Programmable multilayers of nanometer-sized macrocycles on solid support and stimuli-controlled on-surface pseudorotaxane formation

Abstract

Mechanically interlocked molecules (MIMs) such as rotaxanes and catenanes are capable of mechanical motion on the nanoscale and are therefore promising prototypes for molecular machines in recent nanotechnology. However, most of the existing examples are isotropically distributed in solution, which prohibits concerted movement and with it the generation of macroscopic effects. Thus, arranging them in ordered arrays is of huge interest in recent research. We report the deposition of quite densely packed multilayers of tetralactam macrocycles on gold surfaces by metal-coordinated layer-by-layer selfassembly. Linear dichroism effects in angle-resolved NEXAFS spectra indicate a preferential orientation of the macrocycles. The sequence of the metal ions can be programmed by the use of different transition metal ions at each deposition step. Additionally, reversible on-surface pseudorotaxane formation was successfully realized by repeated uptake and release of axle molecules inside the macrocycles cavities.

Photocontrolled On‐Surface Pseudorotaxane Formation with Well‐Ordered Macrocycle Multilayers

“…The pristine macrocycle multilayer (Figure 6a)s hows effects analogous to those observedi ne arlier studies of macrocycleso n at erpyridine-terminated template with gold as the substrate. [30] The p*r esonance exhibits splitting into two characteristic peaks at 285.1 and 285.4 eV,w hich show ac lear linear dichroism in the 90-308 difference spectrum in line with the earlier results. This also includes as ignificant change of the relative heights of the two peaks.…”

“…To get a more detailed insight to the packing of macrocycles with and without cis ‐ 8 , angle‐dependent C K‐edge NEXAFS spectra have been recorded (Figure ). The pristine macrocycle multilayer (Figure a) shows effects analogous to those observed in earlier studies of macrocycles on a terpyridine‐terminated template with gold as the substrate . The π* resonance exhibits splitting into two characteristic peaks at 285.1 and 285.4 eV, which show a clear linear dichroism in the 90–30° difference spectrum in line with the earlier results.…”

“…This indicates that the multilayers are rather densely packed and that not all macrocycles are accessible for the binding of cis‐ 8 . In a previous study, we used a squaraine as the guest molecule that was bound to macrocycle multilayers and a linear increase of bound molecules with an increasing number of layers was observed . This can be explained by the differences between the molecular structure of the guests.…”

“…This indicates that the multilayersa re rather densely packed and that not all macrocycles are accessible for the binding of cis-8.Inaprevious study,w eu sed as quaraine as the guest molecule that was bound to macrocycle multilayers and al inear increase of bound molecules with an increasing number of layers waso bserved. [30] This can be explained by the differences between the molecular structure of the guests.While the squaraine molecule used in the former study is relatively small, has al inear form without stopper-units and can therefore easily slip through the voids in the surfaceo rt he macrocycle cavities, guest molecule 8 used here is stoppered on one end through the xanthene unit, so that the accessibility of deeper macrocycle layersiss ignificantly hampered.…”

Reference-free, depth-dependent characterization of nanolayers and gradient systems with advanced grazing incidence X-ray fluorescence analysis

“…For a more reliable GIXRF modeling and for more complex samples, this does not work. As an example, we used three macrocyclic organic multilayers of different layer thickness deposited by metal ion coordinated layer‐by‐layer self‐assembly . The resulting multilayers consisted of an alternating structure of Fe(II) ions (black balls) and organic tetralactam macrocycles on a SAM (see sketch Fig.…”