Syntheses, crystal structures and antimicrobial activities of thioether ligands containing quinoline and pyridine terminal groups and their transition metal complexes

Inorganica Chimica Acta 374 (2011) 269–277

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Syntheses, crystal structures and antimicrobial activities of thioether ligands containing quinoline and pyridine terminal groups and their transition metal complexes Jing-An Zhang a,b, Mei Pan a,⇑, Ji-Jun Jiang a, Zhi-Gang She a, Zhi-Jin Fan c, Cheng-Yong Su a,⇑ a KLGHEI of Environment and Energy Chemistry, MOE Laboratory of Bioinorganic and Synthetic Chemistry, School of Chemistry and Chemical Engineering, Sun Yat-sen University, Guangzhou 510275, PR China b School of Pharmacy, Guangdong Pharmaceutical University, Guangzhou 510006, PR China c State Key Laboratory of Elemento-Organic Chemistry, Nankai University, Tianjin 300071, PR China

a r t i c l e

i n f o

Article history: Available online 3 March 2011 Dedicated to Professor Wolfgang Kaim on the occasion of his 60th birthday Keywords: Quinoline Pyridine Thioether Crystal structure Bioactivity

a b s t r a c t Eleven transition metal complexes of three asymmetrical tridentate thioether ligands, 8-((pyridin-2yl)methylthio) quinoline (TQMP2), 8-((pyridin-3-yl)methylthio) quinoline (TQMP3), 8-((pyridin-4yl)methylthio) quinoline (TQMP4) and one symmetrical pentadentate ligand 2,6-bis (8-quinolinylthiomethyl) pyridine (DTQMP) were prepared. The structures of all these complexes were identified by means of elemental analysis (EA), infrared spectra (IR) and single-crystal diffraction, providing three different kinds of basic conformations, (1) discrete mononuclear structures, (2) dinuclear rings and (3) 1D polymer chains. The antibacterial, antifungal and pesticide activities of the four ligands and 11 complexes were also studied. Ó 2011 Elsevier B.V. All rights reserved.

1. Introduction Organic ligands containing quinoline and pyridine terminal groups and their complexes have been paid much attention in recent years due to their multifarious crystal conformations as well as unique properties and applications in such fields as lubricant additives, photoluminescence and pharmaceutical activities. A series of transition metal complexes have been reported with symmetrical or asymmetrical thioether ligands containing quinoline groups during the past decades [1–12], showing their potent capacities in coordination chemistry. However, reports on the bioactivities of such kinds of complexes still remain rare [13]. In order to get more information in this field, we synthesized a series of semi-rigid monothioether and dithioether ligands, 8-((pyridin-2-yl)methylthio) quinoline (TQMP2), 8-((pyridin-3-yl)methylthio) quinoline (TQMP3), 8((pyridin-4-yl)methylthio) quinoline (TQMP4) and 2,6-bis(8quinolinylthiomethyl) pyridine (DTQMP) (Scheme 1), which contain both quinoline and pyridine terminal groups with closely correlated structures yet different coordination behaviors. By using these thioether ligands, 11 transition metal complexes, namely, [Co(TQMP2)(NO3)2] (1), [Cu(TQMP2)2](BF4)2(H2O)2 (2) [4], ⇑ Corresponding authors. Tel./fax: +86 20 8411 5178. E-mail addresses: [email protected] (M. Pan), [email protected] (C.-Y. Su). 0020-1693/$ - see front matter Ó 2011 Elsevier B.V. All rights reserved. doi:10.1016/j.ica.2011.02.073

{Cu(TQMP3)(CF3CO2)2}1 (3), [Ni(TQMP4)(H2O)(CF3CO2)2] (4), [Zn(TQMP4)(H2O)(CH3OH)](ClO4)2(CH3OH) (5), [Ag(TQMP4)](CF3SO3)(CH3CN) (6), [Cu(DTQMP)(CF3CO2)](CF3CO2)(H2O)2 (7), [Zn(DTQMP)(H2O)](ClO4)2(H2O) (CH3CN) (8), [Mn(DTQMP)(CF3SO3)](CF3SO3) (9), [Ag2(DTQMP)(CF3COO)2] (10) and [Ag(DTQMP)](CF3SO3) (11) were obtained. The single crystal structural analyses revealed three different structural models for these complexes, namely, discrete mononuclear units, dinuclear rings and 1D polymer chains. The antibacterial, antifungal and pesticide activities of the ligands and complexes were tested. 2. Experimental 2.1. Materials and general methods Cobalt nitrate hexahydrate, copper tetrafluoroborate, copper trifluoroacetate, nickel trifluoroacetate, zinc perchlorate hexahydrate, silver trifluoromethylsulfonate and silver trifluoroacetate were purchased from Aldrich Chemical Co. Inc. and ACROS ORGANICS, while sodium 8-mercaptoquiniline [14], 2-chloromethylpyridine hydrochloride, 3-chloromethylpyridine hydrochloride, 4-chloromethylpyridine hydrochloride and 2,6-dibromomethylpyridine [15] were prepared according to the reported procedures. All the other reagents and solvents were commercially available and employed as received or purified by standard methods prior to use.

