- Email: [email protected]
Crystal structures, DFT calculations and biological activities of three mercury complexes from a pentadentate thioether ligand
Inorganic Chemistry Communications 34 (2013) 4–7
Contents lists available at SciVerse ScienceDirect
Inorganic Chemistry Communications journal homepage: www.elsevier.com/locate/inoche
Crystal structures, DFT calculations and biological activities of three mercury complexes from a pentadentate thioether ligand Yu Li a, b, Jing-An Zhang b,⁎, Yi-Bo Wang b, Mei Pan c,⁎⁎, Cheng-Yong Su c a
Department of Chemical Engineering, Guangdong Industry Technical College, Guangzhou 510300, PR China School of Pharmacy/College of Traditional Chinese Medicine, Guangdong Pharmaceutical University, Guangzhou 510006, PR China MOE Laboratory of Bioinorganic and Synthetic Chemistry/KLGHEI of Environment and Energy Chemistry, State Key Laboratory of Optoelectronic Materials and Technologies, Chemistry and Chemical Engineering College, Sun Yat-Sen University, Guangzhou 510275, PR China
b c
a r t i c l e
i n f o
Article history: Received 18 March 2013 Accepted 16 April 2013 Available online 29 April 2013 Keywords: Mercury complexes 2, 6-Bis (8-quinolinylthiomethyl) pyridine DFT calculation Antibacterial and antifungal activities
a b s t r a c t Three mercury complexes from a symmetric pentadentate ligand 2, 6-bis (8-quinolinyl thiomethyl) pyridine (L) have been prepared by the method of diffusing of diethyl ether or diisopropyl ether. The structures of the complexes have been identified by elemental analysis (EA), infrared spectra (IR) and single-crystal diffraction, and are composed of discrete mononuclear units in complexes 1 and 2 and binuclear units in complex 3. Especially, the valence of Hg in complex 3 is reduced to −1 in-situ during self-assembly and Hg\Hg σ bond is formed, which is further evidenced by the frontier orbital and natural bond orbital (NBO) properties calculated by DFT method. The antibacterial and antifungal activities of the ligand and the three complexes were also determined, which prove foundation information for research and application in pharmaceutical chemicals. © 2013 Elsevier B.V. All rights reserved.
In the past decades, close attention has been paid to flexible thioether ligands and their complexes containing mercaptoquinolinyl terminal groups which have potential applications in biological recognition, electrochemistry and functional materials [1–3]. Tavacoli, Chen, Su and Oh et al. have reported a series of transition metal complexes with symmetric or asymmetric thioether ligands containing quinolinyl groups [4–11]. Reports on the bioactivities of these kinds of complexes have also increased in recent years, and they show considerable antibacterial, antifungal and pesticide activities [12–15]. As a continued work of symmetric pentadentate ligand and its complexes, we synthesized a dithioether ligand, 2, 6-bis (8quinolinylthiomethyl) pyridine (L) (Chart 1) [15], which contains symmetrical quinolinyl terminal groups. We report herein the syntheses and structures of its three mercury complexes [16]. The antibacterial and antifungal activities of the ligand and its complexes have been tested [17], which prove foundation information for research and application in pharmaceutical chemicals. The crystallographic data and structure refinement summary for complexes 1–3 are listed in Table 1. In complex 1, the Hg(II) atom is five-coordinated in a distorted square pyramidal geometry with two S atoms and one N atom from one ligand and two Cl− ions (Fig. 1). The Hg(1)\N(1), Hg(1)\S(1) and Hg(1)\S(2) distances are 2.485(4), 3.031(1) and 2.825(1) Å, respectively. The Hg(1)\Cl −(1) and ⁎ Corresponding author. ⁎⁎ Corresponding author. Tel.: +86 20 84115178. E-mail addresses: [email protected] (J.-A. Zhang), [email protected] (M. Pan). 1387-7003/$ – see front matter © 2013 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.inoche.2013.04.028
Hg(1)\Cl−(2) distances are 2.377(1) and 2.375(1) Å. The N(2) atom and N(3) atom in quinoline ring are not coordinated with Hg(1). The mononuclear units are connected by strong π–π interaction between quinoline rings (3.577 Å), generating 1D supramolecular chain extending along c direction (Fig. S1a). Such a 1D chain is further jointed by various weak hydrogen bonds to form a 3D supramolecular framework (Fig. S1b). Complex 2 has a structural unit consisting of one Hg (II), one ligand and two ClO4− anions. Each Hg (II) atom is five-coordinated by three nitrogen atoms and two sulfur atoms from L ligand (Fig. 2). Different from that in 1, the N atoms on quinoline ring are involved in coordination. The difference may be due to that the coordination sites on Hg(II) ion in 1 are occupied by the soft Cl− rather than the hard N atoms. The ClO4− anions remained uncoordinated, but form weak interactions to the Hg(II) ion (Hg⋯O distance, 2.870 and 3.178 Å). The Hg(1)\N(2), Hg(1)\N(1) and Hg(1)\N(3) bond lengths are 2.410(4), 2.373(4) and 2.208(3) Å, respectively. The Hg(1)\S(1) and Hg(1)\S(2) distances are 2.589(1) and 2.766(1) Å, respectively, which are much shorter than those in 1, and the bond angles of N(1)\Hg(1)\N(2), N(3)\Hg(1)\N(2) and N(3)\Hg(1)\N(1) are 94.9(2), 128.5(1) and 128.2(1)°, respectively. The bond angle of S(1)\Hg(1)\S(2) is 148.4(4)°, which is larger than that in 1 (140.7(4)°), and these may be generated by the steric hindrance. The π–π interactions between quinoline ring and pyridyl ring (3.83 Å) link the mononuclear units into a 1D chain extending along b direction (Fig. S2a), and the 1D chains are further packing into a 3D supramolecular framework via diverse weak interactions (Fig. S2b). The unit structure of complex 3 consists of two metal ions and two ligands. Different from complexes 1 and 2, complex 3 is a double core
Y. Li et al. / Inorganic Chemistry Communications 34 (2013) 4–7
N S
5
N
N
S
Chart 1. Structure of 2, 6-bis (8-quinolinylthiomethyl) pyridine (L).
