4,5-二氰基咪唑構(gòu)筑的鋅（Ⅱ）、鈷（Ⅱ）配合物的合成、晶體結(jié)構(gòu)及熒光性質(zhì)

胡拖平 劉建鋒 呂旭燕 肖立群 宋江鋒

(中北大學(xué)理學(xué)院，化學(xué)實驗室，太原 030051)

4,5-二氰基咪唑構(gòu)筑的鋅（Ⅱ）、鈷（Ⅱ）配合物的合成、晶體結(jié)構(gòu)及熒光性質(zhì)

胡拖平＊劉建鋒 呂旭燕 肖立群 宋江鋒

(中北大學(xué)理學(xué)院，化學(xué)實驗室，太原 030051)

以4,5-二氰基咪唑(HIMDN)配體，用常溫擴散法合成了2個新穎的金屬-有機配合物{[Zn2(IMDN)4(H2O)3]·(H2O)3}n(1)和[Co(IMDN)2(H2O)2]n(2)，并通過元素分析、紅外分析、熱重分析和X-射線單晶衍射對其進行了表征。結(jié)果表明配合物1中2個中心Zn（Ⅱ）離子的配位環(huán)境不同，一個是四配位，另一個是六配位。配合物2的中心鈷（Ⅱ）離子為六配位。2個配合物都為一維鏈狀結(jié)構(gòu)，并且均通過氫鍵作用顯示出三維結(jié)構(gòu)。此外還研究了配合物1的熒光性質(zhì)。

4,5-二氰基咪唑；一維鏈；晶體結(jié)構(gòu)；熒光

1 Experimental

1.1 Materials and methods

All reagents were commercially available and used without further purification．The structures of the complexes were determined on a Bruker Apex II CCD diffractometer and solved by direct methods using the SHELXTLprogram．Elemental analyseswereperformed by a Vario EL analyzer．The IR spectra (KBr pellets)was recorded on a FTIR-8400S spectrometer in the range of 4 000 ～400 cm-1．The thermogravimetric analyses were carried out on a ZCT-A analyzer at the heating rate of 10 ℃·min-1under air atmosphere．Luminescence spectra of solid sample were recorded with a F-2500 FL fluorescence spectrophotometer．

1.2 Synthesis of complex 1

A H2O solution (2 mL)of ZnCl2·3H2O (30 mg,0．015 mmol)was placed at the bottom of a straight glass tube,upon which a solution of HIMDN (15 mg,0．013 mmol)in water(3 mL)with pH=6～7 adjust by 0．5 mol·L-1LiOH was carefully layed．Colorless crystals of 1 suitable for X-ray analysiswere obtained at the junction of the layer after a few days(Yield:65%)．Anal．Calcd．for C20H16N16O6Zn2(%):C,33．898;H,2．400;N,31．628．Found(%):C,33．70;H,4．52;N,31．45．IR(KBr pellet,cm-1):3 515(s),3 120(s),2 355(w),2 240(s),1 630(m),1 455(s),1 300(s),1 220(w),1110(s),650(s)．

1.3 Synthesis of complex 2

A H2O solution(2 mL)of Co(NO3)2·6H2O(30 mg,0．010 mmol)wasplaced at the bottomof a straight glass tube,upon which a solution of HIMDN (15 mg,0．013 mmol)in water(3 mL)with pH=6～7 adjust by 0．5 mol·L-1NaOH wascarefully layed．Red crystalsof 2 suitable for X-ray analysis were obtained at the junction of the layer after a few days (Yield:55%)．Calcd for C10H6CoN8O2(%):C,36．235;H,2．416;N,33．819．Found(%):C,35．46;H,2．58;N,34．22．IR(KBr pellet,cm-1):3 435(m),2 970(w),2 355(w),2 240(s),1 615(w),1450(s),1315(s),1112(s),975(w),870(m),655(s)．

1.4 Structure determination

Crystallographic data for complex 1 (size:0．2 mm×0．15 mm×0．1 mm)and 2(0．15 mm×0．12 mm×0．1 mm)were collected on a Bruker Smart APEXII CCD diffractometer equipped with a graphite-monothematic Mo Kα radiation (λ =0．0710 73 nm)at room temperature．Semi-empirical absorption correction was applied (SADABS)and the program SAINT was used to reduce the data[19]．The structures were solved by direct methods with SHELXS-97 program[20]and refined by the full-matrix least-squares techniques on F2using SHELXL-97[21]．All non-hydrogen atoms were refined anisotropically．The hydrogen atoms were set in calculated positions and refined by a riding mode．A summary of the crystallographic data and structure refinement of complex 1 and 2 are listed in Table 1．The selected bond lengths and bond angels are listed in Table 2．

CCDC:889348,1;889349,2．

Table 1 Crystal data and structure refinement for complex 1 and 2

Continued Table 1

Table 2 Selected bond lengths(nm)and bond angles(°)for complex 1 and 2

2 Results and discussion

2.1 Crystal structures of the complex 1 and 2

2．1．1 {[Zn2(IMDN)4(H2O)3]·(H2O)3}n(1)