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Scheme 1. Structures of the ligands.

All reactions involving thiols were carried out under nitrogen atmosphere. Elemental analyses were performed on a German Vario EL analyzer (Elementar) and IR spectra were recorded on an Avatar 330 FT-IR spectrometer (Thermo Nicolet) with potassium bromide pellets. 1H NMR spectra were recorded on a Mercury-Plus 300 spectrometer (VARIAN) (300 MHz) at 25 °C in CDCl3 with tetramethylsilane as the internal reference. UV–Vis spectra were recorded on a CARY-300 spectrometer (VARIAN). Powder XRD spectra were recorded on a Bruker D8 Advancer at 40 kV, 40 mA with a Cu-target tube and a graphite monochromator.

2.2. Syntheses of ligands and complexes 2.2.1. Preparation of ligands The ligands TQMP2, TQMP3 and TQMP4 were prepared according to our earlier works [13].

2.2.1.1. 2,6-Bis[(8-quinolinylthio)methyl] pyridine (DTQMP). Sodium hydroxide (0.400 g, 10 mmol) and potassium iodide (0.040 g, 0.24 mmol) were dissolved in anhydrous ethanol (70 mL) in a 125 mL three-neck flask with a magnetic stirrer, a reflux condenser and an isobaric drop tundish under nitrogen. Sodium 8-mercaptoquinoline (1.739 g, 9.5 mmol) was added to the above mixture solution and dissolved by stirring under nitrogen. 2,6-Dibromomethylpyridine (1.005 g, 3.8 mmol) in anhydrous ethanol (20 mL) was dropped into the mixed solution under nitrogen and the mixture was heated in an oil bath at 80 °C for further 6 h. The solution was filtered and washed twice with anhydrous ethanol (10 mL). The filtrate was concentrated and then cooled to 4 °C. The pink crystal was collected in 72.2% yield (1.167 g). Mp 130–131 °C. IR (KBr pellet, cm1): 3055(w), 3020(w), 2987(w), 2896(m), 1573(s), 1487(m), 1449(vs), 1417(m), 1373(m), 1304(m), 1269(m), 1213(w), 1073(w), 983(m), 880(w), 777(s), 655(w), 462(w). 1H NMR (CDCl3, 300 MHz): 8.96, 8.95, 8.94(q, 2H), 8.14–8.11 (q, 2H), 7.63–7.60 (q, 2H), 7.57–7.54 (q, 2H), 7.52–7.50 (t, 1H), 7.47–7.42 (q, 2H), 7.41–7.40 (d, 2H), 7.38–7.35 (t, 2H), 4.48 (s, 4H). UV (CH3CN, kmax, nm): 251(A = 1.020), 331(A = 0.281). Anal. Calc. for C25H19N3S2: C, 70.56; H, 4.500; N, 9.870. Found: C, 70.52; H, 4.480; N, 9.730%.

2.2.2. Synthesis of complexes 3–11 The composition and structural model of complexes 1–11 are summarized in Table 1. Among which, the synthesis and structures of complexes 1 and 2 have been reported earlier [13]. 2.2.2.1. {Cu(TQMP3)(CF3CO2)2}1 (3). 8-[(Pyridin-3-yl)methylthio] quinoline (TQMP3) (25 mg, 0.10 mmol) was dissolved in chloroform (3 mL), then Cu(CF3CO2)2 (34 mg, 0.10 mmol) in anhydrous ethanol (2 mL) was added into the above solution. The obtained solution was stirred for 10 min and filtered into the conical flask, and then the flask was sealed with film and put it in the shade. Regular blue single crystals of 3 were yielded after several days. The crystals were filtered and washed several times with anhydrous diethyl ether and then dried in vacuum. Yield was 65%. Anal. Calc. for C19H12CuF6N2O4S: C, 42.11; H, 2.230; N, 5.170. Found: C, 42.31; H, 2.480; N, 5.400%. IR (KBr pellet, cm1): 3028(w), 2925(w), 1596(m), 1489(m), 1457(m), 1425(m), 1375(m), 1251(vs), 1169(s), 1048(s), 985(m), 820(m), 788(m), 712(m), 657(s), 579(m), 520(m). 2.2.2.2. [Ni(TQMP4)(H2O)(CF3CO2)2] (4). 8-[(Pyridin-4-yl)methylthio] quinoline (TQMP4) (30 mg, 0.12 mmol) was dissolved in chloroform (2 mL) and acetone (2 mL) and filtered into a test tube, then a mixed solvent of chloroform (1 mL) and acetonitrile (3 mL) was layered onto the above solution, and Ni(CF3CO2)26H2O (35 mg, 0.12 mmol) in anhydrous acetonitrile (2 mL) was filtered into the upper layer of the mixed solution along the tube. The tube was sealed with film and put in the shade. Colorless crystals of 4 were formed after several days. The crystals were filtered and washed several times with anhydrous diethyl ether and then dried in vacuum. Yield was 71%. Anal. Calc. for C19H14F6N2NiO5S: C, 41.11; H, 2.540; N, 5.050. Found: C, 41.50; H, 2. 983; N, 5.430%. IR (KBr pellet, cm1): 3278(m), 1682(vs), 1617(s), 1500(m), 1432(m), 1383(w), 1201(vs), 1130(vs), 837(m), 794(m), 717(m), 608(w), 506(w). 2.2.2.3. [Zn(TQMP4)(H2O)(CH3OH)](ClO4)2(CH3OH) (5). 8-[(Pyridin4-yl)methylthio] quinoline (TQMP4) (50 mg, 0.20 mmol) was dissolved in dichloromethane (3 mL), then Zn(ClO4)26H2O (86 mg, 0.23 mmol) in anhydrous methanol (2 mL) was added into the above solution. The obtained solution was stirred for 10 min at

