- Email: [email protected]
An anthracene-based fluorescent chemosensor for Zn2+
Tetrahedron Letters 54 (2013) 2415–2418
Contents lists available at SciVerse ScienceDirect
Tetrahedron Letters journal homepage: www.elsevier.com/locate/tetlet
An anthracene-based fluorescent chemosensor for Zn2+ Jin Hoon Kim a,⇑, Jin Young Noh a, In Hong Hwang a, Juhye Kang a, Jinheung Kim b, Cheal Kim a,⇑ a b
Department of Fine Chemistry, Seoul National University of Science and Technology, Seoul 139-743, Republic of Korea Department of Chemistry and Nano Science, Ewha Womans University, Seoul 120-750, Republic of Korea
a r t i c l e
i n f o
Article history: Received 23 January 2013 Revised 25 February 2013 Accepted 28 February 2013 Available online 7 March 2013 Keywords: Fluorescent Chemosensor Dipicolylamine Anthracene Zinc ions
a b s t r a c t A new zinc ion sensor 1-(anthracen-9-yl)-N-(pyridin-2-ylmethyl)-N-(quinolin-2-ylmethyl)methanamine 1 was synthesized by incorporating a dipicolylamine derivative as a binding unit and an anthracene group as a fluorescence signaling unit. The anthracene-based receptor 1 was highly selective for Zn2+ with a fluorescence enhancement and a remarkable red shift in aqueous solution, whereas this chemosensor showed no response to other metals, especially Cd2+ ion. The composition of the complex 1–Zn2+ turned out 1:1, based on Job’s plot, ESI-mass analysis, and 1H NMR titration. Ó 2013 Elsevier Ltd. All rights reserved.
The zinc ion (Zn2+) is the second most abundant transition metal ion in the human body, and plays very important roles in a wide variety of physiological and pathological processes such as neural signal transmitters or modulators, and regulators of gene expression, and apoptosis.1–3 It is known that disorders of zinc metabolism are closely associated with many severe neurological diseases such as Alzheimer’s disease (AD) and Parkinson’s disease (PD).4–7 In addition, zinc ions are present commonly in agricultural and food waste products. Therefore, it is of essential importance to control the detection of Zn2+ in both the environment and biological systems. So far, a great number of Zn2+ fluorescent sensors have been designed and reported.8–23 However, it is still a huge challenge for detecting Zn2+ selectively without interference of other transition metal ions, especially Cd2+, because Zn2+ and Cd2+ display highly similar chemical properties. As a result, they often respond together with similar spectral changes, when coordinated with fluorescent sensors.24 Thus, there is a great need for developing Zn2+ selective sensors that can distinguish Zn2+ from Cd2+.25 As an approach to develop a selective fluorescent chemosensor for Zn2+, a new dipicolylamine derivative 1 was designed and prepared (Scheme 1). To achieve properties for metal chelation and fluorophore, the basic framework for 1 was designed from the combination of a tridentate metal ion chelator (2pyridylmethyl)(2-quinolylmethyl)amine26 and a fluorescent
⇑ Corresponding authors. Tel.: +82 2 970 6693; fax: +82 2 973 9149. E-mail addresses: [email protected] (J.H. Kim), [email protected] (C. Kim). 0040-4039/$ - see front matter Ó 2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.tetlet.2013.02.102
anthracene.27–29 1 was characterized by 1H and 13C NMR, elemental analysis, and ESI-mass spectrometry. To obtain an insight into the sensing properties of 1 as a selective fluorescent chemosensor for Zn2+ ion, the fluorescence properties of 1 were investigated with several metal ions using their nitrate salts in MeOH. The fluorescence spectra were obtained using an excitation wavelength of 390 nm. Upon binding to Zn2+, 1 exhibited a selective fluorescence enhancement with a red-shift of 74 nm from 413 to 487 nm (Fig. 1). When other metal ions such as Mn2+, Fe3+, Co2+, Ni2+, Cu2+, Cd2+, Hg2+, Na+, K+, Mg2+, Ca2+, Ag+, Pb2+, Al3+, and Cr3+ were used, no fluorescence change was observed (Fig. 1). Almost identical results were also obtained in 10% aqueous methanol solution. These results indicate that 1 can effectively discriminate Zn2+ from Cd2+ ion, while DQPMA30 and ADPA30 having similar structures to 1 have little or moderate selectivity for Zn2+ ion.31–34 A fluorescence titration of 1 (5 lM) with Zn2+ in methanol showed a gradual increase until 4 equiv of Zn2+ were added (Fig. 2); after that, the fluorescence reached a maximum due to complete binding of 1 to zinc ions. The UV–vis titration experiments were performed by mixing various amounts of Zn2+ ion with a solution of 1. Upon addition of Zn2+ ion to 1, the absorption peaks were red-shifted and three new peaks at 355, 374, and 396 nm appeared (Fig. 3). Besides, six isosbestic points at 341, 351, 360, 369, 381, and 389 nm demonstrated a clean formation of a 1–Zn2+ complex, which indicates a 1:1 complex formation. Job’s plot also supported the 1:1 complexation between 1 and Zn2+ (see Supplementary data).35 The stoichiometry of the 1–Zn2+ complex has also been confirmed by mass spectroscopic determination. The positive-ion mass spectrum indicated the 1:1 binding model between 1 and Zn2+ [m/z: 661.19;
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J. H. Kim et al. / Tetrahedron Letters 54 (2013) 2415–2418
N
N H
CH 2Cl2 / Et3 N
N
rt, 24 h Cl
N N
N
Scheme 1. Synthesis of receptor 1.
