Molecular Design Strategy toward Diarylethenes That Photoswitch with Visible Light

Abstract

Photoactive molecules that reversibly switch upon visible light irradiation are one of the most attractive targets for biological as well as imaging applications. One possible approach to prepare such photoswitches is to extend π-conjugation length of molecules and shift the absorption bands to longer wavelengths. Although several attempts have been demonstrated based on this approach for diarylethene (DAE) photoswitches, photoreactivity of the DAE derivatives is dramatically suppressed when the conjugation length is extended by connecting aromatic dyes at the side positions of aryl groups in the DAE unit. In this study, we successfully prepared a visible-light reactive DAE derivative by introducing an aromatic dye at the reactive carbon atom of the DAE unit, optimizing orbital level of each component, and controlling the mutual orientation of the aromatic dye and the DAE unit. The DAE derivative (3) undergoes a photocyclization reaction upon irradiation with 560 nm light and the closed-isomer converts to the open-ring isomer upon irradiation with 405 nm light. The high photoconversion yields (>90%) were achieved for both photocyclization and photocycloreversion reactions. The photoreactivity induced by visible light irradiation and the molecular design strategy were discussed based on theoretical calculations.

Fluorescence modulation of cadmium sulfide quantum dots by azobenzene photochromic switches

“…Cadmium sulfide (CdS) QDs have recently been considered as an emerging class of broad band radiating nanoparticles [6,7] having a direct band gap of 2.4 eV, and being widely used in solar cells [2], in light-emitting diodes for flat panel displays [8] and especially in photochrome-fluorophore assemblies as fluorophores [9,10]. The photochromic switching molecules have the tendency of reversible transformation between two isomers upon exposure to electromagnetic radiation.…”

Visible‐Light‐Driven Photoisomerization and Increased Rotation Speed of a Molecular Motor Acting as a Ligand in a Ruthenium(II) Complex

“…[8] These include changing the substituent pattern [9] and BF 2 coordination [10] in azo compounds,a sw ell as the attachment of aromatic dyes to diarylethenes. [11] Them ost widely applied approach though, is by coordination to transition-metal complexes,w hich can act as photosensitizers. [12] This process is not trivial, since it can also lead to aperturbation of the excited state properties of the switching unit.…”

How Adsorption Onto TiO2 Modifies the Properties of Multiswitchable DTE Systems: Theoretical Insights

“…One of the most studied classes of synthetic photochromes, dithienylethenes (DTE) are highly attractive fatigue-resistant compounds that are able to cyclize their π-system thousands of times without degradation of its photochromic properties. [1][2][3] Upon UV irradiation, the colorless open (O) form cyclizes into the extensively conjugated and colored closed (C) form, which can retro-cyclize to the open form upon application of visible light. [1][2][3][4][5] Because the open and closed isomeric forms possess different physical and chemical properties, DTEs have been the subject of numerous studies towards applications such as optical memory devices on the molecular scale.…”

“…[1][2][3] Upon UV irradiation, the colorless open (O) form cyclizes into the extensively conjugated and colored closed (C) form, which can retro-cyclize to the open form upon application of visible light. [1][2][3][4][5] Because the open and closed isomeric forms possess different physical and chemical properties, DTEs have been the subject of numerous studies towards applications such as optical memory devices on the molecular scale. [6][7][8] Going beyond single DTE compounds, multimers combining two or more DTE units together can theoretically attain a maximum of 2 n isomeric states, where n is the number of switchable units.…”