Author's personal copy Journal of Photochemistry and Photobiology A: Chemistry 219 (2011) 243–249 Contents lists available at ScienceDirect Journal of Photochemistry and Photobiology A: Chemistry journal homepage: www.elsevier.com/locate/jphotochem Synthesis, characterization and luminescence property of ternary rare earth complexes with azatriphenylenes as highly efﬁcient sensitizers Hui-Juan Sun a , Xiao-Tao Fu a , Hai-Bin Chu a,b,∗ , Yan Du a , Xue-Mei Lin a , Xin Li a , Yong-Liang Zhao a,∗∗ a College of Chemistry and Chemical Engineering, Inner Mongolia University, Hohhot 010021, China b SINOPEC Beijing Research Institute of Chemical Industry, Beijing 100013, China article info Article history: Received 20 October 2010 Received in revised form 18 February 2011 Accepted 25 February 2011 Available online 3 March 2011 Keywords: Azatriphenylene Carboxylate Rare earth complex Luminescence intensity Quantum efﬁciency abstract A series of novel ternary rare earth complexes showing attractive luminescence properties were pre- pared with both neutral and anion ligands. Three azatriphenylene neutral ligands, 1,10-phenanthroline (phen), dipyrido [3,2-a: 2 ′ ,3 ′ -c] quinoxaline (dpq) and dipyrido [3,2-a: 2 ′ ,3 ′ -c] phenazine (dppz) were investigated systematically as sensitizers in the ternary rare earth complexes. Benzoate ions (BA - ) and phenoxyacetate ions (POA - ) were chosen as anion ligands. The compositions of these complexes were characterized by elemental analysis, rare earth coordination titration, molar conductivity measurement, IR spectroscopy, UV–vis absorption spectroscopy, 1 H NMR spectroscopy and TGA–DTA. The luminescence spectra, luminescence decay time and quantum efﬁciency of the complexes were also studied. The very strong luminescence intensities and rather long luminescence lifetimes (typically > 1.0 ms) were achieved for both Eu 3+ and Tb 3+ ternary complexes with phen and dpq as neutral ligands. Moreover, high quan- tum efﬁciencies (40–60%) were also obtained for Eu 3+ ternary complexes with phen and dpq as neutral ligands. © 2011 Elsevier B.V. All rights reserved. 1. Introduction Rare earth compounds have attracted much attention because of their superior luminescent properties, such as long lumines- cence lifetimes, large Stokes shift and sharp emission proﬁle, and their applications in the ﬁelds of catalysis, information technique, display, lighting, nanoscience, agriculture and military [1–4]. How- ever, the luminescence intensities of rare earth ions are relatively weak because f–f electronic transitions of these ions are forbidden by the parity rule. Direct coordination of the antenna ligands with rare earth ions can effectively sensitize the central ions by ligand-to-metal energy transfer. Both anion ligands and neutral ligands have been recog- nized widely as effective antenna ligands towards rare earth ions. First, anion ligands, such as -diketones and aromatic carboxylic acids, not only can form stable complexes with rare earth ions, but also are able to efﬁciently receive light and transfer energy to rare earth ions [5]. Nonetheless, because of the electrostatic repulsion between anion ligands, anion ligands alone could not meet the high coordination number requirement of rare earth ions. Consequently, ∗ Corresponding author at: College of Chemistry and Chemical Engineering, Inner Mongolia University, Hohhot 010021, China. Tel.: +86 13624849905. ∗∗ Corresponding author. Tel.: +86 13624849905; fax: +86 471 4992984. E-mail addresses: binghai99@gmail.com (H.-B. Chu), hxzhaoyl@163.com (Y.-L. Zhao). solvent molecules are typically evolved in the complexes, resulting in low luminescent efﬁciencies of rare earth ions. The introduc- tion of certain neutral ligands, such as terphenyl-based compounds, azatriphenylenes and pyridine derivatives, can increase the lumi- nous efﬁciency of the rare earth complexes. The reason is that the neutral ligands can replace the solvent molecules to coordi- nate with the central ions as well as eliminate energy loss caused by thermal vibration of solvent molecules [5,6]. Also, they can improve the rigidity and stability of the complex structures, and increase the absorption of light energy and energy transfer efﬁ- ciency so as to enhance the luminous intensity of the complexes [7,8]. However, rare earth complexes with neutral ligands alone typically exhibit poor luminescence quenched by anions such as hydroxyl ions. Besides, the coordination environment as well as crystal structure of the complexes changes signiﬁcantly when both anion and neutral ligands are involved. In addition, intramolecular energy transfer process between the two ligands would improve the luminescence efﬁciency of rare earth complexes. Hence, the design and synthesis of new ternary complexes with both anion and neutral ligands have theoretical signiﬁcance and application value for excellent luminescent rare earth materials. The complexes of rare earth ions with aromatic carboxyl acids have optimal luminescence. Phenanthroline (phen) and 2,2 ′ - bipyridine (bipy) are widely used as neutral ligands in ternary complexes [9–12]. In order to get rare earth complexes with strong luminescence, good thermodynamic stability and high quantum efﬁciency, two neutral azatriphenylene ligands, dipyrido [3,2-a: 1010-6030/$ – see front matter © 2011 Elsevier B.V. All rights reserved. doi:10.1016/j.jphotochem.2011.02.026