Synthesis,Crystal Structure and Fluorescence Property of Cu（Ⅱ）Coordination Polymer with Pyridylimidazolidinone and Bipyridine

ZHANG Zhong LIU Ji-Zhong GAO Peng YIN Xian-Hong REN Tian-Tian WU Wei

(Guangxi Universities Key Laboratory of Green Chemistry and Technology,College of Chemistry and Ecological Engineering,Guangxi University for Nationalities,Nanning 530006,China)

Synthesis,Crystal Structure and Fluorescence Property of Cu（Ⅱ）Coordination Polymer with Pyridylimidazolidinone and Bipyridine

ZHANG Zhong LIU Ji-Zhong GAO Peng YIN Xian-Hong＊REN Tian-Tian WU Wei

(Guangxi Universities Key Laboratory of Green Chemistry and Technology,College of Chemistry and Ecological Engineering,Guangxi University for Nationalities,Nanning530006,China)

A metal-organic coordination polymer framework formulated as{[Cu2(Imazameth)2(bipy)](ClO4)·CH2OH· H2O}n(1)(where Imazameth=(+/-)2-(4,5-Dihydro-4-methyl-4-(1-methylethyl)-5-oxo-1H-imidazol-2-yl)-5-methyl-3-pyridinecarboxylic acid,bipy=4,4′-bipyridine)has been prepared and characterized by spectral method(IR), elemental analysis,fluorescence properties and single crystal X-ray diffraction techniques.It crystallizes in the Monoclinic system,space group P21/c and the asymmetric unit contains hydrogen-bonded water and alcohol molecules.The Cu atom is five-coordinated by three N atoms and two O atoms in distorted pyramid coordination geometry.In fact,it is a new two-dimensional copper complex with the peculiarity of having the 4,4′-bipyridine ligand and Imazameth ligand acting as bridge to form “corrugated”layered structure.Intramolecular N-H…O and intermolecular O-H…O hydrogen bonds result in the formation of a supermolecular crystal,in which they seem to be effective in the stabilization of the structure.The complex displays strong fluorescence property.CCDC:756106.

imazameth;crystal structure;coordination polymer;fluorescence property

The design and synthesis of polynuclear coordination complexes by the self-assembly of transitional metal and flexible bridging ligands have been receiving intense interests because of the effects of their remarkable conformational diversity on the magnetic, optical,and biological properties[1-5]and their potentialapplications in catalysis,optical properties evolution, clathration,etc.[6-10].Synthesis of one-,two-or threedimensional polymeric network by suitable metal and ligand coordination is the main area of current research because both the network structure as well as properties of these coordination networks can be finely tuned via a systematic change of organic ligands[11].In the specific case of coordination polymers,research activity has been motivated by the ability ofmetal-ligand coordination to provide a facile approach to the controlled assembly of extended networks[12].

Much effort has been devoted to the synthesis[13-14], crystal structure[15-16]and catalysis[17-18]of the compounds containing imidazolidinone during the last few years.One of them is (+/-)-2-(4,5-Dihydro-4-methyl-4-(1-methylethyl)-5-oxo-1H-Imidazol-2-yl)-5-methyl-3-pyridinecarboxylic acid (Imazameth),which provides with efficient metal-chelating ability (Scheme 1).The Imazameth contains a pyridine carboxylic acid and an imidazole ring,which are well-known versatile ligands.The pyridine carboxylic acid and its anion have been extensively used in the design ofcoordination compounds,due to a variety of its bonding ability and exhibiting strong hydrogen bonds[19-22].Imidazole ring, which is one of the polydentate amine ligands,generally coordinates to metal ions using the N atoms as donors.To the best of our knowledge,researches have been done into the transition-metal complexes,which are synthesized by the ligands with the similar structure to Imazameth and their respective properties such as asymmetric catalysis,second harmonic generation, piezoelectric and ferroelectric in the past few years[23].As far as we know,the coordination chemistry of Imazameth to metal ions remains largely unexplored though it is a chiral compound,which can be used as a powerful building block to construct metal-organic frameworks(MOF).

Scheme 1 Structure of Imazameth

The reaction ofImazameth,4,4′-bipyridine with Cu(ClO4)2was carried out under hydrothermal conditions to obtain 1.In this work,we report its synthesis,crystal structure,spectral analysis(IR), elemental analysis and fluorescence properties.The title complex is the first planar network polymer derived from Imazameth and 4,4′-bipyridine with the spectral studies.

1 Experimental

1.1 Materials and instrumentation

The ligand,Imazameth,was synthesized from 2-amino-2,3-dimethylbutyronitrile,5-methylpyridine-2,3-dicarboxylic acid and other chemicals and solvents[24-27].All other chemicals were reagent grade and used without further purification.Elemental analysis for C, H,and N was carried out on a Perkin-Elmer 2400Ⅱelemental analyzer.The FTIR spectrum was obtained on a PE Spectrum One FTIR Spectrometer Fourier transform infrared spectroscopy in the 4 000～400 cm-1regions,using KBr pellets.Fluorescence spectra were recorded on Perkin Elmer instruments LS55 Luminescence Spectrometer.

