喹啉-8-甲醛乙酰腙鋅/鎘配合物的晶體結(jié)構(gòu)及熒光性質(zhì)

許志紅 吳偉娜 劉樹陽 寇 凱 王 元

（1許昌學(xué)院化學(xué)化工學(xué)院，化學(xué)生物傳感與檢測重點(diǎn)實(shí)驗室，許昌 461000）

（2河南理工大學(xué)化學(xué)化工學(xué)院，河南省煤炭綠色轉(zhuǎn)化重點(diǎn)實(shí)驗室，焦作 454000）

Schiff bases are an important class of ligands in coordination chemistry and have been found extensive application in different fields[1-2].As one of the most promising systems，the relevant semicarbazones and thiosemicarbazonesinvolve condensed heterocycle，especially quinoline，have been paid much attention due to their potentially biological activities[3-6].However，acylhydrazones，as their structurally analogous，have been paid much less attention[7-8].Recently，several quinoline based acylhydrazone chemosensors for the fluorescent detection of metal ions have been reported in the literature，most of which function by coordination reaction with ions[9-11].Nevertheless，the crystal structures of corresponding complexes are relatively scarce[11].

Our previous work also shows that the acylhydrazone ligand HL （Scheme 1），namely N-（quinolin-8-yl）methylene）acetohydrazide is an excellent fluorescent probe for the detection for Znギ ions[11].Therefore，in this paper，three Znギ and Cdギ complexes with HL have been synthesized and structural determined by single-crystalX-ray diffraction.In addition，the fluorescence properties of the complexes in CH3CN solution were investigated.

Scheme 1 Synthesis route of HL

1 Experimental

1.1 Materials and measurements

Solvents and starting materials for synthesis were purchased commercially and used as received.Elemental analysis was carried out on an Elemental Vario EL analyzer.The IR spectra （ν=4 000～400 cm-1）were determined by the KBr pressed disc method on a Bruker V70 FT-IR spectrophotometer.The UV spectra were recorded on a PurkinjeGeneralTU-1800 spectrophotometer.Fluorescence spectra were determined on a Varian CARY Eclipse spectrophotometer，in the measurementsofemission and excitation spectra the pass width is 5 nm.

1.2 Preparations of complexes 1～3

As shown in Scheme 1，the ligand HL was produced by condensation of 8-formylquinoline and acethydrazide in ethanol at room temperature according to the literature method[11].The complexes 1～3 were generated by reaction of the ligand HL （5 mmol）with equimolar of ZnSO4，CdCl2and CdI2in methanol solution （10 mL）at room temperature for 1 h，respectively.Crystals suitable for X-ray diffraction analysis were obtained by evaporating the corresponding reaction solutions at room temperature.

1：Colorless plates.Anal.Calcd.for C12H15N3O7SZn（%）：C：35.09;H：3.68;N：10.23.Found（%）：C：34.75;H：3.85;N：9.94.FT-IR （cm-1）：ν（C=O）1 655，ν（C=N）1 592，ν（C=N）pyrazine1 560.

2：Colorless blocks.Anal.Calcd.For C12H11N3O Cl2Cd（%）：C：36.35;H：2.80;N：10.60.Found （%）：C：36.42;H：3.05;N：10.37.FT-IR （cm-1）：ν（C=O）1 654，ν（C=N）1 590，ν（C=N）pyrazine1 558.

3：Colorless blocks.Anal.Calcd.For C12H11N3OI2Cd（%）：C：24.87;H：1.91;N：7.25.Found（%）：C：25.00;H：2.18;N：7.02.FT-IR （cm-1）：ν（C=O）1 646，ν（C=N）1 586，ν（C=N）pyrazine1 555.

1.3 X-ray crystallography

The X-ray diffraction measurement for complexes 1～3 were performed on a Bruker SMART APEX ⅡCCD diffractometer equipped with a graphite monochromatized Mo Kα radiation （λ=0.071 073 nm）by using φ-ω scan mode at 296（2）K.Semi-empirical absorption correction was applied to the intensity data using the SADABS program[12].The structures were solved by direct methods and refined by full matrix least-square on F2using the SHELX-97 program[13].All non-hydrogen atoms were refined anisotropically.All the H atoms were positioned geometrically and refined using a riding model.Details of the crystal parameters，data collection and refinements for complexes 1～3 are summarized in Table 1.

