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Syntheses, structural characterization and antimicrobial activities of novel cobalt-pyrazine-2,3-dicarboxylate complexes with N-donor ligands
Journal of Molecular Structure 964 (2010) 39–46
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Syntheses, structural characterization and antimicrobial activities of novel cobalt-pyrazine-2,3-dicarboxylate complexes with N-donor ligands Okan Zafer Yesßilel a,*, Aylin Mutlu a, Cihan Darcan b, Orhan Büyükgüngör c a
Department of Chemistry, Faculty of Arts and Sciences, Eskisßehir Osmangazi University, TR–26480, Eskisßehir, Turkey Department of Biology, Faculty of Arts and Sciences, Dumlupınar University, TR–43100, Kütahya, Turkey c Department of Physics, Faculty of Arts and Sciences, Ondokuz Mayıs University, TR–55139, Kurupelit–Samsun, Turkey b
a r t i c l e
i n f o
Article history: Received 7 September 2009 Received in revised form 30 October 2009 Accepted 30 October 2009 Available online 5 November 2009 Keywords: Pyrazine-2,3-dicarboxylate complexes 1,10-Phenanthroline complex N,N,N,0 N0 -tetramethylethylenediamine complex 2,2-Dimethylpropane-1,3-diamine complex Cobalt complexes Antimicrobial activities
a b s t r a c t Novel cobalt-pyrazine-2,3-dicarboxylate complexes with 1,10-phenanthroline (phen), [Co(pzdca)(phen)2]211H2O (1), N,N,N0 ,N0 -tetramethylethylenediamine (tmen), (H2tmen)[Co(pzdca)2(tmen)]9H2O (2) and 2,2-dimethylpropane-1,3-diamine (dmpen), [Co(CO3)(dmpen)2](pzdca)0.5H2O (3) have been synthesized and characterized by elemental and thermal analyses, spectroscopic (IR and UV–vis) and X-ray diffraction techniques. In 1 and 2, pyrazine-2,3-dicarboxylate ligand coordinated to the Co(II) ions through one nitrogen atoms of pyrazine ring and oxygen atoms of carboxylate group as a bidentate ligand and distorted octahedral geometries of 1 and 2 are completed by phen and tmen ligands, respectively. In 2, the tmen molecules exhibit chemically different functions; it coordinated to the Co(II) ion as a bidentate ligand and in the other form it protonated and acts as counter-ion. In complex 3, Co(III) ion is coordinated by four nitrogen atoms of dmpen and two oxygen atoms of CO3 ligand and the pzdca behaves as a counter-ion. Furthermore, structures of 1 and 2 contain extensive hydrogen bonding between crystal water molecules to form infinite 2D water layers and 1D water chains, respectively. In vitro antimicrobial activities of new complexes were tested against selected wild type and clinical microorganisms by MIC. Complexes exhibited antimicrobial activity at high concentrations against the bacteria, fungi and clinical isolate tested. Ó 2009 Elsevier B.V. All rights reserved.
1. Introduction Organic molecules containing carboxylic acid have been used as building blocks in crystal engineering and many coordination polymers [1–6]. Pyrazine-2,3-dicarboxylic acid (H2pzdca, Scheme 1a) is a well-known versatile ligand, which has been extensively used in the design of coordination complexes due to a variety of its bonding abilities. Pzdca ligand coordinate to metal ions by means of its four oxygen atoms of carboxylate groups and two nitrogen atom of pyrazine ring forming monodentate [1], bidentate [2–5], bis(bidentate) bridge (l2) [6–9], bis(monodentate) bridge (l2) [10], tridentate bridge (l2) [10–15], tetradentate bridge (l3) [15–21] and mixed chelating-bridging ligand [22]. Until now, the crystal structures of two polynuclear and one mononuclear Co(II) complexes with doubly and singly deprotonated pyrazine-2,3-dicarboxylic acid ligands have been reported. In the {[Co(l3-pzdca)(phen)]H2O}n [16] and {[Co(l-pzdca) (H2O)2]2H2O}n [23] and {[Co2(pzdca)(bipy)(H2O)2]3H2O}n [24] polymeric complexes, pzdca2 act as a tridentate and tetradentate bridging ligand, whereas in the [Co(Hpzdca)2(H2O)2] [2] complex, * Corresponding author. Tel.: +90 2222393750; fax: +90 2222397850. E-mail address: [email protected] (O.Z. Yesßilel). 0022-2860/$ - see front matter Ó 2009 Elsevier B.V. All rights reserved. doi:10.1016/j.molstruc.2009.10.048
Hpzdca ligand acts as a chelate manner through the pyrazine nitrogen atom and carboxylate oxygen atom. Surprisingly, in the previously reported data, a few bis(pyrazine-2,3-dicarboxylate) metal complexes have reported [7,8], whereas the counter anion complexes of pzdca have not found. Its known that pyrazine ring is a part of polycyclic derivative be important as biological and industrial. It was reported that pyrazine derivatives have an antituberculotic, antifungal and cytotoxic effect [25–28]. In this study, we report the syntheses, spectral and thermal characterizations and crystal structures, antimicrobial activities of three novel cobalt-pyrazine-2,3-dicarboxylate complexes with 1,10-phenanthroline, N,N,N0 ,N0 -tetramethylethylenediamine and 2,2-dimethylpropane-1,3-diamine ligands (Scheme 1b–d), [Co(pzdca)(phen)2]211H2O (1), (H2tmen)[Co(pzdca)2(tmen)]9H2O (2) and [Co(CO3)(dmpen)2](pzdca)0.5H2O (3). 2. Experimental 2.1. Syntheses of the complexes A solution of pyrazine-2,3-dicarboxylic acid (0.84 g, 5 mmol) in water (20 ml) was added dropwise with stirring to a solution of
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O N
C
H 3C
OH N
N
C (a)
O
OH
N
N (b)
H3C
N
CH3 (c)
CH3
CH3
CH3
NH2
NH2
(d)
Scheme 1. (a) Pyrazine-2,3-dicarboxylic acid, (b) 1,10-phenanthroline, (c) N,N,N0 ,N0 -tetramethylethylenediamine, (d) 2,2-dimethylpropane-1,3-diamine.
Co(CH3COO)24H2O (1.25 g, 5 mmol) in water (20 ml). The mixture was stirred for 4 h at 50 °C and then phenH2O (1.98 g, 10 mmol) in ethanol or tmen (1.16 g, 10 mmol) in acetonitril–water (1:1, 25 ml) or dmpen (1.02 g, 10 mmol) in ethanol was added to this solution and was stirred for 2 h at 50 °C and then cooled to room temperature. The crystals formed were filtered and washed with water and dried in air. The complex 3 was oxidatively reacted with dmpen ligand to give a mixed-ligand cobalt(III) adduct. Elemental analysis for C60H58N12O19Co2 (%) Calcd: C 52.64, H 4.27, N 12.28. Found: C, 53.62; H, 3.55; N, 12.57. Selected IR (cm1, KBr): 3401 vs b, 3056 m, 1655 vs 1643 vs 1623 vs 1599 vs 1566 m, 1450 m, 1425 m, 1377 s, 1332 s, 1224 m, 1164 m, 1119 s, 855 s, 726 s, 642 w, 542 w. Elemental analysis for C24H56N8O17Co (%) Calcd: C 36.60, H 7.17, N 14.23. Found: C, 36.42; H, 7.06; N, 14.95. Selected IR (cm1, KBr): 3465 vs b, 3100 w, 3013 m, 2978 m, 2901 m, 2631 m, 2459 m, 1635 vs 1615 vs 1608 vs 1468 s, 1386 s, 1351 s, 1280 m, 1198 m, 1169 s, 1120 s, 1066 m, 1009 m, 889 m, 739 m, 659 w, 590 w. Elemental analysis for C14H31N5O6Co (%) Calcd: C 38.72, H 7.14, N 16.13. Found: C, 39.27; H, 7.16; N, 16.60. Selected IR (cm1, KBr): 3475 s, 3224 m, 3204 m, 3118 m, 2957 m, 2872 w, 1635 vs 1590 vs 1471 w, 1384 s, 1265 m, 1202 m, 1159 m, 1113 m, 1045 m, 1000 m, 835 w, 749 m, 674 w, 511 w.
