A Dual‐Mode Molecular Switching Device: Bisphenolic Diarylethenes with Integrated Photochromic and Electrochromic Properties

Abstract

AbstractThe bisphenolic dithienylethene molecules 1a and 1b were synthesized in overall yields of 45% from 4‐bromoanisole and 44% from 2.6‐di‐tert‐butyl‐4‐iodophenol, respectively. The corresponding extended quinones 3a and 3b were also prepared. Photochemical studies showed that compounds 1 are photochromic; the open forms 1 could be converted with UV light of 312nm to the closed coloured forms 2 with photostationary states lying at essentially complete conversion (> 98%). The 1a‐2a system was found to exhibit good resistance to photofatigue and thermal stability for both photoisomers. Cyclic voltammetry studies involving the 2/3 couples showed that whereas 2b undergoes irreversible oxidation at + 0.85 V (vs. SCE in THF), the hydroquinone 2a is reversibly oxidized at an E1/2 of + 0.72V (in MeCN, quasi‐reversibly in THF at + 0.81 V); this reflects the differences in deprotonation behaviour of the generated QH2/2+ species. The large difference in oxidation potential between 1a and 2a allows the photochemical switching of redox properties. In a complementary fashion, redox switching of the photochromic properties within the 2a‐3a pair is possible since 3a is stable to visible light. Owing to this unique behaviour, the triad consisting of 1‐3a represents a novel molecular device with mutually regulating photo‐ and electrochromic behaviour. In addition, the ability to interconvert between the three stable states makes the system well‐suited as the basis for an optical memory system with multiple storage and nondestructive readout capacity through a write‐lock‐read‐unlock‐erase cycle.