Tunable Visible and Near Infrared Photoswitches

Abstract

A class of tunable visible and near-infrared donor−acceptor Stenhouse adduct (DASA) photoswitches were efficiently synthesized in two to four steps from commercially available starting materials with minimal purification. Using either Meldrum's or barbituric acid "acceptors" in combination with aniline-based "donors", an absorption range spanning from 450 to 750 nm is obtained. Additionally, photoisomerization results in complete decoloration for all adducts, yielding fully transparent, colorless solutions and films. Detailed investigations using density functional theory, nuclear magnetic resonance, and visible absorption spectroscopies provide valuable insight into the unique structure−property relationships for this novel class of photoswitches. As a final demonstration, selective photochromism is accomplished in a variety of solvents and polymer matrices, a significant advantage for applications of this new generation of DASAs.

Visible Light-Responsive DASA-Polymer Conjugates

“…Reaction of this copolymer with MPDP results in the clean appearance of anisidine proton signals at 6.75 and 6.60 ppm with 1 H NMR monitoring, suggesting high selectivity of the primary amine over the aromatic secondary amine (Figure 2a). Significantly, the complementary loss in fluorine signal with 19 F NMR monitoring reveals quantitative conversion (Figure 2b). Subsequently, reaction with an excess of Meld yields the DASA−polymer conjugate P1 after ∼5 days.…”

“…Conveniently, the syntheses could be tracked using a combination of 19 internal standard reveals the incorporation of PFPA (∼3 mol %) in a copolymer of poly(methyl acrylate-co-PFPA) P(MA-co-PFPA) ( Figure S1). Reaction of this copolymer with MPDP results in the clean appearance of anisidine proton signals at 6.75 and 6.60 ppm with 1 H NMR monitoring, suggesting high selectivity of the primary amine over the aromatic secondary amine (Figure 2a).…”

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.…”

Photochromie jenseits des Sichtbaren: Direkte, im biologischen Fenster addressierbare Einphotonen‐NIR‐Photoschalter

“…Die stärkste Rotverschiebung des geschlossenen Isomers 1c, die bis l = 835 nm reicht, erzielten wir in einer DMSO/ Wasser-Mischung (8:2;s iehe Hintergrundinformationen: Abbildung S4 fürd ie Bestrahlung und Abbildung S8 fürd ie thermische Relaxation). Ein solcher Effekt ist auch bekannt füra ndere Donor-Akzeptor-Photoschalter,d ie eine CT-Bande zeigen, wie DASAs (Donor-Akzeptor-Stenhouse-Addukte), obwohl diese nicht im NIR-Bereich absorbieren und in polaren Lçsungsmitteln häufig kaum isomerisieren, [22,23] weshalb das DHP 1 wegen seines immer noch guten Schaltverhaltens diesen überlegen ist. In unpolaren Lçsungsmitteln sind die Quantenausbeuten unerwartet hoch (0.28 in n-Heptan und 0.18 in Toluol), während sie in eher polaren Lçsungsmitteln, z.…”