Oxidative and reductive cyclization in stiff dithienylethenes.

Area of Science:

• Organic electrochemistry
• Photochromic materials

Background:

• Dithienylethenes are photochromic compounds known for reversible isomerizations.
• Stiff dithienylethenes possess conformational constraints influencing their reactivity.
• Electrochromism in dithienylethenes is typically induced by oxidation.

Purpose of the Study:

• To investigate the electrochemical behavior of stiff dithienylethenes.
• To explore the influence of ring size and substituents on electrocyclization.
• To elucidate the mechanisms of oxidative and reductive electrocyclization pathways.

Main Methods:

• Electrochemical analysis (cyclic voltammetry).
• Synthesis of various stiff dithienylethene derivatives.
• Spectroscopic characterization of isomers and products.

Main Results:

• Electrochromism was observed in most stiff dithienylethene derivatives.
• Oxidative cyclization of open isomers was the major electrochromic pathway.
• Ring size affected cyclization: 6-membered rings cyclized from both E- and Z-isomers, while 7-membered rings only from Z-isomers.
• Benzonitrile substituents enabled a rare reductive electrocyclization pathway for both stiff and normal dithienylethenes.

Conclusions:

• Stiff dithienylethenes display tunable electrochromic properties.
• The conformational rigidity and electronic effects of substituents significantly impact electrocyclization.
• The discovery of reductive electrocyclization broadens the application potential of dithienylethene systems.