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A novel cobalt(II) complex based on nicotinamide and 2-nitrobenzoate mixed ligands: Synthesis, characterization, and biological activity
Inorganic Chemistry Communications 13 (2010) 855–858
Contents lists available at ScienceDirect
Inorganic Chemistry Communications j o u r n a l h o m e p a g e : w w w. e l s ev i e r. c o m / l o c a t e / i n o c h e
A novel cobalt(II) complex based on nicotinamide and 2-nitrobenzoate mixed ligands: Synthesis, characterization, and biological activity Jian-Guo Lin a,b, Ling Qiu a,⁎, Wen Cheng a, Shi-Neng Luo a, Ke Wang a, Qing-Jin Meng b a b
Key Laboratory of Nuclear Medicine, Ministry of Health & Jiangsu Key Laboratory of Molecular Nuclear Medicine, Jiangsu Institute of Nuclear Medicine, Wuxi 214063, PR China Coordination Chemistry Institute, State Key Laboratory of Coordination Chemistry, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing 210093, PR China
a r t i c l e
i n f o
Article history: Received 28 January 2010 Accepted 20 April 2010 Available online 2 May 2010 Keywords: Co(II) complex Nicotinamide Hydrogen bond Biological activity VEGFR-2 TK inhibitor
a b s t r a c t Employing nicotinamide and 2-nitrobenzoate as mixed ligands, a new complex was obtained and characterized by single crystal X-ray diffraction, [Co(C7H5NO4)2(C6H5NO2)2(H2O)2]·2H2O (1). It is connected by the strong O–H…O and N–H…O hydrogen bonds to form a two-dimensional (2-D) supramolecular network. The biological activity of complex 1 was investigated and the results indicate that it is an effective inhibitor of vascular endothelial growth factor receptor-2 tyrosine kinase (VEGFR-2 TK) with an IC50 value of 608 nM. © 2010 Elsevier B.V. All rights reserved.
Nicotinamide, the amide of vitamin B3, has been widely distributed in nature. For example, appreciable amounts are found in liver, fish, yeast, cereal grains, etc. It is also involved in several metabolic processes, such as glycolysis, fatty acid synthesis and respiration [1]. Moreover, nicotinamide has been successfully used to treat various diseases, such as pellagra, psoriasis, schizophrenia and Type I diabetes [2]. However, the nicotinamide for potential applications in antagonistic effect on biological activity has been largely unexplored until now [3,4]. On the other hand, some transition metal complexes were reported to play a pivotal role in biological applications and their biological activities are often larger than those of the corresponding ligands [5–7]. For instance, metallodrugs are increasingly recognized as an important family of pharmaceuticals, including platinum anticancer drugs [8], gadolinium MRI contrast agents [9], technetium radiopharmaceuticals [10], etc. Today, the chemical and clinical search for new selectively acting cis-diamminedichloroplatinum(II) (cisplatin) derivatives or new tumor inhibiting metal complexes goes on. Therefore, developing new complexes combining the nicotinamide with suitable metal ions to feature sound bioactivity is a promising task. As is well known, the cobalt(II) ion performs numerous biological functions in all life forms, especially in the higher organism. To date, many cobalt complexes have been used successfully in the treatment of several diseases. For example, a series of acetylenehexacarbonyldicobalt complexes was reported as a novel class of antitumor agents
⁎ Corresponding author. Tel.: +86 510 85514482; fax: +86 510 85513113. E-mail address: [email protected] (L. Qiu). 1387-7003/$ – see front matter © 2010 Elsevier B.V. All rights reserved. doi:10.1016/j.inoche.2010.04.013
[11] and antiproliferative agents of human leukemia cells [12]. Among this class of compounds, the hexacarbonyl[2-propinylacetylsalicylate] dicobalt complex shows a high selectivity for human breast cancer cells and it is even more active than cisplatin [11]. Herein we synthesized a novel cobalt(II) mononuclear complex based on the mixed ligands nicotinamide and 2-nitrobenzoate to investigate its biological property (Scheme 1). Complex [Co(C7H5NO4)2(C6H5NO2)2(H2O)2]·2H2O (1) was prepared by evaporating the water/ethanol solution containing cobalt nitrate, nicotinamide and 2-nitrobenzoic acid [13]. X-ray diffraction study reveals that the complex 1 crystallizes in the monoclinic space group P21/n [14]. The asymmetric unit of crystal consists of half crystallographically unique Co2+ ion, one nicotinamide ligand, one 2nitrobenzoate ligand, one coordinated water molecule and one lattice water molecule. As shown in Fig. 1, the Co1 ion lies at an inversion
Scheme 1.
