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

Dobkowski J., Sazanovich I.

Polish Journal of Chemistry

2008

Vol. 82, nr 4

831-845

The molecules which possess, as electron donors, dialkylamino 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-wave length fluorescence bands are traditionally assigned as Fb and Fa, respectively. The nature of the excited state from which the Fa 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-di ethyl)-5-cyanopyridine (PEC) and p-N,N-diethylaminoacetophenone (DEABA) were selected. For these molecules different sequence of the two low-lying pi pi* La and Lb 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 Fa emission originates from the ICT state generated by the mutual twist of the donor and acceptor group (TICT model).

Time -Resolved Emission Spectroscopy of Pyrene Derivatives

Dobkowski J., Galievsky V., Jasny J., Sazanovich I.

Polish Journal of Chemistry

2004

Vol. 78 / nr 7

961-972

An improved model of the picosecond time-resolved spectrofluorimeter equipped with an optical Kerr shutter was designed and constructed. The instrument was applied for measurements of time-resolved fluorescence (TRF) spectra of 4_-(pyrenyl-1-yl)acetophenone (Py-BK) and 4_-(pyrenyl-1-yl)benzonitrile (Py-BN). The experimental results indicate that both molecules relax after excitation by mutual twisting of two subunits towards a more planar geometry. In the case of Py-BK the kinetics of creation of excited state hydrogen-bonded complexes was discussed in detail.