Synthesis and Characterization of Nonsymmetric Cyclopentene-Based Dithienylethenes

Nonsymmetric cyclopentene-based dithienylethenes, containing
both
thienyl and benzothienyl units, have been synthesized for the first
time, employing intramolecular McMurry reaction as a key transformation
to target compounds 10 and 16. Photochromic
properties of these compounds were examined in toluene and acetonitrile
solutions, PMMA layers, solid films, and crystal phase. To explain
an unprecedented single-crystalline photochromism phenomena of 10, X-ray crystallographic analysis was performed, revealing
a significant influence of strong S···S interatomic
interactions on the intramolecular distance between two photochemical
reaction centers in the molecule. Compound 16 could be
further synthetically modified in a step-by-step manner, thus serving
as potential key intermediate to various complex bifunctional photochromic
molecules.