Synthesis of a new diarylethene diradical which has extended π-conjugated chains from the 2,5-position of one thiophene ring

A diarylethene diradical having a new switching unit for intramolecular magnetic interaction was synthesized. The photoswitching unit has an extended π-conjugated chain in one aryl unit, and two nitronyl nitroxide radical are placed at both ends of the π-conjugated chain. The diarylethene moiety is located in the middle of the chain. This diarylethene is designed to change the hybrid orbital from sp2 to sp3 at the 2-position of the thiophene ring when this diarylethene undergoes a photochromic reaction. But the new diradical compound did not undergo photocyclic reaction upon irradiation with UV light. The photochemical behavior is perturbed by a resonant quinoid structure which stabilizes the open-ring isomer.

Graphical abstractThis paper describes the synthesis of a new diarylethene having nitronyl nitroxide radicals and discusses its photochemical behavior. Upon irradiation with UV light, photochromic reaction did not take place. Two radicals in the open-ring isomer have the intramolecular exchange interaction (0.04 K < ∣2J/kB∣) and contribution of quinoid structure suppressed photocyclic reaction.Figure optionsDownload full-size imageDownload as PowerPoint slide