Configurational Selection in Azobenzene‐Based Supramolecular Systems Through Dual‐Stimuli Processes

Abstract

Azobenzene is one of the most studied light-controlled molecular switches and it has been incorporated in a large variety of supramolecular systems to control their structural and functional properties. Given the peculiar isomeric distribution at the photoexcited state (PSS), azobenzene derivatives have been used as photoactive framework to build metastable supramolecular systems that are out of the thermodynamic equilibrium. This could be achieved exploiting the peculiar E/Z photoisomerization process that can lead to isomeric ratios that are unreachable in thermal equilibrium conditions. The challenge in the field is to find molecular architectures that, under given external circumstances, lead to a given isomeric ratio in a reversible and predictable manner, ensuring an ultimate control of the configurational distribution and system composition. By reviewing early and recent works in the field, this review aims at describing photoswitchable systems that, containing an azobenzene dye, display a controlled configurational equilibrium by means of a molecular recognition event. Specifically, examples include programmed photoactive molecular architectures binding cations, anions and H-bonded neutral guests. In these systems the non-covalent molecular recognition adds onto the thermal and light stimuli, equipping the supramolecular architecture with an additional external trigger to select the desired configuration composition.[a] Prof. P. Tecilla

Artificial Supramolecular Pumps Powered by Light

“…The present results confirm the general value of the strategy, based on the combination of photoswitching and molecular recognition phenomena, [22] to achieve directional molecular movements. The minimalist design and the unsophisticated structure of the molecular components make our approach viable and flexible.…”

Anion Recognition by a Pincer-Type Host Constructed from Two Polyamide Macrocyclic Frameworks Jointed by a Photo-Addressable Azobenzene Switch

“…In the present study, we decided to expand the family of pincer-type hosts by synthesizing a novel member 1 that contains a photo-responsive linker in place of the nondynamic linker used previously (Scheme 1) [57]. Conceptually, such structural changes enable the modification of the anion-binding properties of the host by a non-invasive and clean light stimulus [58][59][60][61][62][63]. The lariat arm, apart from bringing extra hydrogen bond functionality, introduces a steric hindrance to the binding cavity and further pre-organizes the macrocyclic framework [41][42][43][44].…”

“…In the present study, we decided to expand the family of pincer-type hosts by synthesizing a novel member 1 that contains a photo-responsive linker in place of the non-dynamic linker used previously (Scheme 1) [57]. Conceptually, such structural changes enable the modification of the anion-binding properties of the host by a non-invasive and clean light stimulus [58][59][60][61][62][63].…”

Stimuli-responsive Enaminitrile Molecular Switches as Tunable AIEgens Covering the Chromaticity Space and Acting as Vapor Sensors

“…In particular, the configurational cis/trans-change of carbon-carbon double bonds provides an indispensable tool for a wide variety of applications in biology, materials science, supramolecular and organic chemistry, etc. [6,[11][12][13][14][15][16][17][18] Upon external input, such as irradiation, metalation, or pH changes, the properties of entities bearing responsive moieties, and also the properties of the entire systems, can be practicably modulated at discretion. [10,[19][20][21][22][23][24][25] Of the many potential applications based on these entities, materials that display controllable luminescence under external control are of particular interest.…”