LIU Yin-qiu



SYNTHESIS, STRUCTURE AND FLUORESCENT STUDY OF BIS(4,4’-dimethyl-2,2’-bipyridinato)- TRIS(nitrato-o,o’)-EUROPIUM(III)

LIU Yin-qiu1,2

(1. School of Chemistry and Chemical Engineering, Jinggangshan University, Ji'an, Jiangxi 343009, China; 2. Key Laboratory of Coordination Chemistry of Jiangxi Province, Ji’an, Jingxi 343009, China)

A new europium(III) complex: bis(4,4'-dimethyl-2,2'-bipyridinato)-tris(nitrato-o,o')-europium(III) was prepared by the method of solvothermal synthesis, and its mononuclear crystal structure was determined by X-ray diffraction. The crystal structure of the title compound crystallized in monoclinic, space groupwith= 21.71(5) Å,= 10.203(18) Å,= 16.08(3)Å, ß =118.19(11)°,= 4,D= 1.630Mg/m3,= 3139(11)Å-3. The fluorescent properties show that the compound may be a candidate of red light material for its strong emission at 616 nm under ultraviolet radiation of 321 nm.

rare earth complex; europium(III); luminescence

INTRODUCTION

“Rare earth complexes are good luminescent materials[1-3], having narrow emission lines (with half height width about 10 nm) and a relatively long emitting life (about 10-2to 10-6s); in addition, their emissions cover the bands where the three basic colors (red, green and blue) are located, turning them as potentially good materials for planar displays of high quality. Previous research proved that the luminescent efficiency of simple rare earth ions was very low but could be improved when coordinated to some kind of organic ligands, matching in energy[4], due to the energy transmission of ligand-to-mental ions.”[5]We are very interesting in searching for suitable ligands to build such kinds of complexes. In our previous works, pyridine, multi-pyridylamine and its’ oxide derivatives have been used to build rare earth complexes[6-7], which indicated that aromatic compounds are adequate transmitter of rare earth ions. To confirm our deduction, more intended structures should be designed and synthesized. So, the title complex was prepared, which, to our best learning, is the first europium(III) complex prepared using 4,4’-dimethyl-2,2’-bipyridine as ligand. Herein, we report it here.

1 EXPERIMENTAL

1.1 Synthesis of the title complex

Eu(NO3)3.6H2O (0.0430 g, about 0.2 mmol), 4,4’-dimethyl-2,2’-bipyridine(0.0368 g, about 0.2 mmol), methanol and acetonitrile (about 10mL)were sealed into a steel bomb equipped with a Teflon liner and kept at 384 K for several days. After cooling undisturbed in air, crystals of the title complexof the size suiting for X-ray diffraction were obtained.

1.2 X-ray Structure determination

A yelllow single crystal of the title complex with dimensions of 0.449 0.200 0.150 mm was selected for X-ray diffraction test. Standard procedures were used to mount the crystal on a Bruker Apex-II area-detector diffractometer at 293(2) K or so. Intensity data was collected using a Moradiation (λ= 0.71073 Å) with ascan mode. A total of 8666 reflections were collected, of which 2836 were unique (R(int) = 0.0747). The SAINT and SADABS programs in the Bruker AXS SMART APPEX(II) software package were used for integration and absorption correction. The structure was solved by direct methods using SHELXS-97 program and refined on F2with XSHELL6.2. All non-hydrogen atoms were modeled anisotropically. All hydrogen atoms were positioned geometrically and treaded as riding on their parent atoms with bond length fixed at certain values and withiso(H) being certain ratio to their attached atoms. In the final difference map, the residuals are 0.2918 and -3.719e. Å-3, respectively. The crystallographic data and analysis parameters are given in Table 1。

Supplementary materials have been deposited in the Cambridge Crystallographic Data Centre (CCDC 960223; deposit@ccdc.cam.ac.uk or http://www.ccde. cam. ac.uk).

Table 1 Crystallographic data and experimental details for the Title Complex

2 RESULTS AND DISCUSSION

The title complex was characterized by X-ray diffraction, the model obtained shows it is an mononuclear complex in which europium(III) ion is regularly coordinated: being ten coordinated and displaying a unequal spheral coordination environment(see fig1). Bond lengths of Eu-O in coordination core EuN4O6are between 2.450(11) Å and 2.548(13) Å, Bond lengths of Eu-N are 2.499(15) Å and 2.505(12) Å, all in the normal rang. Bis(4,4’-dimethyl-2,2’-bipyridine) as bi-dentate ligand bonded to Europium(III) ion with two N atoms. Each molecule contains three nitrate anions and those nitrate anions coordinates to the central europium(III) ion with two O atoms, at the same time balance the central europium(III) ions’ positive charges. In addition, there is a free methanol molecule in each asymmetric unit of its’ crystal.

Fig.1 The coordination environment of europium(III) ion in the title complex, showing 20% probability displacement ellipsoids,all H atoms were omitted for clarity

Luminescent investigation was performed on LS-55 luminescence meter. The solid-state luminescent properties of the title complex were investigated at room temperature. Exiting test with emission fixed at 614nm showed that the best emission condition was under ultraviolet radiation of 321nm (see Fig2). Emitting spectrum was recorded with the exciting conditions fixed at 321nm, and the results were shown in Fig.3, two main lines appear at 593nm, 616nm (the stronger one), which can be assigned to the europium(III) ions’ election transition of5D0-7F1and5D0-7F2,, respectively. The title complex may be a candidate of red light material.

Fig.2 Exciting spectrum of the title complex, recorded with emission fixed at 614 nm

Fig.3 Emitting spectrum of the title complex under ultraviolet radiation of 321 nm

In summary, we have reported in this paper a new mononuclear europium(III) complex which may be a candidate of red light material because of its’ strong emission at 616nm under ultraviolet radiation of 321 nm. Further works are conducted in our laboratory, more intended structures with some modification to the ligand are in preparation.

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二(4，4’-二甲基-2，2’-联二吡啶)-三硝酸合铕(III)的合成，结构和荧光性质

刘荫秋1,2

（1. 井冈山大学化学化工学院，江西，吉安 343009；2. 江西省配位化学重点实验室，江西，吉安 343009）

用溶剂热法合成了一种新的单核铕配合物，二（4，4’-二甲基-2，2’-联二吡啶）-三硝酸合铕（III），该配合物的晶体属单斜晶系，空间群晶胞参数分别是：= 21.71(5) Å,= 10.203(18) Å,= 16.08(3) Å, ß = 118.19(11)°,= 4,D= 1.630 Mg/m3,= 3139(11) Å-3。配合物在321 nm的紫外光的照射下，在616 nm波长处有强的荧光发射，可望成为一种有实用价值的红光材料。

稀土配合物；三价铕；荧光

O633

A

10.3969/J.issn.1674-8085.2013.05.006

O633

A

10.3969/j.issn.1674-8085.2013.05.007

2013-05-09

2013-07-10

This work was supported by the Natural Science Foundation of Jinggangshan University (JZ0815).

1674-8085(2013)05-0023-03

LIU Yin-qiu(1969-), male(Han nationality),born in Anfu county, Jiangxi province, senior experimentalist(master degree), mainly engaged in coordination chemistry study(E-mail: lyqja@sina.com).