A Schiff base platform: structures, sensing of Zn(II) and PPi in aqueous medium and anticancer activity

摘要

A reaction of N-1,N-3-bis(3-methoxysalicylidene) diethylenetriamine (H(2)Vd) and Zn(NO3)(2)center dot 6H(2)O, ZnBr2, ZnI2 and Cd(NO3)(2)center dot 4H(2)O in a methanol solution led to zinc and cadmium complexes of different nuclearities, [Zn-2(Vd center dot H)(2)(X)(2)]center dot CH3OH (X = NO3, Br, I) [1a, 1b and 1c] and Cd-3(Vd)(2)(NO3)(2) (2). In 1(a-c), two H(2)Vd ligands bridge the two metal centers whereas in 2, they provide sideways support to two terminal Cd2+ ions, providing an all-oxygen envelope to the central Cd2+ ion. All four compounds were characterized by elemental analysis, FT-IR spectroscopy and single crystal X-ray diffraction analysis. Complexes 1(a-c) exhibit dinuclear structures, whereas 2 exhibits a nearly linear trinuclear structure. The structural differences among these complexes are attributable to various coordination modes and flexible configurations of the H(2)Vd ligand. The ligand H(2)Vd is an excellent probe for sensing Zn2+ in solution, whereas complexes 1(a-c) are able to selectively detect pyrophosphate (PPi) in aqueous medium. The structure of the pyrophosphate (PPi) complex has been proposed using DFT calculations and the selectivity is due to the unique ability of this anion to simultaneously coordinate to both the Zn metal centers. The anticancer activity of complexes 1(a-c) was also explored.