structure consisting of a binuclear [Hg2(L)2] 2+ cation and two ClO4− anions and one water. Each mercury center is coordinated to two nitrogen atoms and one sulfur atom from L ligand. Furthermore, two such metal centers are connected by Hg\Hg bond (2.532 Å) to generate a binuclear cation. Interestingly, the valence state of each Hg in complex 3 is reduced to − 1 by the reductive activity of the thioether ligand in-situ. In addition, the other nitrogen atom and sulfur atom in the ligands do not participate in coordination (Fig. 3). The bridged Hg(1)\Hg(2) distance is 2.607(5) Å, suggesting the formation of σ bond between them. In contrast to complexes 1 and 2, there are no intermolecular π–π interactions in complex 3, however, intramolecular π–π interaction between two quinoline rings from two different ligands are observed. No significant strong interactions between the binuclear units are found in complex 3. The binuclear units and ClO4− anions are packing into a 3D framework via various weak interactions (Fig. S3). The calculated frontier molecular orbitals of the three complexes show different contours (Fig. 4). Although both complexes 1 and 2 have mononuclear configuration, the HOMO orbital of the former has a large
Table 1 Crystallographic data and structure refinement summary for complexes 1–3.
Empirical formula Fw Crystal system Space group a/Å b/Å c/Å α/° β/° γ/° V/Å3 Z ρ calc/mg mm−3 μ (Mo–Kα)/mm−1 Reflections collected R1, [I > 2σ(I)] wR2 [I > 2σ(I)] R1 [all data] wR2 [all data]
1
2
3
C25H19Cl2HgN3S2 697.04 Orthorhombic P212121 8.7143(6) 11.3589(7) 23.473 90 90 90 2323.5(3) 4 1.993 7.055 12,760 0.0232 0.0557 0.0242 0.0562
C25H19Cl2HgN3S2 825.04 Triclinic P-1 7.886(2) 9.231(3) 19.263(6) 86.239(5) 86.353(5) 84.678(5) 1390.9(7) 2 1.970 5.930 11,828 0.0304 0.0774 0.0397 0.0833
C50H40Cl2Hg2N6O9S4 1469.2 Orthorhombic P212121 13.492(4) 14.668(4) 25.940(7) 90 90 90 5134(4) 4 1.901 6.303 30,637 0.0308 0.0622 0.0594 0.0727
Fig. 1. The coordination environment of Hg (II) atom in 1 (H atoms are omitted).
Fig. 2. The molecular structure of 2 (H atoms are omitted).
part of contribution from Hg(II) center, while that of complex 2 has barely any contribution from Hg(II). This may be due to the fact that the coordination of Cl − or N with very different electronegativity in the two complexes affords different charge distribution on the two Hg(II) centers, respectively. The HOMO orbital of complex 3 is mainly contributed by Hg\Hg bimetallic center, as well as uncoordinated S atoms and quinolinyl rings. From NBO analyses, there is a σ-bonding orbital between the two Hg(I) centers, described as 0.7072s0.87p 0.13Hg1 + 0.7070s0.85p0.15Hg2, as well as a σ-antibonding orbital, described as 0.7070s0.87p 0.13Hg1 − 0.7072s0.85p0.15Hg2. From the antibacterial results listed in Table 2, we can see that the ligand and its complexes show different inhibition activities against various kinds of bacteria. The ligand has good efficiency in inhibiting Pseudomonas aeruginosa (MIC value is 3.13 μg/mL), and poor against Staphylococcus aureus, Escherichia coli and Sarcina ureae (MIC values are over 50 μg/mL). Among the complexes, most of them appear to be poor against both the bacteria with G + (S. aureus and S. ureae) and those with G − (P. aeruginosa and E. coli) (MIC values are over 50 μg/mL). While complex 2 appears to be better than others against S. aureus, showing potential MIC value (25 μg/mL). The antifungal activities of the ligand and its three complexes show that all of them have poor effect against the three fungals (MIC > 125 μg/mL). In conclusion, three mercury complexes from a symmetric thioether ligand have been prepared and characterized, and they have been shown to have discrete or connected binuclear sub-units, which are also reflected in their frontier orbitals and NBOs as calculated by DFT methods. Different kinds of intermolecular interactions,
Fig. 3. The molecular structure of 3 (H atoms, anions and water are omitted).
