Wen-Sheng Chung ( 鍾文聖 ) Department of Applied Chemistry, National Chiao Tung University

1. 方教授泰山榮退教育學術回顧與 感恩研討會 December 24, 2011 Ditopic Fluorescent Sensing of Heavy Metal Ions Based on Functionalized Calix[4]arenes Wen-Sheng Chung (鍾文聖) Department of Applied Chemistry, National Chiao Tung University Hsinchu, Taiwan

2. (c) 1,3-alternatene cone partial cone 1,2-alternate Advantagesof using calix[4]arene as a scaffold for molecular sensing studies include:(1) flexible in modification, (2) conformational flexibility, and (3) multiple reaction sites. Upper rim p-tert-Butylcalix[4]arene Lower rim • Gutsche, C. D. Calix[4]arenes Revisited; The Royal Society of Chemistry: Cambridge, U.K., 1998.

3. What is our approach? Using the powerful and versatile 1,3-dipolar cycloaddition and its subsequent ring-opening reactions to create arrays of bifunctional compounds with appended chromophores and/or fluorophores for molecular sensing studies. • Click Chemistry by Sharpless, K. B.; Fokin, V. V. et al. J. Am. Soc. Chem.2005, 127, 210.

4. Ring-Opening Products of Isoxazolines or Isoxazoles • J. Chinese Chem. Soc. 2000, 47, 173. Using Mo(CO)6 in Calix[4]arenes • For a leading reference please see: Kozikowski, A. Acc. Chem. Res. 1984, 17, 410. • Tetrahedron Lett. 2006, 47, 7179; 9077.

5. Fluorogenic Chemosensor • High sensitivity • Low background • Fast response time • Small amount of ligands • Low cost Figure 1. Fundamentals and Functions of a Metal Ion Chemosensor. Ref : Fabbrizzi, L.; Poggi, A. Chem. Soc. Rev. 1995, 197.

6. Allosteric Effects on the Triazole-modified Calix[4]crown toward K+ and Pb2+ Ions. • 1,3-Alternate Calix[4]arene as a Homoditopic Fluorescent Chemosensor for Ag+ Ions.

7. The concept of allosteric proteins was developed in the early 1960s by Monod and Koshland. • Allosteric is derived from the Greek root allo, means “the other”. • Kramer, R. Chem. Rev.2004, 104, 3161.

8. Scheme 1. Synthetic pathways for fluoroionophores 4and5

9. Figure 1. Fluorescence intensity changes ((I – Io)/Io 100%) of fluoroionophores 4 and 5 (each of 10 M) in MeCN/CHCl3 (1000:4, v/v) at 298K upon addition of various metal perchlorates (10 equiv). These results suggest that Hg2+, Cu2+ and Cr3+ ions can be recognized by the mono-triazole group of sensor 5 alone; however, the complexation of Pb2+ requires the coordination of the two triazole groups of 4.

10. Allosteric Effect of 4•Pb2+ by K+ Ion Figure 2. Fluorescence emission change for the 4Pb2+ complex in CH3CN/CHCl3 (700:3, v/v) upon addition of K+. Excitation wavelength was at 367 nm.

11. Allosteric Effect of 4•K+ by Pb2+ Ion Figure 3. Fluorescence emission change for the 4K+ complex in CH3CN/CHCl3 (700:3, v/v) upon addition of Pb2+. Excitation wavelength was at 367 nm.

12. Allosteric Binding • Watkinson and Todd in Chem. Soc. Rev.,2011, 40, 2848–2866, “Chemical sensors that incorporate click-derived triazoles” mentioned that: Chung and co-workers were the first to utilize click chemistry on calixarene frameworks to construct sensors. • Chang, K.-C. et al Org. Lett. 2007, 9, 3363.

13. Chromogenic calix[4]arene sensor, with bistriazoles as the metal ion binding sites and azo groups as the signaling units, showed selective coloration toward Ca2+ and Pb2+ ions. 66Ca2+ 6Pb2+ • Chang, K.-C.; Chung, W.-S. et al. Tetrahedron Lett.2007, 48, 7274. • I-Ting Hoet al. Chem. Asian. J.2011, 6, 2738. Special issue on • the 10th anniversary of Click chemistry.

14. Fluorescence heteroditopic sensing of Cu(II) and anions • Senthilvelan, A.; Ho, I-T.; Chang, K.-C.; Lee, G.-H.; Liu, Y.-H.; Chung, W.-S. Chem. Eur. J. 2009, 15, 6152 2 + Cu2+ + Cu2+/F- + Cu2+/CH3COO-

15. Selective Fluorescence Turn-on Chemosensor for Two Cu(II) Ions Recognition site Fluorescence (signaling moiety) • I-Ting Ho, J.-H. Chu, W.-S. Chung Eur. J. Org. Chem. 2011

16. Allosteric Effects on the Triazole-modified Calix[4]crown toward K+ and Pb2+ Ions. • 1,3-Alternate Calix[4]arene as a Homoditopic Fluorescent Chemosensor for Ag+ Ions.