2.2. Materials and measurements All chemicals used were analytical reagent and were commercially purchased. IR spectra were obtained with a Bruker Tensor 27 FT-IR spectrometer using KBr pellets in the 4000–400 cm1 range. UV–vis spectra were obtained for the aqueous solution of the complex (103 M) with a Shimadzu UV-3150 spectrometer in the range 900–190 nm. Elemental analysis for C, H and N was car_ ried out at the TÜBITAK Marmara Research Centre. Magnetic susceptibility measurements at room temperature were performed using a Sherwood Scientific MXI model Gouy magnetic balance. Perkin Elmer Diamond TG/DTA thermal analyzer was used to record simultaneous TG, DTG and DTA curves in the static air atmosphere at a heating rate of 10 K min1 in the temperature range 30–1000 °C using platinum crucibles.
2.3. Crystallographic analyses Details of crystal structures are given in Table 1. Selected bond lengths, bond angles and the hydrogen bonds are listed in Table S1, S2 and S3, respectively. Data collection were performed on a STOE IPDS II image plate detector using MoKa radiation (k = 0.71019 Å). Intensity data were collected in the h range 1.3–27.89° at 293(2) K. Data collections: Stoe X-AREA [29]. Cell refinement: Stoe X-AREA [29]. Data reduction: Stoe X-RED [29]. The structures were solved by direct-methods and anisotropic displacement parameters were applied to non-hydrogen atoms in a full-matrix least-squares refinement based on F2 using SHELXL-97 [30]. Molecular drawings were obtained using Mercury program [31].
Table 1 The details of crystals and experimental data for 1, 2 and 3. Empirical formula Formula weight Temperature (K) Wavelength (Å) Crystal system Space group Unit cell dimensions a (Å) b (Å) c (Å) a (°) b (°) c (° V (Å3) Z l (mm1) Dcalc (Mg m3) h Range (°) Measured reflections Independent reflections Flack parameter [37] Absorption correction Refinement method Final R indices [I > 2r(I)] R[F2 > 2r(F2)] wR(F2) Goodness-of-fit on F2 Largest difference peak and hole (Å3)
C60H58N12O19Co2 1369.06 293(2) 0.71073 Triclinic P1
C24H56N8O17Co 787.69 293(2) 0.71073 Triclinic P1
C14H31N5O6Co 424.37 293(2) 0.71073 Orthorhombic Fdd2
14.7074(4) 15.0107(4) 17.4194(5) 71.202(2) 65.883(2) 61.810(2) 3053.48(15) 2 0.63 1.482 1.30–26.75 31344 11989
8.997(1) 14.736(1) 15.760(1) 67.210(6) 88.845(6) 88.553(6) 1925.4(3) 2 0.52 1.355 1.40–26.89 16601 7415
19.617(1) 32.596(2) 12.460(6) 90 90 90 7967.8(7) 16 0.90 1.415 1.62–27.89 13658 3898
– – Integration Full-matrix least-squares on F2 0.085 0.078
0.031
0.052 0.147 1.01 1.20; 0.47
0.077 0.086 1.03 0.34; 0.46
0.064 0.167 0.95 0.99; 0.72
0.041 (15)
2.4. Antimicrobial activities of the complexes The antimicrobial activities were tested against standard bacterial strains of Gram positive (Staphylococcus aureus ATCC6535, Bacillus cereus ATCC7064) and Gram negative (Escherichia coli W3110, Pseudomonas aeruginosa ATCC27853), one yeast (Candida albicans ATCC10231) and clinical isolates (Methicillin Resistant S. aureus, Proteus vulgaris, P. aeruginosa, Enterobacter aerogenes) (Faculty of Medicine, Ondokuz Mayıs University) by using minimal _ inhibitory concentration method (MIC). The complexes were dissolved in double distilled water at proper concentration. For the broth dilution method, cultures were grown in 5 ml nutrient broth (Merck) at 37 °C for 18 h in shaking at 175 rpm. Bacterial and yeast cells were suspended in 50 ml nutrient broth at a concentration of approximately 106 cells/ml by matching with 0.5 McFarland turbidity standards. Nutrient broth containing microorganisms were transferred 1 ml in test tubes and were added complexes, and made 2-fold serial dilution; eventually the ranges were narrowed to define more exact values. All the test cultures were grown at 37 °C in incubator. The incubation period was 24 h for bacterial strains and fungal strains. The minimum inhibitor concentration, at which no growth was observed, was taken as the MIC value (lg/ml), and represents the mean of at least three determinations. 3. Result and discussion 3.1. UV–vis spectra and magnetic susceptibilities of the complexes The [Co(pzdca)(phen)2]211H2O and (tmenH2)[Co(pzdca)2 (tmen)]9H2O complexes exhibit 5.71 and 4.28 BM magnetic moment values which corresponds to three unpaired electrons. The complexes are consistent with a weak field octahedral geometry as expected. The [Co(CO3)(dmpen)2](pzdca)0.5H2O exhibits diamagnetic property and a strong-field octahedral complex.
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Fig. 1. The crystal structure of 1 showing the atom-numbering scheme (Hydrogen atoms are omitted for clarity).
All complexes exhibit mainly two maxima between 209 (e = 4516 Lmol1cm1) and 284 nm (e = 4817 Lmol1cm1) due to p ? p* and n ? p* intraligand transitions of pzdca and neutral ligands. The kmax values of the two absorption bands in the spectrum of 1 are 346 and 876 nm. These values were assigned to the following d–d transitions, 4T1g ? 4T1g (P) and 4T1g ? 4T2g, respectively. 4 T1g ? 4A2g transition was not observed which has high energy and shifts to the UV region and hidden under the intraligand transitions in the spectrum.
The UV–vis spectrum for 2 exhibits only one weak d–d absorption transition at 346 nm (e = 1126 Lmol1cm1). This value was assigned to 4T1g ? 4A2g. The 4T1g ? 4T1g (P) and 4T1g ? 4T2g transitions were not observed, which shift to the IR region. The complex [Co(CO3)(dmpen)2](pzdca)0.5H2O has a band around 521 nm (e = 54 Lmol1cm1), which is assignable to the 1 A1g ? 1T1g transition and suggests a distorted octahedral stereochemistry. The absorption spectra indicate that the cobalt(III) complex forms a stronger crystal field than the cobalt(II) compound.
Fig. 2. The pp and C–Hp interactions of 1 (Water molecules and hydrogen atoms are omitted for clarity).
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and 923 °C. The final decomposition product was identified by IR spectroscopy (the overall weight loss, found 89.25, calcd. 89.05%).
3.2. Thermal analyses 3.2.1. [Co(pzdca)(phen)2]211H2O The first endothermic stage (DTAmax = 82, 102 and 144 °C) in the temperature range of 43–156 °C, corresponds to the loss of eleven crystal water molecules (found 13.55, calcd. 14.46% Fig. S1). In the temperature range of 213–488 °C, the two stages of the Co(II) complex are related to the successively decomposition of the neutral phen ligands and decomposition of pzdca, by giving exothermic contribution (DTAmax = 275 and 431 °C). The solid product of the thermal decomposition, Co3O4, converts to CoO between 907
3.2.2. (H2tmen)[Co(pzdca)2(tmen)]9H2O The first stage is related to endothermic removal of crystal water molecules in the 58–122 °C temperature range (DTGmax = 87, 117 °C, mass loss found 19.39, calc. 20.57%). The second stage is related to the release of the one tmen molecule in the 145–214 °C temperature range (found 15.61, calcd. 15.01%). In the following successively stages, tmen and pzdca ligands are decomposed as an exothermic effect (DTAmax = 234 and 263 °C) and remain organ-
Fig. 3. The hydrogen bonding motif of the self-assembled infinite layer of water molecules in 1.
