Synthesis，Structure and Photoluminescence Properties of a two Dimensional CadmiumCoordination Polymer

WANG Shujun，LIU Dong，MA Wei

（College of Chemistry and Material Science，Huaibei Normal University，235000，Huaibei，Anhui，China）

Synthesis，Structure and Photoluminescence Properties of a two Dimensional Cadmium
Coordination Polymer

WANG Shujun，LIU Dong，MA Wei

（College of Chemistry and Material Science，Huaibei Normal University，235000，Huaibei，Anhui，China）

A novel two dimensional cadmium coordination polymer，formulated as｛［Cd（1，3-PDA）（ppene）］·H2O｝n（1）has been synthesized through hydrothermal reaction between Cd（NO3）2?4H2O and 1，3-phenylendiacetic acid（1，3-H2PDA）in the presence of 4-pyr-poly-2-ene（ppene）.The complex was structurally characterized by infra?red spectroscopy，elemental analysis and single crystal X-ray diffraction.Single-crystal X-ray diffraction analysis shows that the compound belongs to the triclinic system with space group Pī and a=9.524 8（19），b=10.430（2），c= 1.138 9（2）nm，α=88.65（3）°，β=86.79（3）°，γ=69.70（3）°，V=1.059 5（3）nm3，Z=2，R1=0.030 4，wR2=0.074 8. CCDC number 1038885.Compound 1 exhibits a two dimensional（4，4）network.Photoluminescence properties of 1 was also investigated.

coordination polymer;structure;characterization;photoluminescence properties

1 Introduction

The crystal engineering of coordination polymers（CPs）has drawn great interest within chemistry and materials science in recent years mainly due to their intriguing structures and widespread applications in the fields of catalysis，opticals，magnetism，photoluminescence，ion exchange，gas storage，intercalation chemistry，photochemistry and so on［1-6］.It is well known that multidentate organic ligands acting as linkers are con?firmed to play an important role in the construction of MOFs［3］.Although some prospective structures with specific properties can be constructed based on a careful selection of the properties of the ligands，such as flexibility，shape，symmetry，length and substituent groups，it still remains a great challenge to rationally de?sign and construct the desired compounds by controlling the factors that affect their structures［4］.Among the properties of a ligand，flexibility is very critical for the construction of a coordination polymer because the shape，symmetry and length of a ligand can be affected by its flexibility.Actually，the rigid ligands are prone to form coordination polymers with expected structures.However，the structures of coordination polymers con?structed from flexible ligands are not easy to predict since the flexible ligands can freely rotate and adopt a variety of conformations according to the restrictions imposed by the coordination geometry of the metal ions.

In view of the various ligands，dicarboxylic acids are found to be good candidates to build various MOFs with novel topologies and properties.Dicarboxylates are often employed as bridging ligands to afford coordina?tion polymers due to their diverse coordinative fashions，high stability and the ability to balance the positive charges of metal ions［5］.On the other hand，dipyridyl ligands can be used as ancillary ligands，together with

the dicarboxylate ligands，to meet and satisfy the requirements for coordination geometries of metal centers in the assembly processes［6］.By combining these O-donor and N-donor ligands with transition metal ions，for example，CdII，which possess d10configurations，the resulted coordination polymers can exhibit appealing struc?tures as well as photoluminescence properties.In this work，a flexible dicarboxylic acid 1，3-phenylendiacetic acid（1，3-H2PDA）was selected as a O-donor ligand to react with Cd（NO3）2and a conjugated dipyridyl li?gand 4-pyr-poly-2-ene（ppene）.Finally，a novel two dimensional coordination polymer｛［Cd（1，3-PDA）（ppene）］·H2O｝n（1）was obtained.In this paper，we report the preparation，crystal structure and photolumi?nescence properties of the title complex.

2 Experiment

2.1 Materials and physical measurements

The dipyridyl ligand 4-pyr-poly-2-ene（ppene）was synthesized as reported previously［7］.Other chemi?cals and solvents were purchased from Sigma-Aldrich Co.Infrared（IR）sample was prepared as a KBr pellet. The spectrum was measured by a Nicolet Avatar 360 FT-IR spectrophotometer in the range of 4 000-400 cm-1.The elemental analysis was characterized by an EA1110 elemental analyzer.The photoluminescence spectrum of compound 1 was measured on a JASCO FP-8600 spectrofluorometer.

2.2 X-Ray Data collection and structure determination

Single-crystal X-ray diffraction（SCXRD）data for compound 1 was collected on a Bruker SMART APEX II CCD diffractometer by using the Φ/ω scan technique.Absorption correction was handled with the SADABS program［8］.The structure of compound 1 was refined with the SHELXL-97 program，based on full-matrix least-squares methods［9］.The H atoms of the solvent water molecule in 1 was located from the Fourier map and included in the final refinement.All other H atoms were introduced at the calculated positions and includ?ed in the structure-factor calculations.