Table 1 Lists of informations for the complexes. No.

Mn+

L

Anion

Structural model

MF

1 2 3 4 5 6 7 8 9 10 11

Co2+ Cu2+ Cu2+ Ni2+ Zn2+ Ag+ Cu2+ Zn2+ Mn2+ Ag+ Ag+

TQMP2 TQMP2 TQMP3 TQMP4 TQMP4 TQMP4 DTQMP DTQMP DTQMP DTQMP DTQMP

NO3  BF4  BF4CF3 CO2  CF3 CO2  ClO4  CF3 SO3  CF3 CO2  ClO4  CF3 SO3  CF3 CO2  CF3 SO3 

ML ML2 {ML}1 M2L2 M2L2 M2L2 ML ML ML M2L {ML}1

[Co(TQMP2)(NO3)2] [Cu(TQMP2)2](BF4)2(H2O)2 {Cu(TQMP3)(CF3CO2)2}1 [Ni(TQMP4)(H2O)(CF3CO2)2] [Zn(TQMP4)(H2O)(CH3OH)](ClO4)2(CH3OH) [Ag(TQMP4)](CF3SO3)(CH3CN) [Cu(DTQMP)(CF3CO2)](CF3CO2)(H2O)2 [Zn(DTQMP)(H2O)](ClO4)2(H2O)(CH3CN) [Mn(DTQMP)(CF3SO3)](CF3SO3) [Ag2(DTQMP)(CF3COO)2] [Ag(DTQMP)](CF3SO3)