O.Z. Yesßilel et al. / Journal of Molecular Structure 964 (2010) 39–46
ic residue is burned as a strong exothermic effect (DTAmax = 397 °C). The decomposition product Co3O4 converts to CoO. The overall weight loss of 89.14% (calcd. 90.49%) agrees with the propose structure well (Fig. S2). 3.2.3. [Co(CO3)(dmpen)2](pzdca)0.5H2O The endothermic peak of DTA curve in the temperature range of 35–205 °C related to the loss of the crystal water molecule. The second stage between 197 and 258 °C corresponds to the release of one dmpen and carbonate ligands by giving an endothermic effect (DTGmax = 232 °C). The last strong exothermic stage involves the decomposition of the dmpen and pzdca ligands (DTAmax = 342 °C). In the endothermic stage (910–914 °C, DTAmax = 913 °C), the Co3O4 converts to CoO (found 81.63, calcd. 82.42%). 3.3. Crystal structures 3.3.1. [Co(pzdca)(phen)2]211H2O The asymmetric unit of 1 composed of two crystallographic independent [Co(pzdca)(phen)2] complexes and eleven lattice water molecules as shown in Fig. 1. Details of crystal structures are given in Table 1. The Co(II) ion is coordinated by nitrogen atom of pyrazine ring and deprotonated oxygen atom of carboxylate group from bidentate pzdca ligand and four nitrogen atoms from bidentate two phen ligands. The carboxylate oxygen (O1/O5) and the nitrogen atoms (N2, N3, N5/N8, N9, N11) comprise the equatorial plane, where as the axial position are filled by the nitrogen atoms of phen ligands (N1, N4/N7, N10). The deprotonated carbox-
43
ylate oxygen and pyrazine nitrogen atoms chelate to the Co(II) centre to form a five-membered chelate ring. The other carboxylate oxygen atoms do not participate in coordination. The Co1–N5, Co1–O1 and Co2–N11, Co2-O5 bond distances are 2.147(3), 2.025(2) and 2.151(3), 2.021(2) Å, respectively. The discrepancy between the carboxylate C29–O1 and C29–O2 (1.239 and 1.201 Å) or C59–O5, C59–O6 (1.271 and 1.215 Å) distances reflect the coordination. The phen and pzdca ligands are essentially planar. The dihedral angles between the pzdca and phen ligands are 89.88° and 82.40° in Co1 and 67.19° and 83.24° in Co2. The dihedral angles between the two phen molecules are 79.24° and 87.30°, respectively. Furthermore, the dihedral angles between the pzdca ligand and carboxyl groups are 16.08°, 77.20° and 12.44°, 84.39°, respectively. There are inter-molecular hydrogen-bonding interactions and pp stacking interactions between the phen ligands of neighbouring layers, with distances between the aromatic rings ranging from 3.503 to 3.950 Å. Furthermore, there is also weak C–Hp interactions between the C(9)–H(9) and phen ring (Fig. 2). Moreover, the complex 1 contains extensive hydrogen bonding between crystal water molecules to form infinite 2D water layers (Fig. 3). These 2D layers interact each other though water bridges by strong hydrogen bonds to forming a zig-zag chain along the b-axis (Fig. 3) All of these inter-molecular interactions give a two-dimensional network.
3.3.2. (H2tmen)[Co(pzdca)2(tmen)]9H2O The crystallographic analysis revealed that the complex consists of discrete [Co(pzdca)2(tmen)]2 anion, bis(protonated) H2tmen2+
Fig. 4. The crystal structure of 2 showing the atom-numbering scheme (Hydrogen atoms are omitted for clarity).
Fig. 5. The pp interactions of 2 (Water molecules, hydrogen atoms and H2tmen cation are omitted for clarity).
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cation and nine crystal water molecules (Fig. 4). One of the interesting features of the structure is that the tmen molecules exhibit chemically different functions. While, in one form, it coordinates to Co(II) ion as a bidentate ligand, in the other form it act as a counter-ion. In addition, there are two pzdca ligands coordinated to Co(II) ion as a cis position. Although, there are many metal complexes of pyrazine-2,3-dicarboxylate ligand with transition metal ions, until now, this type behaviour complexes has not been reported. Co1 adopts a distorted octahedral geometry and coordinated by two pzdca ligands and one tmen ligand. The pzdca ligands coordinated to the Co(II) ion through the N atom of pyrazine ring and the O atom of carboxyl group, creating a chelate ring, while tmen ligand coordinated to the Co(II) ion via N atoms as a bidentate ligand. Two nitrogen atoms (N2, N4) from the pyrazine ring and two nitrogen atoms (N5 and N6) from tmen ligand comprise the equatorial plane, while two oxygen atom (O1 and O5) from the carboxylate group occupy the axial positions [O1–Co1– O5 = 163.79(11)°]. The Co1–N5 and Co1–N6 bond distances of 2.174(3) and 2.187(3) Å, respectively, are similar that found in the [Ni(acac)2 (tmen)] (2.152(2), 2.166(2) Å) [32]. The Co1–N2/N4 and Co1–O1/ O5 bond distances are 2.151(3), 2.151(3), 2.063(3) and 2.076(3) Å, respectively. The angles of N2–Co1–O1 [77.27(11)°] and N4–Co1–O5 [77.04(11)°] are nearly equal. The pzdca ligands are essentially planar with r.m.s. deviation 0.0056 (C2) and 0.0069 Å (C7) and the dihedral angle between the pzdca ligands is 81.56°. Furthermore, the dihedral angles between the pzdca ligand and uncoordinated carboxyl groups are 88.66° and 79.15°. The carboxylate C–O distances in the pzdca ligands also display some variability, depending on their environment. The crystal packing is mainly stabilized by hydrogen bonds. The H2tmen cation is involved in intra- and inter-molecular hydrogen bonding with the carbonyl oxygen atoms (O3 and O7). There are also pp interactions [3.833 Å] between the CgA–CgAi rings (CgA: N1– C1–C2–C3–C4–N4, i: 1 x, 1 y, 1 z) and [3.736 Å] between the CgB–CgBii rings (CgB: N3–C7–C8–C9–C10–N4, ii: 1 x, 2 y, z). Some of these interactions are illustrated in Fig. 5. Furthermore, the complex 2 contains extensive hydrogen bonding between crystal water molecules to form infinite 1D water chains containing cyclic water cluster and generate T 4(2)7(2)6(2) motif (Fig. 6) [33].
Fig. 7. The crystal structure of 3 showing the atom-numbering scheme (Hydrogen atoms is omitted for clarity).
positions are occupied by atoms N1 and N3. The equatorial plane and pzdca ligand are approximately planar. The dihedral angle between the pyrazine ring and carboxyl group is 49.18°. The crystal packing is stabilized by intra and inter-molecular hydrogen bonding between the dmpen ligand and pzdca anion. Each pzdca anion is surrounded by four centrosymmetric [Co (CO3)(dmpen)2]2+ cations (Fig. 8). Two cations are connected by a hydrogen bond interaction between the amine groups (N1, N2 and N3) of dmpen and O4, O5 of the pzdca anion [N1O4 = 2.910(3), N2O4 = 3.068(3), N2O4 = 3.068(3) and N2O5 = 3.024 (4) Å] and also carboxyl group O(5) and crystal water molecules (O6) [O5O6 = 2.926 Å], while there are inter-molecular hydrogen bonds between NH2 group (N4) of dmpen ligand and N atom of pzdca anion [N4N6 = 2.146 Å].