1.2 Synthesis of the complex 1

A solution of Imazameth (0.41 g,1.5 mmol)in 10mL ethanol was added dropwise with stirring at room temperature to a solution of Cu(ClO4)2(0.39 g,1.5 mmol)in 5 mL water.The mixture was stirred at room temperature until it was homogeneous,and then added to a solution of 4,4′-bipyridine(0.16 g,1 mmol)in 5 mL ethanol.Then,the mixture was sealed in a 25mL Teflon-lined stainless reactor,kept under autogenous pressure at 110℃for 24 h,and then slowly cooled to room temperature at a rate of 5℃·h-1.After 15 d,blue block crystals suitable for X-ray diffraction were separated and washed with water,which were stable in air and insoluble in water and common organic solvents. (Yield:79%based on Cu).Calcd.For C21H30N4O10ClCu(%):C 42.21,H 5.06,N 9.38;Found (%):C 42.19,H.04,and N 9.39.

1.3 X-raydatacollectionandstructurerefinement

Crystallographic data were collected on a Bruker SMART APEX CCD diffractometerwithgraphite monochromated Mo Kα radiation(λ=0.071 073 nm)at T=296(2)K.Absorption corrections were applied by using the SADABS program[28].The structure was solved by direct methods and successive Fourier difference syntheses (SHELXS-97),and anisotropicthermal parameters for all nonhydrogen atoms were refined by full-matrix least-squares procedure against F2(SHELXL -97)[29-30].Hydrogen atoms were located by geometric calculations.H atoms for H2O molecules were located in different synthesis and refined isotropically(O-H 0.084 98～0.085 01 nm,Uiso(H)=1.2Ueq(carrier atoms of H2O)).TheremainingH atomswere positioned geometrically,with N-H 0.086 nm(for NH),O-H 0.082 nm(for OH),C-H 0.098 nm(for CH),C-H 0.097 nm(for CH2),C-H 0.096 nm (for CH3)and C-H 0.093 nm for aromatic H atoms,respectively.In addition,they were constrained to ride on their parent atoms with Uiso(H)= 1.2Ueq(carrier atoms of CH,CH2,OH,NH)and Uiso(H)= 1.5Ueq(carrier atoms of CH3).

CCDC:756106.

2 Results and discussion

2.1 FTIR spectrum

The mostsignificantfrequenciesin the IR spectrum of complex 1 are given in Table 1.The strong and broad absorption bands at about 3 660～3 450 and 1 615 cm-1are attributed to the symmetric O-H stretching modes and O-H bending modes of crystal water molecules in the crystal,respectively.Single crystal X-ray data support the presence of water in the complex.The shift to lower frequencies of these stretching modes and the shift to higher frequencies of the accompanying O-H bending modes may be attributed to hydrogen bonding.Other peculiar feature is observed,which exhibits a band at 1 369 cm-1.An intense absorption of similar wavenumber was observed previously for a Co（Ⅲ）complex of Imazapyr coordinating through the deprotonated lactam group[15].Compared with complex [Mn(Imz)2][15],the title complex exhibit the similar wavenumber values for the carboxylate stretches.The COO groups of the title complex are νas(O-C-O)1 610 cm-1, νs(O-C-O)1481 cm-1,Δν=129 cm-1and the [Mn(Imz)2]are 1559 cm-1,1416 cm-1,Δν=143 cm-1, respectively.While in complex[Co(Imz)3]·3H2O,the COO groups are νas(O-C-O)1628 cm-1,νs(O-C-O)1401 cm-1,Δν=227 cm-1.The difference results form the O atoms of COO groups are engaged in the metal coordination in the Mn（Ⅱ）and Cu（Ⅱ）complex,except for the O…H-N hydrogen bonding,while there is only O…H-N hydrogen bonding in the Co（Ⅲ） complex.As regards the ν(C=N)modes,these are distinguished at 1695 cm-1in Imazameth and at 1615 cm-1in the Cu（Ⅱ）complex,which is consistent with the [Mn(Imz)2] complex,1 627 cm-1.In comparison,the[Co(Imz)3]· 3H2O derivative exhibits a high wavenumber value (1 661 cm-1)consistent with the decreased length of the C=N bond(0.129 nm).

Table 1 IR spectral data of complex 1 (cm-1)

2.2 Fluorescence properties

Fig.1 Fluorescence emission spectra of complex and free ligand

The fluorescence spectra of complex 1 and free ligand Imazameth in the solid state atroom temperature are presented in Fig.1.The free ligand Imazameth shows intense emission bands at 377 and 420 nm when exited with light of 230 nm,which might be assigned to intraligand π-π*and n-π* charge transfer.On the contrary the copper complex shows very strong emission and red-shifted to 424 and 488 nm respectively,which is ca.47 and ca.68 nm red-shifted compared to the free ligand,could be assigned to the emission of ligand to metal charge transfer according o the previous literatures[27-28].It is evident from some cases that complex formation sometimes increases the fluorescence inten-sity due to the reduction of symmetry of the ligand or charge transfer emission (MLCT or LMCT emission).In the presentcase sharp increase offluorescence on complex formation may be due to charge transfer.