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room temperature and slowly filtered into a 15 mL tube, and then the tube was sealed with film and put into a 500 mL wide-neck flask filled with 50 mL diethyl ether. Slow diffusion of diethyl ether into the resulting solution yielded colorless crystals of 5 after several days. The crystals were filtered and washed several times with anhydrous diethyl ether and then dried in vacuum. Yield was 81%. Anal. Calc. for C17H24Cl2N2O12SZn: C, 33.47; H, 3.97; N, 4.85. Found: C, 33.65; H, 3.870; N, 4.770%. IR (KBr pellet, cm1): 3568(m), 3422(m), 3053(m), 2937(m), 1657(s), 1432(s), 1374(s), 1301(m), 1078(vs), 987(s), 822(s), 781(s), 692(s), 631(s), 494(s). 2.2.2.4. [Ag(TQMP4)](CF3SO3)(CH3CN) (6). Colorless crystal 6 was synthesized as complex 5 except that 8-[(pyridin-4-yl)methylthio] quinoline (TQMP4)) (25 mg, 0.10 mmol) was dissolved in dichloromethane (5 mL), then AgCF3SO3 (26 mg, 0.10 mmol) in anhydrous acetonitrile (5 mL) was used instead of Zn(ClO4)26H2O. Yield was 65%. Anal. Calc. for C18H15AgF3N3O3S2: C, 39.28; H, 2.750; N, 7.640. Found: C, 39.13; H, 2.366; N, 7.705%. IR (KBr pellet, cm1): 3039(w), 1595(m), 1487(w), 1415(w), 1364(m), 1282(vs), 1175(vs), 1032(s), 986, 823(m), 778(m), 649(w), 580(w), 517(w). 2.2.2.5. [Cu(DTQMP)(CF3CO2)](CF3CO2)(H2O)2 (7). Green crystal 7 was synthesized as complex 5 except that 2,6-bis(8quinolinylmethylthio) pyridine (DTQMP) (24 mg, 0.056 mmol) was dissolved in chloroform (2 mL), then Cu(CF3CO2)2 (20 mg, 0.069 mmol) in anhydrous acetonitrile (2 mL) was used instead of Zn(ClO4)26H2O. Yield was 62%. Anal. Calc. for C29H23CuF6N3O6S2: C, 46.37; H, 3.090; N, 5.590. Found: C, 46.66; H, 2.989; N, 5.793%. IR (KBr pellet, cm1): 3440(m), 3069(w), 1686(vs), 1498(w), 1410(m), 1308(w), 1192(s), 1129(m), 1004(w), 833(m), 785(m), 717(w), 614(w), 464(w). 2.2.2.6. [Zn(DTQMP)(H2O)](ClO4)2(H2O)(CH3CN) (8). Colorless crystal 8 was synthesized as complex 5 except that 2,6-bis(8quinolinylmethylthio) pyridine (DTQMP) (21 mg, 0.050 mmol) was dissolved in chloroform (1 mL) and tetrahydrofuran (THF) (1 mL), then Zn(ClO4)26H2O (32 mg, 0.086 mmol) in anhydrous acetonitrile (2 mL) was added into the above solution. Yield was 33%. Anal. Calc. for C54H52Cl4N8O20S4Zn2: C, 42.28; H, 3.420; N, 7.310. Found: C, 42.29; H, 3.175; N, 7.290%. IR (KBr pellet, cm1): 3407(m), 3075(m), 2992(m), 1594(m), 1498(m), 1454(m), 1391(m), 1310(w), 1099(vs), 898(w), 833(w), 781(m), 677(w), 626(m), 459(w). 2.2.2.7. [Mn(DTQMP)(CF3SO3)](CF3SO3) (9). Brown crystal 9 was synthesized as complex 5 except that 2,6-bis(8-quinolinylmethylthio) pyridine (DTQMP) (48 mg, 0.11 mmol) was dissolved in chloroform (3 mL) , then Mn(CF3SO3)2 (51 mg, 0.14 mmol) in anhydrous acetonitrile (2 mL) was used instead of Zn(ClO4)26H2O. Yield was 75%. Anal. Calc. for C27H19F6MnN3O6S4: C, 41.65; H, 2.460; N, 5.400. Found: C, 41.46; H, 2.467; N, 5.783%. IR (KBr pellet, cm1): 3071(w), 2922(w), 1592(m), 1497(w), 1454(w), 1386(w), 1274(vs), 1161(s), 1030(m), 833(w), 780(m), 639(m), 575(w), 518(w). 2.2.2.8. [Ag2(DTQMP)(CF3COO)2] (10). Colorless transparent crystal 10 was synthesized as complex 5 except that 2,6-bis(8quinolinylmethylthio) pyridine (DTQMP) (22 mg, 0.05 mmol) was dissolved in chloroform (2 mL), then AgCF3CO2 (22 mg, 0.10 mmol) in anhydrous acetonitrile (2 mL) was used instead of Zn(ClO4)26H2O. Yield was 67%. Anal. Calc. for C29H19Ag2F6N3O4S2: C, 40.16; H, 2.210; N, 4.840. Found: C, 40.20; H, 2.184; N, 4.589%. IR (KBr pellet, cm1): 3052(w), 2982(w), 2922(w), 1679(vs), 1580(m), 1491(m), 1449(m), 1368(m), 1301(w), 1210(s), 1129(s), 985(m), 823(m), 792(m), 656(w).

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2.2.2.9. [Ag(DTQMP) ](CF3SO3) (11). Colorless transparent crystal 11 was synthesized as complex 5 except that 2,6-bis(8quinolinylmethylthio) pyridine (DTQMP) (36 mg, 0.084 mmol) was dissolved in chloroform (3 mL), then AgCF3SO3 (43 mg, 0.168 mmol) in anhydrous acetonitrile (2 mL) was used instead of Zn(ClO4)26H2O. Yield was 65%. Anal. Calc. for C26H19AgF3N3O3S3: C, 45.75; H, 2.810; N, 6.160. Found: C, 45.56; H, 2.733; N, 6.336%. IR (KBr pellet, cm1): 3462(m), 3061(m), 2992(m), 2928(m), 1587(m), 1492(m), 1452(m), 1372(m), 1268(vs), 1153(s), 1081(m), 1033(s), 987(m), 824(m), 785(m), 642(s), 575(m), 519(m). 2.3. X-ray structure analyses Single-crystal X-ray diffraction measurements of complexes 3–11 were carried out on an Oxford Gemini S Ultra CCD diffractometer equipped with a graphite monochromator at 150 K. The determination of unit cell parameters and data collections were performed with Mo Ka radiation (k = 0.71073 Å). The unit cell parameters were obtained with least-squares refinements and all structures were solved by direct methods [16]. The metal atoms in each complex were located from E-maps. The other non-hydrogen atoms were located in successive difference Fourier syntheses. The final refinement was performed by full matrix least-squares methods with anisotropic thermal parameters for non-hydrogen atoms against F 20 [17]. Hydrogen atoms were added in calculated positions. The crystallographic data and structure refinement summary data for complexes 3–11 are listed in Table 2 and the main bond lengths (Å) and angles (°) are listed in Table S1. 2.4. Antimicrobial activities The complexes were dissolved in DMSO (dimethylsulfoxide) and tested against five aerobic reference strains for their inhibitory activity. The antimicrobial activities were performed using a modified version of the 2-fold serial dilutions method as R.A. Fromtling (1993), in which two starting yeast inoculum sizes (5  104 and 2.5  103 cells per ml) were compared, and readings were taken after 24 and 48 h of incubation. The resultant turbidities in all tubes were estimated visually on a scale from 0 to ++++ turbidity, and MIC-0, MIC-1 and MIC-2 were defined as the lowest drug concentrations that reduced the growth to 0, + or ++ turbidity, respectively [18]. Experimental results were presented in Table 3. Tests of pesticide activities of the complexes against five botanic bacteria were shown in Table 4. 3. Results and discussion 3.1. Spectroscopic characterization The IR data for the four ligands and 11 complexes are listed in part 2. We can see that in the complexes, except for the peaks relevant to the ligands, they also show the typical peaks of the corresponding anions, for example, 1580–1617, 1489–1500, 820–837 cm1 for CF3 CO2  in complexes 3, 4 and 10, 1078–1099, 987 cm1 for ClO4  in complex 5 and 8, and 1268–1282, 1153–1175, 1032–1033, 639–649 cm1 for CF3 SO3  in complexes 6, 9 and 11. These data prove the formation of coordination complexes. 3.2. Crystal structures According to the different kinds of ligands and anions used in the assembly of coordination compounds, the coordination models of the 11 complexes can be divided into various kinds, as