Figure 1. Fluorescence spectra of 1 (5 lM) in the presence of 20 equiv metal ions.
Figure 2. Fluorescence spectra of 1 (5 lM, kex = 390 nm) upon the addition of Zn2+ ions (0.5, 1.0, 1.5. 2.0, 2.5, 3.0, 3.5, 4.0, 4.5, 5.0, 6.0, 7.0, 8.0, 9.0, 10.0, 12.0, 14.0, 16.0, 18.0, and 20.0 lM) at room temperature. Inset: fluorescence intensity at 480 nm versus equivalents of Zn2+ added.
Calcd, 661.20] (Fig. 4). From the results of UV–vis and fluorescence titration, the association constants of the complex between 1 and Zn2+ were calculated to be 2.0 105 and 1.0 106 M 1, respectively, by a Benesi–Hildebrand plot (see Supplementary data).36 The detection limit of receptor 1 was determined to be 2.4 10 6 M (see Supplementary data).37 The fluorescence quantum yield of 1 was calculated to be 0.04 after binding of Zn2+ ion.38 To explore the ability of 1 for selective Zn2+ detection, competition experiments were performed in the presence of Zn2+ mixed with various metal ions. The fluorescence intensity of 1 was
Figure 3. Absorption spectral changes of 1 (20 lM) in the presence of different concentrations of Zn2+ ions (2, 4, 6, 8, 10, 12, 14, 16, 18, 20, and 22 lM) at room temperature. Inset: absorption at 400 nm versus equivalents of Zn2+ added.
Figure 4. Positive-ion electrospray ionization mass spectrum of 1 upon addition of 1 equiv Zn2+ in MeOH.
inhibited with metal ions such as Cu2+ and Hg2+ (Fig. 5). However, other metal ions such as Fe3+, Al3+, Na+, K+, Mg2+, Ca2+, Ag+, Pb2+, and Cr3+ did weakly. Thus, the receptor 1 displays a good selectivity for Zn2+ over other competing metal ions. To further understand the binding mode of 1 with Zn2+, the 1H NMR titration experiments were studied in CD3OD-d4. The addition of 1 equiv Zn2+ promoted a downfield shift of Ha and Hb protons of the methylene groups and the Hc proton of the pyridine group (Fig. 6). No obvious changes in 1H NMR were observed with more
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J. H. Kim et al. / Tetrahedron Letters 54 (2013) 2415–2418
nitrogen atoms of (2-pyridylmethyl)(2-quinolylmethyl)amine. Based on the 1H NMR titration, Job’s plot, and ESI-mass analysis, a 1:1 complex between 1 and Zn2+ was proposed in methanol solution, as shown in Scheme 2. In conclusion, we have successfully designed and synthesized an anthracene-based fluorescence chemosensor 1. This receptor 1 showed a good selectivity and sensitivity for Zn2+ with a remarkable red shift and an enhancement of emission. Importantly, this receptor 1 can selectively distinguish Zn2+ from Cd2+. The studies of 1H NMR titration, Job’s plot, and ESI-mass analysis suggest a 1:1 stoichiometry for association between 1 and Zn2+. Future study will focus on enhancing the water solubility of Zn2+-selective chemosensors and their potential applications in biological systems. Acknowledgements
Figure 5. Competitive selectivity of 1 (5 lM) toward Zn2+ (2 equiv) in the presence of other metals (2 equiv) with an excitation of 390 nm.