6
Y. Li et al. / Inorganic Chemistry Communications 34 (2013) 4–7
HOMO
LUMO
Complex 1
-0.002
-0.016
Complex 2
-0.456
-0.288
Complex 3
-0.366
-0.242
Fig. 4. The contours of frontier orbitals of complexes 1–3 calculated by DFT method.
Table 2 Tests of MIC (μg/mL) of the compounds against four bacteria and three fungal strains.a Compounds
L 1 2 3 Ampb Strb Nysb a b
Strains Staphylococcus aureus ATCC 27,154 (G+)
Escherichia coli ATCC 25,922 (G−)
P. aeruginosa (G−)
Sarcina ureae (G+)
Aspergillus niger
Saccharomyces cerevisiae
Fusarium oxysporum f. sp. cubense
>50 >50 25 >50 12.5 1.56 NT
>50 >50 >50 >50 6.25 3.13 NT
3.13 >50 >50 >50 3.13 1.56 NT
>50 >50 >50 >50 3.13 3.13 NT
>125 >125 >125 >125 NT NT 3.9
>125 >125 >125 >125 NT NT 3.9
>125 >125 >125 >125 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.
such as H-bonds, π–π interactions, extend the structures into higher dimensions. The antibacterial activity tests show that complex 2 appears to be effective against S. aureus.
Acknowledgments The authors gratefully acknowledge the Guangdong Province Universities and Colleges High Level Talent Project (2011QY01), the Natural Science Foundation of Guangdong Industry Technical College (KJ201007) and the Education Reform Project of Guangdong Industry Technical College (JG201004) for financial support.
Appendix A. Supplementary material Supplementary data to this article can be found online at http:// dx.doi.org/10.1016/j.inoche.2013.04.028.
References [1] S. Liao, C.Y. Su, H.X. Shi, J.L. Zhang, Z.Y. Zhou, H.Q. Liu, A.S.C. Chan, B.S. Kang, Helical complexes from the self-assembly of silver salts and the polydentate thioether a, a?-bis(8-thioquinoline)-m-xylene, Inorg. Chim. Acta 336 (2002) 151–156. [2] C.L. Chen, C.Y. Su, Y.P. Cai, H.X. Zhang, A.W. Xu, B.S. Kang, H.C. Zur Loye, Multidimensional frameworks assembled from silver(I) coordination polymers
Y. Li et al. / Inorganic Chemistry Communications 34 (2013) 4–7
[3]
[4]
[5]
[6]
[7] [8]
[9]
[10]
[11]
[12]
[13]
[14]
containing flexible bis(thioquinolyl) ligands: role of the intra- and intermolecular aromatic stacking interactions, Inorg. Chem. 42 (2003) 3738–3750. C.L. Chen, Z.Q. Yu, Q. Zhang, M. Pan, J.Y. Zhang, C.Y. Zhao, C.Y. Su, Formation of disilver(I) metallacycle and 1D polymeric chain from the same mononuclear building block: assembly mechanism upon crystallization, Cryst. Growth Des. 8 (3) (2008) 897–905. S. Tavacoli, T.A. Miller, R.L. Paul, J.C. Jeffery, M.D. Ward, Synthesis and coordination chemistry of tetradentate ligands containing two bidentate thioquinoline units: mononuclear complexes with Cu(I) and Cu(II), and a coordination polymer with Cu(I), Polyhedron 22 (4) (2003) 507–514. C.L. Chen, C.Y. Su, Y.P. Cai, H.X. Zhang, A.W. Xu, B.S. Kang, A noninterpenetrating 2D coordination polymer from spacer (CH2)8 based highly flexible linear ligand and AgCF3CO2, New J. Chem. 27 (2003) 790–792. C.Y. Su, S. Liao, M. Wanner, J. Fiedler, C. Zhang, B.S. Kang, W. Kaim, The copper(I)/copper(II) transition in complexes with 8-alkylthioquinoline based multidentate ligands, Dalton Trans. 2 (2003) 189–202. M. Oh, C.L. Stern, C.A. Mirkin, Coordination polymers with macrocyclic cages and pockets within their backbones, Chem. Commun. 23 (2004) 2684–2685. R.F. Song, Y.B. Xie, J.R. Li, X.H. Bu, Syntheses and crystal structures of the copper(I) complexes with quinoline-based monothioether ligands, CrystEngComm 7 (2005) 249–254. S. Bhattacharyya, D.F. Dye, M. Pink, J.M. Zaleski, A geometric switching approach toward thermal activation of metalloenediynes, Chem. Commun. 42 (2005) 5295–5297. L. Canovese, F. Visentin, G. Chessa, C. Santo, P. Uguagliati, Novel heteropolymetallic derivatives of palladium bearing pyridylthioether fragments incorporating a Fe2(CO)6 cluster core as ligand, Inorg. Chem. Commun. 8 (2005) 1120–1124. L. Canovese, F. Visentin, G. Chessa, C. Levi, A. Dolmella, Synthesis, stability constant determination, and structural study of some complexes of a zinc triad containing pyridyl-amine-quinoline and pyridyl-thio-quinoline, Eur. J. Inorg. Chem. 23 (2007) 3669–3680. J.A. Zhang, M. Pan, J.Y. Zhang, B.S. Kang, C.Y. Su, Syntheses, structures and bioactivities of cadmium(II) complexes with a tridentate heterocyclic N- and S-ligand, Inorg. Chim. Acta 162 (2009) 3519–3525. J.A. Zhang, M. Pan, J.Y. Zhang, H.K. Zhang, Z.J. Fan, B.S. Kang, C.Y. Su, Syntheses, structures and bioactivities of silver(I) complexes with a tridentate heterocyclic N- and S-ligand, Polyhedron 28 (1) (2009) 145–149. J.A. Zhang, M. Pan, R. Yang, Z.G. She, W. Kaim, Z.J. Fan, C.Y. Su, Structure, biological and electrochemical studies of transition metal complexes from N, S, N′ donor ligand 8-(2-pyridinylmethylthio)quinoline, Polyhedron 29 (2010) 581–591.
