Bipyridinium-bis(carboxylate) Radical Based Materials: X-ray, EPR and Paramagnetic Solid-State NMR Investigations

Autor: Shashi Kumar Kumara Swamy, Abdelhadi Kassiba, Magali Allain, Nicolas Mercier, Jens Dittmer, Maxime Leroux, Oksana Toma
Přispěvatelé: MOLTECH-Anjou, Université d'Angers (UA)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS), Chimie, Ingénierie Moléculaire et Matériaux d'Angers (CIMMA), Université d'Angers (UA)-Centre National de la Recherche Scientifique (CNRS), Institut des Molécules et Matériaux du Mans (IMMM), Le Mans Université (UM)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)
Jazyk: angličtina
Rok vydání: 2016
Předmět:
Zdroj: European Journal of Inorganic Chemistry
European Journal of Inorganic Chemistry, Wiley-VCH Verlag, 2016, 2016 (7), pp.1036-1043. ⟨10.1002/ejic.201501206⟩
ISSN: 1434-1948
1099-0682
DOI: 10.1002/ejic.201501206⟩
Popis: The zwitterionic 1,1′-bis(4-carboxyphenyl)-4,4′-bipyridinium (bp4pc) has been synthesized and crystals of its hydrated form bp4pc·2H2O and of its protonated reduced form H-bp4pc have been obtained. Upon heating, bp4pc·2H2O undergoes partial dehydration, leading to bp4pc·H2O at 160 °C, together with a color change from yellow (room temperature) to green (140 °C) and finally to brown (160–180 °C). Analysis of bond lengths in the solid state reveals the expected short (d = 1.425 A) and long (d = 1.485 A) C–C central bond lengths in the all-radical salt H-bp4pc and bp4pc·2H2O, respectively, whereas the distance of 1.475 A in bp4pc·H2O does not allow a conclusion to be drawn regarding the presence of radicals in this compound. EPR and solid-state paramagnetic NMR experiments of H-bp4pc and the hydrated zwitterion bp4pc·2H2O at different temperatures, however, show that the color change of the latter upon heating is due to the presence of bipyridinium radicals, the concentration of which, although low, increases with increasing temperature. The nature of the electron donor involved in this thermal-induced electron transfer is not fully understood. Most plausible is the possibility that it is the carboxylate group with an intramolecular electron-transfer process; on the other hand it, cannot be excluded that the electron stems from the water molecule, which decomposes into O2, H+, and e– giving H-bp4pc entities.
Databáze: OpenAIRE
Externí odkaz: