 1 pA is used for imaging.…”