基于一种柔性和角型有机芳香多酸配体的两种3D配位聚合物的合成、结构和荧光性

李付安徐伏杨维春

基于一种柔性和角型有机芳香多酸配体的两种3D配位聚合物的合成、结构和荧光性

李付安＊徐伏杨维春

(平顶山学院化学与环境工程学院，平顶山467000)

通过水热合成的方法制得具有三维超分子结构的2种配位聚合物{[Zn(L)(bpa)0.5(H2O)2]·2.25H2O}n(1)和{[Cd(L)(H2O)]·2H2O}n(2)，其中，H3LCl为氯化5-(4-羟基吡啶基甲基)间苯二甲酸，bpa为1，2-二(4-吡啶基)乙烷。这2种化合物的结构通过单晶X射线衍射、红外光谱(IR)、元素分析、热重分析(TG)等方法进行了表征。结构解析表明：化合物1是一种梯型链式结构，并通过链间氢键作用延伸成了3D超分子网络；化合物2为含有大量一维隧道空腔的2D配位网络。此外，研究了这2种化合物的荧光性质。

氯化5-(4-羟基吡啶基甲基)间苯二甲酸；1，2-二(4-吡啶基)乙烷；锌；镉

In recent years,the complexes based on organic aromaticcarboxylateligandshavebecomean interesting research area due to their pluridentated and excellent coordinated ability[1-4]as well as their charming architectures and potential applications in adsorption,catalysis,and luminescence,and so on[5-6]. Among the reported compounds,the coordination polymers from flexible or angular organic aromatic multi-carboxylate ligands are especially interesting because they can adopt a variety of coordination modes resulting in diverse multidimensional architectures[7-10].Up to now,many aromatic carboxylate ligands with flexible or angular structures have been synthesized and reported.For example,Li et al.havereported a series of metal-organic frameworks based on flexible ligand 4-carboxy-1-(3,5-dicarboxy-benzyl) pyridinium chloride[11];Sun et al.have synthesized a flexible and angular ligands 5-(imidazol-1-ylmethyl) isophthalic acid,and report a series of coordination polymers with novel networks[12-13];Zang et al.have investigated a series of angular carboxylate ligands, 3,5-bis(imidazol-1-ylmethyl)benzoic acid hydrochloride[14],2,3,2′,3′-thiaphthalic acid[15],1-(pyridin-4-ylthio)benzene-2,4-dioic acid[16].Recently,we have also synthesized a versatile ligand,H3LCl(5-(4-hydroxypyridinium-1-ylmethyl)isophthalic acid chloride),and its corresponding coordination polymers have been reported[17].To continue our effort in this area,two coordination polymers,{[Zn(L)(bpa)0.5(H2O)2]·2.25H2O}n(1)and{[Cd(L)(H2O)]·2H2O}n(2),with novel networks from H2L ligand have been hydrothermally synthesized and structurally characterized by X-ray diffraction analyses and further characterized by infrared spectra (IR),elemental analyses and thermogravimetric(TG) analyses.

Scheme 1Coordination mode of the ligand H3LCl found in compounds 1(a)and in 2(b)

1 Experimental

1.1 Materials and physical measurement

H3LClwassynthesizedaccordingtotheliterature[17], and other starting materials were of reagent quality and obtained from commercial sources without further purification.Elemental analysis for C,H and N was performed on a Perkin-Elmer 240 elemental analyzer. The FT-IR spectra were recorded from KBr pellets in the range from 4 000 to 400 cm-1on a Nicolet NEXUS 470-FTIRspectrometer.Thermalanalysiswas performed on a SDT 2960 thermal analyzer from room temperature to 800℃with a heating rate of 10℃· min-1under nitrogen flow.Powder X-ray diffraction (PXRD)for compounds 1 and 2 were measured at 293 K on a Rigaku D/max-3B diffractometer equipped with Cu Kα(λ=0.154 06 nm)radiation(45 kV,200 mA). The crushed single crystalline powder samples were prepared by crushing the crystals and the 2θ scanning angle range was from 5°to 50°.Luminescence spectra for the solid samples were recorded on a Hitachi 850 fluorescence spectrophotometer.

