115560-43-5Relevant articles and documents
Synthetic control over intra- and intermolecular charge transfer can turn on the fluorescence emission of non-emissive coumarin
Jhun, Byung Hak,Ohkubo, Kei,Fukuzumi, Shunichi,You, Youngmin
, p. 4556 - 4567 (2016)
Conjugated molecules bearing carbonyl groups typically exhibit weak fluorescence emission due to the presence of a non-radiative n-π? transition state. Strong fluorescence emission from n-π? chromophores has been sought through the use of synthetic approaches that incorporate strong electron donors, such as amines, into the conjugated structures. As an alternative to these existing approaches, we investigated two charge-transfer strategies using a series of 1-benzopyran-2-one (coumarin) derivatives. The first strategy involved attaching chromophoric aryl moieties at the 7 position of coumarin. This molecular control produced two effects: the n-π? transition state was destabilized and an intramolecular charge-transfer (ICT) state was generated. The photoluminescence quantum yields (PLQYs) of the bichromophoric dyads increased with the π-conjugation length of the aryl groups, and a PLQY as high as 0.80 was achieved. The second strategy facilitated exciplex fluorescence in poly(N-vinylcarbazole) (PVK) films within which coumarin derivatives have been molecularly dispersed. A thermodynamic analysis based on electrochemical data indicated that exciplex generation involved electron transfer from PVK to photoexcited coumarin molecules. Exciplex fluorescence was uniquely advantageous in its ability to tune the fluorescence emission color upon addition of electron donors having oxidation potentials less positive than that of PVK. Mechanistic studies, including femtosecond laser flash photolysis, were conducted to identify the molecular parameters that governed the two fluorescence properties. A mechanistic understanding may provide useful insights into the development of electrofluorescent materials that harness triplet as well as singlet excitons.
Bichromatic Photosynthesis of Coumarins by UV Filter-Enabled Olefin Metathesis
Eivgi, Or,Sutar, Revannath L.,Reany, Ofer,Lemcoff, N. Gabriel
, p. 2352 - 2357 (2017/07/22)
Herein, we report on a two-step bichromatic synthesis of coumarins involving UV-A and UV-C light. The first step is a UV-A-photoinduced ruthenium-catalyzed cross-metathesis (CM) reaction of 2-nitrobenzyl-protected 2-hydroxystyrenes with acrylates, using an external solution of 1-pyrenecarboxaldehyde as a UV filter. Irradiation in the absence of the filter permanently inhibits the light-activated catalyst due to photocleavage of the photolabile protecting group (PPG) and ensuing phenolate chelation to the ruthenium. The simple removal of the external filter after CM allows further photochemical reactions with UV-C light to achieve more complex architectures, such as the coumarins presented in this work. (Figure presented.).
One-pot catalysis of dehydrogenation of cyclohexanones to phenols and oxidative Heck coupling: Expedient synthesis of coumarins
Kim, Donghee,Min, Minsik,Hong, Sungwoo
supporting information, p. 4021 - 4023 (2013/07/26)
One-pot reactions leading to highly functionalized coumarins have been developed via a Pd(ii)-catalyzed dehydrogenation-oxidative Heck-cyclization process.
