Stiff-Stilbene Photoswitches: From Fundamental Studies to Emergent Applications

Abstract

Stiff-stilbene, a sterically restricted fused ring analogue of stilbene, has been regularly used as a model compound in theoretical studies of stilbene photoisomerization. Lately, owing to its excellent photoswitching properties, it is increasingly being applied to reversibly control the properties and function of chemical as well as biological systems. Stiff-stilbene photoswitches possess a number of advantageous properties including a high quantum yield for photoisomerization and a high thermal stability. Furthermore, they undergo a large geometrical change upon isomerization and their synthesis is straightforward. Herein, we provide an overview of the basic properties of stiff-stilbene and of recent applications in supramolecular chemistry, catalysis, and biological systems.

Keywords: catalysis; molecular switches; photochromism; self-assembly; stiff-stilbene.

Scheme 1

a) Stilbene isomerization, cyclization and oxidation and b) chemical structures of stiff‐stilbene and molecular motor.

Scheme 2

Different approaches to the synthesis of stiff‐stilbene.

Figure 1

a) Line drawings of stiff‐stilbenes 1, 2 and 13–17 and b) X‐ray crystal structures of E‐15 (left) and Z‐15 (right).

Figure 2

UV/Vis spectral changes of E‐1 upon 313 nm irradiation (top) and UV/Vis absorption spectra of E‐1 and Z‐1 (bottom). Adapted with permission from Ref. 44. Copyright 2014 American Chemical Society.

Scheme 3

a) Switchable anion binding to bis‐urea stiff‐stilbene 18, b) supramolecularly induced rotational motion in bis‐thiourea stiff‐stilbene 19 and c) phototriggered blockage and exposure of a urea binding site in 21 and 22.

Scheme 4

Crown ether based photoresponsive cryptand 23.

Scheme 5

Pillar[5]arene translocation in rotaxane‐like structure 24.

Figure 3

Different stiff‐stilbene monomers able to self‐assemble into a polymer.

Scheme 6

Supramolecular assembly processes of compound 25. Reproduced with permission from Ref. 56. Copyright 2013 Wiley‐VCH.

Scheme 7

Di‐Pt^II‐induced formation of metallacycles and metallosupramolecular polymers.

Scheme 8

Stiff‐stilbene 29 and water soluble pillar[5]arene.

Scheme 9

Use of a molecular force probe to accelerate C−C bond dissociation.

Scheme 10

a) Isomers of bis‐phosphine ligand 39 and b) asymmetric Heck arylation reaction.

Scheme 11

a) Stiff‐stilbene based proton carrier 42 and b) bis‐pyridinium ligand 43.