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J.-G. Lin et al. / Inorganic Chemistry Communications 13 (2010) 855–858
Fig. 1. ORTEP view of complex 1 with thermal ellipsoids drawn at the 50% probability level (Symmetry code A: −x + 1, −y + 1, −z + 1). Selected bond lengths (Å) and angles (°) in 1: Co(1)–O(1W) 2.090(6), Co(1)–N(2) 2.153(7), Co(1)–O(1) 2.159(6), O(1W)–Co(1)– O(1WA) 180.0(3), O(1W)–Co(1)–N(2) 89.6(3), O(1WA)–Co(1)–N(2) 90.4(3), N(2)– Co(1)–N(2A) 180.000(1), O(1W)–Co(1)–O(1) 86.4(2), O(1WA)–Co(1)–O(1) 93.6(2), N(2)–Co(1)–O(1) 91.0(2), N(2A)–Co(1)–O(1) 89.0(2), O(1)–Co(1)–O(1A) 180.0(3).
center and exhibits a distorted octahedral geometry. The apical positions are occupied by two nitrogen atoms from two nicotinamide ligands, while the basal plane is completed by two carboxylate oxygen atoms and two water molecules. The angles of the coordinated N and O atoms subtended at the center Co(II) atom vary from 86.3(2) to
180.0(4)°, and the bond lengths of Co–O and Co–N both range between 2.093(6) and 2.158(6) Å (see Fig. 1), which are comparable to the observations in other Co(II) complexes. From Fig. 2 and Table 1, one can see that there are strong hydrogen bonds throughout the complex, which connect the mononuclear units into 2-D supramolecular network. It is also noteworthy that there are two kinds of intermolecular hydrogen bonds. One exists between the coordinated carboxylate oxygen atom (O1) and oxygen atoms (O1w and O2w) from the coordinated and lattice water molecules respectively [O2W–H2B…O1 2.943 Å; O1W–H1A…O2W#3 2.804 Å (see Table 1)]. And an interesting one-dimensional (1-D) chain [CoO(H2O)2]n was formed along the a axis (see Fig. 2b). Another kind of hydrogen bonds exists between the nitrogen atom of the amide group (N3) and the uncoordinated carboxylate oxygen atom (O2) and the oxygen atom from the nicotinamide (O5) [N3– H3B…O2#5 2.979 Å; N3–H3A…O5#4 2.874 Å], which link the mononuclear units along the c axis (see Fig. 2c). As shown in Fig. 3, the FT-IR spectrum of the title compound exhibits strong peaks at 3387 and 3152 cm− 1 respectively due to the amide N–H stretching vibration of nicotinamide ligand. In the middle range of the IR spectrum, the vibration modes are commonly employed to distinguish the coordination modes of the carboxylate groups [15]. It is also known that the general correlation between the carboxylate coordination modes and the metal ions can be described by the difference in the infrared frequencies [Δν(COO) = νas(COO) − νs(COO)] of the coordination compounds [16]. As for the title complex, the stretching vibrations of νas(COO) and νs(COO) occur at 1602 and 1402 cm− 1, respectively. And the carboxylate group of the 2-
Fig. 2. (a) Perspective view of the 2-D supramolecular network connected by hydrogen bonding interactions along ac plane. (b) View of 1-D chain [CoO(H2O)2]n connected by O–H…O hydrogen bonds along a direction. (c) View of the 2-D supramolecular network showing the N–H…O interactions along c direction. All the hydrogen bonds are marked in magenta dash lines.
J.-G. Lin et al. / Inorganic Chemistry Communications 13 (2010) 855–858
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Table 1 Hydrogen bonds of 1 (Å and °). D–H
d(D–H)
d(H…A)
∠DHA
d(D…A)
A
O2W–H2B O2W–H2A O1W–H1B O1W–H1A N3–H3A N3–H3B
0.84(12) 0.80(13) 0.81(14) 0.78(13) 0.860(10) 0.860(13)
2.13(12) 2.10(13) 1.87(14) 2.03(13) 2.050(13) 2.179(13)
165.54(10) 174.29(12) 157.60(13) 167.98(13) 160.34(13) 154.73(13)
2.943(9) 2.900(10) 2.640(9) 2.804(9) 2.874(9) 2.979(9)
O1 O5#1 O2#2 O2W#3 O5#4 O2#5
Symmetry codes: #1: x + 1, y, z; #2: −x + 1, −y + 1, −z + 1; #3: −x + 2, −y + 1, −z + 1; #4: −x, −y + 1, −z + 2; #5: x, y, z + 1.
nitrobenzoate exhibits monodentate coordination mode which can also be seen from the separations between ν(COO) of 200 cm− 1. In this case, the X-ray diffraction analysis was allowed unambiguous assignment which is the binding mode of the carboxylate group. The absorption spectra of complex 1 at an identical concentration of 10− 5 M in different solvents at the room temperature are shown in Fig. 4. It exhibits clearly a large red-shift in DMSO and DMF compared to that in ethanol, showing intense absorption at 259 nm and 266 nm, respectively [17]. The observed red-shift in the absorption peak may be ascribed to the decreased energies of π* orbitals in the solvents with higher polarity, which leads to lower energies of π–π* transition. So the strong solvent-dependent of absorption can be assigned to π–π* transition centered on the aromatic carboxylic acid ligands [18,19].
