108826-49-9Relevant articles and documents
Preparation, proprietes spectroscopiques et electrochimiques de sels de pyrylium a structure bloquee
Tripathi, S.,Simalty, M.,Pouliquen, J.,Kossanyi, J
, p. 600 - 612 (2007/10/02)
The blocked pyrylium salts described in the present article show an increased fluorescence emission as compared to their nonblocked analogues.Due to its polarization along the C-4/O/C-10 axis, the long wavelength absorption band is not modified when the 7-phenyl group of the 5,6,8,9-tetrahydro 7-phenyl dibenzoxanthylium ion is substituted with electron donating or electron withdrawing groups.The compounds studied show an important Stokes effect which is suppressed in part when the temperature is decreased.This shift of the emission has been attributed to a large change in the dipole moment of the excited molecule, as compared to that of the ground state; a change which induces a rapid reorganization of the surrounding polar solvent molecules.Under electrochemical conditions, the pyrylium cations undergo two equilibrated one-electron redox reactions leading successively to the pyranyl radical and the pyranylate anion; on the other hand, the oxidation forms the dication-radical pyrylium.The intermediate pyranyl radical gives an equilibrated dimerization reaction which is favoured when the C-7 carbon atom is unsubstituted.