Financial support from Converging Research Center Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education, Science and Technology (2012001725, 2011K000675, and 2012008875) is gratefully acknowledged. We thank Professor Mi Sook Seo (Ewha Womans University) for ESI-mass running. Supplementary data Supplementary data associated with this article can be found, in the online version, at http://dx.doi.org/10.1016/j.tetlet.2013.02. 102. References and notes 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11.
Figure 6. 1H NMR spectra of 1 with Zn(NO3)2 in CD3OD-d4: (I) 1; (II) 1 with 0.2 equiv of Zn2+; (III) 1 with 0.4 equiv of Zn2+; (IV) 1 with 0.6 equiv of Zn2+; (V) 1 with 0.8 equiv of Zn2+; (VI) 1 with 1.0 equiv of Zn2+.
12. 13. 14.
addition of Zn2+. In addition, after coordinating with Zn2+, two CH2 groups adjacent to the central nitrogen atom of dipicolylamine derivative group (4.02 and 3.95 ppm) split as a doublet of triplets, presumably due to the restriction of bond rotation as a result of complex formation.39 These results imply that Zn2+ might bind to
15. 16. 17. 18.
Vallee, B. L.; Falchuk, K. H. Physiol. Rev. 1993, 73, 79–118. Berg, J. M.; Shi, Y. Science 1996, 271, 1081–1085. Xie, X.; Smart, T. G. Nature 1991, 349, 521–524. Bush, A. I. Curr. Opin. Chem. Biol. 2000, 4, 184–191. Bush, A. I. Trends Neurosci. 2003, 26, 207–214. Cuajungco, M. P.; Lees, G. J. Brain Res. 1997, 23, 219–236. Takeda, A. Biometals 2001, 14, 343–351. de Silva, A. P.; Gunaratne, H. Q. N.; Gunnlaugsson, T.; Huxley, A. J. M.; MCCoy, C. P.; Rademacher, J. T.; Rice, T. E. Chem. Rev. 1997, 97, 1515–1566. Goldsmith, C. R.; Lippard, S. J. Inorg. Chem. 2006, 45, 555–561. Kiyose, K.; Kojima, H.; Urano, Y.; Nagano, T. J. Am. Chem. Soc. 2006, 128, 6548– 6549. Meeusen, J.; Tomasiewicz, H.; Nowakowski, A.; Petering, D. H. Inorg. Chem. 2011, 50, 7563–7573. Yang, X. B.; Yang, B. X.; Ge, J. F.; Xu, Y. J.; Xu, Q. F.; Liang, J.; Lu, J. M. Org. Lett. 2011, 13, 2710–2713. Das, P.; Bhattacharya, S.; Mishra, S.; Das, A. Chem. Commun. 2011, 47, 8118– 8120. Lee, A. E.; Grace, M. R.; Meyer, A. G.; Tuck, K. L. Tetrahedron Lett. 2010, 51, 1161–1165. Liu, Z.; Zhang, C.; Li, Y.; Wu, Z.; Qian, F.; Yang, X.; He, W.; Gao, X.; Guo, Z. Org. Lett. 2009, 11, 795–798. Fahrni, C. J.; O’Halloran, T. V. J. Am. Chem. Soc. 1999, 121, 11448–11458. Xu, Z.; Baek, K. H.; Kim, H. N.; Cui, J.; Qian, X.; Spring, D. R.; Shin, I.; Yoon, J. J. Am. Chem. Soc. 2010, 132, 601–610. Lee, H. G.; Lee, J. H.; Jang, S. P.; Park, H. M.; Kim, S. J.; Kim, Y.; Kim, C.; Harrison, R. G. Tetrahedron 2011, 67, 8073–8078.
+
Zn(NO3 )2
N N
N
N N
N Zn
CH3 OH
CH 3OH CH3 OH
Scheme 2. Proposed structure of a 1:1 complex of 1 and Zn2+.
