Related Experiment Video
Updated: Jun 13, 2026
08:40
Light-driven Molecular Motors on Surfaces for Single Molecular Imaging
Published on: March 13, 2019
Amino-nitro-azobenzene dimers as a prototype for a molecular-level machine
J Henzl1, M Mehlhorn, K Morgenstern
1Leibniz Universität Hannover, Institut für Festkörperphysik, Abteilung Oberflächen, Appelstrasse 2, D-30167 Hannover, Germany. henzl@fkp.uni-hannover.de
Nanotechnology
|May 6, 2010
Summary
Researchers demonstrated molecular-level machines using azobenzene molecules. Electron-induced switching of one molecule controlled the movement of another, performing mechanical work.
Area of Science:
- Surface science
- Molecular nanotechnology
- Chemical physics
Background:
- Azobenzene molecules exhibit light- and electron-induced cis-trans isomerization.
- Precise manipulation of individual molecules on surfaces is crucial for molecular machines.
Purpose of the Study:
- To investigate the potential of azobenzene dimers for molecular machine applications.
- To demonstrate controlled mechanical work at the molecular level.
Main Methods:
- Low-temperature scanning tunneling microscopy (LT-STM) on a Au(111) surface.
- Electron-induced manipulation of an X-shaped dimer of amino-nitro-azobenzene molecules.
Main Results:
- Reversible cis-trans isomerization of azobenzene molecules was achieved via electron-induced manipulation.
- Switching of the upper molecule in the dimer resulted in controlled movement of the lower molecule.
- Demonstrated the performance of mechanical work at the single-molecule level.
Conclusions:
- Azobenzene molecules can function as components of molecular machines.
- Electron-induced isomerization provides a viable mechanism for controlling molecular motion and performing work.
- This study serves as a proof-of-principle for nanoscale mechanical devices.
Related Concept Videos
01:19Structure of Amines
The hybridized nitrogen atom in amines possesses a lone pair of electrons and is bound to three substituents with a bond angle of around 108°, which is less than the tetrahedral angle of 109.5°. However, the C–N–H bond angle is slightly larger at 112°, with a carbon–nitrogen bond length of 147 pm. This carbon–nitrogen bond length of of amines is longer than the carbon–oxygen bond of alcohols (143 pm) but shorter than alkanes’ carbon–carbon bond (154 pm). These aspects are illustrated in Figure...
01:371° Amines to Diazonium or Aryldiazonium Salts: Diazotization with NaNO2 Mechanism
Nitrous acid is a relatively weak and unstable acid prepared in situ by the reaction of sodium nitrite and cold, dilute hydrochloric acid. In an acidic solution, the nitrous acid undergoes protonation when it loses water to form a nitrosonium ion—an electrophile. Nitrous acid reacts with primary amines to give diazonium salts. The reaction is called diazotization of primary amines.
02:00Molecular Models
Physical models representing molecular architectures of chemical compounds play essential roles in understanding chemistry. The use of molecular models makes it easier to visualize the structures and shapes of atoms and molecules.
01:22Preparation of 1° Amines: Azide Synthesis
Direct alkylation of ammonia produces polyalkylated amines, along with a quaternary ammonium salt. To exclusively prepare primary amines, the azide synthesis method can be used.
Azide ions act as good nucleophiles and react with unhindered alkyl halides to form alkyl azides. Alkyl azides do not participate in further nucleophilic substitution reactions, thereby eliminating the chances of polyalkylated products. Alkyl azides are reduced by hydride-based reducing agents, like lithium aluminum...
Azide ions act as good nucleophiles and react with unhindered alkyl halides to form alkyl azides. Alkyl azides do not participate in further nucleophilic substitution reactions, thereby eliminating the chances of polyalkylated products. Alkyl azides are reduced by hydride-based reducing agents, like lithium aluminum...
01:23Aldehydes and Ketones with Amines: Imine Formation Mechanism
Imine formation involves the addition of carbonyl compounds to a primary amine. It begins with the generation of carbinolamine through a series of steps involving an initial nucleophilic attack and then several proton transfer reactions. The second part includes the elimination of water, as a leaving group, to give the imine.
Imines are formed under mildly acidic conditions. A pH of 4.5 is ideal for the reaction.
If the pH is low or the solution is too acidic, the reaction slows down in the...
Imines are formed under mildly acidic conditions. A pH of 4.5 is ideal for the reaction.
If the pH is low or the solution is too acidic, the reaction slows down in the...
01:29Preparation of Amines: Reduction of Oximes and Nitro Compounds
Oximes can be reduced to primary amines using catalytic hydrogenation, hydride reduction, or sodium metal reduction. The reduction of aliphatic and aromatic nitro compounds to primary amines takes place by either catalytic hydrogenation or by using active metals like Fe, Zn, and Sn in the presence of an acid.
Though catalytic hydrogenation can reduce nitrobenzenes, the reduction is nonselective in the presence of other functional groups. For instance, if nitrobenzene contains an aldehyde group,...
Though catalytic hydrogenation can reduce nitrobenzenes, the reduction is nonselective in the presence of other functional groups. For instance, if nitrobenzene contains an aldehyde group,...