CCDC：1562151，1;1562152，2;1562153，3.

Table 1 Crystal data and structure refinement for complexes 1～3

2 Results and discussion

2.1 Crystal structures description

The diamond drawings of complexes 1～3 are shown in Fig.1.Selected bond distances and angles are listed in Table 2.As shown in Fig.1a，1 contains one discrete cationic Znギcomplex and one crystal water molecule in the asymmetric unit.The center Znギionwith a distorted octahedron geometry is coordinated by one neutral hydrazone with ONN donor set，one coordinated water molecule and two O atoms from two independent μ2-bridged sulfate anions，thus forming one dimension chain-like framework along b axis.In addition，in the solid state，the chains were further linked into a 2D supramolecular network by intermolecular N-H…O and O-H…O hydrogen bonds（Fig.1d and Table 3）.

Table 2 Selected bond lengths(nm)and angles(°)in complexes 1～3

Continued Table 2

Fig.1 Diamond drawing of 1～3 （a～c）with 30%thermal ellipsoids;Extended 2D supramolecular structure in complex 1 （d）;Chain-like structures in complex 2 （e，along c axis）and 3 （f）formed by hydrogen bonds （shown in dashed line），respectively

Table 3 Hydrogen bonds information for complexes 1～3

Similarly，the hydrazone HL acts as a neutral tridentate ligand in complexes 2 and 3 （Fig.1b and 1c）.Coordinated by two additional halide anions（chloride for 2，while iodide for 3），the Cdギ ion adopts a distorted square pyramid coordination geometry （τ=0.348 and 0.345 for complex 2 and 3，respectively）[7].In the crystal，intermolecular N-H…Cl or N-H…I hydrogen bonds link the complex molecules of 2 or 3 into one dimension chains （Fig.1e and 1f）.

2.2 IR spectra

The FT-IR spectral region for both complexes is more or less similar due to the similar coordination modes of the ligands.The ν（C=O），ν（C=N）imineand ν（C=N）quinolinebands are at 1 673，1 615 and 1 584 cm-1，respectively.They shift to lower frequency values in the complexes，indicating that the carbonyl O，imine N and quinoline N atoms take part in the coordination[7-8，14-15].It is in accordance with the crystal structure study.

2.3 UV spectra

The UV spectra of the ligand HL，complexes 1～3 in CH3CN solution （c=1×10-5mol·L-1）were measured at room temperature （Fig.2）.The spectra of HL features two main band located around 230 nm （ε=35 288 L·mol-1·cm-1）and 320 nm （ε=16 955 L·mol-1·cm-1），which could be assigned to characteristic π-π*transition of quinoline and imine units，respe-ctively[8].Both bands have no shift while with absorption intensity change in the spectra of complexes 1～3 （ε1=34 327，16 575 L·mol-1·cm-1;ε2=30 131，14 854 L·mol-1·cm-1;ε3=38 244，14 870 L·mol-1·cm-1）.This fact supports the neutral mode of the ligand HL in three complexes[7].

2.4 Fluorescence spectra

The fluorescence spectra of the ligand HL and complexes 1～3 have been studied in CH3CN solution（c=1 ×10-5mol·L-1）at room temperature.The free Schiff base ligand HL exhibits almost none fluorescenceemission when excited at320 nm，primarily due to C=N isomerization.However，complexes 1 and 2 show remarkable peaks at about 428 and 408 nm under the same tested condition，respectively.Obviously，binding with Zn2+/Cd2+inhibits the isomerization of C=N，thereby increasing the fluorescence intensity through the CHEF mechanism[9-11].In addition，it should be noted that complex 3 gives similar emission as the free ligand because of the heavy atom effect of the coordinated iodide anions.

Fig.3 Fluorescence emission spectra of the ligand HL，complexes 1～3 in CH3CN solution at room temperature

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