Strategy for Molecular Design of Photochromic Diarylethenes Having Thermal Functionality

Area of Science:

• Organic Chemistry
• Materials Science
• Photochemistry

Background:

• Photochromic diarylethenes are molecules that change color upon light exposure.
• Controlling the thermal stability and reactivity of these molecules is crucial for practical applications.
• Substituent effects on diarylethene thermal behavior are not fully understood.

Purpose of the Study:

• To investigate how different substituents influence the thermal reactivities of photochromic diarylethene closed-ring isomers.
• To explore the potential applications of these tailored diarylethenes in areas like reusable image recording and secret data storage.
• To establish a strategy for molecular design of diarylethenes with specific thermal functionalities.

Main Methods:

• Synthesis and characterization of diarylethene derivatives with various substituents (alkyl, alkoxy, trimethylsilyl, methoxymethyl).
• Evaluation of thermal cycloreversion and by-product formation reactivities.
• Correlation of thermal reactivity with steric substituent constants and quantum chemistry calculations.

Main Results:

• Bulky alkyl groups promote thermal cycloreversion.
• Alkoxy groups induce thermal cycloreversion with low photocycloreversion quantum yields, suitable for reusable photoresponsive recordings.
• Trimethylsilyl or methoxymethyl groups lead to thermally irreversible reactions, useful for secret-image recordings.
• Thiophene-S,S-dioxidized diarylethenes with secondary alkyl groups exhibit thermal by-product formation and photostability, applicable to light-starting thermosensors.

Conclusions:

• Molecular design by substituent control effectively tunes the thermal reactivities of diarylethene closed-ring isomers.
• Specific substituents enable diverse applications, including reusable image storage, secure data recording, and thermosensing.
• The study provides a framework for developing advanced photochromic materials with tailored thermal properties.