3.4. Antimicrobial activity studies 3.3.3. [Co(CO3)(dmpen)2](pzdca)0.5H2O A view of the molecule and its atom-numbering scheme are shown in Fig. 7 and selected bond lengths and bond angels are given in Table S1. The crystal structure consists of a complex cation, [Co(CO3)(dmpen)2]2+, and half pzdca anion. In the complex cation, the Co(III) ion exhibits a distorted octahedral coordination geometry and it is coordinated by four nitrogen atoms from two chelating dmpen ligands together with one bidentate carbonate ligand. The Co–N distances are different from each other and lie in a wide range [1.967(2)–2.322(3) Å]. The carbonate ligand is symmetrically coordinated to the Co(III) ion [Co–O1 = 1.918(2) Å, Co–O2 = 1.906(2) Å]. The angle N3–Co1–N1 (178.82(12)°) is virtually linear, whereas O1–Co1–N4 (165.35(10)°) and O2–Co1–N2 (168.65(10)°) deviate much from linearity. On this basis, atoms O1, O2, N2 and N4 can be chosen to form the basal plane of the octahedron, and the equatorial
At present study, in vitro potential antimicrobial activity of complexes were tested according to minimal inhibitory concentration method, are given in Table 2. As can clearly be seen from Table 2, complexes 2 and 3 were studied as much 5000 lg/ml, while MIC values of the complexes 2 and 3 were determined as higher than 5000 lg/ml at all microorganism used with exception P. aeruginosa (3250 lg/ml at complex 2), complex 1 is determined in range 1850–3000 lg/ml (Table 2). Complex 1 is more effect than complexes 2 and 3. Complexes exhibited antimicrobial activity at high concentrations against the bacteria, fungi and clinical isolate tested. Antimicrobial activities of complexes did not changed to be gram (+), gram () and eukaryot in point of effective dose. It is known that there are a disparity between procaryote (gram +, gram ) and eukaryote.
Fig. 6. The hydrogen bonding motif of the self-assembled infinite chain (T 4(2)7(2)6(2)) of water molecules in 2.
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Fig. 8. The hydrogen-bonding interactions for 3, shown as dashed lines (Water molecules and hydrogen atoms are omitted for clarity).
Table 2 Minimal inhibitory concentrations (MIC) values of the complexes against wild type and clinical microorganisms (lg/ml). Compound
1 2 3
Gram (+)
Gram ()
Eucaryote
Clinical isolate
S. aureus
B. cereus
E. coli
P. aeruginosa
C. albicans
MRSA
P. vulgaris
P. aeruginosa
E. aerogenes
2250 >5000 >5000
2000 >5000 >5000
2250 >5000 >5000
2000 3250 >5000
2250 >5000 >5000
2000 >5000 >5000
2000 >5000 >5000
2250 >5000 >5000
2250 >5000 >5000
But this difference not important for antimicrobial effect of complexes and did not seen a important difference between wild type and clinical isolate at antimicrobial activities of complexes. It is a well-known fact that hospital infections are quite important for the public healthy and quite resistant against standard antibiotics. Therefore, there is an urgent demand for new antibiotics and new classes chemical formula that will efficiently inhibit the growth of pathogenic microorganism. Tuberculosis still remains a serious health problem in many regions of the world, especially in developing nations. With the spread of AIDS and the increase in the number of immune compromised patients, the problem of tuberculosis has been greatly exacerbated because of the susceptibility of such patients to mycobacteria. Currently, chemotherapy using multiple drug regimens with isoniazid, rifampin, streptomycin, pyrazinamide, and ethambutol is the recommended treatment for tuberculosis. The presence of drug resistance is still a major concern and new generations of more effective antimycobacterial agents. It is reported that Pyrazine dicarboxylic acid derivatives is a candidate for Mycobacterium tuberculosis [34,35]. Furthermore, Premkumar and Govindarajan reported that the free acids and some new hydrazinium salts of 2-pyrazinecarboxylate,
2,3-pyrazinedicarboxylate, 3,5-pyrazoledicarboxylate and 4,5-imidazoledicarboxylate show more promising activity than the corresponding free acids and the standard positive control antibiotic (Co-trimoxazole) against E. coli, Salmonella typhii and Vibrio cholerae [36].
4. Conclusion We have synthesized and structurally characterized three novel cobalt-pyrazine-2,3-dicarboxylate complexes with 1,10-phenanthroline, N,N,N0 ,N0 -tetramethylethylenediamine and 2,2-dimethylpropane-1,3-diamine ligands. In the [Co(pzdca)(phen)2]211H2O and (H2tmen)[Co(pzdca)2(tmen)]9H2O complexes, the pzdca dianion acts as a bidentate ligand, its coordination sites being the carboxylate oxygen atom and nitrogen atom of pyrazine ring. The tmen molecule exhibits chemically different functions; in one form, it coordinates to Co(II) ion as a bidentate ligand, in the other form it act as a counter-ion. In the [Co(CO3)(dmpen)2] (pzdca)0.5H2O complex is the first example, the anionic pzdca exhibiting as a counter-ion.
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Acknowledgement This work was supported by the Eskisßehir Osmangazi University by Project No. 200819042. Appendix A. Supplementary data CCDC 675311, 675310 and 675309 contain the supplementary crystallographic data for 1, 2 and 3. These data can be obtained free of charge via http://www.ccdc.cam.ac.uk/conts/retrieving.html, or from the Cambridge Crystallographic Data Centre, 12 Union Road, Cambridge CB2 1EZ, UK; fax: +44 1223 336 033; or e-mail: [email protected]. Supplementary data associated with this article can be found, in the online version, at doi:10.1016/j.molstruc. 2009.10.048. References [1] O.Z. Yesßilel, A. Mutlu, O. Büyükgüngör, Polyhedron 27 (2008) 2471. [2] C.J. O’Connor, E. Sinn, Inorg. Chem. 20 (1981) 545. [3] M. Wenkin, M. Devillers, B. Tinant, J.P. Declercq, Inorg. Chim. Acta 258 (1997) 113. [4] M.S. Wang, L.Z. Cai, G.W. Zhou, G.C. Guo, J.G. Mao, J.S. Huang, Acta Crystallogr. E 59 (2003) m212. [5] O.Z. Yesßilel, A. Mutlu, O. Büyükgüngör, J. Coord. Chem. 61 (2008) 3267. [6] C.J. O’Connor, C.L. Klein, R.J. Majeste, L.M. Trefonas, Inorg. Chem. 21 (1982) 64. [7] H. Xu, H. Ma, M. Xu, W. Zhao, B. GuO, Acta Crystallogr. E 64 (2008) m104. [8] R. Burriel, C.J. O’Conner, R.L. Carlin, Inorg. Chem. 24 (1985) 3706. [9] T. Okubo, M. Kondo, S. Kitagawa, Synth. Met. 85 (1997) 1661. [10] H.D. Yin, F.H. Li, C.H. Wang, Inorg. Chim. Acta 360 (2007) 2797.