NO3
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19. Lee, H. G.; Lee, J. H.; Jang, S. P.; Hwang, I. H.; Kim, S. J.; Kim, Y.; Kim, C.; Harrison, R. G. Inorg. Chim. Acta 2013, 394, 542–551. 20. Zhang, Y.; Guo, X.; Si, W.; Jia, L.; Qian, X. Org. Lett. 2008, 10, 473–476. 21. Zhou, X.; Yu, B.; Guo, Y.; Tang, X.; Zhang, H.; Liu, W. Inorg. Chem. 2010, 49, 4002–4007. 22. Jiang, J.; Xiaoliang, T.; Yang, L.; Dou, W.; Liu, W.; Fang, R.; Liu, W. Dalton Trans. 2011, 40, 6367–6370. 23. Jiang, P.; Guo, Z. Coord. Chem. Rev. 2004, 248, 205–229. 24. Nolan, E. M.; Ryu, J. W.; Jaworski, J.; Feazell, R. P.; Sheng, M.; Lippard, S. J. J. Am. Chem. Soc. 2006, 128, 15517–15528. 25. Wang, J.; Lin, W.; Li, W. Chem. Eur. J. 2012, 18, 13629–13632. 26. Sascha, M. B.; Caroline, H. S.; Bernt, K.; Annette, R. Inorg. Chim. Acta 2004, 357, 3295–3303. 27. Rajamalli, P.; Prasad, E. Org. Lett. 2011, 13, 3714–3717. 28. Antonio, C.; Rosa, T.; Arturo, E.; Maria, D. V.; Alberto, T.; Miguel, A. M.; Molina, P. Org. Lett. 2004, 6, 4599–4602. 29. Rosario, M.; Fabiola, Z.; Antonio, C.; Arturo, E.; Alberto, T.; Molina, P. Org. Lett. 2006, 8, 3235–3238.
30. DQPMA = N,N-bis(2-methylquinoline)-2-(2-aminomethyl)pyridine and ADPA = N-(9-anthracenylmethyl)-N-(2-pyridinylmethyl)-2pyridinemethanamine. 31. Kubo, K.; Mori, A. J. Mater. Chem. 2005, 15, 2902–2907. 32. Hancock, R. D. Chem. Soc. Rev. 2013, 42, 1500–1524. 33. Lee, H.; Lee, H.-S.; Reibenspies, J. H.; Hancock, R. D. Inorg. Chem. 2012, 51, 10904–10915. 34. Gan, W.; Jones, S. B.; Reibenspies, J. H.; Hancock, R. D. Inorg. Chim. Acta 2005, 358, 3958–3966. 35. Job, P. Ann. Chim. 1928, 9, 113–203. 36. Benesi, H. A.; Hildebrand, J. H. J. Am. Chem. Soc. 1949, 71, 2703–2707. 37. Shiraishi, Y.; Sumiya, S.; Hirai, T. Chem. Commun. 2011, 47, 4953–4955. 38. Burdette, S. C.; Walkup, G. K.; Spingler, B.; Tsien, R. Y.; Lippard, S. J. J. Am. Chem. Soc. 2001, 123, 7831–7841. 39. As shown in Figure 6, 1H NMR spectra became broad with the increase of the concentration of Zn2+ ion. This might be due to a low solubility of the complex 1–Zn2+.
Contents lists available at SciVerse ScienceDirect
Tetrahedron Letters journal homepage: www.elsevier.com/locate/tetlet
An anthracene-based fluorescent chemosensor for Zn2+ Jin Hoon Kim a,⇑, Jin Young Noh a, In Hong Hwang a, Juhye Kang a, Jinheung Kim b, Cheal Kim a,⇑ a b
Department of Fine Chemistry, Seoul National University of Science and Technology, Seoul 139-743, Republic of Korea Department of Chemistry and Nano Science, Ewha Womans University, Seoul 120-750, Republic of Korea
a r t i c l e
i n f o
Article history: Received 23 January 2013 Revised 25 February 2013 Accepted 28 February 2013 Available online 7 March 2013 Keywords: Fluorescent Chemosensor Dipicolylamine Anthracene Zinc ions
a b s t r a c t A new zinc ion sensor 1-(anthracen-9-yl)-N-(pyridin-2-ylmethyl)-N-(quinolin-2-ylmethyl)methanamine 1 was synthesized by incorporating a dipicolylamine derivative as a binding unit and an anthracene group as a fluorescence signaling unit. The anthracene-based receptor 1 was highly selective for Zn2+ with a fluorescence enhancement and a remarkable red shift in aqueous solution, whereas this chemosensor showed no response to other metals, especially Cd2+ ion. The composition of the complex 1–Zn2+ turned out 1:1, based on Job’s plot, ESI-mass analysis, and 1H NMR titration. Ó 2013 Elsevier Ltd. All rights reserved.
