Photoresponsive Supramolecular Systems: Self‐Assembly of Azodibenzoic Acid Linear Tapes and Cyclic Tetramers

Abstract

A new strategy to effect photoinduced control over molecular self-assembly is reported. This strategy uses the reversible trans-cis photoisomerization of a novel azobenzene system, where the trans- and cis-forms self-assemble into dramatically different higher-order structures. The trans-azobenzene form of this molecule associates into infinite hydrogen-bonded linear tapes, while the cis-azobenzene form undergoes hydrogen-bonded self-assembly into cyclic tetramers. This results in a second level of association, where the cis-hydrogen-bonded supramolecular cycles ultimately form long, rod-like aggregates through stacking interactions.

Photocontrollable Self‐Assembly

“…[10] In this system, two geometrical isomers of azobenzene dicarboxylic acid derivative 7 form dramatically different superstructures by using intermolecular hydrogen-bonding as well as aromatic stacking interactions. In noncompeting solvents such as chloroform and dichloromethane, the trans isomer forms linear tapelike aggregates.…”

Light driven mesoscale assembly of a coordination polymeric gelator into flowers and stars with distinct properties

“…At the photostationary state ∼37.5% of cis -ADA can trigger this anisotropic growth mechanism by varying the crystal growth rates along different facets. It is known that the cis isomer of azobenzene can form energetically less favourable self-assembled structures 22. In case of a coordination bond driven self-assembly, the non-planar nature of cis -ADA can further hamper the chain building process as the geometry of the inorganic cluster brings cis -ADA closer to the coordination polymeric chain, where it remains in a sterically unfavourable position to undergo further reaction.…”

Advances in Switchable Supramolecular Nanoassemblies

“…These advantages are reflected by the amount of research in the field of supramolecular photocontrolled nanoassemblies. [5][6][7] It is known that the trans-and cis-configurations of azobenzene-groups containing surfactants have different critical micelle concentrations (CMC). [8,9] This feature was recently Abstract: Supramolecular nanoassemblies are gaining increasing importance as promising new materials with considerable potential for novel and promising applications.…”