Photochromic switching behaviour of donor–acceptor Stenhouse adducts in organic solvents

Abstract

We report photochromic donor-acceptor Stenhouse adducts (DASAs) capable of fully reversible photoisomerization with visible light in organic solvents including chloroform, acetonitrile and benzene. The rates of photoisomerization and thermal reversion can be tuned by altering the electronics of the donor adduct. X-Ray crystallography and photo-NMR experiments unambiguously establish molecular structures.

Taking Photochromism beyond Visible: Direct One‐Photon NIR Photoswitches Operating in the Biological Window

“…In nonpolar solvents the quantum yields are unexpectedly high (0.28 in n-heptane and 0.18 in toluene) while in rather polar solvents, such as DCM, acetonitrile,a nd DMSO,t he quantum yields are somewhat lower (ca. Such an effect is well known for other donor-acceptor photoswitches,w hich display aC Tb and,such as DASAs (donoracceptor Stenhouse adducts);however,these do not absorb in the NIR and often exhibit diminished performance in polar solvents, [22,23] rendering the still good switching DHP 1 superior in comparison. Such an effect is well known for other donor-acceptor photoswitches,w hich display aC Tb and,such as DASAs (donoracceptor Stenhouse adducts);however,these do not absorb in the NIR and often exhibit diminished performance in polar solvents, [22,23] rendering the still good switching DHP 1 superior in comparison.…”

It's a Trap: Thiol‐Michael Chemistry on a DASA Photoswitch

“…Upon the formation of the cyclized form,t he DASA contains ad ouble bond featuring a b-carbonp rone to nucleophilica ttack.H ere, an isomer selective thiol-Michael reaction betweenthe cyclized DASA and ab ase-activated thiol is introduced. [6][7][8][9] The equilibrium between the two forms is dependent on the solvente nvironment andt he structural motifs of the DASA derivatives, consistingo fa ne lectron donor and an acceptorm oiety,r esultingi napush-pull system.U pon irradiation, the equilibrium is shifted towardst he ring cyclized isomer (cyclized form) and, upon thermalr elaxation, it returns to the initialc onjugated state (linear form). Undero ptimized conditions,t he reactionp roceeds preferentially in the presenceo fl ight and base.…”

“…[1] Light, as ar eadily available and adjustable reactiont rigger,i sp articularly interesting for implementing spatiotemporal control on reaction outcomes. [6][7][8][9] The equilibrium between the two forms is dependent on the solvente nvironment andt he structural motifs of the DASA derivatives, consistingo fa ne lectron donor and an acceptorm oiety,r esultingi napush-pull system.U pon irradiation, the equilibrium is shifted towardst he ring cyclized isomer (cyclized form) and, upon thermalr elaxation, it returns to the initialc onjugated state (linear form). [2][3][4][5] Photoswitches, such as derivatives of the donor-acceptor Stenhouse adduct (DASA), coexisti na ne quilibrium between two isomeric forms.O ne isomer consists of an intensely colored (blue, purple or orange)n onpolar linear form, whereas the other isomer is cyclized, polar,c olorless and commonly zwitterionic (Scheme 1).…”

Visible Light-Responsive DASA-Polymer Conjugates

“…11−18 However, transitioning to aromatic amine-based donors provides second generation DASA derivatives, allowing for tunable absorption (450−750 nm) and improved switchability in a variety of solvents. 19,20 To fully exploit these new properties in visible light-responsive materials it became apparent that a synthetic strategy to conjugate DASAs to polymers needed to be developed. Herein we describe a modular approach using activated ester chemistry.…”