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Manifestation of π–π Stacking Interactions in Luminescence Properties and Energy Transfer in Aromatically-Derived Tb, Eu and Gd Tris(pyrazolyl)borate Complexes

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posted on 06.04.2015, 00:00 authored by Elena A. Mikhalyova, Anastasiya V. Yakovenko, Matthias Zeller, Mikhail A. Kiskin, Yuriy V. Kolomzarov, Igor L. Eremenko, Anthony W. Addison, Vitaly V. Pavlishchuk
The three new complexes TpPyLn­(CH3CO2)2(H2O) (Ln = Eu (1), Gd­(2), or Tb (3)) were prepared and characterized crystallographically. In the crystal lattices of these complexes, separate molecules are connected in infinite chains by π-stacking interactions. Complexes 1 and 3 display intense photoluminescence and triboluminescence (red and green respectively), while compound 3 exhibits electroluminescence commencing at 9 V in an ITO/PVK/3/Al device (ITO = indium-tin oxide, PVK = poly­(N-vinylcarbazole)). A series of Eu/Tb-doped Gd compounds was prepared by cocrystallization from mixtures of 1 and 2 or 2 and 3, respectively. It was shown that π-stacking interactions are involved in increasing the efficiency of energy transfer from the gadolinium complex to emitting [TpPyEu]2+ or [TpPyTb]2+ centers, and this energy transfer occurs through hundreds of molecules, resembling the process of energy harvesting in chloroplast stacks.