2.3 Preparation of｛［Cd（1，3-PDA）（ppene）］·H2O｝n（1）

To a 15 mL Pyrex glass tube was loaded Cd（NO3）2·4H2O（31 mg，0.1 mmol），ppene（21 mg，0.1 mmol），1，3-H2PDA（21 mg，0.1 mmol），and 4 mL of H2O.The glass tube was sealed and heated in an oven to 150℃for 3 d，and then cooled to ambient temperature at the rate of 5℃·h-1.Yellow block crystals were col?lected.Yield：40 mg（76%yield based on Cd）.Anal.calcd for C24H22CdN2O5：C 54.30：H 4.18：N 5.28.Found：C 53.98 H 4.26：N 5.15.IR（KBr，cm-1）：3 474 m，2 928 w，1 611 s，1 569 s，1 497 m，1 411 s，1 387 s，1 281 m，1 202 w，1 130 m，1 095 m，1 045 m，996 m，879 m，835 s，797 m，772 m，737 s，698 m，652 m，574 m，525 s，441 m.

3 Results and discussion

3.1 Crystal structure of｛［Cd（1，3-PDA）（ppene）］·H2O｝n（1）

Compound 1 belongs to the triclinic space group Pī.The asymmetric unit of this structure consists of one［Cd（1，3-PDA）（ppene）］unit and one solvent H2O molecule.Each Cd1 atom in 1 is seven-coordinated with a distorted pentagonal bipyramid environment.Five sites are occupied by the O atoms from three differ?ent 1，3-PDA ligands，while the remaining two sites are filled with the N atom from the ppene molecule（Fig.1a）.Cd1 and its symmetry-related Cd1A atoms are bridged by four 1，3-PDA ligands to generate a di?nuclear［Cd2（1，3-PDA）4］unit.Each［Cd2（1，3-PDA）4］unit is interlinked via the 1，3-PDA bridges to its equivalent ones to form a［Cd（1，3-PDA）］nchain extending along the a axis（Fig.1b）.Such a chain con?nects its adjacent ones through ppene bridges to form a 2D（4，4）layer of［Cd（1，3-PDA）（ppene）］nwith rectangular grids（0.952 5×1.633 5 nm2）extending in the ac plane（Fig.1c）.The solvent H2O molecules were firmly anchored by the main framework of 1 via O5-H1W…O3 hydrogen bonding interactions（O5…O3，0.280 3（7）nm：O5-H1W…O3，166.9°）.

Fig.1 a The coordination mode of Cd1 in compound 1；b View of the 1D［Cd（1，3-PDA）］nchain in 1；c View of the 2D［Cd（1，3-PDA）（ppene）］nnetwork of 1.The nitrogen，oxygen and zinc atoms are represented by blue，red and cyan balls，respectively.Symmetry codes：（A）-x，-y，-z+1：（B）x+1，y，z：（C）x-1，y+1，z-1

3.2 Photoluminescence Properties

In the solid state，the photoluminescence spectrum of compound 1 was examined at room temperature（Fig.2）.The ppene ligand displays photoluminescence with emission maxima at 549 nm（λex=430 nm），as?signed to π*→π transition of ppene［10］.As reported previously，the 1，3-H2PDA ligand did not show any emission in the free state［11］，so the 1，3-H2PDA ligand almost have no contribution to the fluorescent emis?sion of as-synthesized compound 1.The emission spectrum exhibit maximum emission peaks at 421 nm，un?der the exciation at 537 nm.According to the literature，the CdIIion is difficult to oxidize or reduce because of the d10configuration［10］.Consequently，the emission of 1 may be assigned to a mixture characteristics of π*→π intraligand fluorescence since similar emission was also observed for the ppene ligand［10］.

Fig2 Solid state emission and excitation spectrum of compound 1

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一個二維鎘配位聚合物的合成、結構及熒光性能研究

王淑軍，劉 東，馬 偉
（淮北師范大學 化學與材料科學學院，安徽 淮北 235000）

在水熱條件下，一個新的二維鎘配位聚合物｛［Cd（1，3-PDA）（ppene）］·H2O｝n（1）通過Cd（NO3）2?4H2O，1，3-phenylendiacetic acid以及4-pyr-poly-2-ene的反應而被合成.該化合物通過紅外光譜，元素分析以及X-射線單晶衍射進行了表征.X-射線單晶結構分析表明，該化合物屬于三斜晶系，Pī空間群，晶胞參數(shù)：a= 9.524 8（19），b=10.430（2），c=1.138 9（2）nm，α=88.65（3）°，β=86.79（3）°，γ=69.70（3）°，V=1.059 5（3）nm3，Z=2，R1=0.030 4，wR2=0.074 8.CCDC號為1038885.化合物1為一個二維（4，4）網(wǎng)格結構的網(wǎng)絡.我們對該化合物的熒光性質也作了研究.

配位聚合物；結構；表征；熒光性質

O 614

A

2095-0691（2015）04-0025-04

2015-05-06

國家自然科學基金項目（21201068）；安徽省自然科學基金項目（1208085QB26）

王淑軍（1987- ），男，安徽濉溪人，碩士生，主要從事功能配合物的研究；通訊作者：馬 偉（1977- ），男，安徽潁上人，副教授，主要從事分析化學和配位化學的研究.

O 614 Document Code：A Article ID：2095-0691（2015）04-0025-04

Received date:2015-05-06

Funded by:National natural science foundation project(21201068);Natural science foundation of Anhui province(1208085QB26)

Author:Wang Shujun(1987-),male,Anhui Suixi,postgraduate student,mainly engaged in the research of functional coordination compounds;Ma Wei(1977-),male,Anhui Yingshang,associate professor,mainly engaged in the research of analytical chemistry and coordination chemistry.