Photoswitchable Fluorescent Diarylethene Derivatives with Thiophene 1,1-Dioxide Groups: Effect of Alkyl Substituents at the Reactive Carbons.

Masakazu Morimoto,Takaki Sumi,Masahiro Irie

doi:10.3390/ma10091021

Abstract

Photoswitching and fluorescent properties of sulfone derivatives of 1,2-bis(2-alkyl-4-methyl-5-phenyl-3-thienyl)perfluorocyclopentene, 1–5, having methyl, ethyl, n-propyl, i-propyl, and i-butyl substituents at the reactive carbons (2- and 2′-positions) of the thiophene 1,1-dioxide rings were studied. Diarylethenes 1–5 underwent isomerization reactions between open-ring and closed-ring forms upon alternate irradiation with ultraviolet (UV) and visible light and showed fluorescence in the closed-ring forms. The alkyl substitution at the reactive carbons affects the fluorescent property of the closed-ring isomers. The closed-ring isomers 2b–5b with ethyl, n-propyl, i-propyl, and i-butyl substituents show higher fluorescence quantum yields than 1b with methyl substituents. In polar solvents, the fluorescence quantum yield of 1b markedly decreases, while 2b–5b maintain the relatively high fluorescence quantum yields. Although the cycloreversion quantum yields of the derivatives with methyl, ethyl, n-propyl, and i-propyl substituents are quite low and in the order of 10−5, introduction of i-butyl substituents was found to increase the yield up to the order of 10−3. These results indicate that appropriate alkyl substitution at the reactive carbons is indispensable for properly controlling the photoswitching and fluorescent properties of the photoswitchable fluorescent diarylethenes, which are potentially applicable to super-resolution fluorescence microscopies.

Highlights

Fluorescent molecules with photoswitching ability have attracted much attention because of their potential applications to optical information storage as well as super-resolution fluorescence microscopies [1,2,3,4,5]
It has been demonstrated that chains, such as ethyl, n-propyl, and n-butyl groups [26,27,34]. It has been such demonstrated turn-on mode fluorescent diarylethene derivatives can be utilized as molecular probes for that such turn-on mode fluorescent diarylethene derivatives can be utilized as super-resolution fluorescence microscopies, such as PALM/STORM
The fluorescence quantum yield of the closed-ring isomer is significantly improved by replacing the sulfone derivatives of 1,2-bis(2-alkyl-6-phenyl-1-benzothiophen-3-yl)perfluorocyclopentene methyl substituents with the longer branched alkyl

Summary

Introduction

Fluorescent molecules with photoswitching ability have attracted much attention because of their potential applications to optical information storage as well as super-resolution fluorescence microscopies [1,2,3,4,5]. In order to improve the fluorescent property, various f isomer undergoes a cyclization reaction to produce the fluorescent closed-ring isomer. It has been demonstrated that chains, such as ethyl, n-propyl, and n-butyl groups [26,27,34] Very recently, it has been such demonstrated turn-on mode fluorescent diarylethene derivatives can be utilized as molecular probes for that such turn-on mode fluorescent diarylethene derivatives can be utilized as super-resolution fluorescence microscopies, such as PALM/STORM [35,36,37]. 1,2-bis(2-alkyl-4-methyl-5-phenyl-3-thienyl)perfluorocyclonentene (2–5), as shown in Scheme 1, 1,2-bis(2-alkyl-4-methyl-5-phenyl-3-thienyl)perfluorocyclonentene (2–5), as shown in Scheme 1, to to improve the properties These derivatives possess different improve thephotoswitching photoswitching and and fluorescent fluorescent properties.

Results and Discussion

Relationship

Materials and Methods