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Table 2 Crystallographic data and structure refinement summary for complexes 3–11.

Formula Fw Crystal system Space group a (Å) b (Å) c (Å) a (°) b (°) c (°) V/Å3 Z qcalc (mg mm3) l (Mo Ka) (mm1) Reflections collected R1, [I > 2r(I)]a wR2 [all data]

Formula Fw Crystal system Space group a (Å) b (Å) c/Å a (°) b (°) c (°) V (Å3) Z qcalc (mg mm3) l (Mo Ka) (mm1) Reflections collected R1, [I > 2r(I)]a wR2 (all data) a

3

4

5

6

7

C19H12CuF6N2O4S 541.91 monoclinic P2(1) 8.662(5) 9.998(5) 12.599(5) 90 107.466(5) 90 1040.8(9) 2 1.729 1.233 7556 0.0265 0.0591

C38H28F12N4Ni2O10S2 1110.18 monoclinic C2/c 21.6208(5) 9.2023(5) 20.8054(14) 90 91.016(8) 90 4138.8(4) 4 1.775 1.129 10296 0.0425 0.0969

H34C48Cl4N4O24S2Zn2 1233.42 monoclinic P21/c 11.8253(4) 16.9450(5) 12.8239(4) 90 107.525(4) 90 2450.38(13) 2 1.672 1.369 14004 0.0432 0.1286

C36H30Ag2F6N6O6S4 1100.64 monoclinic P21/c 7.5092(5) 21.2209(17) 12.5828(5) 90 95.834(4) 90 1994.7(2) 2 1.833 1.274 11636 0.0361 0.0790

C29H23CuF6N3O6S2 751.16 triclinic P-1 9.652(4) 11.618(4) 14.759(6) 88.482(6) 80.713(6) 67.031(6) 1502.6(10) 2 1.66 0.952 12685 0.0425 0.1230

8

9

10

11

C27H23Cl2N4O10S2Zn 663.88 triclinic  P1

C27H19F6MnN3O6S4 778.63 monoclinic P21/n 15.1071(5) 12.3165(4) 17.9525(8) 90 113.348(4) 90 3066.8(2) 4 1.686 0.787 17 563 0.0378 0.1114

C29H19Ag2F6N3O4S2 867.33 orthorhombic Pbca 18.2291(14) 17.9463(14) 19.2775(15) 90 90 90 6306.5(8) 8 1.827 1.450 31 620 0.1077 0.2856

C26H19AgF3N3O3S3 682.49 monoclinic C2/c 24.1887(12) 8.6033(3) 26.3898(14) 90 109.470(5) 90 5177.7(4) 8 1.751 1.078 26 265 0.027 0.0779

12.667(11) 13.169(12) 22.78(2) 12.667(11) 13.169(12) 22.78(2) 3363(5) 4 1.509 1.071 23 306 0.0959 0.2816

The value of R1 is based on selected data with I > 2r(I); the value of wR2 is based on all data.

