Although alkaline earth metal cations play an important role in our daily life, little attention has been paid to the field of fast quantitative analysis of their content due to a lack of satisfactory precision, and a fast and convenient means of detection. In this study, we have designed a set of molecular tweezers based on the calix[4]arene chemosensor L, which was found to exhibit high selectivity and sensitivity towards Ca 2+ , Sr 2+ and Ba 2+ (by UV-vis and fluorescence methods) with low detection limits of the order of 10 -7 to 10 -8 M and high association constants (of the order of 10 6 ). More significantly, sensor L not only can recognize Ca 2+ , Sr 2+ and Ba 2+ , but can also further discriminate between these three cations via the differing red shifts in their UVvis spectra (560 nm for L•Ca 2+ , 570 nm for L•Sr 2+ and 580 nm for L•Ba 2+ complex) which is attributed to their different atomic radii. A rare synergistic effect for the recognition mechanism has been demonstrated by 1 H NMR spectroscopic titration. Sensor L constructed a high shielding field by the cooperation of Tris with alkaline earth metal ion after complex. Additionally, the presence of acetoxymethyl group in sensor L results in enhancement of cell permeability and as a consequence, sensor L exhibited excellent sensing and imaging (in vivo) in living cells and in Zebrafish.
ASSOCIATED CONTENTSupporting Information. Detailed characterization, spectra and 1 H NMR titration data (PDF). This material is available free of charge via the Internet at http://pubs.acs.org.