Fig. 3. IR spectrum of the complex 1.
Fig. 4. Absorption spectra of the complex 1 in different solvents at room temperature. Color code: ethanol, black; DMF, red; DMSO, green.
Fig. 5. Inhibition of phosphate transfer activity of VEGFR-2 TK by the complex 1.
As we know, vascular endothelial growth factor (VEGF) and vascular endothelial growth factor receptor-2 tyrosine kinase (VEGFR-2 TK) are important regulators in angiogenesis, which almost locate exclusively on the endothelial cells [20]. VEGF is thought to exert its effect via binding with VEGFR-2 TK and trigger a cascade of phosphorylation which eventually leads to vascularization. Therefore, VEGFR-2 TK is recognized as the target of the development of therapeutic drugs against angiogenesis [21]. In this work, we further investigated the inhibition activity of the title complex to VEGFR-2 TK via a new simple and effective VEGFR-2 TK inhibitors screening model. The bioactivity of 1 was proved via the time-resolved fluoroimmunoassay (TRFIA) method [22], as shown in Fig. 5. The results display that complex 1 inhibits the phosphorylation of VEGFR-2 TK in a dose-dependent manner with an IC50 value of 608 nM, while SU11248 (a known VEGFR-2 TK inhibitor used as the positive control) inhibits VEGFR-2 TK with an IC50 value of 135 nM. This demonstrates that complex 1 is an effective VEGFR-2 TK inhibitor. In addition, Fig. 5 also clearly exhibits that the phospho-transfer inhibition activity is concentration-dependent. That is, as the concentration of the complex 1 increases, the phospho-transfer inhibition activity decreases. Furthermore, we have also investigated the inhibition mechanism of the title complex, which was conducted in the presence of several fixed concentration of complex 1 with adenosine-triphosphate (ATP) as the varying substrate. The results are presented in Fig. 6, which also demonstrated complex 1 was an effective VEGFR-2 TK inhibitor and it appeared to inhibit competitively with respect to ATP. In summary, we present the synthesis, crystal structure, IR, and UV–vis spectra of the cobalt(II) mononuclear complex based on the mixed N and O-donor ligands and further studied its biological activity via the TRFIA method. The results showed complex 1 inhibited VEGFR-2 TK effectively with an IC50 value of 608 nM and it appeared
Fig. 6. Kinetic analysis of inhibition of VEGFR-2 TK by the complex 1.
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J.-G. Lin et al. / Inorganic Chemistry Communications 13 (2010) 855–858
to inhibit competitively with respect to ATP. These promising results encourage us to further investigate its biological properties, such as cell-based and functional activity. Acknowledgements The authors are very grateful to the National Natural Science Foundation of China (20801024), the Natural Science Foundation of Jiangsu Province (BK2009077), the Science Foundation of Health Department of Jiangsu Province (H200963) and the Wu Jieping Medical Foundation (320.6750.08056) for their financial support. Appendix A. Supplementary material CCDC 756979 contains the supplementary crystallographic data for this paper. These data can be obtained free of charge from The Cambridge Crystallographic Data Centre via 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.inoche.2010.04.013. References [1] S.J. Lin, L. Guarente, Curr. Opin. Cell Biol. 15 (2003) 241. [2] M. Knip, I.F. Douek, W.P. Moore, H.A. Gillmor, A.E. McLean, P.J. Bingley, Diabetologia 43 (2000) 1337. [3] C. Kim, I. Novozhilova, M.S. Goodman, K.A. Bagley, P. Coppens, Inorg. Chem. 39 (2000) 5791. [4] V. Zeleňák, M. Sabo, W. Massa, P. Llewellyn, Inorg. Chim. Acta 357 (2004) 2049. [5] C. Dendrinou-Samara, G. Tsotsou, L.V. Ekateriniadou, A.H. Kortsaris, C.P. Raptopoulou, A. Terzis, D.A. Kyriakidis, D.P. Kessissoglou, J. Inorg. Biochem. 71 (1998) 171. [6] Z.H. Chohan, S.K.A. Sherazi, Met. Based Drugs 4 (1997) 327. [7] B. Rosenberg, L. Vancamp, T. Krigas, Nature 205 (1965) 698. [8] L.R. Kelland, N.P. Farrell, Platinum-based Drugs in Cancer Therapy, Humana Press, Totowa, NJ, 2000. [9] C.H. Reynolds, N. Annan, K. Beshah, J.H. Huber, S.H. Shaber, R.E. Lenkinski, J.A. Wortman, J. Am. Chem. Soc. 122 (2000) 8940. [10] M.J. Heeg, S.S. Jurisson, Acc. Chem. Res. 32 (1999) 1053.
