Excited-State Dynamics of 1-Piperidino- or 1-Pyrrolidino-anthraquinone for Formation of N−Ylide and Reduced Compounds

Abstract

By means of subpicosecond laser photolysis of the title compound at room temperature, time-dependent shift of an absorption band has been observed at short delay times which is ascribed to solvent reorganization around the lowest excited singlet state of the solute molecule with an intramolecular charge-transfer character. In comparison with the results obtained by nanosecond laser photolysis and steady-state photolysis at 77 K, it is concluded that the lowest excited singlet state undergoes rapid intramolecular proton transfer forming an N-ylide compound. For formation of the N-ylide compound from the lowest excited singlet state of 1-piperidino-anthraquinone, it is considered that there exists an intermediate which can be ascribed to transfer of the equatorial proton to the carbonyl oxygen anion. At room temperature, no formation of N-ylide compound as a stable compound can be observed due to its rapid reversion to 1-piperidino- or 1-pyrrolidino-anthraquinone. Steady-state photolysis in ethanol at room ...