The zinc ion (Zn2+) is the second most abundant transition metal ion in the human body, and plays very important roles in a wide variety of physiological and pathological processes such as neural signal transmitters or modulators, and regulators of gene expression, and apoptosis.1–3 It is known that disorders of zinc metabolism are closely associated with many severe neurological diseases such as Alzheimer’s disease (AD) and Parkinson’s disease (PD).4–7 In addition, zinc ions are present commonly in agricultural and food waste products. Therefore, it is of essential importance to control the detection of Zn2+ in both the environment and biological systems. So far, a great number of Zn2+ fluorescent sensors have been designed and reported.8–23 However, it is still a huge challenge for detecting Zn2+ selectively without interference of other transition metal ions, especially Cd2+, because Zn2+ and Cd2+ display highly similar chemical properties. As a result, they often respond together with similar spectral changes, when coordinated with fluorescent sensors.24 Thus, there is a great need for developing Zn2+ selective sensors that can distinguish Zn2+ from Cd2+.25 As an approach to develop a selective fluorescent chemosensor for Zn2+, a new dipicolylamine derivative 1 was designed and prepared (Scheme 1). To achieve properties for metal chelation and fluorophore, the basic framework for 1 was designed from the combination of a tridentate metal ion chelator (2pyridylmethyl)(2-quinolylmethyl)amine26 and a fluorescent
⇑ Corresponding authors. Tel.: +82 2 970 6693; fax: +82 2 973 9149. E-mail addresses: [email protected] (J.H. Kim), [email protected] (C. Kim). 0040-4039/$ - see front matter Ó 2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.tetlet.2013.02.102
anthracene.27–29 1 was characterized by 1H and 13C NMR, elemental analysis, and ESI-mass spectrometry. To obtain an insight into the sensing properties of 1 as a selective fluorescent chemosensor for Zn2+ ion, the fluorescence properties of 1 were investigated with several metal ions using their nitrate salts in MeOH. The fluorescence spectra were obtained using an excitation wavelength of 390 nm. Upon binding to Zn2+, 1 exhibited a selective fluorescence enhancement with a red-shift of 74 nm from 413 to 487 nm (Fig. 1). When other metal ions such as Mn2+, Fe3+, Co2+, Ni2+, Cu2+, Cd2+, Hg2+, Na+, K+, Mg2+, Ca2+, Ag+, Pb2+, Al3+, and Cr3+ were used, no fluorescence change was observed (Fig. 1). Almost identical results were also obtained in 10% aqueous methanol solution. These results indicate that 1 can effectively discriminate Zn2+ from Cd2+ ion, while DQPMA30 and ADPA30 having similar structures to 1 have little or moderate selectivity for Zn2+ ion.31–34 A fluorescence titration of 1 (5 lM) with Zn2+ in methanol showed a gradual increase until 4 equiv of Zn2+ were added (Fig. 2); after that, the fluorescence reached a maximum due to complete binding of 1 to zinc ions. The UV–vis titration experiments were performed by mixing various amounts of Zn2+ ion with a solution of 1. Upon addition of Zn2+ ion to 1, the absorption peaks were red-shifted and three new peaks at 355, 374, and 396 nm appeared (Fig. 3). Besides, six isosbestic points at 341, 351, 360, 369, 381, and 389 nm demonstrated a clean formation of a 1–Zn2+ complex, which indicates a 1:1 complex formation. Job’s plot also supported the 1:1 complexation between 1 and Zn2+ (see Supplementary data).35 The stoichiometry of the 1–Zn2+ complex has also been confirmed by mass spectroscopic determination. The positive-ion mass spectrum indicated the 1:1 binding model between 1 and Zn2+ [m/z: 661.19;
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N
N H
CH 2Cl2 / Et3 N
N
rt, 24 h Cl
N N
N
Scheme 1. Synthesis of receptor 1.
Figure 1. Fluorescence spectra of 1 (5 lM) in the presence of 20 equiv metal ions.
Figure 2. Fluorescence spectra of 1 (5 lM, kex = 390 nm) upon the addition of Zn2+ ions (0.5, 1.0, 1.5. 2.0, 2.5, 3.0, 3.5, 4.0, 4.5, 5.0, 6.0, 7.0, 8.0, 9.0, 10.0, 12.0, 14.0, 16.0, 18.0, and 20.0 lM) at room temperature. Inset: fluorescence intensity at 480 nm versus equivalents of Zn2+ added.
