Akademik Veri Yönetim Sistemi
European Journal of Inorganic Chemistry, cilt.2016, sa.32, ss.5079-5088, 2016 (SCI-Expanded)
© 2016 WILEY-VCH Verlag GmbH & Co. KGaA, WeinheimA ruthenium(II) tris(bipyridine)–rhodamine triad was prepared to control the triplet-state properties with external stimuli (acid). The rhodamine moiety is an acid-responsive module, and the RuII coordination center is responsible for triplet-state formation upon photoexcitation. Through steady-state UV/Vis absorption and luminescence spectroscopy, electrochemical characterization, and nanosecond/femtosecond transient absorption spectroscopy, we found that the dyad gives a quenched triplet metal-to-ligand charge-transfer (3MLCT) excited state (lifetime τT = 103.6 ns vs. τT = 1.58 µs) in the absence of acid, owing to a photoinduced electron transfer (PET) process. In the presence of acid, the rhodamine unit transforms reversibly from the spirolactam structure into the open-amide structure; thus, the PET is inhibited, the triplet-state lifetime (5.70 µs) is prolonged, and the T1 state is relocated to the rhodamine unit. This is the first time that the fundamental triplet-excited-state properties of a RuII complex, that is, the triplet lifetime and localization, have been controlled simultaneously. Intramolecular singlet–triplet energy transfer and triplet–triplet energy transfer (TTET, 3MLCT→3IL) were observed for the triad in the femtosecond and nanosecond transient absorption spectra, respectively. The dyad was used for acid-controllable triplet–triplet annihilation upconversion.