[11] K. Schmidt, M. Jung, R. Keilitz, B. Schnurr, R. Gust, Inorg. Chim. Acta 306 (2000) 6. [12] I. Ott, A. Abraham, P. Schumacher, H. Shorafa, G. Gastl, R. Gust, B. Kircher, J. Inorg. Biochem. 100 (2006) 1903. [13] Crystals of 1 were obtained from a slowly evaporation of water–ethanol solution in the air. A water/ethanol (1:2 v/v) solution (3 ml) of cobalt nitrate trihydrate (0.290 g, 1 mmol) was added to a water/ethanol (1:2 v/v) solution (8 ml) of 2nitrobenzoic acid (0.167 g, 1 mmol) and nicotinamide (0.122 g, 1 mmol). Purple block crystals were obtained after several days (yield: 51.2%). Anal. Calcd for C26H28CoN6O14: C 46.19, H 3.59, N 12.43%; found: C 46.37, H 3.41, N 12.60%. [14] Crystallographic data for 1: C26H28CoN6O14, M = 707.47, Monoclinic, P21/n, a = 7.8545(4), b = 19.2802(8), c = 10.0280(4) Å, β = 102.4090(10), V = 1483.13 (11) Å3 , Z = 2, D c = 1.589 g cm − 3 , F(000) = 730, R int = 0.0304, S = 1.077, R = 0.1214, and wR = 0.2377. X-ray diffraction data of 1 (0.30 × 0.28 × 0.20 mm3) were collected on a Bruker SMART APEX CCD diffractometer using graphitemonochromatized Mo Kα radiation (λ = 0.71073 Å) at room temperature using the ω-scan technique. Data reductions and absorption corrections were performed with the SAINT and SADABS software packages, respectively. The structures were solved by direct methods using the SHELXS-97 program and were further refined by the full-matrix least-squares technique using the SHELXL-97 program. All nonhydrogen atoms were refined with anisotropic displacement parameters. Hydrogen atoms were generated geometrically with assigned isotropic thermal parameters. [15] G.B. Deacon, R.J. Phillips, Coord. Chem. Rev. 33 (1980) 227. [16] K. Nakamoto, Infrared and Raman Spectra of Inorganic and Coordination Compounds, Wiley, New York, 1997. [17] S. David, P. Roberto, S. Sabine, S. Biprajit, Dalton Trans. (2009) 9291. [18] Y. Sheng, B. Uwe, G. Tobias, L. Marina, W. Frank, J. Am. Chem. Soc. 126 (2004) 8336. [19] V. Giorgio, G. Claudio, S. Luca, F. Jan, I.H. Kenneth, G. Roberto, N. Carlo, Chem. Eur. J. 15 (2009) 6415. [20] G. Conn, M.L. Bayne, D.D. Soderman, P.W. Kwok, K.A. Sullivan, T.M. Palisi, D.A. Hope, K.A. Thomas, Proc. Natl. Acad. Sci. 87 (1990) 2628. [21] K. Holmes, O.L. Roberts, A.M. Thomas, M.J. Cross, Cell Signal. 19 (2007) 2003. [22] Detailed experiment method as follows: 100 μL of 5 μg/mL PolyE4Y was coated onto a 96-well immunoplate overnight at 4 °C then with 250 μL/well of 3% BSA in PBS (0.05 M phosphate buffer, pH 7.2, 0.15 M NaCl) for 2 hours at 4 °C followed by washing with PBST (0.1% Tween 20 in PBS). 95 μL reaction solution (200 ng/mL VEGFR-2 TK, 60 mM HEPES, Ph 7.4, 20 mM MgCl2, 5 μM DTT, 1.5 mM DTT, 50 μM ATP) and 5 μL compound at varying concentrations were added to each well and incubated for 1 h at room temperature. After washed for three times, 100 μL/well of 1:1000 dilution of anti-phosphotyrosine antibody (PY99) in PBST was added and incubated as above. Then the plate was washed for three times and 100 μL Eulabeled goat anti-mouse IgG in PBST was added and incubated for 0.5 h. Finally, the plate was washed for six times and 200 μL enhancement solution was added and the solution was incubated for 5 min.
