| Résumé | The time-dependent DFT calculations for the low-lying excited electronic states of 4- and 3-di-tert-butylaminobenzonitrile, and 2,4,6-tricyano-N,N-dimethylaniline and 2,4,6-tricyanoaniline have been performed to investigate the mechanism of photo-induced intramolecular charge transfer (ICT). In addition, CC2-RI calculations were performed for TCDMA. For di-tert-butylaminobenzonitriles, we found evidence for the πσ *-state mediated mechanism associated with the sequential state-switches: ππ * → πσ * → ICT. It is predicted that 2,4,6-tricyano-N,N-dimethylaniline (TCDMA), but not 2,4,6-tricyanoaniline, possesses two ICT states, one of which shows the ICT-characterized quinoidal geometry and lies below the initially photo-excited S1(ππ *) state. The ππ * → ICT formation in TCDMA feasibly occurs in accord with the observed time-resolved excited-state absorption spectra and the biexponential fluorescence decay from the mixed S1(ππ *)/ICT state of TCDMA. |
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