Fig.2 Coordination environments of Cu atoms with 50%thermal ellipsoids of the complex

2.2 Description of crystal structure

A perspective view of the molecular structure of the complex 1 along with the atom-numbering scheme is depicted in Fig.2.The crystallographic data are listed in Table 2,and selected bond lengths and angles and hydrogen-bond geometry are given in Table 3 and 4, respectively.

The X-ray crystal structure determination of complex 1 reveals thatthe localcoordination environment around the Cu ion can be best described as a slightly distorted pyramid (5-coordinated)with three N atoms(two N atoms from pyridyl rings and the oxo-imidazole rings of Imazethapyr ions,respectively, and one N atom from 4,4′-bipyridine)and two O atoms (one O atom from a carboxylate group,and the otherfrom H2O)to complete such a 5-coordinate mode.Thus, each Imazethapyr ion links two Cu ions through one of the two O atoms of the carboxylate moiety and two N atoms of pyridyl and oxo-imdazole rings to complex each Cu ion with a stable planar five-membered chelating ring (1Cu2N2C,as shown in Fig.2).A comparison of the bond lengths in the chelated ring reveals that the pyridine N(2)-Cu bond is significantly longer than the imidazole N(3)-Cu bond.Most probably, this is a consequence of the different basicity of the N(2)and N(3)donors.As usual in such systems,the NCu-N angle of the chelated ring(80.15°)is significantly contracted relative to that for the regular pyramid geometry.The rings A(Cu1/N2/N3/C6/C8),B(N3/C8/ N4/C10/C9),and C(C2/C3/C4/C5/C6/N2)are,of course, planar and the dihedral angles between them are A/B 5.71(5)°,A/C 5.06(9)°,and B/C 4.70(9)°,thus they are also nearly co-planar.In fact,complex 1 is a new onedimensional copper complex with the peculiarity of having the Imazethapyr ligand very unusually acting as bridges,which form polymeric chainsalong the crystallographic c axis(Fig.3a).Furthermore,each 4,4′-bipyridine ligand links two different Cu atoms from contiguous chains,which forms a two-dimensional condensed framework as depicted in Fig.3b.The dihedral angles between ring B and 4,4′-bipyridine is 54.62°,which results from stereochemical effect.In addition,the intramolecular N-H…O and intermolecular O-H…O hydrogen bonds seem to be effective in the stabilization of the structure,resulting in the formation of a supramolecular structure.

Table 2 Crystallographic data for complex 1

Table 3 Selected bond lengths(nm)and angles(°)

Table 4 Hydrogen-bond geometry

Fig.2 Coordination environments of Cu atoms with 50%thermal ellipsoids of the complex

Fig.3 (a)1D;(b)2D view of the complex with H atoms are omitted for clarity

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以吡啶基咪唑酮及聯(lián)吡啶為配體的銅配位聚合物的合成、晶體結(jié)構(gòu)及熒光性質(zhì)

張 眾 劉積中 高 鵬 尹顯洪＊任田田 武 偉

(廣西高校綠色化學(xué)與技術(shù)重點(diǎn)實(shí)驗(yàn)室，化學(xué)與生態(tài)工程學(xué)院，廣西民族大學(xué)，南寧 530006)

合成了1個(gè)銅配位聚合物{[Cu2(Imazameth)2(bipy)](ClO4)·CH2OH·H2O}n(1，Imazameth=(+/-2-(4-異丙基-4-甲基-5-氧-2-咪唑啉-2-基)-5-甲基煙酸，又稱(chēng)甲基咪草煙；bipy=4，4′-聯(lián)吡啶)。并對(duì)其進(jìn)行了元素分析，IR，熒光性質(zhì)和X射線-單晶衍射表征。晶體結(jié)構(gòu)表明：配合物1屬于單斜晶系，P21/c空間群并且其不對(duì)稱(chēng)單元中包含水和乙醇分子。配合物1是由橋聯(lián)配體4，4′-聯(lián)吡啶和甲基咪草煙連接成“瓦楞”形層狀結(jié)構(gòu)，并通過(guò)分子內(nèi)N-H…O氫鍵和分子間O-H…O氫鍵拓展成三維超分子結(jié)構(gòu)。配合物1有較強(qiáng)的熒光性質(zhì)。

甲基咪草煙；晶體結(jié)構(gòu)；配位聚合物；熒光性質(zhì)

O614.121

A

1001-4861(2012)01-0195-06

2011-05-09。收修改稿日期：2011-09-20。

國(guó)家自然科學(xué)基金(No.20761002)，廣西民族大學(xué)2011年研究生教育創(chuàng)新計(jì)劃(No.gxun-chx2011084)資助項(xiàng)目。＊

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