1.2 Synthesis

1.2.1 Synthesis of{[Zn(L)(bpa)0.5(H2O)2]·2.25H2O}n(1)

Compound 1 was synthesized hydrothermally in a 25 mL Teflon-lined autoclave by heating a mixture of bpa(0.009 1 g,0.05 mmol),Zn(OAc)·2H2O(0.022 g, 0.1 mmol),H3LCl(0.015 4 g,0.05 mmol),and LiOH (0.004 2 g,0.1 mmol)at 160℃in 6 mL H2O for three days.Colorless block-wise crystals of 1 were obtained in 80%yield based on H2L.Anal.Calcd.for C20H23.5N2O9.25Zn(%):C 47.54,H 4.69,N 5.54;Found (%):C 47.51,H 4.73,N 5.50.IR(KBr,cm-1):3 388 (m,br),3 120(m),1 640(s),1 620(s),1 582(s),1 556 (s),1 361(s),1 239(w),1 226(w),1 193(m),1 029(w), 847(w),774(w),729(w).

1.2.2 Synthesis of{[Cd(L)(H2O)]·2H2O}n(2)

A mixture of Cd(OAc)2·2H2O(0.026 g,0.1 mmol), H2L(0.016 8 g,0.05 mmol),LiOH(0.004 2 g,0.1 mmol),and H2O(6 mL)was placed in a 25 mL Teflon -lined stainless steel vessel,and heated at 160℃for three days.After the mixture was slowly cooled to room temperature,colorless crystals of 2 were obtained in 76%yield based on H2L.Anal.Calcd.for C14H15NO8Cd (%):C 38.42,H 3.45,N 3.30;Found(%):C 38.39,H 3.51,N 3.20.IR(KBr,cm-1):3 410(s,br),3 045(m), 1647(s),1 619(s),1 563(m),1 524(s),1 447(w),1 340(s), 1 293(w),1 187(m),1 049(w),1 028(w),856(s),774(s), 726(w).

1.3 Crystallographic data collection and structure determination

Single-crystal X-ray diffraction data of compounds 1 and 2 were collected on a Bruker SMART APEX CCD diffractometer[18]equipped with graphite monochromatized Mo Kα radiation(λ=0.071 073 nm) at room temperature using the φ-ω scan technique. Empirical absorption corrections were applied to the intensities using the SADABS program[19].The struct-ures were solved with direct methods using the program SHELXS-97[20]and refined anisotropically with the program SHELXL-97[21]using full matrix leastsquares procedures.All non-hydrogen atoms were refined anisotropically.The hydrogen atoms of the coordinationwatermolecules,andligandswere included in the structure factor calculation at idealized positionsbyusingaridingmodelandrefined isotropically.The hydrogen atoms of the solvent water molecules were located from the difference Fourier maps,then restrained at fixed positions and refined isotropically.Analytical expressions of neutral atom scatteringfactorswereemployed,andanomalous dispersion corrections were incorporated.The crystallographic data for 1 and 2 are summarized in Table 1. Selected bond lengths and angles are given in Table 2.

CCDC:908522,1;908526,2.

Table1 Crystal data and structure refinement for compounds 1 and 2

Table2 Selected bond lengths(nm)and bond angles(°)for compounds 1 and 2

Symmetry codes:ix+1,y,z for 1;ix,1+y,z;ii2-x,1-y,1-z;iii3-x,1-y,-z for 2.

