Mono- and bithiophene-substituted diarylethene photoswitches with emissive open or closed forms

Abstract

We present a new series of photochromic 1,2-bis(2-ethylbenzo[b]thiophen-3-yl)perfluorocyclopentenes with an oxidized benzothiophene core (O) or a nonoxidized one, decorated with mono- (Th1) and bithiophene (Th2) units attached to positions 6 and 6′ (Sy = symmetric) or only to position 6 (As = asymmetric). “Oxidized” compounds have highly fluorescent closed forms emitting in the visible region (yellow to red). The dyes with nonoxidized benzothiophenes possess fluorescent open forms with rather low emission efficiency. The photoswitching kinetics was studied at several wavelengths with UV and visible light. New diarylethenes underwent ring-closure reactions by irradiation with UV light (365 nm, 405 nm), and the reversible ring-opening by irradiation with visible light (470 nm, 530 nm). The on-switching of fluorescence due to the ring-closure reaction was observed also with visible light of 470 nm (to an extent of 10% for compound SyOTh 1) and attributed to the Urbach tail effect. Due to a high degree of fluorescence modulation (>270), good fatigue resistance and large fluorescence quantum yield, compound SyOTh 1 emerged as a candidate for single-molecule based super-resolution fluorescence microscopy.

Turn-on mode diarylethenes for bioconjugation and fluorescence microscopy of cellular structures

“…The oxidized compounds with thienyl substituents underwent ring closure reactions to produce fluorescent CFs upon irradiation with UV (365 nm, 405 nm) as well as visible (470 nm) light. Remarkably, the on−off switching with visible light-alternating blue (470 nm) and green (530 nm) irradiation-demonstrated the Urbach tail effect (40).…”

“…Dye Design and Synthesis of Thienyl-Substituted fDAEs. We reported 1,2-bis(2-ethyl-1-benzothiophen-3-yl)perfluorocyclopentenes with oxidized and nonoxidized benzothiophene cores, as well as additional thiophene rings (one or two) attached to C-6 and/or C-6′ in a symmetric or asymmetric fashion (33,40). The oxidized compounds with thienyl substituents underwent ring closure reactions to produce fluorescent CFs upon irradiation with UV (365 nm, 405 nm) as well as visible (470 nm) light.…”

“…The oxidized compounds with thienyl substituents underwent ring closure reactions to produce fluorescent CF s upon irradiation with UV (365 nm, 405 nm) as well as visible (470 nm) light. Remarkably, the on−off switching with visible light—alternating blue (470 nm) and green (530 nm) irradiation—demonstrated the Urbach tail effect ( 40 ). To impart water solubility and improve the photofatigue resistance, we incorporated the branched linkers with terminal carboxylic acids into the structures of fDAEs ( 36 – 38 , 41 ).…”

“…In this range, where the absorption is very weak, the absorption coefficient was reported to obey the Urbach rule ( Eq. 3 ) for fluorescent dyes, including diarylethenes ( 40 ), where and are the absorption coefficients at the (irradiation) wavelengths corresponding to E and the 0–0 band ( E 0–0 ), k B is the Boltzmann constant, T is the absolute temperature, and σ is the steepness parameter ( 45 ).…”

Bis-Pyrene Photo-Switch Open- and Closed-Form Differently Bind to ds-DNA, ds-RNA and Serum Albumin and Reveal Light-Induced Bioactivity

“…Particularly, diarylethenes (DAE) drew our attention due to the high conversion rate (mostly close to 100%), at variance to lower conversion rates of other photo-switches (e.g., diaza mostly being about 70–80%, although some analogues showed promising increase [ 23 ]). In addition, some diarylethene derivatives showed highly fluorescent “closed” forms [ 24 ], very promising property for the applications like super-resolution microscopy [ 25 ].…”