Contents lists available at ScienceDirect
Inorganic Chemistry Communications j o u r n a l h o m e p a g e : w w w. e l s ev i e r. c o m / l o c a t e / i n o c h e
A novel cobalt(II) complex based on nicotinamide and 2-nitrobenzoate mixed ligands: Synthesis, characterization, and biological activity Jian-Guo Lin a,b, Ling Qiu a,⁎, Wen Cheng a, Shi-Neng Luo a, Ke Wang a, Qing-Jin Meng b a b
Key Laboratory of Nuclear Medicine, Ministry of Health & Jiangsu Key Laboratory of Molecular Nuclear Medicine, Jiangsu Institute of Nuclear Medicine, Wuxi 214063, PR China Coordination Chemistry Institute, State Key Laboratory of Coordination Chemistry, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing 210093, PR China
a r t i c l e
i n f o
Article history: Received 28 January 2010 Accepted 20 April 2010 Available online 2 May 2010 Keywords: Co(II) complex Nicotinamide Hydrogen bond Biological activity VEGFR-2 TK inhibitor
a b s t r a c t Employing nicotinamide and 2-nitrobenzoate as mixed ligands, a new complex was obtained and characterized by single crystal X-ray diffraction, [Co(C7H5NO4)2(C6H5NO2)2(H2O)2]·2H2O (1). It is connected by the strong O–H…O and N–H…O hydrogen bonds to form a two-dimensional (2-D) supramolecular network. The biological activity of complex 1 was investigated and the results indicate that it is an effective inhibitor of vascular endothelial growth factor receptor-2 tyrosine kinase (VEGFR-2 TK) with an IC50 value of 608 nM. © 2010 Elsevier B.V. All rights reserved.
Nicotinamide, the amide of vitamin B3, has been widely distributed in nature. For example, appreciable amounts are found in liver, fish, yeast, cereal grains, etc. It is also involved in several metabolic processes, such as glycolysis, fatty acid synthesis and respiration [1]. Moreover, nicotinamide has been successfully used to treat various diseases, such as pellagra, psoriasis, schizophrenia and Type I diabetes [2]. However, the nicotinamide for potential applications in antagonistic effect on biological activity has been largely unexplored until now [3,4]. On the other hand, some transition metal complexes were reported to play a pivotal role in biological applications and their biological activities are often larger than those of the corresponding ligands [5–7]. For instance, metallodrugs are increasingly recognized as an important family of pharmaceuticals, including platinum anticancer drugs [8], gadolinium MRI contrast agents [9], technetium radiopharmaceuticals [10], etc. Today, the chemical and clinical search for new selectively acting cis-diamminedichloroplatinum(II) (cisplatin) derivatives or new tumor inhibiting metal complexes goes on. Therefore, developing new complexes combining the nicotinamide with suitable metal ions to feature sound bioactivity is a promising task. As is well known, the cobalt(II) ion performs numerous biological functions in all life forms, especially in the higher organism. To date, many cobalt complexes have been used successfully in the treatment of several diseases. For example, a series of acetylenehexacarbonyldicobalt complexes was reported as a novel class of antitumor agents
⁎ Corresponding author. Tel.: +86 510 85514482; fax: +86 510 85513113. E-mail address: [email protected] (L. Qiu). 1387-7003/$ – see front matter © 2010 Elsevier B.V. All rights reserved. doi:10.1016/j.inoche.2010.04.013
[11] and antiproliferative agents of human leukemia cells [12]. Among this class of compounds, the hexacarbonyl[2-propinylacetylsalicylate] dicobalt complex shows a high selectivity for human breast cancer cells and it is even more active than cisplatin [11]. Herein we synthesized a novel cobalt(II) mononuclear complex based on the mixed ligands nicotinamide and 2-nitrobenzoate to investigate its biological property (Scheme 1). Complex [Co(C7H5NO4)2(C6H5NO2)2(H2O)2]·2H2O (1) was prepared by evaporating the water/ethanol solution containing cobalt nitrate, nicotinamide and 2-nitrobenzoic acid [13]. X-ray diffraction study reveals that the complex 1 crystallizes in the monoclinic space group P21/n [14]. The asymmetric unit of crystal consists of half crystallographically unique Co2+ ion, one nicotinamide ligand, one 2nitrobenzoate ligand, one coordinated water molecule and one lattice water molecule. As shown in Fig. 1, the Co1 ion lies at an inversion
Scheme 1.
