Maciejewski, JanSobczuk, Adam AntoniClaveau, AlexisNicolai, Adrien G.Petraglia, RiccardoCervini, LucaBaudat, EmilieMieville, PascalFazzi, DanieleCorminboeuf, ClemenceSforazzini, Giuseppe2016-08-182016-08-182016-08-18201610.1039/C6SC03196Jhttps://infoscience.epfl.ch/handle/20.500.14299/128755WOS:000391454500040Here we present a molecular architecture that can reversibly change the geometric conformation of its π-system backbone via irradiation with two different wavelengths. The proposed ‘molecular actuator’ consists of a photoswitchable azobenzene orthogonally connected to a π-conjugated bithiophene by both direct and aliphatic linker-assisted bonding. Upon exposure to 350 nm light, the trans azobenzene moiety isomerizes to its cis form, causing the bithiophene to assume a semiplanar anti conformation (extended π-conjugation). Exposure to 254 nm light promotes the isomerization of the azobenzene unit back to its initial extended trans conformation, thus forcing the bithiophene fragment to twist out of coplanarity (restricted π-conjugation). The molecular conformation of the bithiophene was characterized using steady-state UV-Vis and nuclear magnetic resonance spectroscopy, as well as ab initio computations. The proposed molecular design could be envisaged as a π-conjugation modulator, which has potential to be incorporated into extended linear π-systems, i.e. via the terminal alfa-thiophene positions, and used to tune their optical and electronic properties.photoswitchmolecular electronicstext::journal::journal article::research article