7
[15] J.A. Zhang, M. Pan, J.J. Jiang, Z.G. She, Z.J. Fan, C.Y. Su, Syntheses, crystal structures and antimicrobial activities of thioether ligands containing quinoline and pyridine terminal groups and their transition metal complexes, Inorg. Chim. Acta 374 (2011) 269–277. [16] Syntheses of the complexes: Complex 1 ([Hg(L1)Cl2]): 2, 6-Bis [(8quinolinylthio) methyl] pyridine (L) (26 mg, 0.060 mmol) was dissolved in chloroform (3 mL), then HgCl2 (16 mg, 0.060 mmol) in acetonitrile (2 mL) was added into the above solution and mixed. The obtained solution was stirred for 10 min in room temperature and filtrated into a tube slowly, and slow diffusion of diethyl ether into the filtrate gave colorless crystals of 1 after several days. The crystals were filtered and washed several times in anhydrous diethyl ether and then dried in vacuum. Yield was 64% (27 mg). Anal. Calcd. for C25H19Cl2HgN3S2: calcd. C, 43.08; H, 2.75; N, 6.03; found: C, 42.88; H, 2.87, N, 6.07. IR (KBr pellet, cm−1): 3031(w), 2926(w), 1588(m), 1569(m), 1489(m), 1449(s), 1416(m), 1379(m), 1303(w), 1211(w), 1090(w), 1069(w), 1003(m), 982(m), 821(m), 784(s), 760(m), 657(m). Complex 2 ([Hg(L1)] · (ClO4)2): 2, 6-Bis [(8-quinolinylthio) methyl] pyridine (L) (43 mg, 0.10 mmol) was dissolved in chloroform (2 mL), then Hg(ClO4)2 · 3H2O(16 mg, 0.060 mmol) in acetonitrile (2 mL) was added into the above solution and mixed. The obtained solution was stirred for 30 min in room temperature and filtrated into a tube slowly, and slow diffusion of isopropyl ether into the filtrate gave colorless crystals of 2 after several days. The crystals were filtered and washed several times in anhydrous diethyl ether and then dried in vacuum. Yield was 65% (27 mg). Anal. Calcd. for C25H19Cl2HgN3O8S2: calcd. C, 36.39; H, 2.32; N, 5.093; found:C, 36.58; H, 2.341; N, 5.164. IR (KBr pellet, cm−1): 3057(w), 2995(w), 2928(w), 1587(m), 1492(m), 1454(m), 1376(m), 1302(w), 1207(m), 1091(vs), 987(m), 825(m), 781(m), 626(m). Complex 3 ([Hg2(L1)2](ClO4)2 · H2O) was synthesized as complex 2 except that 2, 6-bis(8-quinolinyl methylthio) pyridine (L) (22 mg, 0.050 mmol) was dissolved in chloroform (3 mL) and Hg(ClO4)2⋅3H2O (23 mg, 0.050 mmol) in anhydrous acetonitrile (2 mL). Yield was 75% (55 mg). Anal. Calcd. for C50H40Cl2Hg2N6O9S4: calcd. C, 40.87; H, 2.74; N, 5.72; found: C, 40.81; H, 2.87; N, 6.01. IR (KBr pellet, cm−1): 3444(w), 3074(w), 3004(w), 2928(w), 1586(m), 1497(m), 1455(m), 1379(m), 1308(w), 1208(w), 1098(vs), 886(w), 831(m), 774(m), 677(w), 622(m), 451(w). [17] The complexes were dissolved in DMSO (dimethyl sulphoxide) and tested against four bacteria and three fungal strains for their inhibitory activities. Antimicrobial assays were performed using a modified version of the 2-fold serial dilution method as R.A. Fromtling (1993), in which two starting yeast inoculum sizes (5 × 10(4) and 2.5 × 10(3) cells per ml) were compared, and readings were taken after 24 and 48 h of incubation. All other test conditions were standardized.
