Rhodamine-Based Hg 2+ -Selective Chemodosimeter in Aqueous Solution: Fluorescent OFF-ON Jia-Sheng Wu, ² In-Chul Hwang, ‡ Kwang S. Kim, ‡ and Jong Seung Kim* ,² Department of Chemistry, Dankook UniVersity, Seoul 140-714, Korea, and Department of Chemistry and Basic Science Research Institute, Pohang UniVersity of Science and Technology, Pohang 790-784, Korea jongskim@dankook.ac.kr Received January 15, 2007 ABSTRACT N-(Rhodamine-6G)lactam-N′-phenylthiourea-ethylenediamine (1) was developed as a fluorescent and colorimetric chemodosimeter in aqueous solution with a broad pH span (5∼10) and high selectivity toward Hg 2+ but no significant response toward other competitive cations, such as Fe 2+ , Co 2+ , Ni 2+ , Cu 2+ , Zn 2+ , Pb 2+ , Cd 2+ , Ca 2+ , Mg 2+ ,K + , Na + , etc. The Hg 2+ -promoted ring opening of spirolactam of the rhodamine moiety induced cyclic guanylation of the thiourea moiety, which resulted in the dual chromo- and fluorogenic observation (OFF-ON). Mercury contamination is widespread and arises from a variety of natural sources. 1 As we know, once introduced into the marine environment, bacteria convert inorganic Hg 2+ ions into methylmercury, which is neurotoxic and has been implicated as a cause of mercury pollution related to serious irreversible neurological damage. 2 Thus, the pollution by Hg 2+ ions will have severe effects on human health and the environment. Recently, many fluorescent chemosensors for Hg 2+ -selective detection have become available. 3 However, most of them have shortcomings in practical application, such as cross-sensitivities toward other metal cations, low water solubility, a narrow pH span, and delayed response, etc. Accordingly, the demand for analytical methods for the selective and sensitive determination of Hg 2+ ions is of topical interest, especially in the presence of miscellaneous competitive metal cations and a wide pH span in practical use. Recently, a particularly attractive alternative presented herein is the use of chemodosimeters as analytes through a specific chemical reaction between dosimeter molecules and target species, leading to the formation of a fluorescent or colored product. One of the more attractive approaches in this field involves the use of highly selective reactions (usually irreversible) induced by target analytes, in which an accumulative effect is directly related to the analyte concentration. Thus, high selectivity toward the analyte is a welcome feature of chemodosimeters, which is preferable for the detection of the Hg 2+ ion. However, only a few Hg 2+ chemodosimeters are available to date. 4 Herein, we report a rhodamine-based Hg 2+ chemodosim- eter (compound 1) as a new advance in this field. Our design ² Dankook University. ‡ Pohang University of Science and Technology. (1) (a) Renzoni, A.; Zino, F.; Franchi, E. EnViron. Res. 1998, 77, 68. (b) Benoit, J. M.; Fitzgerald, W. F.; Damman, A. W. EnViron. Res. 1998, 78, 118. (2) Boening, D. W. Chemosphere 2000, 40, 1335. (3) (a) Caballero, A.; Martinez, R.; Lloveras, V.; Ratera, I.; Vidal- Gancedo, J.; Wurst, K.; Tarraga, A.; Molina, P.; Veciana, J. J. Am. Chem. Soc. 2005, 127, 15666. (b) Coskun, A.; Akkaya, E. U. J. Am. Chem. Soc. 2006, 128, 14474. (c) Avirah, R. R.; Jyothish, K.; Ramaiah, D. Org. Lett. 2007, 9, 121. (d) Kim, S. H.; Kim, J. S.; Park, S. M.; Chang, S.-K. Org. Lett. 2006, 8, 371. (e) Zheng, H.; Qian, Z.-H.; Xu, L.; Yuan, F.-F.; Lan, L.-D.; Xu, J.-G. Org. Lett. 2006, 8, 859. (f) Choi, M. J.; Kim, M. Y.; Chang, S.-K. Chem. Commun. 2001, 1664. (g) Youn, N. J.; Chang, S.-K. Tetrahedron Lett. 2005, 46, 125. (h) Moon, S.-Y.; Youn, N. J.; Park, S. M.; Chang, S.-K. J. Org. Chem. 2005, 70, 2394. ORGANIC LETTERS 2007 Vol. 9, No. 5 907-910 10.1021/ol070109c CCC: $37.00 © 2007 American Chemical Society Published on Web 02/08/2007 Downloaded by KOREA UNIV LIB on November 1, 2009 | http://pubs.acs.org Publication Date (Web): February 8, 2007 | doi: 10.1021/ol070109c