Complex 1 crystallizes in monoclinic system,P21/c space group．The scheme of the asymmetric unit of complex 1 isin Fig．1．The asymmetric unit of 1 consists of two Zn（Ⅱ）ions,four IMDN-anions and three coordinated and three uncoordinated water molecules．One nitrogen atom in every imidazole ring is deprotonated．The coordination environment of two zinc ionsisdifferent．The Zn(1)ion is four-coordinated with four nitrogen atoms(N1,N5,N9,N13)from four IMDN-anions to form a tetrahedron configuration．The minimumbond angle(N1-Zn1-N5)is 104．32(17)and the biggest bond angle(N1-Zn1-N13)is 114．58(16)°．The Zn(2)ion is six-coordinated with three oxygen atoms(O1,O2,O3)from three coordinated water molecules and three nitrogen atoms(N15,N11#1,#1:-x,1/2+y,1/2-z;N3#2,#2:-x,-1/2+y,1/2-z)fromthree IMDN-,respectively．The Zn-N bonds length are in the range 0．198 9～0．202 3 nm．The average length of Zn-O bonds are 0．211 8 nm,all of which are accordant with the normal reported Zn-N and Zn-Obonds lengths[22-23]．The Zn(1)and Zn(2)ions are connected through IMDN-anions to expand a one dimensional(1D)double chains(Fig．2)．The distance of Zn(1)-Zn(2)are 0．605 9 and 0．613 4 nm,respectively．

There are abundant H-bonding interactions in the complex 1．The intramolecular H-bonding interactions between uncoordinated water molecules and coordinated water molecules(O(2)-H(2B)…O(5),O(3)-H(3B)…O(4),O(5)-H(5A)…O(2),O(6)-H(6A)…O(1))firmly fix the three uncoordinated water molecules on 1D chain.In addition,the adjacent 1D chains further extend to be 3D structure by H-bonding interactions(O(3)-H(3A)…N(7)#9,#9:-x,2-y,1-z;O(6)-H(6B)…N(14)#10,#10:-x,2-y,-z)(Fig.3).The data of all H-bonding interactions for 1 are listed in Table 3.

Fig．1 Asymmetric unit of complex 1

Fig．2 1D double chain of complex 1

Fig.3 H-bonding interactions of complex 1

Table 3 Hydrogen bond lengths and bond angles for complex 1 and 2

2.1.2 [Co(IMDN)2(H2O)2]n(2)

Complex 2 crystallizes in monoclinic system,C2/c space group.The scheme of the asymmetric unit of complex 2 isshown in Fig.4.Unlike 1,there are no free water molecules in 2.The asymmetric unit of 2 consists of 1/2 Co（Ⅱ）ion,one IMDN-anion and two 1/2 coordinated water molecules.One nitrogen atom in every imidazole ring is deprotonated.The central Co（Ⅱ）ion is six-coordinated by four nitrogen atoms from four IMDN-anions and two oxygen atoms from two coordinated water molecules to form a octahedron configuration.Its equatorial plane is occupied by four coordinated nitrogen atoms from two imidazole rings and two cyano groups.While two oxygen atoms occupy the axial position(the O2-Co1-O1 bond angle is180°).The average lengths of Co-O and Co-N bonds are 0.207 43(19)nmand 0.213 66(14)nm,respectively.All of which are accordant with the normal reported Co-N and Co-O bonds lengths[24].The adjacent Co（Ⅱ）centers are connected by the IMDN-anions to afford a 1D chain motif(Co…Co=0．623 8 nm)(Fig．5)．

Fig.4 Asymmetric unit of complex 2

There are also H-bonding interactions in the complex 2 (Fig．6)． The H-bonding interactions between coordinated water molecules and IMDN-anions(O(1)-H(1A)…N(4)#11,#11:1/2-x,1/2-y,1-z;O(2)-H(2)…N(2)#12,#12:1/2-x,1/2+y,1/2-z)expand complexe 2 to a 3D wave-like layer supramolecular architecture．The data of all H-bonding interactions for 2 are listed in table 3．

Fig．5 View of the 1D chain of the complex 2

Fig．6 H-bonding interactions of complex 2

2.2 IR spectra of the complex 1 and 2

In the IR spectrum of complex 1,the broad peak centered at 3 515 cm-1indicates the O-H characteristic stretching vibrations of uncoordinated water molecular．The sharp characteristic peak at 2 240 cm-1isattributed to the characteristic stretching vibrations of cyano group．The very characteristic bandsν(-NH-), ν(C=N)of HIMDNligand moved from3 100 and 1 650 cm-1to 3 120 and 1 630 cm-1indicate the nitrogen atoms of imidazoleringcoordinated with Zn（Ⅱ） ion．