Contents lists available at SciVerse ScienceDirect
Inorganic Chemistry Communications journal homepage: www.elsevier.com/locate/inoche
Crystal structures, DFT calculations and biological activities of three mercury complexes from a pentadentate thioether ligand Yu Li a, b, Jing-An Zhang b,⁎, Yi-Bo Wang b, Mei Pan c,⁎⁎, Cheng-Yong Su c a
Department of Chemical Engineering, Guangdong Industry Technical College, Guangzhou 510300, PR China School of Pharmacy/College of Traditional Chinese Medicine, Guangdong Pharmaceutical University, Guangzhou 510006, PR China MOE Laboratory of Bioinorganic and Synthetic Chemistry/KLGHEI of Environment and Energy Chemistry, State Key Laboratory of Optoelectronic Materials and Technologies, Chemistry and Chemical Engineering College, Sun Yat-Sen University, Guangzhou 510275, PR China
b c
a r t i c l e
i n f o
Article history: Received 18 March 2013 Accepted 16 April 2013 Available online 29 April 2013 Keywords: Mercury complexes 2, 6-Bis (8-quinolinylthiomethyl) pyridine DFT calculation Antibacterial and antifungal activities
a b s t r a c t Three mercury complexes from a symmetric pentadentate ligand 2, 6-bis (8-quinolinyl thiomethyl) pyridine (L) have been prepared by the method of diffusing of diethyl ether or diisopropyl ether. The structures of the complexes have been identified by elemental analysis (EA), infrared spectra (IR) and single-crystal diffraction, and are composed of discrete mononuclear units in complexes 1 and 2 and binuclear units in complex 3. Especially, the valence of Hg in complex 3 is reduced to −1 in-situ during self-assembly and Hg\Hg σ bond is formed, which is further evidenced by the frontier orbital and natural bond orbital (NBO) properties calculated by DFT method. The antibacterial and antifungal activities of the ligand and the three complexes were also determined, which prove foundation information for research and application in pharmaceutical chemicals. © 2013 Elsevier B.V. All rights reserved.
In the past decades, close attention has been paid to flexible thioether ligands and their complexes containing mercaptoquinolinyl terminal groups which have potential applications in biological recognition, electrochemistry and functional materials [1–3]. Tavacoli, Chen, Su and Oh et al. have reported a series of transition metal complexes with symmetric or asymmetric thioether ligands containing quinolinyl groups [4–11]. Reports on the bioactivities of these kinds of complexes have also increased in recent years, and they show considerable antibacterial, antifungal and pesticide activities [12–15]. As a continued work of symmetric pentadentate ligand and its complexes, we synthesized a dithioether ligand, 2, 6-bis (8quinolinylthiomethyl) pyridine (L) (Chart 1) [15], which contains symmetrical quinolinyl terminal groups. We report herein the syntheses and structures of its three mercury complexes [16]. The antibacterial and antifungal activities of the ligand and its complexes have been tested [17], which prove foundation information for research and application in pharmaceutical chemicals. The crystallographic data and structure refinement summary for complexes 1–3 are listed in Table 1. In complex 1, the Hg(II) atom is five-coordinated in a distorted square pyramidal geometry with two S atoms and one N atom from one ligand and two Cl− ions (Fig. 1). The Hg(1)\N(1), Hg(1)\S(1) and Hg(1)\S(2) distances are 2.485(4), 3.031(1) and 2.825(1) Å, respectively. The Hg(1)\Cl −(1) and ⁎ Corresponding author. ⁎⁎ Corresponding author. Tel.: +86 20 84115178. E-mail addresses: [email protected] (J.-A. Zhang), [email protected] (M. Pan). 1387-7003/$ – see front matter © 2013 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.inoche.2013.04.028
Hg(1)\Cl−(2) distances are 2.377(1) and 2.375(1) Å. The N(2) atom and N(3) atom in quinoline ring are not coordinated with Hg(1). The mononuclear units are connected by strong π–π interaction between quinoline rings (3.577 Å), generating 1D supramolecular chain extending along c direction (Fig. S1a). Such a 1D chain is further jointed by various weak hydrogen bonds to form a 3D supramolecular framework (Fig. S1b). Complex 2 has a structural unit consisting of one Hg (II), one ligand and two ClO4− anions. Each Hg (II) atom is five-coordinated by three nitrogen atoms and two sulfur atoms from L ligand (Fig. 2). Different from that in 1, the N atoms on quinoline ring are involved in coordination. The difference may be due to that the coordination sites on Hg(II) ion in 1 are occupied by the soft Cl− rather than the hard N atoms. The ClO4− anions remained uncoordinated, but form weak interactions to the Hg(II) ion (Hg⋯O distance, 2.870 and 3.178 Å). The Hg(1)\N(2), Hg(1)\N(1) and Hg(1)\N(3) bond lengths are 2.410(4), 2.373(4) and 2.208(3) Å, respectively. The Hg(1)\S(1) and Hg(1)\S(2) distances are 2.589(1) and 2.766(1) Å, respectively, which are much shorter than those in 1, and the bond angles of N(1)\Hg(1)\N(2), N(3)\Hg(1)\N(2) and N(3)\Hg(1)\N(1) are 94.9(2), 128.5(1) and 128.2(1)°, respectively. The bond angle of S(1)\Hg(1)\S(2) is 148.4(4)°, which is larger than that in 1 (140.7(4)°), and these may be generated by the steric hindrance. The π–π interactions between quinoline ring and pyridyl ring (3.83 Å) link the mononuclear units into a 1D chain extending along b direction (Fig. S2a), and the 1D chains are further packing into a 3D supramolecular framework via diverse weak interactions (Fig. S2b). The unit structure of complex 3 consists of two metal ions and two ligands. Different from complexes 1 and 2, complex 3 is a double core
Y. Li et al. / Inorganic Chemistry Communications 34 (2013) 4–7
N S
5
N
N
S
Chart 1. Structure of 2, 6-bis (8-quinolinylthiomethyl) pyridine (L).