Table 3 Tests of MIC (lg/mL) of the compounds against four bacteria and three fungal strains.a Compounds

TQMP2 TQMP3 TQMP4 DTQMP 1 2 3 4 5 6 7 8 9 10 11 Ampb Strb Nysb a b

Strains Staphylococcus aureus ATCC 27154 (G+)

Escherichia coli ATCC 25922 (G-)

P. aeruginosa (G-)

Sarcina ureae (G+)

Aspergillus niger

Saccharomyces cerevisiae

Fusarium oxysporum f. sp. cubense

>50 >50 >50 >50 3.13 1.56 1.56 50 25 0.125 3.13 12.5 >50 6.25 1.56 12.5 1.56 NT

12.5 25 6.25 3.13 0.78 1.56 3.13 6.25 25 25 3.13 6.25 >50 0.125 3.13 6.25 3.13 NT

>50 >50 >50 >50 0.78 6.25 1.56 25 >50 0.25 12.5 25 >50 12.5 >50 3.13 1.56 NT

>50 >50 >50 >50 >50 6.25 >50 12.5 >50 0.125 1.56 50 >50 0.25 >50 3.13 3.13 NT

>125 >125 >125 >125 >125 62.5 >125 >125 >125 >125 31.25 62.5 >125 15.6 31.25 NT NT 3.9

>125 >125 >125 >125 125 62.5 >125 >125 >125 >125 62.5 31.25 >125 31.25 15.6 NT NT 3.9

>125 >125 >125 >125 125 125 >125 >125 >125 62.5 15.6 15.6 >125 31.25 7.8 NT NT 7.8

The results are expressed as the minimum inhibitory concentration (MIC). Ampicillin (Amp), streptomycin sulfate (Str), nystatin (Nys): positive control; NT, not tested.

summarized in Table 1 and Scheme 2. As for the tridentate asymmetrical ligands TQMP2 to TQMP4, due to the difference in the orientations between the quinolinylthio group (N+S coordination sites) and pyridine group (N coordination site), the structures of complexes 1–6 vary from mononuclear discrete to linear infinite

and then dinuclear discrete. Adding another quinolinylthio group onto the pyridine heterocycle to get ligand DTQMP, we find that its coordination characters are something like the combination of two TQMP2, but according to the different metal centers and anions we applied, three different coordination models can be

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J.-A. Zhang et al. / Inorganica Chimica Acta 374 (2011) 269–277 Table 4 Tests of pesticide activities of the complexes against five botanic bacteria. Compounds

Bacteria code C

TQMP2 TQMP3 TQMP4 DTQMP 1 2 3 4 5 6 7 8 9 10 11

12.73 30.91 1.82 20.00 12.73 1.82 30.91 16.36 16.36 52.73 16.36 27.27 16.36 NT 56.36

F      –    +    +

61.11 55.56 11.11 50.00 27.78 50.00 22.22 16.67 16.67 55.56 83.33 38.89 66.67 NT 72.22

U + +  +  +    + ++  + ++

I

94.12 58.82 0.00 5.88 23.53 23.53 17.65 5.88 0.00 70.59 64.71 29.41 41.18 NT 76.47

+++ +  –     ++ +   ++

67.09 46.84 11.39 26.58 8.86 21.52 3.80 46.84 21.52 72.15 77.22 62.03 31.65 NT 90.00

D +      –   ++ ++ +  +++

60.00 52.00 4.00 68.00 12.00 12.00 20.00 20.00 12.00 36.00 60.00 52.00 44.00 NT 76.00

+ + – +       + +  ++

Notes: (1) Biological activity is shown with killing or restraining percentage. (2) Grades of biological activity to insect bacteria are +++ is P90%; ++ is P70–89%; + is P50–69%;  is < 50%. (3) C is cucumber fusarium wilt (Fusarium oxysporum f. cucumerinum); F is tomato early blight (A. solani); U is watermelon anthracnose (C. lagenarium); I is apple ring rot (Physalospora piricola); D is peanut brown spot (Cercospora rachidicola). (4) NT is not tested.

Scheme 2. The various coordination modes in the 11 complexes according to different ligands applied.

obtained, i.e., mononuclear, dinuclear discretes and infinite chains. Among the eleven complexes, the structure of complexes 1 and 2 have been reported in Ref. [13], and we will focus on the other nine complexes in the following paragraphs. In complex 3, the self-assembly of Cu(II) ions and TQMP3 ligands affords the infinite 1D polymer chain. In each [Cu(TQMP3)(CF3CO2)2] asymmetric unit, there are one Cu(II) ion, one TQMP3 ligand and two CF3 CO2  anions. The central Cu(II) ion is six coordinated by one S atom (dCu–S = 2.585(1) Å), one quinoline N atom (dCu–N = 1.986(3) Å) from one ligand, and one pyridyl N atom (dCu–N = 1.994(3) Å) from another TQMP3 ligand. Furthermore, three O atoms (dCu–O = 1.982(5)–2.725(5) Å) from two different trifluoroacetate anions help to satisfy the coordination sphere, forming a distorted octahedral configuration (Fig. 1a). The coordination unit is then extended to a 1D coordination helical chain along b axis by the linkage of the ligands (Fig. 1b and c). The unit structures of complexes 4, 5 and 6 are basically the same, composed of a dimetallic ring, as shown in Figs. 2–4. Take 4 as an example, in its asymmetric unit [Ni(TQMP4)(H2O)(CF3CO2)2]2, the Ni(II) is located in the center of a very slightly distorted octahedral geometry and coordinated by quinoline N and S atoms