[11] M. Gryz, W. Starosta, J. Leciejewicz, J. Coord. Chem. 58 (2005) 931. [12] K.Y. Choi, J. Incl. Phen. Macr. Chem. 43 (2002) 195. [13] S. Konar, S.C. Manna, E. Zangrando, N.R. Chaudhuri, Inorg. Chim. Acta 357 (2004) 1593. [14] X.H. Li, Q. Shi, M.L. Hu, H.P. Xiao, Inorg. Chem. Com. 7 (2004) 912. [15] H. Yin, S.X. Liu, Polyhedron 26 (2007) 3103. [16] Z. Bi-Song, Chin. J. Struct. Chem. 24 (2005) 478. [17] Y. Ma, Y.K. He, Z.B. Han, Acta Crystallogr. E 62 (2006) m2528. [18] J.Z. Zou, Z. Xu, W. Chen, K.M. Lo, X.Z. You, Polyhedron 18 (1999) 1507. [19] M.L. Hu, J.X. Yuan, F. Chen, Q. Shi, Acta Crystallogr. C 60 (2004) m186. [20] M. Kondo, T. Okubo, A. Asami, S. Noro, T. Yoshitomi, S. Kitagawa, T. Ishii, H. Matsuzaka, K. Seki, Angew. Chem. Int. Ed. 38 (1999) 1433. [21] G. Beobide, O. Castillo, A. Luque, U. Garcia-Coucerio, J.P. Garcia-Teran, P. Roman, Inorg. Chem. 45 (2006) 5367. [22] X.J. Zheng, L.P. Jin, S.Z. Lu, Eur. J. Inorg. Chem. (2002) 3356. [23] M. Long, S.J. Rettig, R.C. Thompson, J. Trotter, S. Xia, Can. J. Chem. 74 (1996) 433. [24] M.J. Fang, M.X. Li, X. He, M. Shao, W. Pang, S.R. Zhu, J. Mol. Struct. 921 (2009) 137. [25] E.L. Seitz, J.W. Suling, C.R. Reynolds, J. Med. Chem. 45 (2002) 5604. [26] T.B. Adams, J. Doull, V.J. Ferron, Food Chem. Toxicol. 40 (2002) 429. [27] M. Dolezal, J. Jampilek, Z. Osicka, Farmaco (Pavia) 58 (2003) 1105. [28] M. Dolezal, P. Cmedlova, L. Palek, Eur. J. Med. Chem. 43 (2008) 1105. [29] Stoe & Cie (2002). XArea (Version 1.18) and XRed32 (Version 1.04), Stoe & Cie, Darmstadt, Germany, 2001. [30] G.M. Sheldrick, SHELXS-97 and SHELXL-97. Program for Refinement of Crystal Structures, University of Göttingen, Germany, 1997. [31] Mercury: Visualization and analysis of crystal structures C.F. Macrae, P.R. Edgington, P. McCabe, E. Pidcock, G.P. Shields, R. Taylor, M. Towler, J. van de Streek, J. Appl. Cryst. 39 (2006) 453. [32] A. Zeller, E. Herdtweck, Th. Strassner, Inorg. Chem. Commun. 7 (2004) 296. [33] L. Infantes, S. Motherwell, CrysEngComm 4 (2002) 454. [34] O. Zimhony, C. Vilcheze, M. Arai, Antimicrob. Agents Chemother. 51 (2007) 752. [35] T. Premkumar, S. Govindarajan, World J. Microbiol. Biotechnol. 22 (2006) 1105. [36] T. Premkumar, S. Govindarajan, World J. Microbiol. Biotechnol. 21 (2005) 479. [37] H.D. Flack, Acta Crystallogr. A 39 (1983) 876.
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Syntheses, structural characterization and antimicrobial activities of novel cobalt-pyrazine-2,3-dicarboxylate complexes with N-donor ligands Okan Zafer Yesßilel a,*, Aylin Mutlu a, Cihan Darcan b, Orhan Büyükgüngör c a
Department of Chemistry, Faculty of Arts and Sciences, Eskisßehir Osmangazi University, TR–26480, Eskisßehir, Turkey Department of Biology, Faculty of Arts and Sciences, Dumlupınar University, TR–43100, Kütahya, Turkey c Department of Physics, Faculty of Arts and Sciences, Ondokuz Mayıs University, TR–55139, Kurupelit–Samsun, Turkey b
a r t i c l e
i n f o
Article history: Received 7 September 2009 Received in revised form 30 October 2009 Accepted 30 October 2009 Available online 5 November 2009 Keywords: Pyrazine-2,3-dicarboxylate complexes 1,10-Phenanthroline complex N,N,N,0 N0 -tetramethylethylenediamine complex 2,2-Dimethylpropane-1,3-diamine complex Cobalt complexes Antimicrobial activities
a b s t r a c t Novel cobalt-pyrazine-2,3-dicarboxylate complexes with 1,10-phenanthroline (phen), [Co(pzdca)(phen)2]211H2O (1), N,N,N0 ,N0 -tetramethylethylenediamine (tmen), (H2tmen)[Co(pzdca)2(tmen)]9H2O (2) and 2,2-dimethylpropane-1,3-diamine (dmpen), [Co(CO3)(dmpen)2](pzdca)0.5H2O (3) have been synthesized and characterized by elemental and thermal analyses, spectroscopic (IR and UV–vis) and X-ray diffraction techniques. In 1 and 2, pyrazine-2,3-dicarboxylate ligand coordinated to the Co(II) ions through one nitrogen atoms of pyrazine ring and oxygen atoms of carboxylate group as a bidentate ligand and distorted octahedral geometries of 1 and 2 are completed by phen and tmen ligands, respectively. In 2, the tmen molecules exhibit chemically different functions; it coordinated to the Co(II) ion as a bidentate ligand and in the other form it protonated and acts as counter-ion. In complex 3, Co(III) ion is coordinated by four nitrogen atoms of dmpen and two oxygen atoms of CO3 ligand and the pzdca behaves as a counter-ion. Furthermore, structures of 1 and 2 contain extensive hydrogen bonding between crystal water molecules to form infinite 2D water layers and 1D water chains, respectively. In vitro antimicrobial activities of new complexes were tested against selected wild type and clinical microorganisms by MIC. Complexes exhibited antimicrobial activity at high concentrations against the bacteria, fungi and clinical isolate tested. Ó 2009 Elsevier B.V. All rights reserved.
1. Introduction Organic molecules containing carboxylic acid have been used as building blocks in crystal engineering and many coordination polymers [1–6]. Pyrazine-2,3-dicarboxylic acid (H2pzdca, Scheme 1a) is a well-known versatile ligand, which has been extensively used in the design of coordination complexes due to a variety of its bonding abilities. Pzdca ligand coordinate to metal ions by means of its four oxygen atoms of carboxylate groups and two nitrogen atom of pyrazine ring forming monodentate [1], bidentate [2–5], bis(bidentate) bridge (l2) [6–9], bis(monodentate) bridge (l2) [10], tridentate bridge (l2) [10–15], tetradentate bridge (l3) [15–21] and mixed chelating-bridging ligand [22]. Until now, the crystal structures of two polynuclear and one mononuclear Co(II) complexes with doubly and singly deprotonated pyrazine-2,3-dicarboxylic acid ligands have been reported. In the {[Co(l3-pzdca)(phen)]H2O}n [16] and {[Co(l-pzdca) (H2O)2]2H2O}n [23] and {[Co2(pzdca)(bipy)(H2O)2]3H2O}n [24] polymeric complexes, pzdca2 act as a tridentate and tetradentate bridging ligand, whereas in the [Co(Hpzdca)2(H2O)2] [2] complex, * Corresponding author. Tel.: +90 2222393750; fax: +90 2222397850. E-mail address: [email protected] (O.Z. Yesßilel). 0022-2860/$ - see front matter Ó 2009 Elsevier B.V. All rights reserved. doi:10.1016/j.molstruc.2009.10.048
Hpzdca ligand acts as a chelate manner through the pyrazine nitrogen atom and carboxylate oxygen atom. Surprisingly, in the previously reported data, a few bis(pyrazine-2,3-dicarboxylate) metal complexes have reported [7,8], whereas the counter anion complexes of pzdca have not found. Its known that pyrazine ring is a part of polycyclic derivative be important as biological and industrial. It was reported that pyrazine derivatives have an antituberculotic, antifungal and cytotoxic effect [25–28]. In this study, we report the syntheses, spectral and thermal characterizations and crystal structures, antimicrobial activities of three novel cobalt-pyrazine-2,3-dicarboxylate complexes with 1,10-phenanthroline, N,N,N0 ,N0 -tetramethylethylenediamine and 2,2-dimethylpropane-1,3-diamine ligands (Scheme 1b–d), [Co(pzdca)(phen)2]211H2O (1), (H2tmen)[Co(pzdca)2(tmen)]9H2O (2) and [Co(CO3)(dmpen)2](pzdca)0.5H2O (3). 2. Experimental 2.1. Syntheses of the complexes A solution of pyrazine-2,3-dicarboxylic acid (0.84 g, 5 mmol) in water (20 ml) was added dropwise with stirring to a solution of
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O N
C
H 3C
OH N
N
C (a)
O
OH
N
N (b)
H3C
N
CH3 (c)
CH3
CH3
CH3
NH2
NH2
(d)
Scheme 1. (a) Pyrazine-2,3-dicarboxylic acid, (b) 1,10-phenanthroline, (c) N,N,N0 ,N0 -tetramethylethylenediamine, (d) 2,2-dimethylpropane-1,3-diamine.
