Circular Dichroism Photoswitching with a Twist: Axially Chiral Hemiindigo

Abstract

Chiroptical properties play a crucial role not only for molecular structures and their functions but also for advanced applications such as molecular sensing, absolute asymmetric synthesis, or information processing and storage. Manipulating chiroptical characteristics in a predictable and reversible fashion by outside means is therefore a highly desirable option to enhance the functions and reporting abilities of a molecular system. Herein, we present axially chiral hemiindigo photoswitches showing unusual chiroptical changes upon visible-light irradiation. While absorption remains high throughout the spectrum, the corresponding ECD signals can be reversibly erased and reestablished in an ON/OFF manner upon photoswitching. Taken together with exceptionally high thermal bistabilities, leading to half-lives of the metastable states up to 3400 years at ambient temperature, and high photoswitching quantum yields these chiral hemiindigos offer unique possibilities for, e.g., smart molecule, photonic materials, or sensing applications.

Controlling Pyrene Association in DNA Duplexes by B‐ to Z‐DNA Transitions

“…The nature of the chromophore association depends on the structure of the DNA templates. As such, the use of DNA structural transitions as a driving force for controlling the association behavior of chromophores represents a challenge for developing functional DNA nanotechnologies that use chiroptical molecular switches . In this work, we prepared DNA structures with non‐nucleosidic pyrene residues in the middle of d(CG) repeat sequences to transform the pyrene associations into self‐complementary duplexes (Scheme ) and evaluated the B‐ to Z‐DNA transition of the pyrene association mechanism.…”

Design, synthesis and investigation of water-soluble hemi‑indigo photoswitches for bioapplications

“…In particular, nowadays the development of photopharmacology is based mainly on azobenzene chemistry [10,11] and, therefore, finding of new biocompatible photochromes with complementary properties is highly desirable to speed up the progress in this important field. In this context, an emerging class of hemi-indigo photoswitches attracts special attention [12][13][14][15][16]. Despite the fact that the hemi-indigo dyes are known for more than 100 years [17], their photochemical properties are still essentially unexplored and no targeted studies on their photoswitching in aqueous media were performed.…”

Reversible Photoswitching of Isolated Ionic Hemiindigos with Visible Light

“…Many potential applications of photoswitches, particularly in biological contexts require them to respond within the biooptical window, prompting synthetic efforts aimed at shifting their absorptions to longer wavelength. [4][5][6][7][8][9] Recently, new classes of photoswitches such as DASAs, [10][11][12] hydrazones, [13,14] and indigoid chromophores [15][16][17][18][19] have been developed with strong absorptions in the red region of the spectrum, and with high photoisomerization quantum yields.Indigoid photoswitches such as hemithioindigo (HTI) [20][21][22][23] and hemiindigo (HI) [24][25][26] are chromophores derived from the parent indigo dye. [27] Although HI molecules were first synthesized over a century ago [24] and their basic photoswitching characteristics have been known for at least two decades, [25] interest has recently grown due to the development of new derivatives that respond to red light, have high thermal stability of their switching states, are simple to synthesize and function-alize, and exhibit high photostability.…”

“…[27] Although HI molecules were first synthesized over a century ago [24] and their basic photoswitching characteristics have been known for at least two decades, [25] interest has recently grown due to the development of new derivatives that respond to red light, have high thermal stability of their switching states, are simple to synthesize and function-alize, and exhibit high photostability. [17] Recent contributions have reported asymmetric HI systems that exhibit photoswitching of chiroptical properties, [26] and HTI chromophores that can be deployed as controllable molecular motors, [23,[28][29][30][31][32] receptors [33][34] or tweezers. [19,35] Other applications include light controlled peptide structure [36][37][38] and supramolecular chemistry.…”

“…Indigoid photoswitches such as hemithioindigo (HTI) [20][21][22][23] and hemiindigo (HI) [24][25][26] are chromophores derived from the parent indigo dye. [27] Although HI molecules were first synthesized over a century ago [24] and their basic photoswitching characteristics have been known for at least two decades, [25] interest has recently grown due to the development of new derivatives that respond to red light, have high thermal stability of their switching states, are simple to synthesize and function-alize, and exhibit high photostability.…”