structure consisting of a binuclear [Hg2(L)2] 2+ cation and two ClO4− anions and one water. Each mercury center is coordinated to two nitrogen atoms and one sulfur atom from L ligand. Furthermore, two such metal centers are connected by Hg\Hg bond (2.532 Å) to generate a binuclear cation. Interestingly, the valence state of each Hg in complex 3 is reduced to − 1 by the reductive activity of the thioether ligand in-situ. In addition, the other nitrogen atom and sulfur atom in the ligands do not participate in coordination (Fig. 3). The bridged Hg(1)\Hg(2) distance is 2.607(5) Å, suggesting the formation of σ bond between them. In contrast to complexes 1 and 2, there are no intermolecular π–π interactions in complex 3, however, intramolecular π–π interaction between two quinoline rings from two different ligands are observed. No significant strong interactions between the binuclear units are found in complex 3. The binuclear units and ClO4− anions are packing into a 3D framework via various weak interactions (Fig. S3). The calculated frontier molecular orbitals of the three complexes show different contours (Fig. 4). Although both complexes 1 and 2 have mononuclear configuration, the HOMO orbital of the former has a large
Table 1 Crystallographic data and structure refinement summary for complexes 1–3.
Empirical formula Fw Crystal system Space group a/Å b/Å c/Å α/° β/° γ/° V/Å3 Z ρ calc/mg mm−3 μ (Mo–Kα)/mm−1 Reflections collected R1, [I > 2σ(I)] wR2 [I > 2σ(I)] R1 [all data] wR2 [all data]
1
2
3
C25H19Cl2HgN3S2 697.04 Orthorhombic P212121 8.7143(6) 11.3589(7) 23.473 90 90 90 2323.5(3) 4 1.993 7.055 12,760 0.0232 0.0557 0.0242 0.0562
C25H19Cl2HgN3S2 825.04 Triclinic P-1 7.886(2) 9.231(3) 19.263(6) 86.239(5) 86.353(5) 84.678(5) 1390.9(7) 2 1.970 5.930 11,828 0.0304 0.0774 0.0397 0.0833
C50H40Cl2Hg2N6O9S4 1469.2 Orthorhombic P212121 13.492(4) 14.668(4) 25.940(7) 90 90 90 5134(4) 4 1.901 6.303 30,637 0.0308 0.0622 0.0594 0.0727
Fig. 1. The coordination environment of Hg (II) atom in 1 (H atoms are omitted).
Fig. 2. The molecular structure of 2 (H atoms are omitted).
part of contribution from Hg(II) center, while that of complex 2 has barely any contribution from Hg(II). This may be due to the fact that the coordination of Cl − or N with very different electronegativity in the two complexes affords different charge distribution on the two Hg(II) centers, respectively. The HOMO orbital of complex 3 is mainly contributed by Hg\Hg bimetallic center, as well as uncoordinated S atoms and quinolinyl rings. From NBO analyses, there is a σ-bonding orbital between the two Hg(I) centers, described as 0.7072s0.87p 0.13Hg1 + 0.7070s0.85p0.15Hg2, as well as a σ-antibonding orbital, described as 0.7070s0.87p 0.13Hg1 − 0.7072s0.85p0.15Hg2. From the antibacterial results listed in Table 2, we can see that the ligand and its complexes show different inhibition activities against various kinds of bacteria. The ligand has good efficiency in inhibiting Pseudomonas aeruginosa (MIC value is 3.13 μg/mL), and poor against Staphylococcus aureus, Escherichia coli and Sarcina ureae (MIC values are over 50 μg/mL). Among the complexes, most of them appear to be poor against both the bacteria with G + (S. aureus and S. ureae) and those with G − (P. aeruginosa and E. coli) (MIC values are over 50 μg/mL). While complex 2 appears to be better than others against S. aureus, showing potential MIC value (25 μg/mL). The antifungal activities of the ligand and its three complexes show that all of them have poor effect against the three fungals (MIC > 125 μg/mL). In conclusion, three mercury complexes from a symmetric thioether ligand have been prepared and characterized, and they have been shown to have discrete or connected binuclear sub-units, which are also reflected in their frontier orbitals and NBOs as calculated by DFT methods. Different kinds of intermolecular interactions,
Fig. 3. The molecular structure of 3 (H atoms, anions and water are omitted).
