Diarylethenes with Electroactive Substituents: A Theoretical Study to Understand the Effect on the IR Spectrum and a Simple Way to Read Optical Memory in the Mid-IR

Diarylethenes bearing electro-donating and electro-withdrawing substituents in the 5,5‘-positions of the thiophene unit were studied theoretically (DFT, B3LYP) to understand the effect of the substituents on the infrared spectrum in the two stable forms. The photochromic molecule with the electro-donating substituent showed the largest difference in the infrared (IR) spectrum due to the push−pull−push structure. It was chosen to build a memory film with a readout process in the mid-IR. Information written on the photochromic film was read using a setup based on an infrared camera (multibolometer) and a filtered broadband Globar source. The results showed that the readout process worked without matching any specific absorption band. A good contrast was obtained also with a single camera frame (45 ms).