2 Results and discussion

2.1 Crystal structure of{[Zn(L)(bpa)0.5(H2O)2]· 2.25H2O}n(1)

The compound 1 crystallizes in the monoclinic system with space group P1.Its asymmetric unit consists of one Zncenter,half of a bpa ligand,one L2-anion,two coordinated water molecules,and three free water molecules with the total site occupancies of 2.25(Fig.1a).The Zncenter is five-coordinated by two carboxylic oxygen atoms(O1,O4i)from two different L2-ligands,two oxygen atoms(O1W,O2W)from two water molecules and one nitrogen atom(N2)from one bpa ligand.The coordination geometry of Zn1 atom is a distorted trigonal bipyramidal with two water oxygen atoms(O1W and O2W)at the axial position(Fig.1a). The Zn1-O bond lengths range from 0.195 2(2)to 0.229 1(2)nm,andthe Zn1-N bond distance is 0.205 5(2)nm.The L2-anion bridges two Znatoms with both two carboxylic groups in μ2-η1∶η1modes (Scheme 1a).In this way,L2-anions link neighboring Zn1 atoms to yield an infinite 1D(Zn-L)nchain.Such (Zn-L)nchains are further bridged by bpa molecules into an infinite 1D ladder-like chain(Fig.1b).Such chainsarefurtherunitedtogetherbynumerous hydrogen bonds involving the coordinated waters, lattice waters and carboxyl oxygen atoms to generate a 3D supramolecular architecture(Fig.1c).According to graph set analysisnomenclature[22],the hydrogen motifs within the water cluster can be assigned to be R42(8)and R66(16),respectively(Fig.1d,Table 3).

Fig.1 (a)Metal coordination and atom labeling in compound 1 with thermal ellipsoids at 50%probability level; (b)1D ladder-like chain;(c)View of 3D supramolecular framework of 1 via hydrogen bonds(the dashed lines represent the hydrogen bonds);(d)Hydrogen bonds in compound 1

2.2 Crystalstructureof{[Cd(L)(H2O)]·2H2O}n(2) Compound 2 crystallizes in the triclinic space group P1.The asymmetric unit contains one Cdcenter,one L2-anion,one coordinated water molecule, and two lattice water molecules.The Cd1 is sevencoordinated in a pentagonal bipyramidal geometry.As shown in Fig.2a,five carboxylate oxygen atoms(O1, O2,O3i,O4i,and O3iii)from three distinct L2-anions form the equatorial plane;O5ii(HO-L2)and O1W (H2O)occupy the axial positions.The bond length of Cd1-O is in the range of 0.227 4(3)～0.239 8(2)nm. Each L2-ligand bridges fourcrystallographically identical Cd1 ions with one of the carboxylate groups in a μ2-η1∶η1mode,while the other in a μ3-η1∶η2coordinationmodeandthehydroxylgroupin monodentate coordination mode(Scheme 1b).Thus, two cadmium ions are first linked by two L2-anions via the carboxylate groups and monodentate hydroxyl group to generate a[Cd2(L)2]metallamacrocycle with the Cd-Cd distance being 1.129 1 nm(Fig.2b).Each metallamacrocycle links two distinct metallamacrocycle together to form the tube(Fig.2c).The carboxylate groups in μ3-η1∶η2coordination mode further participate in the coordination with Cd1 ions of the tube.Thus, the tubes are connected together to give rise to a 2D layer with tubular channels(Fig.2d).Furthermore,the 2D layers are further extended into 3D supramolecular architecture via hydrogen-bonding interactions(Fig.2e, Table 3).

Fig.2 (a)Metal coordination and atom labeling in compound 2;(b)Dinuclear metallamacrocycle unit; (c)Side view of the tubular structure;(d)Tubular channels perpendicular to the ab plane of 2; (e)Three dimensional supramolecular structure of 2

Table3 Geometrical parameters of hydrogen bonds in compounds 1～2

2.3 Thermal analyses and PXRD analyses

Thermal gravimetric analysis(TGA)was used to characterize the thermal stability of compounds,and the TGA of compounds 1～2 were carried out in nitrogen atmosphere(Fig.3).For compound 1,the weight loss of 14.99%from 30 to 117℃is assigned to the loss of two coordinated and 2.25 lattice water molecules (Calcd.15.15%).There is no further weight loss from 117 to 362℃,After 362℃,the organic components start to decompose.In the TG curve of compound 2, the weight loss in the range of 30～209℃(Obsd. 11.53%,Calcd.12.35%)can be attributed to the removal of two lattice and one coordinated water molecules.The further weight losses represented the decomposition of the compound 2.