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J.-G. Lin et al. / Inorganic Chemistry Communications 13 (2010) 855–858
Fig. 1. ORTEP view of complex 1 with thermal ellipsoids drawn at the 50% probability level (Symmetry code A: −x + 1, −y + 1, −z + 1). Selected bond lengths (Å) and angles (°) in 1: Co(1)–O(1W) 2.090(6), Co(1)–N(2) 2.153(7), Co(1)–O(1) 2.159(6), O(1W)–Co(1)– O(1WA) 180.0(3), O(1W)–Co(1)–N(2) 89.6(3), O(1WA)–Co(1)–N(2) 90.4(3), N(2)– Co(1)–N(2A) 180.000(1), O(1W)–Co(1)–O(1) 86.4(2), O(1WA)–Co(1)–O(1) 93.6(2), N(2)–Co(1)–O(1) 91.0(2), N(2A)–Co(1)–O(1) 89.0(2), O(1)–Co(1)–O(1A) 180.0(3).
center and exhibits a distorted octahedral geometry. The apical positions are occupied by two nitrogen atoms from two nicotinamide ligands, while the basal plane is completed by two carboxylate oxygen atoms and two water molecules. The angles of the coordinated N and O atoms subtended at the center Co(II) atom vary from 86.3(2) to
180.0(4)°, and the bond lengths of Co–O and Co–N both range between 2.093(6) and 2.158(6) Å (see Fig. 1), which are comparable to the observations in other Co(II) complexes. From Fig. 2 and Table 1, one can see that there are strong hydrogen bonds throughout the complex, which connect the mononuclear units into 2-D supramolecular network. It is also noteworthy that there are two kinds of intermolecular hydrogen bonds. One exists between the coordinated carboxylate oxygen atom (O1) and oxygen atoms (O1w and O2w) from the coordinated and lattice water molecules respectively [O2W–H2B…O1 2.943 Å; O1W–H1A…O2W#3 2.804 Å (see Table 1)]. And an interesting one-dimensional (1-D) chain [CoO(H2O)2]n was formed along the a axis (see Fig. 2b). Another kind of hydrogen bonds exists between the nitrogen atom of the amide group (N3) and the uncoordinated carboxylate oxygen atom (O2) and the oxygen atom from the nicotinamide (O5) [N3– H3B…O2#5 2.979 Å; N3–H3A…O5#4 2.874 Å], which link the mononuclear units along the c axis (see Fig. 2c). As shown in Fig. 3, the FT-IR spectrum of the title compound exhibits strong peaks at 3387 and 3152 cm− 1 respectively due to the amide N–H stretching vibration of nicotinamide ligand. In the middle range of the IR spectrum, the vibration modes are commonly employed to distinguish the coordination modes of the carboxylate groups [15]. It is also known that the general correlation between the carboxylate coordination modes and the metal ions can be described by the difference in the infrared frequencies [Δν(COO) = νas(COO) − νs(COO)] of the coordination compounds [16]. As for the title complex, the stretching vibrations of νas(COO) and νs(COO) occur at 1602 and 1402 cm− 1, respectively. And the carboxylate group of the 2-
Fig. 2. (a) Perspective view of the 2-D supramolecular network connected by hydrogen bonding interactions along ac plane. (b) View of 1-D chain [CoO(H2O)2]n connected by O–H…O hydrogen bonds along a direction. (c) View of the 2-D supramolecular network showing the N–H…O interactions along c direction. All the hydrogen bonds are marked in magenta dash lines.
J.-G. Lin et al. / Inorganic Chemistry Communications 13 (2010) 855–858
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Table 1 Hydrogen bonds of 1 (Å and °). D–H
d(D–H)
d(H…A)
∠DHA
d(D…A)
A
O2W–H2B O2W–H2A O1W–H1B O1W–H1A N3–H3A N3–H3B
0.84(12) 0.80(13) 0.81(14) 0.78(13) 0.860(10) 0.860(13)
2.13(12) 2.10(13) 1.87(14) 2.03(13) 2.050(13) 2.179(13)
165.54(10) 174.29(12) 157.60(13) 167.98(13) 160.34(13) 154.73(13)
2.943(9) 2.900(10) 2.640(9) 2.804(9) 2.874(9) 2.979(9)
O1 O5#1 O2#2 O2W#3 O5#4 O2#5
Symmetry codes: #1: x + 1, y, z; #2: −x + 1, −y + 1, −z + 1; #3: −x + 2, −y + 1, −z + 1; #4: −x, −y + 1, −z + 2; #5: x, y, z + 1.
nitrobenzoate exhibits monodentate coordination mode which can also be seen from the separations between ν(COO) of 200 cm− 1. In this case, the X-ray diffraction analysis was allowed unambiguous assignment which is the binding mode of the carboxylate group. The absorption spectra of complex 1 at an identical concentration of 10− 5 M in different solvents at the room temperature are shown in Fig. 4. It exhibits clearly a large red-shift in DMSO and DMF compared to that in ethanol, showing intense absorption at 259 nm and 266 nm, respectively [17]. The observed red-shift in the absorption peak may be ascribed to the decreased energies of π* orbitals in the solvents with higher polarity, which leads to lower energies of π–π* transition. So the strong solvent-dependent of absorption can be assigned to π–π* transition centered on the aromatic carboxylic acid ligands [18,19].
