Novel photochromic dithienylalkenes for the development of molecular scale devices

Photochromic and electrochromic compounds are molecules that interconvert between two distinct structural forms, differing in their absorption spectra, when triggered with an appropriate light or electrochemical stimulus, respectively. 1,2-Dithienylcyclopentenes are photochromic compounds that reversibly interconvert between colourless ring-open and coloured ring-closed forms when irradiated with ultraviolet and visible light, respectively. A series of novel photochromic and electrochromic compounds, based on the dithienylcyclopentene skeleton, were synthesized and evaluated for potential use in molecular scale devices.; A series of covalently linked double 1,2-dithienylcyclopentene photochromic systems were prepared for potential use as high-density optical storage materials. Irradiation of the binary dithienylperhydrocyclopentene systems with ultraviolet light resulted in ring-closure of only one of the photochromic moieties, followed by quantitative production of a photostable side-product. The side-product, however, did not form as rapidly when the perfluorinated cyclopentene derivatives were irradiated with UV light.; Terthiophene oligomers were incorporated into the dithienylcyclopentene backbone in such a way that the linear π-conjugation of the terthiophene units were severed upon ring-cyclization and re-routed through the backbone of the molecule. This compound, as well as other 1,2-dithienylcyclopentene derivatives bearing either thiophene or phenyl groups on the carbon atoms involved in forming the new single bond in the ring-closing reaction were found to have both photochromic and unprecedented electrochromic properties. These compounds could be reversibly interconverted between their ring-open and ring-closed states using UV and visible light, respectively, and catalytically transformed from their ring-closed to their ring-open states through electrochemical or chemical oxidation. Unprecedented electrochemical ring-closing was also observed for two 1,2-bis(dithienyl)cyclopentene derivatives. The ring-opening reaction was accomplished by irradiation using visible light, however, the ring-closing reaction could be triggered by using either UV light irradiation or electrochemical oxidation.; A photochromic dithienylcyclopentene derivative was used to photoregulate helicene formation. A [7]-thiahelicene could be reversibly created and destroyed by alternate irradiation with ultraviolet and visible light respectively.; A new class of photochromic compounds based on the hexatriene backbone was developed which consisted of a thiophene ring, a perfluorocyclopentene ring, and a trisubstituted olefin. These systems reversibly undergo photoinduced ring-opening and ring-closing reactions when irradiated with UV and visible light, respectively.