Emitting and electron-transfer electronic states of tertiary amine–fluorophore sensor systems

The excited electronic states of a series of tertiary amine–fluorophore systems have been investigated by time-dependent density functional theory (TDDFT) calculations. These systems exhibit suppression of emission due to a photoinduced electron-transfer process (PET) from the amine to the fluorophore. The present calculations in the case of the pyrene as the fluorophore show clearly the PET process through a change in the character of the excited state accompanying its geometry optimization. In agreement with experimental observations the suppression of emission diminishes with the length of the aliphatic spacer between the amine and pyrene.