6
Y. Li et al. / Inorganic Chemistry Communications 34 (2013) 4–7
HOMO
LUMO
Complex 1
-0.002
-0.016
Complex 2
-0.456
-0.288
Complex 3
-0.366
-0.242
Fig. 4. The contours of frontier orbitals of complexes 1–3 calculated by DFT method.
Table 2 Tests of MIC (μg/mL) of the compounds against four bacteria and three fungal strains.a Compounds
L 1 2 3 Ampb Strb Nysb a b
Strains Staphylococcus aureus ATCC 27,154 (G+)
Escherichia coli ATCC 25,922 (G−)
P. aeruginosa (G−)
Sarcina ureae (G+)
Aspergillus niger
Saccharomyces cerevisiae
Fusarium oxysporum f. sp. cubense
>50 >50 25 >50 12.5 1.56 NT
>50 >50 >50 >50 6.25 3.13 NT
3.13 >50 >50 >50 3.13 1.56 NT
>50 >50 >50 >50 3.13 3.13 NT
>125 >125 >125 >125 NT NT 3.9
>125 >125 >125 >125 NT NT 3.9
>125 >125 >125 >125 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.
such as H-bonds, π–π interactions, extend the structures into higher dimensions. The antibacterial activity tests show that complex 2 appears to be effective against S. aureus.
Acknowledgments The authors gratefully acknowledge the Guangdong Province Universities and Colleges High Level Talent Project (2011QY01), the Natural Science Foundation of Guangdong Industry Technical College (KJ201007) and the Education Reform Project of Guangdong Industry Technical College (JG201004) for financial support.
Appendix A. Supplementary material Supplementary data to this article can be found online at http:// dx.doi.org/10.1016/j.inoche.2013.04.028.
References [1] S. Liao, C.Y. Su, H.X. Shi, J.L. Zhang, Z.Y. Zhou, H.Q. Liu, A.S.C. Chan, B.S. Kang, Helical complexes from the self-assembly of silver salts and the polydentate thioether a, a?-bis(8-thioquinoline)-m-xylene, Inorg. Chim. Acta 336 (2002) 151–156. [2] C.L. Chen, C.Y. Su, Y.P. Cai, H.X. Zhang, A.W. Xu, B.S. Kang, H.C. Zur Loye, Multidimensional frameworks assembled from silver(I) coordination polymers
Y. Li et al. / Inorganic Chemistry Communications 34 (2013) 4–7
[3]
[4]
[5]
[6]
[7] [8]
[9]
[10]
[11]
[12]
[13]
[14]
containing flexible bis(thioquinolyl) ligands: role of the intra- and intermolecular aromatic stacking interactions, Inorg. Chem. 42 (2003) 3738–3750. C.L. Chen, Z.Q. Yu, Q. Zhang, M. Pan, J.Y. Zhang, C.Y. Zhao, C.Y. Su, Formation of disilver(I) metallacycle and 1D polymeric chain from the same mononuclear building block: assembly mechanism upon crystallization, Cryst. Growth Des. 8 (3) (2008) 897–905. S. Tavacoli, T.A. Miller, R.L. Paul, J.C. Jeffery, M.D. Ward, Synthesis and coordination chemistry of tetradentate ligands containing two bidentate thioquinoline units: mononuclear complexes with Cu(I) and Cu(II), and a coordination polymer with Cu(I), Polyhedron 22 (4) (2003) 507–514. C.L. Chen, C.Y. Su, Y.P. Cai, H.X. Zhang, A.W. Xu, B.S. Kang, A noninterpenetrating 2D coordination polymer from spacer (CH2)8 based highly flexible linear ligand and AgCF3CO2, New J. Chem. 27 (2003) 790–792. C.Y. Su, S. Liao, M. Wanner, J. Fiedler, C. Zhang, B.S. Kang, W. Kaim, The copper(I)/copper(II) transition in complexes with 8-alkylthioquinoline based multidentate ligands, Dalton Trans. 2 (2003) 189–202. M. Oh, C.L. Stern, C.A. Mirkin, Coordination polymers with macrocyclic cages and pockets within their backbones, Chem. Commun. 23 (2004) 2684–2685. R.F. Song, Y.B. Xie, J.R. Li, X.H. Bu, Syntheses and crystal structures of the copper(I) complexes with quinoline-based monothioether ligands, CrystEngComm 7 (2005) 249–254. S. Bhattacharyya, D.F. Dye, M. Pink, J.M. Zaleski, A geometric switching approach toward thermal activation of metalloenediynes, Chem. Commun. 42 (2005) 5295–5297. L. Canovese, F. Visentin, G. Chessa, C. Santo, P. Uguagliati, Novel heteropolymetallic derivatives of palladium bearing pyridylthioether fragments incorporating a Fe2(CO)6 cluster core as ligand, Inorg. Chem. Commun. 8 (2005) 1120–1124. L. Canovese, F. Visentin, G. Chessa, C. Levi, A. Dolmella, Synthesis, stability constant determination, and structural study of some complexes of a zinc triad containing pyridyl-amine-quinoline and pyridyl-thio-quinoline, Eur. J. Inorg. Chem. 23 (2007) 3669–3680. J.A. Zhang, M. Pan, J.Y. Zhang, B.S. Kang, C.Y. Su, Syntheses, structures and bioactivities of cadmium(II) complexes with a tridentate heterocyclic N- and S-ligand, Inorg. Chim. Acta 162 (2009) 3519–3525. J.A. Zhang, M. Pan, J.Y. Zhang, H.K. Zhang, Z.J. Fan, B.S. Kang, C.Y. Su, Syntheses, structures and bioactivities of silver(I) complexes with a tridentate heterocyclic N- and S-ligand, Polyhedron 28 (1) (2009) 145–149. J.A. Zhang, M. Pan, R. Yang, Z.G. She, W. Kaim, Z.J. Fan, C.Y. Su, Structure, biological and electrochemical studies of transition metal complexes from N, S, N′ donor ligand 8-(2-pyridinylmethylthio)quinoline, Polyhedron 29 (2010) 581–591.
