trans12diarylethenes

Trans12diarylethenes are a class of organic compounds defined by a central carbon–carbon double bond bearing two aryl groups in a trans arrangement. They correspond to trans-1,2-diarylethenes (Ar1–CH=CH–Ar2), a motif closely related to stilbenes. The conjugation between the aryl rings imparts significant electronic delocalization, influencing absorption properties and redox behavior. The trans geometry is generally more thermodynamically stable than the cis form due to reduced steric interactions between the rings.

Synthesis methods commonly used to prepare trans12diarylethenes include McMurry coupling of diaryl ketones or aldehydes to form the stilbene-like backbone, which often furnishes the trans isomer. Direct olefination strategies, such as Wittig or Horner–Wadsworth–Emmons reactions, can also yield E-configured diarylethenes from appropriate aryl aldehydes and phosphoranes. Additionally, cross-coupling approaches, including Heck-type couplings or related vinylation methods, enable assembly of the Ar–CH=CH–Ar framework from aryl halides and vinyl partners.

Properties and applications typically arise from the extended π-conjugation of the diarylethene core. Substituents on the aryl rings allow tuning of the absorption maximum and fluorescence, enabling color changes and photophysical modulation. The trans isomer is often the thermodynamically favored open form in photoswitchable systems; in many diarylethenes, irradiation can drive reversible transformations to a closed-ring isomer, producing reversible changes in color and optical properties. Consequently, trans12diarylethenes are studied as molecular switches, components of smart materials, and candidates for nonlinear optical applications.