Co(CH3COO)24H2O (1.25 g, 5 mmol) in water (20 ml). The mixture was stirred for 4 h at 50 °C and then phenH2O (1.98 g, 10 mmol) in ethanol or tmen (1.16 g, 10 mmol) in acetonitril–water (1:1, 25 ml) or dmpen (1.02 g, 10 mmol) in ethanol was added to this solution and was stirred for 2 h at 50 °C and then cooled to room temperature. The crystals formed were filtered and washed with water and dried in air. The complex 3 was oxidatively reacted with dmpen ligand to give a mixed-ligand cobalt(III) adduct. Elemental analysis for C60H58N12O19Co2 (%) Calcd: C 52.64, H 4.27, N 12.28. Found: C, 53.62; H, 3.55; N, 12.57. Selected IR (cm1, KBr): 3401 vs b, 3056 m, 1655 vs 1643 vs 1623 vs 1599 vs 1566 m, 1450 m, 1425 m, 1377 s, 1332 s, 1224 m, 1164 m, 1119 s, 855 s, 726 s, 642 w, 542 w. Elemental analysis for C24H56N8O17Co (%) Calcd: C 36.60, H 7.17, N 14.23. Found: C, 36.42; H, 7.06; N, 14.95. Selected IR (cm1, KBr): 3465 vs b, 3100 w, 3013 m, 2978 m, 2901 m, 2631 m, 2459 m, 1635 vs 1615 vs 1608 vs 1468 s, 1386 s, 1351 s, 1280 m, 1198 m, 1169 s, 1120 s, 1066 m, 1009 m, 889 m, 739 m, 659 w, 590 w. Elemental analysis for C14H31N5O6Co (%) Calcd: C 38.72, H 7.14, N 16.13. Found: C, 39.27; H, 7.16; N, 16.60. Selected IR (cm1, KBr): 3475 s, 3224 m, 3204 m, 3118 m, 2957 m, 2872 w, 1635 vs 1590 vs 1471 w, 1384 s, 1265 m, 1202 m, 1159 m, 1113 m, 1045 m, 1000 m, 835 w, 749 m, 674 w, 511 w.
2.2. Materials and measurements All chemicals used were analytical reagent and were commercially purchased. IR spectra were obtained with a Bruker Tensor 27 FT-IR spectrometer using KBr pellets in the 4000–400 cm1 range. UV–vis spectra were obtained for the aqueous solution of the complex (103 M) with a Shimadzu UV-3150 spectrometer in the range 900–190 nm. Elemental analysis for C, H and N was car_ ried out at the TÜBITAK Marmara Research Centre. Magnetic susceptibility measurements at room temperature were performed using a Sherwood Scientific MXI model Gouy magnetic balance. Perkin Elmer Diamond TG/DTA thermal analyzer was used to record simultaneous TG, DTG and DTA curves in the static air atmosphere at a heating rate of 10 K min1 in the temperature range 30–1000 °C using platinum crucibles.
2.3. Crystallographic analyses Details of crystal structures are given in Table 1. Selected bond lengths, bond angles and the hydrogen bonds are listed in Table S1, S2 and S3, respectively. Data collection were performed on a STOE IPDS II image plate detector using MoKa radiation (k = 0.71019 Å). Intensity data were collected in the h range 1.3–27.89° at 293(2) K. Data collections: Stoe X-AREA [29]. Cell refinement: Stoe X-AREA [29]. Data reduction: Stoe X-RED [29]. The structures were solved by direct-methods and anisotropic displacement parameters were applied to non-hydrogen atoms in a full-matrix least-squares refinement based on F2 using SHELXL-97 [30]. Molecular drawings were obtained using Mercury program [31].
Table 1 The details of crystals and experimental data for 1, 2 and 3. Empirical formula Formula weight Temperature (K) Wavelength (Å) Crystal system Space group Unit cell dimensions a (Å) b (Å) c (Å) a (°) b (°) c (° V (Å3) Z l (mm1) Dcalc (Mg m3) h Range (°) Measured reflections Independent reflections Flack parameter [37] Absorption correction Refinement method Final R indices [I > 2r(I)] R[F2 > 2r(F2)] wR(F2) Goodness-of-fit on F2 Largest difference peak and hole (Å3)
C60H58N12O19Co2 1369.06 293(2) 0.71073 Triclinic P1
C24H56N8O17Co 787.69 293(2) 0.71073 Triclinic P1
C14H31N5O6Co 424.37 293(2) 0.71073 Orthorhombic Fdd2
14.7074(4) 15.0107(4) 17.4194(5) 71.202(2) 65.883(2) 61.810(2) 3053.48(15) 2 0.63 1.482 1.30–26.75 31344 11989
8.997(1) 14.736(1) 15.760(1) 67.210(6) 88.845(6) 88.553(6) 1925.4(3) 2 0.52 1.355 1.40–26.89 16601 7415
19.617(1) 32.596(2) 12.460(6) 90 90 90 7967.8(7) 16 0.90 1.415 1.62–27.89 13658 3898
– – Integration Full-matrix least-squares on F2 0.085 0.078
0.031
0.052 0.147 1.01 1.20; 0.47
0.077 0.086 1.03 0.34; 0.46
0.064 0.167 0.95 0.99; 0.72
0.041 (15)
2.4. Antimicrobial activities of the complexes The antimicrobial activities were tested against standard bacterial strains of Gram positive (Staphylococcus aureus ATCC6535, Bacillus cereus ATCC7064) and Gram negative (Escherichia coli W3110, Pseudomonas aeruginosa ATCC27853), one yeast (Candida albicans ATCC10231) and clinical isolates (Methicillin Resistant S. aureus, Proteus vulgaris, P. aeruginosa, Enterobacter aerogenes) (Faculty of Medicine, Ondokuz Mayıs University) by using minimal _ inhibitory concentration method (MIC). The complexes were dissolved in double distilled water at proper concentration. For the broth dilution method, cultures were grown in 5 ml nutrient broth (Merck) at 37 °C for 18 h in shaking at 175 rpm. Bacterial and yeast cells were suspended in 50 ml nutrient broth at a concentration of approximately 106 cells/ml by matching with 0.5 McFarland turbidity standards. Nutrient broth containing microorganisms were transferred 1 ml in test tubes and were added complexes, and made 2-fold serial dilution; eventually the ranges were narrowed to define more exact values. All the test cultures were grown at 37 °C in incubator. The incubation period was 24 h for bacterial strains and fungal strains. The minimum inhibitor concentration, at which no growth was observed, was taken as the MIC value (lg/ml), and represents the mean of at least three determinations. 3. Result and discussion 3.1. UV–vis spectra and magnetic susceptibilities of the complexes The [Co(pzdca)(phen)2]211H2O and (tmenH2)[Co(pzdca)2 (tmen)]9H2O complexes exhibit 5.71 and 4.28 BM magnetic moment values which corresponds to three unpaired electrons. The complexes are consistent with a weak field octahedral geometry as expected. The [Co(CO3)(dmpen)2](pzdca)0.5H2O exhibits diamagnetic property and a strong-field octahedral complex.
O.Z. Yesßilel et al. / Journal of Molecular Structure 964 (2010) 39–46
41
Fig. 1. The crystal structure of 1 showing the atom-numbering scheme (Hydrogen atoms are omitted for clarity).
All complexes exhibit mainly two maxima between 209 (e = 4516 Lmol1cm1) and 284 nm (e = 4817 Lmol1cm1) due to p ? p* and n ? p* intraligand transitions of pzdca and neutral ligands. The kmax values of the two absorption bands in the spectrum of 1 are 346 and 876 nm. These values were assigned to the following d–d transitions, 4T1g ? 4T1g (P) and 4T1g ? 4T2g, respectively. 4 T1g ? 4A2g transition was not observed which has high energy and shifts to the UV region and hidden under the intraligand transitions in the spectrum.
The UV–vis spectrum for 2 exhibits only one weak d–d absorption transition at 346 nm (e = 1126 Lmol1cm1). This value was assigned to 4T1g ? 4A2g. The 4T1g ? 4T1g (P) and 4T1g ? 4T2g transitions were not observed, which shift to the IR region. The complex [Co(CO3)(dmpen)2](pzdca)0.5H2O has a band around 521 nm (e = 54 Lmol1cm1), which is assignable to the 1 A1g ? 1T1g transition and suggests a distorted octahedral stereochemistry. The absorption spectra indicate that the cobalt(III) complex forms a stronger crystal field than the cobalt(II) compound.