7
[15] J.A. Zhang, M. Pan, J.J. Jiang, Z.G. She, Z.J. Fan, C.Y. Su, Syntheses, crystal structures and antimicrobial activities of thioether ligands containing quinoline and pyridine terminal groups and their transition metal complexes, Inorg. Chim. Acta 374 (2011) 269–277. [16] Syntheses of the complexes: Complex 1 ([Hg(L1)Cl2]): 2, 6-Bis [(8quinolinylthio) methyl] pyridine (L) (26 mg, 0.060 mmol) was dissolved in chloroform (3 mL), then HgCl2 (16 mg, 0.060 mmol) in acetonitrile (2 mL) was added into the above solution and mixed. The obtained solution was stirred for 10 min in room temperature and filtrated into a tube slowly, and slow diffusion of diethyl ether into the filtrate gave colorless crystals of 1 after several days. The crystals were filtered and washed several times in anhydrous diethyl ether and then dried in vacuum. Yield was 64% (27 mg). Anal. Calcd. for C25H19Cl2HgN3S2: calcd. C, 43.08; H, 2.75; N, 6.03; found: C, 42.88; H, 2.87, N, 6.07. IR (KBr pellet, cm−1): 3031(w), 2926(w), 1588(m), 1569(m), 1489(m), 1449(s), 1416(m), 1379(m), 1303(w), 1211(w), 1090(w), 1069(w), 1003(m), 982(m), 821(m), 784(s), 760(m), 657(m). Complex 2 ([Hg(L1)] · (ClO4)2): 2, 6-Bis [(8-quinolinylthio) methyl] pyridine (L) (43 mg, 0.10 mmol) was dissolved in chloroform (2 mL), then Hg(ClO4)2 · 3H2O(16 mg, 0.060 mmol) in acetonitrile (2 mL) was added into the above solution and mixed. The obtained solution was stirred for 30 min in room temperature and filtrated into a tube slowly, and slow diffusion of isopropyl ether into the filtrate gave colorless crystals of 2 after several days. The crystals were filtered and washed several times in anhydrous diethyl ether and then dried in vacuum. Yield was 65% (27 mg). Anal. Calcd. for C25H19Cl2HgN3O8S2: calcd. C, 36.39; H, 2.32; N, 5.093; found:C, 36.58; H, 2.341; N, 5.164. IR (KBr pellet, cm−1): 3057(w), 2995(w), 2928(w), 1587(m), 1492(m), 1454(m), 1376(m), 1302(w), 1207(m), 1091(vs), 987(m), 825(m), 781(m), 626(m). Complex 3 ([Hg2(L1)2](ClO4)2 · H2O) was synthesized as complex 2 except that 2, 6-bis(8-quinolinyl methylthio) pyridine (L) (22 mg, 0.050 mmol) was dissolved in chloroform (3 mL) and Hg(ClO4)2⋅3H2O (23 mg, 0.050 mmol) in anhydrous acetonitrile (2 mL). Yield was 75% (55 mg). Anal. Calcd. for C50H40Cl2Hg2N6O9S4: calcd. C, 40.87; H, 2.74; N, 5.72; found: C, 40.81; H, 2.87; N, 6.01. IR (KBr pellet, cm−1): 3444(w), 3074(w), 3004(w), 2928(w), 1586(m), 1497(m), 1455(m), 1379(m), 1308(w), 1208(w), 1098(vs), 886(w), 831(m), 774(m), 677(w), 622(m), 451(w). [17] The complexes were dissolved in DMSO (dimethyl sulphoxide) and tested against four bacteria and three fungal strains for their inhibitory activities. Antimicrobial assays were performed using a modified version of the 2-fold serial dilution method as R.A. Fromtling (1993), in which two starting yeast inoculum sizes (5 × 10(4) and 2.5 × 10(3) cells per ml) were compared, and readings were taken after 24 and 48 h of incubation. All other test conditions were standardized.