from one TQMP4 ligand (dNi–N = 2.103(3) Å and one pyridine N atom (dNi–N = 2.093(3) Å) from another ligand. The remaining coordinated sites are occupied by one O atom from water molecule (dNi–O = 2.048(2) Å) and two O atoms from two trifluoroacetate anions (dNi–O = 2.058(2) and 2.066(2) Å). Interestingly, two asymmetric units generate a very stable dinuclear building block which contains a 14-membered ring of two Ni1 centers and the corresponding atoms on the two ligands (Fig. 2a). And furthermore, a 1D Zigzag polymer chain is formed by hydrogen-bond interactions between coordinated water molecules and uncoordinated O atom from trifluoroacetate anions (Fig. 2b). The asymmetric unit of complex 5 is almost the same as that of complex 4, except that the ClO4  anions do not participate in the coordination and only act as counter anions for charge equilibrium, yet one methanol (dZn–O = 2.082(2) Å) is involved in the coordination sphere. Similarly, a 14-membered ring is formed by the two Zn(II) centers and the corresponding atoms on the two ligands (Fig. 3a). Since the ligand TQMP4 is flexible, each molecular ring piles up with the bordering rings by strong p–p interactions and the central distance between the two parallel pyridine planes is 3.602 Å. Altogether, there exist four different kinds of hydrogen bonds in crystal 5 (Fig. 3b): between H–O2W from coordinated

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Fig. 1. The molecular structure (a) and 1D helical chain in complex 3 ((b), H atoms are omitted), and the schematic R helical axis (c).

Fig. 2. The molecular structure (a) and 1D Zigzag chain (b) in complex 4 (H atoms are omitted).

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Fig. 3. The molecular structure (a) and hydrogen bonding interactions (b) in complex 5 (H atoms are omitted).

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2.749(1) Å, respectively. Similar to complex 5, a 14-membered ring is formed by the two Ag(I) centers and the corresponding atoms on the two ligands (Fig. 4). Each unit packs four neighboring units on both sides along a axis and is linked by hydrogen bonding with other four neighboring units along b axis, thus extending into 3D supramolecular nets. The asymmetric units of complexes 7–9 are basically the same, and we only take complex 7 as an example, in which [Cu(DTQMP)(CF3CO2)](CF3CO2) (H2O)2 forms a mononuclear structure, consisting of one metal and one ligand. The Cu(II) atom is coordinated in an octahedral coordinated geometry with an N3S2O donor set (Fig. 5), coming from one pyridine N, two quinoline N and two S atoms from one DTQMP ligand and one O atom from CF3 CO2  anion. The Cu–N1, Cu–N3, Cu–S1, Cu–S2, Cu–N2 and Cu–O1 distances are within 1.999(3)–2.582(1) Å. The structure of complex 10 is composed of discrete binuclear unit [Ag2(DTQMP)(CF3COO)2], in which each Ag(I) atom is coordinated in a T-shaped tri-coordinated geometry with an NOS donor set (Fig. 6a) coming from one quinolinyl N and one S atom from DTQMP ligand and one O atom from CF3COO. The Ag–N1, Ag– N2, Ag–S2, Ag–S1, Ag–O3 and Ag–O1 distances are within 2.227(1)–2.547(4) Å. There exist weak coordinated interactions between two Ag(I) ions and N3 atom on the pyridine ring (dAg–N = 2.598 and 2.651 Å), and strong interactions between the two Ag(I) ions themselves (dAg–Ag = 3.098 Å). The binuclear building block is further linked into a 1D chain by weak C–HO hydrogen bond interactions (d = 3.381–3.421 Å) between the coordinated counter anions and ligands (Fig. 6b). The structure of complex 11 forms an infinite chain. Each Ag(I) atom is located in a hexa-coordinated geometry with an N3S3 donor set coming from two N atoms of quinoline ring (dAg–N2 = 2.423(2) Å, dAg–N3 = 2.539(2) Å) and three S atoms from two DTQMP ligands (dAg–S = 2.672(1), 2.664(1), 2.767(1) Å) and one N atom from a pyridine ring (dAg–N1 = 2.653(2) Å). The bridging of the ligand extends the coordinated Ag(I) structural units into a 1D chain (Fig. 7). From the above crystal structures of complexes, we have found that their structural conformations were mainly controlled by the ligands and metal centers and also influenced by the coordination capabilities of counter anions at the same time. The intramolecular weak interactions also help to assemble the crystal structures into different dimensions.