Calcd, 661.20] (Fig. 4). From the results of UV–vis and fluorescence titration, the association constants of the complex between 1 and Zn2+ were calculated to be 2.0 105 and 1.0 106 M 1, respectively, by a Benesi–Hildebrand plot (see Supplementary data).36 The detection limit of receptor 1 was determined to be 2.4 10 6 M (see Supplementary data).37 The fluorescence quantum yield of 1 was calculated to be 0.04 after binding of Zn2+ ion.38 To explore the ability of 1 for selective Zn2+ detection, competition experiments were performed in the presence of Zn2+ mixed with various metal ions. The fluorescence intensity of 1 was
Figure 3. Absorption spectral changes of 1 (20 lM) in the presence of different concentrations of Zn2+ ions (2, 4, 6, 8, 10, 12, 14, 16, 18, 20, and 22 lM) at room temperature. Inset: absorption at 400 nm versus equivalents of Zn2+ added.
Figure 4. Positive-ion electrospray ionization mass spectrum of 1 upon addition of 1 equiv Zn2+ in MeOH.
inhibited with metal ions such as Cu2+ and Hg2+ (Fig. 5). However, other metal ions such as Fe3+, Al3+, Na+, K+, Mg2+, Ca2+, Ag+, Pb2+, and Cr3+ did weakly. Thus, the receptor 1 displays a good selectivity for Zn2+ over other competing metal ions. To further understand the binding mode of 1 with Zn2+, the 1H NMR titration experiments were studied in CD3OD-d4. The addition of 1 equiv Zn2+ promoted a downfield shift of Ha and Hb protons of the methylene groups and the Hc proton of the pyridine group (Fig. 6). No obvious changes in 1H NMR were observed with more
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J. H. Kim et al. / Tetrahedron Letters 54 (2013) 2415–2418
nitrogen atoms of (2-pyridylmethyl)(2-quinolylmethyl)amine. Based on the 1H NMR titration, Job’s plot, and ESI-mass analysis, a 1:1 complex between 1 and Zn2+ was proposed in methanol solution, as shown in Scheme 2. In conclusion, we have successfully designed and synthesized an anthracene-based fluorescence chemosensor 1. This receptor 1 showed a good selectivity and sensitivity for Zn2+ with a remarkable red shift and an enhancement of emission. Importantly, this receptor 1 can selectively distinguish Zn2+ from Cd2+. The studies of 1H NMR titration, Job’s plot, and ESI-mass analysis suggest a 1:1 stoichiometry for association between 1 and Zn2+. Future study will focus on enhancing the water solubility of Zn2+-selective chemosensors and their potential applications in biological systems. Acknowledgements
Figure 5. Competitive selectivity of 1 (5 lM) toward Zn2+ (2 equiv) in the presence of other metals (2 equiv) with an excitation of 390 nm.
Financial support from Converging Research Center Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education, Science and Technology (2012001725, 2011K000675, and 2012008875) is gratefully acknowledged. We thank Professor Mi Sook Seo (Ewha Womans University) for ESI-mass running. Supplementary data Supplementary data associated with this article can be found, in the online version, at http://dx.doi.org/10.1016/j.tetlet.2013.02. 102. References and notes 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11.
Figure 6. 1H NMR spectra of 1 with Zn(NO3)2 in CD3OD-d4: (I) 1; (II) 1 with 0.2 equiv of Zn2+; (III) 1 with 0.4 equiv of Zn2+; (IV) 1 with 0.6 equiv of Zn2+; (V) 1 with 0.8 equiv of Zn2+; (VI) 1 with 1.0 equiv of Zn2+.
12. 13. 14.
addition of Zn2+. In addition, after coordinating with Zn2+, two CH2 groups adjacent to the central nitrogen atom of dipicolylamine derivative group (4.02 and 3.95 ppm) split as a doublet of triplets, presumably due to the restriction of bond rotation as a result of complex formation.39 These results imply that Zn2+ might bind to
15. 16. 17. 18.
