Excited State Energy Migration and Photochromic Reaction in 1,2-Bis(2,4-dimethyl-3-thienyl)perfluorocyclopentene Single Crystal

Abstract

An excited state energy migration was found to compete with a photocyclization reaction in the single crystal of 1,2-bis(2,4-dimethyl-3-thienyl)perfluorocyclopentene.Photochromic diarylethenes belong to the most promising photochromic compounds because of thermal stability of both isomers and fatigue-resistant property.1 Some diarylethene derivatives can undergo photochromism even in the single-crystalline phase.2 The colored forms of diarylethenes are stable in the crystals even at 100 C. Such thermally irreversible crystalline photochromic materials are potentially applicable to various optoelectronic devices, such as holographic and three-dimensional optical recording memories and displays. [3][4][5][6][7] In the course of study on single-crystalline photochromism of diarylethenes, we prepared a binary co-crystal composed of two types of diarylethenes. 8,9 Both diarylethenes can undergo photochromism in the home-crystals phase. However, in the co-crystals only one diarylethene selectively undergoes a photocyclization reaction to give the closed-ring isomer upon irradiation with ultraviolet light. This suggests that an excited state energy migration takes place in the crystal. The purpose of this paper is to examine the excited state energy migration in a single-component crystal of 1,2-bis(2,4-dimethyl-3-thienyl)perfluorocyclopentene (1a) (Scheme 1).In solution, diarylethenes have two stable conformations with the aryl rings in mirror symmetry (named parallel conformation) and C 2 symmetry (named antiparallel conformation) in almost equal amounts, and they interconvert with each other in solution. The interconversion rate between the two conformations is much slower than the lifetime of photoexcited states. 10The conrotatory cyclization can proceed only from the antiparallel conformation.11 Diarylethenes in crystal cannot undergo the thermal interconversion between the two conformers. The photocyclization reactivity of diarylethenes in the crystalline phase depends on the distance between the reactive carbon atoms. When the distance is longer than 4.2 # A, the photocyclization cannot take place. When the distance is shorter than 4.2 # A, efficient photocyclization reactions take place.

Photochromism of Diarylethene Molecules and Crystals: Memories, Switches, and Actuators

“…The colors remain stable in the dark, but disappear by irradiation with visible light. The molecular structures and colors of diarylethenes showing photochromism in the crystalline phase are summarized in Table (refs , , , , , , , , , , , , , , , and − ). Photoinduced coloration/decoloration cycles of the crystals can be repeated more than 30 000 times while maintaining the photochromic performance and the bulk crystal shape .…”

Cyclization Dynamics and Competitive Processes of Photochromic Perfluorocyclopentene Dithienylethylene in Solution

“…Our leitmotiv was the attempt to detangle the photochemistry of the antiparallel (AP) conformers from the photophysics of parallel (P) conformers by comparing bridged/ constrained versus free analog molecules (the initial purpose of the former being the blockade of the molecule into a photoactive conformation). Due to its commercial availability, normal dithienylethene 1,2-bis(2,4-dimethyl-5-phenyl-3-thienyl) perfluorocyclopentene (denoted as DTE, hereafter) has become a reference [26,[35][36][37][38] of photoswitch, that is the reason why we reinvestigated its photochemistry together with a series of polyether bridged analogs. The main outcomes [32] were: (i) for the P* conformer, an Intersystem crossing (ISC) occurred (40-150 ps) to produce a first triplet state ( 3 P) after ultrafast relaxation toward S 1 relaxed state.…”

“…In this paper, we decided to reinvestigate a smaller structural analogue of DTE without the two terminal phenyl groups, the 1,2bis(2,5-dimethyl-3-thienyl)-perfluorocyclopentene noticed in the following DMTPF (Scheme 1). Such molecule has been studied in the past in crystalline phase [35,36] and in solution [37,38] with the main features to present a photocyclization more efficient in crystalline phase (ϕ cycl = 0.5) as compared to hexane solution (ϕ cycl = 0.21) while photoreversion yields are almost identical (ϕ cycl = 0.12) in both phases. Knowing that AP population was restricted to 17 % in the solid state (compared to almost 50 % in solution), the authors concluded for an excited state energy migration during photoconversion, the P conformer acting as a sensitizer.…”

Functionalization of a Simple Dithienylethene via Palladium-Catalyzed Regioselective Direct Arylation

“…Unfortunately, the use of other iodoarenes such as iodobenzene resulted in quite low yields under the optimized reaction conditions. However, this type of reaction is promising because a diarylethene bearing β-arylated thienyl groups is difficult to synthesize through conventional protocols …”