3.3. The antibacterial, antifungal and pesticide activities of the four ligands and their complexes

Fig. 4. The molecular structure of complex 6 (H atoms are omitted).

water to O5 and O2 from two different ClO4  anions (dO–O = 2.856(1), 2.762(1) Å), and between H–O10 from one solvent methanol to two ClO4  anions (dO–O = 2.936(1), and 2.985(1) Å). Significantly, the eight-membered hydrogen bonding ring formed by ClO4  anions and methanol molecules increase the stability of the crystal packing. The structure of the asymmetric unit in complex 6 [Ag(TQMP4)](CF3SO3) (CH3CN) is basically similar to that of complexes 4 and 5, which also forms binuclear ring, in which the Ag(I) atom is coordinated in a T-shaped tri-coordinated geometry with an N2S donor set coming from quinoline N and S atoms of one TQMP4 ligand and pyridinyl N atom of another. The Ag–N(1), Ag–N(2) and Ag–S distances are 2.187(3), 2.222(3) and

From the antibacterial results listed in Table 3, we can see that the four ligands and their complexes show different inhibition activities against various kinds of bacteria. Ligands TQMP4 and DTQMP have good efficiency in inhibiting Escherichia coli (G), while others are poor against Staphylococcus aureus, Pseudomonas

Fig. 5. The molecular structure of complex 7 (H atoms are omitted).

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Fig. 6. The molecular structure (a) and 1D chain (b) in complex 10 (H atoms are omitted).

Fig. 7. The molecular structure and 1D chain in complex 11 (H atoms are omitted).

aeruginosa and Sarcina ureae. Among the complexes, 6 and 10 appear to be the most powerful ones, which afford quite good MIC values (0.125, 0.25 and 0.125 lg/mL) against both the bacteria with G+ (S. aureus, S. ureae) and those with G (P. aeruginosa) except for E. coli, showing potential applications in the broad spectrum anti-bacteria field. The antifungal activities of the four ligands are all poor against the three fungi (MIC > 125 lg/mL). The antifungal activities of the 11 complexes show that only complex 11 has good effect against Fusarium oxysporum f. sp. cubense (F. o) and Saccharomyces cerevisiae (S. c) (MIC = 7.8 and 15.6 lg/mL). The effects of the other complexes are poor in inhibiting fungal activities. The pesticidal activities of the four ligands and 11 complexes against five botanic bacteria are shown in Table 4. Ligand TQMP2 has distinct effects to inhibit watermelon anthracnose (Colletotrichum lagenarium, U) and definite effects to inhibit tomato early blight (Alternaria solani, F), apple ring rot (Physalospora piricola, I) and peanut brown spot (Cercospora rachidicola, D). The other ligands also have distinct pesticidal effects except for cucumber fusarium wilt (C). Among the complexes, complex 11 is the most powerful one to inhibit apple ring rot (I). Complexes 6 and 7 have the powerful effect against F, U and I. From the above results, we can see that for asymmetrical ligands TQMP2–4, only TQMP4 has good antimicrobial activities to

inhibit E. coli; symmetrical ligand DTQMP also has better antimicrobial activities to inhibit E. coli, yet they have poor antimicrobial activities to inhibit S. aureus, P. aeruginosa and S. ureae. In asymmetrical ligands TQMP2–4, as nitrogen atom has the isomerous position in pyridine ring, they have different biological activities. The pesticidal activities of the four ligands against five botanic bacteria show that only ligand TQMP2 has distinct effects to inhibit watermelon anthracnose (U). We can also see that in general, most of the complexes show much better results in antibacterial and antifungal tests than the pure ligands, showing their inhibition mechanism is mainly due to the introduction of the metal centers. Relatively, complex 9 has poor effects compared with other complexes. This may be due to the fact that the introduction of Mn(II) do not favor such kinds of antimicrobial activities.

4. Conclusions Eleven transition metal complexes from four thioether ligands have been prepared and characterized, and they have been shown to have discrete mononuclear units, binuclear subunit rings or polymeric chains in the crystal structures. Different kinds of intramolecular interactions, such as H-bonds, p–p interactions or Ag– Ag interactions, extend the structures into higher dimension. The antibacterial and pesticide activity tests show that the 11 complexes are quite efficient in inhibiting certain bacteria, such as S. aureus and E. coli and some botanic bacteria, while their antifungal activities are not quite so good. In general, the introduction of metal ions improves the biological activities of such kinds of thioether ligands and provides informative choice in practical application and screening.

Acknowledgements This work has been supported by the Natural Science Foundation of China (20903120, U0934003, 20821001, 20731005), the RFDP of Higher Education of China, and the Fundamental Research Funds for the Central Universities.

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Appendix A. Supplementary material CCDC 805975–805983 contain the supplementary crystallographic data for 3–11. These data can be obtained free of charge from The Cambridge Crystallographic Data Centre via http:// www.ccdc.cam.ac.uk/data_request/cif. Supplementary data associated with this article can be found, in the online version, at doi:10.1016/j.ica.2011.02.073.

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