Fig. 2. The pp and C–Hp interactions of 1 (Water molecules and hydrogen atoms are omitted for clarity).
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and 923 °C. The final decomposition product was identified by IR spectroscopy (the overall weight loss, found 89.25, calcd. 89.05%).
3.2. Thermal analyses 3.2.1. [Co(pzdca)(phen)2]211H2O The first endothermic stage (DTAmax = 82, 102 and 144 °C) in the temperature range of 43–156 °C, corresponds to the loss of eleven crystal water molecules (found 13.55, calcd. 14.46% Fig. S1). In the temperature range of 213–488 °C, the two stages of the Co(II) complex are related to the successively decomposition of the neutral phen ligands and decomposition of pzdca, by giving exothermic contribution (DTAmax = 275 and 431 °C). The solid product of the thermal decomposition, Co3O4, converts to CoO between 907
3.2.2. (H2tmen)[Co(pzdca)2(tmen)]9H2O The first stage is related to endothermic removal of crystal water molecules in the 58–122 °C temperature range (DTGmax = 87, 117 °C, mass loss found 19.39, calc. 20.57%). The second stage is related to the release of the one tmen molecule in the 145–214 °C temperature range (found 15.61, calcd. 15.01%). In the following successively stages, tmen and pzdca ligands are decomposed as an exothermic effect (DTAmax = 234 and 263 °C) and remain organ-
Fig. 3. The hydrogen bonding motif of the self-assembled infinite layer of water molecules in 1.
O.Z. Yesßilel et al. / Journal of Molecular Structure 964 (2010) 39–46
ic residue is burned as a strong exothermic effect (DTAmax = 397 °C). The decomposition product Co3O4 converts to CoO. The overall weight loss of 89.14% (calcd. 90.49%) agrees with the propose structure well (Fig. S2). 3.2.3. [Co(CO3)(dmpen)2](pzdca)0.5H2O The endothermic peak of DTA curve in the temperature range of 35–205 °C related to the loss of the crystal water molecule. The second stage between 197 and 258 °C corresponds to the release of one dmpen and carbonate ligands by giving an endothermic effect (DTGmax = 232 °C). The last strong exothermic stage involves the decomposition of the dmpen and pzdca ligands (DTAmax = 342 °C). In the endothermic stage (910–914 °C, DTAmax = 913 °C), the Co3O4 converts to CoO (found 81.63, calcd. 82.42%). 3.3. Crystal structures 3.3.1. [Co(pzdca)(phen)2]211H2O The asymmetric unit of 1 composed of two crystallographic independent [Co(pzdca)(phen)2] complexes and eleven lattice water molecules as shown in Fig. 1. Details of crystal structures are given in Table 1. The Co(II) ion is coordinated by nitrogen atom of pyrazine ring and deprotonated oxygen atom of carboxylate group from bidentate pzdca ligand and four nitrogen atoms from bidentate two phen ligands. The carboxylate oxygen (O1/O5) and the nitrogen atoms (N2, N3, N5/N8, N9, N11) comprise the equatorial plane, where as the axial position are filled by the nitrogen atoms of phen ligands (N1, N4/N7, N10). The deprotonated carbox-
43
ylate oxygen and pyrazine nitrogen atoms chelate to the Co(II) centre to form a five-membered chelate ring. The other carboxylate oxygen atoms do not participate in coordination. The Co1–N5, Co1–O1 and Co2–N11, Co2-O5 bond distances are 2.147(3), 2.025(2) and 2.151(3), 2.021(2) Å, respectively. The discrepancy between the carboxylate C29–O1 and C29–O2 (1.239 and 1.201 Å) or C59–O5, C59–O6 (1.271 and 1.215 Å) distances reflect the coordination. The phen and pzdca ligands are essentially planar. The dihedral angles between the pzdca and phen ligands are 89.88° and 82.40° in Co1 and 67.19° and 83.24° in Co2. The dihedral angles between the two phen molecules are 79.24° and 87.30°, respectively. Furthermore, the dihedral angles between the pzdca ligand and carboxyl groups are 16.08°, 77.20° and 12.44°, 84.39°, respectively. There are inter-molecular hydrogen-bonding interactions and pp stacking interactions between the phen ligands of neighbouring layers, with distances between the aromatic rings ranging from 3.503 to 3.950 Å. Furthermore, there is also weak C–Hp interactions between the C(9)–H(9) and phen ring (Fig. 2). Moreover, the complex 1 contains extensive hydrogen bonding between crystal water molecules to form infinite 2D water layers (Fig. 3). These 2D layers interact each other though water bridges by strong hydrogen bonds to forming a zig-zag chain along the b-axis (Fig. 3) All of these inter-molecular interactions give a two-dimensional network.
3.3.2. (H2tmen)[Co(pzdca)2(tmen)]9H2O The crystallographic analysis revealed that the complex consists of discrete [Co(pzdca)2(tmen)]2 anion, bis(protonated) H2tmen2+
Fig. 4. The crystal structure of 2 showing the atom-numbering scheme (Hydrogen atoms are omitted for clarity).
Fig. 5. The pp interactions of 2 (Water molecules, hydrogen atoms and H2tmen cation are omitted for clarity).
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cation and nine crystal water molecules (Fig. 4). One of the interesting features of the structure is that the tmen molecules exhibit chemically different functions. While, in one form, it coordinates to Co(II) ion as a bidentate ligand, in the other form it act as a counter-ion. In addition, there are two pzdca ligands coordinated to Co(II) ion as a cis position. Although, there are many metal complexes of pyrazine-2,3-dicarboxylate ligand with transition metal ions, until now, this type behaviour complexes has not been reported. Co1 adopts a distorted octahedral geometry and coordinated by two pzdca ligands and one tmen ligand. The pzdca ligands coordinated to the Co(II) ion through the N atom of pyrazine ring and the O atom of carboxyl group, creating a chelate ring, while tmen ligand coordinated to the Co(II) ion via N atoms as a bidentate ligand. Two nitrogen atoms (N2, N4) from the pyrazine ring and two nitrogen atoms (N5 and N6) from tmen ligand comprise the equatorial plane, while two oxygen atom (O1 and O5) from the carboxylate group occupy the axial positions [O1–Co1– O5 = 163.79(11)°]. The Co1–N5 and Co1–N6 bond distances of 2.174(3) and 2.187(3) Å, respectively, are similar that found in the [Ni(acac)2 (tmen)] (2.152(2), 2.166(2) Å) [32]. The Co1–N2/N4 and Co1–O1/ O5 bond distances are 2.151(3), 2.151(3), 2.063(3) and 2.076(3) Å, respectively. The angles of N2–Co1–O1 [77.27(11)°] and N4–Co1–O5 [77.04(11)°] are nearly equal. The pzdca ligands are essentially planar with r.m.s. deviation 0.0056 (C2) and 0.0069 Å (C7) and the dihedral angle between the pzdca ligands is 81.56°. Furthermore, the dihedral angles between the pzdca ligand and uncoordinated carboxyl groups are 88.66° and 79.15°. The carboxylate C–O distances in the pzdca ligands also display some variability, depending on their environment. The crystal packing is mainly stabilized by hydrogen bonds. The H2tmen cation is involved in intra- and inter-molecular hydrogen bonding with the carbonyl oxygen atoms (O3 and O7). There are also pp interactions [3.833 Å] between the CgA–CgAi rings (CgA: N1– C1–C2–C3–C4–N4, i: 1 x, 1 y, 1 z) and [3.736 Å] between the CgB–CgBii rings (CgB: N3–C7–C8–C9–C10–N4, ii: 1 x, 2 y, z). Some of these interactions are illustrated in Fig. 5. Furthermore, the complex 2 contains extensive hydrogen bonding between crystal water molecules to form infinite 1D water chains containing cyclic water cluster and generate T 4(2)7(2)6(2) motif (Fig. 6) [33].