Fig. 3. IR spectrum of the complex 1.
Fig. 4. Absorption spectra of the complex 1 in different solvents at room temperature. Color code: ethanol, black; DMF, red; DMSO, green.
Fig. 5. Inhibition of phosphate transfer activity of VEGFR-2 TK by the complex 1.
As we know, vascular endothelial growth factor (VEGF) and vascular endothelial growth factor receptor-2 tyrosine kinase (VEGFR-2 TK) are important regulators in angiogenesis, which almost locate exclusively on the endothelial cells [20]. VEGF is thought to exert its effect via binding with VEGFR-2 TK and trigger a cascade of phosphorylation which eventually leads to vascularization. Therefore, VEGFR-2 TK is recognized as the target of the development of therapeutic drugs against angiogenesis [21]. In this work, we further investigated the inhibition activity of the title complex to VEGFR-2 TK via a new simple and effective VEGFR-2 TK inhibitors screening model. The bioactivity of 1 was proved via the time-resolved fluoroimmunoassay (TRFIA) method [22], as shown in Fig. 5. The results display that complex 1 inhibits the phosphorylation of VEGFR-2 TK in a dose-dependent manner with an IC50 value of 608 nM, while SU11248 (a known VEGFR-2 TK inhibitor used as the positive control) inhibits VEGFR-2 TK with an IC50 value of 135 nM. This demonstrates that complex 1 is an effective VEGFR-2 TK inhibitor. In addition, Fig. 5 also clearly exhibits that the phospho-transfer inhibition activity is concentration-dependent. That is, as the concentration of the complex 1 increases, the phospho-transfer inhibition activity decreases. Furthermore, we have also investigated the inhibition mechanism of the title complex, which was conducted in the presence of several fixed concentration of complex 1 with adenosine-triphosphate (ATP) as the varying substrate. The results are presented in Fig. 6, which also demonstrated complex 1 was an effective VEGFR-2 TK inhibitor and it appeared to inhibit competitively with respect to ATP. In summary, we present the synthesis, crystal structure, IR, and UV–vis spectra of the cobalt(II) mononuclear complex based on the mixed N and O-donor ligands and further studied its biological activity via the TRFIA method. The results showed complex 1 inhibited VEGFR-2 TK effectively with an IC50 value of 608 nM and it appeared
Fig. 6. Kinetic analysis of inhibition of VEGFR-2 TK by the complex 1.
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to inhibit competitively with respect to ATP. These promising results encourage us to further investigate its biological properties, such as cell-based and functional activity. Acknowledgements The authors are very grateful to the National Natural Science Foundation of China (20801024), the Natural Science Foundation of Jiangsu Province (BK2009077), the Science Foundation of Health Department of Jiangsu Province (H200963) and the Wu Jieping Medical Foundation (320.6750.08056) for their financial support. Appendix A. Supplementary material CCDC 756979 contains the supplementary crystallographic data for this paper. These data can be obtained free of charge from The Cambridge Crystallographic Data Centre via 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.inoche.2010.04.013. References [1] S.J. Lin, L. Guarente, Curr. Opin. Cell Biol. 15 (2003) 241. [2] M. Knip, I.F. Douek, W.P. Moore, H.A. Gillmor, A.E. McLean, P.J. Bingley, Diabetologia 43 (2000) 1337. [3] C. Kim, I. Novozhilova, M.S. Goodman, K.A. Bagley, P. Coppens, Inorg. Chem. 39 (2000) 5791. [4] V. Zeleňák, M. Sabo, W. Massa, P. Llewellyn, Inorg. Chim. Acta 357 (2004) 2049. [5] C. Dendrinou-Samara, G. Tsotsou, L.V. Ekateriniadou, A.H. Kortsaris, C.P. Raptopoulou, A. Terzis, D.A. Kyriakidis, D.P. Kessissoglou, J. Inorg. Biochem. 71 (1998) 171. [6] Z.H. Chohan, S.K.A. Sherazi, Met. Based Drugs 4 (1997) 327. [7] B. Rosenberg, L. Vancamp, T. Krigas, Nature 205 (1965) 698. [8] L.R. Kelland, N.P. Farrell, Platinum-based Drugs in Cancer Therapy, Humana Press, Totowa, NJ, 2000. [9] C.H. Reynolds, N. Annan, K. Beshah, J.H. Huber, S.H. Shaber, R.E. Lenkinski, J.A. Wortman, J. Am. Chem. Soc. 122 (2000) 8940. [10] M.J. Heeg, S.S. Jurisson, Acc. Chem. Res. 32 (1999) 1053.
