The Excited State Relaxation Path of N,N-Diethyl-5-cyanopyridine and N,N-Diethylbenzaldehyde

摘要

The molecules which possess,as electron donors,dialky lam ino groups linked by a single bond with the acceptor subunits undergo fast excited state intramolecular charge transfer(ICT),emitting dual fluorescence in polar solvents.The short and the long-wavelength fluorescence bands are traditionally assigned as F_b and F_a,respectively.The nature of the excited state from which the F_a emission originates,as well as the mechanism of energy degradation have been the subject of many controversies.As the objects of this study,2-(N,N-diethyl)·5-cyanopyridine(PEC)and p-N,N-diethylaminoacetophenone(DEABA)were selected.For these molecules different sequence of the two low-lying pipi*L_a and L_b states was postulated,which can help to verify the excited state mechanisms of the charge separation.The experimental results obtained by stationary and time-resolved spectroscopy show that the anomalous F_a emission originates from the ICT state generated by the mutual twist of the donor and acceptor group(TICT model).