Fig. 7. The crystal structure of 3 showing the atom-numbering scheme (Hydrogen atoms is omitted for clarity).
positions are occupied by atoms N1 and N3. The equatorial plane and pzdca ligand are approximately planar. The dihedral angle between the pyrazine ring and carboxyl group is 49.18°. The crystal packing is stabilized by intra and inter-molecular hydrogen bonding between the dmpen ligand and pzdca anion. Each pzdca anion is surrounded by four centrosymmetric [Co (CO3)(dmpen)2]2+ cations (Fig. 8). Two cations are connected by a hydrogen bond interaction between the amine groups (N1, N2 and N3) of dmpen and O4, O5 of the pzdca anion [N1O4 = 2.910(3), N2O4 = 3.068(3), N2O4 = 3.068(3) and N2O5 = 3.024 (4) Å] and also carboxyl group O(5) and crystal water molecules (O6) [O5O6 = 2.926 Å], while there are inter-molecular hydrogen bonds between NH2 group (N4) of dmpen ligand and N atom of pzdca anion [N4N6 = 2.146 Å].
3.4. Antimicrobial activity studies 3.3.3. [Co(CO3)(dmpen)2](pzdca)0.5H2O A view of the molecule and its atom-numbering scheme are shown in Fig. 7 and selected bond lengths and bond angels are given in Table S1. The crystal structure consists of a complex cation, [Co(CO3)(dmpen)2]2+, and half pzdca anion. In the complex cation, the Co(III) ion exhibits a distorted octahedral coordination geometry and it is coordinated by four nitrogen atoms from two chelating dmpen ligands together with one bidentate carbonate ligand. The Co–N distances are different from each other and lie in a wide range [1.967(2)–2.322(3) Å]. The carbonate ligand is symmetrically coordinated to the Co(III) ion [Co–O1 = 1.918(2) Å, Co–O2 = 1.906(2) Å]. The angle N3–Co1–N1 (178.82(12)°) is virtually linear, whereas O1–Co1–N4 (165.35(10)°) and O2–Co1–N2 (168.65(10)°) deviate much from linearity. On this basis, atoms O1, O2, N2 and N4 can be chosen to form the basal plane of the octahedron, and the equatorial
At present study, in vitro potential antimicrobial activity of complexes were tested according to minimal inhibitory concentration method, are given in Table 2. As can clearly be seen from Table 2, complexes 2 and 3 were studied as much 5000 lg/ml, while MIC values of the complexes 2 and 3 were determined as higher than 5000 lg/ml at all microorganism used with exception P. aeruginosa (3250 lg/ml at complex 2), complex 1 is determined in range 1850–3000 lg/ml (Table 2). Complex 1 is more effect than complexes 2 and 3. Complexes exhibited antimicrobial activity at high concentrations against the bacteria, fungi and clinical isolate tested. Antimicrobial activities of complexes did not changed to be gram (+), gram () and eukaryot in point of effective dose. It is known that there are a disparity between procaryote (gram +, gram ) and eukaryote.
Fig. 6. The hydrogen bonding motif of the self-assembled infinite chain (T 4(2)7(2)6(2)) of water molecules in 2.
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Fig. 8. The hydrogen-bonding interactions for 3, shown as dashed lines (Water molecules and hydrogen atoms are omitted for clarity).
Table 2 Minimal inhibitory concentrations (MIC) values of the complexes against wild type and clinical microorganisms (lg/ml). Compound
1 2 3
Gram (+)
Gram ()
Eucaryote
Clinical isolate
S. aureus
B. cereus
E. coli
P. aeruginosa
C. albicans
MRSA
P. vulgaris
P. aeruginosa
E. aerogenes
2250 >5000 >5000
2000 >5000 >5000
2250 >5000 >5000
2000 3250 >5000
2250 >5000 >5000
2000 >5000 >5000
2000 >5000 >5000
2250 >5000 >5000
2250 >5000 >5000
But this difference not important for antimicrobial effect of complexes and did not seen a important difference between wild type and clinical isolate at antimicrobial activities of complexes. It is a well-known fact that hospital infections are quite important for the public healthy and quite resistant against standard antibiotics. Therefore, there is an urgent demand for new antibiotics and new classes chemical formula that will efficiently inhibit the growth of pathogenic microorganism. Tuberculosis still remains a serious health problem in many regions of the world, especially in developing nations. With the spread of AIDS and the increase in the number of immune compromised patients, the problem of tuberculosis has been greatly exacerbated because of the susceptibility of such patients to mycobacteria. Currently, chemotherapy using multiple drug regimens with isoniazid, rifampin, streptomycin, pyrazinamide, and ethambutol is the recommended treatment for tuberculosis. The presence of drug resistance is still a major concern and new generations of more effective antimycobacterial agents. It is reported that Pyrazine dicarboxylic acid derivatives is a candidate for Mycobacterium tuberculosis [34,35]. Furthermore, Premkumar and Govindarajan reported that the free acids and some new hydrazinium salts of 2-pyrazinecarboxylate,
2,3-pyrazinedicarboxylate, 3,5-pyrazoledicarboxylate and 4,5-imidazoledicarboxylate show more promising activity than the corresponding free acids and the standard positive control antibiotic (Co-trimoxazole) against E. coli, Salmonella typhii and Vibrio cholerae [36].
4. Conclusion We have synthesized and structurally characterized three novel cobalt-pyrazine-2,3-dicarboxylate complexes with 1,10-phenanthroline, N,N,N0 ,N0 -tetramethylethylenediamine and 2,2-dimethylpropane-1,3-diamine ligands. In the [Co(pzdca)(phen)2]211H2O and (H2tmen)[Co(pzdca)2(tmen)]9H2O complexes, the pzdca dianion acts as a bidentate ligand, its coordination sites being the carboxylate oxygen atom and nitrogen atom of pyrazine ring. The tmen molecule exhibits chemically different functions; in one form, it coordinates to Co(II) ion as a bidentate ligand, in the other form it act as a counter-ion. In the [Co(CO3)(dmpen)2] (pzdca)0.5H2O complex is the first example, the anionic pzdca exhibiting as a counter-ion.
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Acknowledgement This work was supported by the Eskisßehir Osmangazi University by Project No. 200819042. Appendix A. Supplementary data CCDC 675311, 675310 and 675309 contain the supplementary crystallographic data for 1, 2 and 3. These data can be obtained free of charge via http://www.ccdc.cam.ac.uk/conts/retrieving.html, or from the Cambridge Crystallographic Data Centre, 12 Union Road, Cambridge CB2 1EZ, UK; fax: +44 1223 336 033; or e-mail: [email protected]. Supplementary data associated with this article can be found, in the online version, at doi:10.1016/j.molstruc. 2009.10.048. References [1] O.Z. Yesßilel, A. Mutlu, O. Büyükgüngör, Polyhedron 27 (2008) 2471. [2] C.J. O’Connor, E. Sinn, Inorg. Chem. 20 (1981) 545. [3] M. Wenkin, M. Devillers, B. Tinant, J.P. Declercq, Inorg. Chim. Acta 258 (1997) 113. [4] M.S. Wang, L.Z. Cai, G.W. Zhou, G.C. Guo, J.G. Mao, J.S. Huang, Acta Crystallogr. E 59 (2003) m212. [5] O.Z. Yesßilel, A. Mutlu, O. Büyükgüngör, J. Coord. Chem. 61 (2008) 3267. [6] C.J. O’Connor, C.L. Klein, R.J. Majeste, L.M. Trefonas, Inorg. Chem. 21 (1982) 64. [7] H. Xu, H. Ma, M. Xu, W. Zhao, B. GuO, Acta Crystallogr. E 64 (2008) m104. [8] R. Burriel, C.J. O’Conner, R.L. Carlin, Inorg. Chem. 24 (1985) 3706. [9] T. Okubo, M. Kondo, S. Kitagawa, Synth. Met. 85 (1997) 1661. [10] H.D. Yin, F.H. Li, C.H. Wang, Inorg. Chim. Acta 360 (2007) 2797.
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