17. Synthesis, UV/vis, and Fluorescence screening of L3 2.29 Å 2.69 Å (b) (a) • UV-Vis titration spectrum Fluorescence titration spectrum [L3] = 20 mM MeOH-CHCl3 (49:1, v/v) lex = 372 nm

18. The non-linear least-squares analysis for 1:2 ligand-to-metal complexation of L3 K1 = 4.46 x103 M-1 K2 = 9.2 x104 M-1 Figure 4. The non-linear least-squares fitting of L3 with AgClO4. The higher K2revealed that a positiveallosteric effect participated in the complexation of L3with the second equiv of Ag+. • Jiwan, J.-L. H.; Branger, C.; Soumillion, J.-Ph.; Valeur, B. J. Photoch. Photobio. A 1998, 116, 127-133.

19. 1H NMR Titration of L3 with 2 equivalents of AgClO4 ◎ # ※ h’ -CH2-bridge a’ g’ f’ b’ * ☆ 2.0 * ☆ 1.0 * ☆ 0.5 h g a f b * 0 ☆ -CH2-bridge Figure 5. The 1H NMR titration of L3 (3 mM) in the presence of different amount of AgClO4 in CD3OD-CDCl3 (9:1, v/v). (a) 0, (b) 0.5, (c) 1.0 and (d) 2.0. #: CHD2OD, *: CD3OH, ※: H2O, ☆: external CHCl3, ◎: internal CHCl3.

20. UV-Vis and Fluorescence Titration of 4 with AgClO4 in MeOH-CHCl3 (49:1, v/v) Stern-Volmer Plot Io/I = 1 + Ksv[M]

21. 1H NMR Titration of 4 with AgClO4 # ※ ◎ -CH2-bridge g’ f’ h’ a’ ☆ b’ 1.5 * * ☆ 1.0 ☆ * 0.5 -CH2-bridge h a g b f 0 ☆ * Figure 6. The 1H NMR titration of 4 (3 mM) in the presence of different amount of AgClO4 in CD3OD-CDCl3 (3:1, v/v). (a) 0, (b) 0.5, (c) 1.0 and (d) 1.5. #: CHD2OD, *: CD3OH, ※: H2O, ☆: external CHCl3, ◎: internal CHCl3.

22. 4·Ag+ formula: [C84H64N8O6Ag]+ ESI-MS spectra L3·(Ag+)2 formula: [C84H68N8O6Ag2]2+

23. L3 exhibited as a homoditopic fluorescent chemosensor for Ag+ ions. A strong fluorescence enhancement was due to complexation-induced rigidity of its structure. Compound 4 without the ring-opening enaminone moieties did not have the ability to recognize two Ag+ ions simultaneously. The complexation of 4 with Ag+ led to a severe fluorescence quenching due to an inverse PET from anthracenes to the Ag+ bound nitrogen atoms of the triazole rings. Fluorescence Titration • I.-T. Ho; K.-C. Haung, and W.-S. Chung Chem. Asian J. 2011, 6, 2738.

24. The Binding Sequence of the L3 The absorbance changes of the triazole linked anthracene at 387 nm were almost saturated by adding 1 equiv of Ag+, whereas the absorbance of the enaminone at 332 nm was still increasing by the addition of more than 1 equiv of Ag+. The results indicated that the first equiv of Ag+prefer to be bound with the bis-triazole sites, and the reoriented structure helped to bind the second equiv of Ag+ by the bis-enaminone sites.

25. Summary • We have designed and synthesized various hetero- and homoditopic fluorescent chemosensors for metal ions based on calix[4]arenes functionalized by 1,3-dipolar cycloaddition reactions followed by ring opening reactions. • These hosts are found to be selective sensors for different metal ions and/or anions depending on the ligands appended. Allosteric effects were observed in the upper-rim calix[4]crown and lower-rim triazolyl anthracenes.

26. Acknowledgements Mr. Kuan-Chang Haung Dr. A. Senthilvelan Dr. I-Ting Ho Dr. Kai-Chi Chang Dr. Jean-Ho Chu Lifetime measurements Prof. Eric W.-G. Diau X-ray analysis Prof. Shie-Ming Peng Dr. Gene-Hsiang Lee Mr. Yi-Hung Liu (National Taiwan University) Mr. Wen-Hsing Wu Dr. Jun Luo Mr. Fu-Ming Yang Financial Support $$$ National Science Council, Taiwan MOE ATU project National Chiao Tung University

27. Science II Building of NCTU (科學二館) Thanks for Your Kind Attentions