[11] K. Schmidt, M. Jung, R. Keilitz, B. Schnurr, R. Gust, Inorg. Chim. Acta 306 (2000) 6. [12] I. Ott, A. Abraham, P. Schumacher, H. Shorafa, G. Gastl, R. Gust, B. Kircher, J. Inorg. Biochem. 100 (2006) 1903. [13] Crystals of 1 were obtained from a slowly evaporation of water–ethanol solution in the air. A water/ethanol (1:2 v/v) solution (3 ml) of cobalt nitrate trihydrate (0.290 g, 1 mmol) was added to a water/ethanol (1:2 v/v) solution (8 ml) of 2nitrobenzoic acid (0.167 g, 1 mmol) and nicotinamide (0.122 g, 1 mmol). Purple block crystals were obtained after several days (yield: 51.2%). Anal. Calcd for C26H28CoN6O14: C 46.19, H 3.59, N 12.43%; found: C 46.37, H 3.41, N 12.60%. [14] Crystallographic data for 1: C26H28CoN6O14, M = 707.47, Monoclinic, P21/n, a = 7.8545(4), b = 19.2802(8), c = 10.0280(4) Å, β = 102.4090(10), V = 1483.13 (11) Å3 , Z = 2, D c = 1.589 g cm − 3 , F(000) = 730, R int = 0.0304, S = 1.077, R = 0.1214, and wR = 0.2377. X-ray diffraction data of 1 (0.30 × 0.28 × 0.20 mm3) were collected on a Bruker SMART APEX CCD diffractometer using graphitemonochromatized Mo Kα radiation (λ = 0.71073 Å) at room temperature using the ω-scan technique. Data reductions and absorption corrections were performed with the SAINT and SADABS software packages, respectively. The structures were solved by direct methods using the SHELXS-97 program and were further refined by the full-matrix least-squares technique using the SHELXL-97 program. All nonhydrogen atoms were refined with anisotropic displacement parameters. Hydrogen atoms were generated geometrically with assigned isotropic thermal parameters. [15] G.B. Deacon, R.J. Phillips, Coord. Chem. Rev. 33 (1980) 227. [16] K. Nakamoto, Infrared and Raman Spectra of Inorganic and Coordination Compounds, Wiley, New York, 1997. [17] S. David, P. Roberto, S. Sabine, S. Biprajit, Dalton Trans. (2009) 9291. [18] Y. Sheng, B. Uwe, G. Tobias, L. Marina, W. Frank, J. Am. Chem. Soc. 126 (2004) 8336. [19] V. Giorgio, G. Claudio, S. Luca, F. Jan, I.H. Kenneth, G. Roberto, N. Carlo, Chem. Eur. J. 15 (2009) 6415. [20] G. Conn, M.L. Bayne, D.D. Soderman, P.W. Kwok, K.A. Sullivan, T.M. Palisi, D.A. Hope, K.A. Thomas, Proc. Natl. Acad. Sci. 87 (1990) 2628. [21] K. Holmes, O.L. Roberts, A.M. Thomas, M.J. Cross, Cell Signal. 19 (2007) 2003. [22] Detailed experiment method as follows: 100 μL of 5 μg/mL PolyE4Y was coated onto a 96-well immunoplate overnight at 4 °C then with 250 μL/well of 3% BSA in PBS (0.05 M phosphate buffer, pH 7.2, 0.15 M NaCl) for 2 hours at 4 °C followed by washing with PBST (0.1% Tween 20 in PBS). 95 μL reaction solution (200 ng/mL VEGFR-2 TK, 60 mM HEPES, Ph 7.4, 20 mM MgCl2, 5 μM DTT, 1.5 mM DTT, 50 μM ATP) and 5 μL compound at varying concentrations were added to each well and incubated for 1 h at room temperature. After washed for three times, 100 μL/well of 1:1000 dilution of anti-phosphotyrosine antibody (PY99) in PBST was added and incubated as above. Then the plate was washed for three times and 100 μL Eulabeled goat anti-mouse IgG in PBST was added and incubated for 0.5 h. Finally, the plate was washed for six times and 200 μL enhancement solution was added and the solution was incubated for 5 min.