Novel selective and sensitive optical chemosensor based on phenylfluorone derivative for detection of Ge(IV) ion in aqueous solution.

A water soluble chemosensor for Ge ion based on fluorone derivative containing 3,4-bis(2-(diethylamino)-2-oxoethoxy)phenyl (R8) has been synthesized. The binding abilities between R8 and 10 equiv. of Na, K, Ca, Fe, Cu, Cd, Hg, Pb, Al, Cr, Fe and Ge ions in 1% v/v EtOH-water (tris-buffer pH 7.0) were studied using UV-vis and fluorescence spectrophotometry. When observed by naked-eyes, the color of R8 changed from yellow-orange to pink and the fluorescent color changed from green to non-fluorescence when complexed with Ge ion. The spectral analysis showed that UV-vis absorption and fluorescence emission intensity of R8 decreased dramatically when Ge ion was added comparing with other ions. To explain this behavior, the quantum calculation was performed using the hybrid density functional at B3LYP /LanL2DZ level of theory. The calculated orbital energies indicated that the decreasing of UV-vis absorption and the quenching of fluorescence were due to the complexation induced metal to ligand charge transfer. The association constants (K) of R8-Ge complexes calculated from Benesi-Hildebrand equation was 6.21 × 10 M. The UV-vis detection limit for Ge was 4.40 × 10 M which was three orders of magnitude lower than those of Al, Cd, Cu and Na ion.