In the IR spectrum of complex 2,the sharp characteristic peak at 2 240 cm-1is also attributed to the characteristic stretching vibrations of cyano group．The very characteristic bands ν(-NH-),ν(C=N)of HIMDN ligand moved to 3 435 and 1 615 cm-1indicate the nitrogen atoms of imidazole ring coordinated with Co（Ⅱ） ion．

2.3 Thermogravimetric analysis

Thermogravimetric analysis has been measured for complex 1 and 2．The thermostability of complex 1 is weak,it begins to loss weight from 45℃．The weight loss of 14．8%from 45 to 225 ℃ corresponds to the loss of uncoordinated and coordinated water molecules(Calcd．15．3%)．The weight loss of 64．1%from 225 to 646℃dues to the removal of coordinated IMDN-anions (Calcd．66．4%)．No weight loss is observed after 646℃,and the resulting residue is zinc oxide(ZnO)(Obsd．21．1%,Calcd．20．6%)．

The complex 2 is stable up to 130℃,the weight loss of 8．10%from 130 to 280 ℃ corresponds to the loss of coordinated water molecules (Calcd．10．8%)．The weight loss of 72．8%from 280 to 565 ℃ dues to the removal of coordinated IMDN-anions(Calcd．70．7%)．No weight loss is observed after 565 ℃,and the resulting residue is cobalt oxide (Obsd．20．1%,Calcd．22．6%)．

2.4 Fluorescence properties

The emission spectra of complex 1 and free HIMDN in the solid state were investigated at room temperature． Complex 1 exhibits blue photoluminescence with two emission peaks at 450 nm and 472 nm upon excitation at 237 nm (Fig．7)．However,no obvious emission bands are observed for the free HIMDN in the range of 400～800 nm under the same experimental conditions．Thus, The fluorescence emission of 1 could be assigned to the emission of ligand-to metal charge transfer(LMCT)[25].For possesses strong fluorescent intensity,it appears to be good candidates for novel hybrid inorganicorganic photoactive materials.

Fig.7 Solid-state emission spectrum of 1 at room temperature

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Syntheses,Crystal Structures and Fluorescent Properties of Two Complexes(Zn（Ⅱ） and Co（Ⅱ）)Based on 2H-Imidazole-4,5-dicarbonitrile

HU Tuo-Ping＊LIU Jian-Feng Lü Xu-Yan XIAO Li-Qun SONG Jiang-Feng
(Department of Chemistry,College of Science,North University of China,Taiyuan 030051,China)

Two novel metal-organic complexes {[Zn2(IMDN)4(H2O)3]·(H2O)3}n(1)and [Co(IMDN)2(H2O)2]n(2)(HIMDN=2H-imidazole-4,5-dicarbonitrile)based on HIMDN have been synthesized by the method of normal temperature diffusion,and characterized by elemental analysis,FTIR,thermal gravimetric analysis and X-ray diffraction single-crystal structural analysis.The coordination environment of two Zn（Ⅱ）ions is different in 1.One Zn（Ⅱ）ion is four-coordinated and the other is six-coordinated.The central Co（Ⅱ）ion is six-coordinated in 2.Both complexes show one dimensional (1D)chain structure and connected by hydrogen bonds to form threedimensional structure.Moreover,the fluorescent property of complex 1 had been investigated in the solid state.CCDC:889348,1;889349,2.

2H-imidazole-4,5-dicarbonitrile;1D chain;crystal structure;fluorescence

A lot of attention has been

in supramolecular chemistry and crystal engineering of metal-organic frameworks (MOFs)due to their potential power in the design and synthesis of functional materials with interesting structures,applications and desired topologies[1-5].Of the many MOFs investigated,the nitrogen-containing ligands constitute an important family and give rise to fascinating crystal structures[6-10].As is known,2H-imidazole-4,5-dicarbonitrile (HIMDN)is a potential versatile nitrogen-containing ligand in the construction of MOFs due to (i)four coordination sites N atoms with different orientations;(ii)versatile deprotonated forms; (iii)vulnerable CN group which can form a carboxylate or tetrazole group through in situ ligand reaction[11-12]. So the complexes constructed by imidazole and its derivatives with transition metal ions have gained considerable attention for a long time,and some of them can be used potentially to optics,magnetic, catalysis materials[13-17]．Nevertheless,because the cyano groups strongly withdraw the charge on the easily formed IMDN anion bridge and diminish the electron count on theπpathway between the metal centres,the complexes including IMDN are scarce[18]．So,we choose nitrogen-containing ligands HIMDN as ligand and transition metal Zn（Ⅱ） and Co（Ⅱ）ions to construct MOFs materials by the method of normal temperature diffusion．

O614.24+1;O614.81+2

A

1001-4861(2013)091928-07

10.3969/j.issn.1001-4861.2013.00.270

2013-10-09。收修改稿日期：2013-05-01。

國家國際科技合作(No.2011DFA51980)和省自然科學(xué)基金(No.2011081022)資助項目。