Molecular Tweezers-like Calix[4]arene Based Alkaline Earth Metal Cation (Ca2+, Sr2+, and Ba2+) Chemosensor and Its Imaging in Living Cells and Zebrafish.

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 toward Ca2+, Sr2+, and Ba2+ (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 106). More significantly, sensor L not only can recognize Ca2+, Sr2+, and Ba2+ but also can further discriminate between these three cations via the differing red shifts in their UV-vis spectra (560 nm for L·Ca2+, 570 nm for L·Sr2+, and 580 nm for L·Ba2+ complex) which is attributed to their different atomic radii. A rare synergistic effect for the recognition mechanism has been demonstrated by 1H 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.

An efficient ICT-based ratio/colorimetric tripodal azobenzene probe for the recognition/discrimination of F-, AcO- and H2PO4- anions.

The tripodal probe L was readily prepared via introducing rhodamine and azobenzene groups in a two-step procedure. Studies of the recognition properties indicated that probe L exhibited high sensitivity and selectivity towards F-, AcO- and H2PO4- through a ratiometric colorimetric response with low detection limits of the order of 10-7 M. The complexation behaviour was fully investigated by spectral titration, 1H NMR spectroscopic titration and mass spectrometry. Probe L not only recognizes F-, AcO- and H2PO4-, but can also distinguish between these three anions via the different ratiometric behaviour in their UV-vis spectra (387/505 nm for L-H2PO4-, 387/530 nm for L-AcO- and 387/575 nm for L-F- complex) or via different colour changes (light coral for L-H2PO4-, light pink for L-AcO- and violet for the L-F- complex). Additionally, given the presence of NH and OH groups in probe L, which can be protonated and deprotonated, probe L further exhibited an excellent pH response over a wide pH range (pH 3 to pH 12).