Vallee, B. L.; Falchuk, K. H. Physiol. Rev. 1993, 73, 79–118. Berg, J. M.; Shi, Y. Science 1996, 271, 1081–1085. Xie, X.; Smart, T. G. Nature 1991, 349, 521–524. Bush, A. I. Curr. Opin. Chem. Biol. 2000, 4, 184–191. Bush, A. I. Trends Neurosci. 2003, 26, 207–214. Cuajungco, M. P.; Lees, G. J. Brain Res. 1997, 23, 219–236. Takeda, A. Biometals 2001, 14, 343–351. de Silva, A. P.; Gunaratne, H. Q. N.; Gunnlaugsson, T.; Huxley, A. J. M.; MCCoy, C. P.; Rademacher, J. T.; Rice, T. E. Chem. Rev. 1997, 97, 1515–1566. Goldsmith, C. R.; Lippard, S. J. Inorg. Chem. 2006, 45, 555–561. Kiyose, K.; Kojima, H.; Urano, Y.; Nagano, T. J. Am. Chem. Soc. 2006, 128, 6548– 6549. Meeusen, J.; Tomasiewicz, H.; Nowakowski, A.; Petering, D. H. Inorg. Chem. 2011, 50, 7563–7573. Yang, X. B.; Yang, B. X.; Ge, J. F.; Xu, Y. J.; Xu, Q. F.; Liang, J.; Lu, J. M. Org. Lett. 2011, 13, 2710–2713. Das, P.; Bhattacharya, S.; Mishra, S.; Das, A. Chem. Commun. 2011, 47, 8118– 8120. Lee, A. E.; Grace, M. R.; Meyer, A. G.; Tuck, K. L. Tetrahedron Lett. 2010, 51, 1161–1165. Liu, Z.; Zhang, C.; Li, Y.; Wu, Z.; Qian, F.; Yang, X.; He, W.; Gao, X.; Guo, Z. Org. Lett. 2009, 11, 795–798. Fahrni, C. J.; O’Halloran, T. V. J. Am. Chem. Soc. 1999, 121, 11448–11458. Xu, Z.; Baek, K. H.; Kim, H. N.; Cui, J.; Qian, X.; Spring, D. R.; Shin, I.; Yoon, J. J. Am. Chem. Soc. 2010, 132, 601–610. Lee, H. G.; Lee, J. H.; Jang, S. P.; Park, H. M.; Kim, S. J.; Kim, Y.; Kim, C.; Harrison, R. G. Tetrahedron 2011, 67, 8073–8078.
+
Zn(NO3 )2
N N
N
N N
N Zn
CH3 OH
CH 3OH CH3 OH
Scheme 2. Proposed structure of a 1:1 complex of 1 and Zn2+.
NO3
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19. Lee, H. G.; Lee, J. H.; Jang, S. P.; Hwang, I. H.; Kim, S. J.; Kim, Y.; Kim, C.; Harrison, R. G. Inorg. Chim. Acta 2013, 394, 542–551. 20. Zhang, Y.; Guo, X.; Si, W.; Jia, L.; Qian, X. Org. Lett. 2008, 10, 473–476. 21. Zhou, X.; Yu, B.; Guo, Y.; Tang, X.; Zhang, H.; Liu, W. Inorg. Chem. 2010, 49, 4002–4007. 22. Jiang, J.; Xiaoliang, T.; Yang, L.; Dou, W.; Liu, W.; Fang, R.; Liu, W. Dalton Trans. 2011, 40, 6367–6370. 23. Jiang, P.; Guo, Z. Coord. Chem. Rev. 2004, 248, 205–229. 24. Nolan, E. M.; Ryu, J. W.; Jaworski, J.; Feazell, R. P.; Sheng, M.; Lippard, S. J. J. Am. Chem. Soc. 2006, 128, 15517–15528. 25. Wang, J.; Lin, W.; Li, W. Chem. Eur. J. 2012, 18, 13629–13632. 26. Sascha, M. B.; Caroline, H. S.; Bernt, K.; Annette, R. Inorg. Chim. Acta 2004, 357, 3295–3303. 27. Rajamalli, P.; Prasad, E. Org. Lett. 2011, 13, 3714–3717. 28. Antonio, C.; Rosa, T.; Arturo, E.; Maria, D. V.; Alberto, T.; Miguel, A. M.; Molina, P. Org. Lett. 2004, 6, 4599–4602. 29. Rosario, M.; Fabiola, Z.; Antonio, C.; Arturo, E.; Alberto, T.; Molina, P. Org. Lett. 2006, 8, 3235–3238.
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