The synthesized products of 1～2 havebeen characterized by powder X-ray diffraction(PXRD).As shown in Fig.4,the experimental PXRD patterns correspond well with the results simulated from thesingle crystal data,indicating the high purity of the synthesized samples and single phases of compounds 1～2.

Fig.3 TG curves for compounds 1 and 2

Fig.4 Simulated and experimental PXRD patterns for compounds 1(a)and 2(b)

2.4 Photochemical properties

The solid-state photo-luminescent properties of the free H3LCl ligand,coordination polymers 1 and 2 have been investigated in the solid state at room temperature.The emission spectra of these compounds are shown in Fig.5.An intense band is observed at 412 nm(λex=317 nm)for H2L.Compared to the H3LCl ligand,compound 1 results in red shift of 13 nm(425 nm,λex=364 nm).The shift of the emission maximum between 1 and H3LCl is considered to mainly originate from the influence of the coordination of the ligand to metal atom[23-24].The compound 2 has same emission peak of 412 nm(λex=315 nm)with the free H2L,which indicates that it may originate from metal-perturbed intraligand charge transfers[25-27].

Fig.5 Solid-state emission spectra of free H2L and compounds 1 and 2 at room temperature

3 Conclusions

We have reported the syntheses,crystal structures and properties of two coordination polymers,{[Zn(L) (bpa)0.5(H2O)2]·2.25H2O}n(1)and{[Cd(L)(H2O)]·2H2O}n(2)with different structure derived from 5-(4-hydroxypyridinium-1-ylmethyl)isophthalicacidchloride ligand.Both compound 1 and 2 have a 3D supramoleculararchitectureextendedbyhydrogen-bonding interactions,but the 3D network of compound 1 is constructed by an infinite 1D ladder-like chain,and that of compound 2 is formed by a 2D layer structure with tubular channels.In addition,the coordination modes of carboxylate groups in two compounds are different:μ2-η1∶η1mode for compound 1,μ3-η1∶η2mode for 2.Compared to the compounds based on the present ligand and reported in the literature[17],they have not only different structure,but also different coordination modes,which indicate that H3LCl ligand is a favorable and fashionable building block for compounds with abundant structural features and useful properties. Subsequent studies will focuse on the structures and properties of the novel functional coordination polymers constructed by the present ligand with a wide range of rareearthmetals.Furtherinvestigationsonthis domain are underway.

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Syntheses,Structures and Photoluminescent Properties of Two 3D Coordination Polymers Based on a Flexible and Angular Organic Aromatic Multi-carboxylate Ligand

LI Fu-An＊XU FuYANG Wei-Chun
(College of Chemistry and Environmental Engineering,Pingdingshan University,Pingdingshan,Henan 467000,China)

Two coordination polymers with 3D supramolecular network,{[Zn(L)(bpa)0.5(H2O)2]·2.25H2O}n(1)and {[Cd(L)(H2O)]·2H2O}n(2)(H3LCl=5-(4-hydroxypyridinium-1-ylmethyl)isophthalic acid chloride,bpa=1,2-bis(4-pyridyl)ethane)were hydrothermally synthesized and structurally characterized by X-ray diffraction analyses and further characterized by infrared spectra(IR),elemental analyses,and thermogravimetric(TG)analyses. Compound 1 exhibits a ladder-like chain structure,and such chains are further united together to generate a 3D supramolecular structure through the hydrogen bonding interactions.Compound 2 possesses a 2D coordination network with a 1D channel that run parallel to the coordination layers.Meanwhile,their luminescent properties have also been investigated in detail.CCDC:908522,1;908526,2.

5-(4-hydroxypyridinium-1-ylmethyl)isophthalic acid chloride;1,2-bis(4-pyridyl)ethane;zinc;cadmium

O614.24+1；O614.24+2

A

1001-4861(2017)09-1631-08

10.11862/CJIC.2017.190

2017-03-14。收修改稿日期：2017-05-26。

河南省高等学校重点科研项目(No.15A150068)和平顶山学院应用化学重点实验室(No.201201)资助。＊

。E-mail：lifuanpds@163.com