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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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journal contribution
posted on 06.04.2015 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.