Synthesis and characterization of uranyl(VI) chiral Schiff-base complexes derived from salicylaldehyde and L-aminoacids

Complexes of uranyl(VI) (U(VI)) with tridentate ligands derived from salicylaldehyde and aminoacids are reported, bis 2-((2-hydroxybenzylidene)amino)acetic acid U(VI), UO2(SalGly)2 (1); tri aqua 2-((2-hydroxybenzylidene)amino)propanoic acid U(VI) nitrate, [UO2(SalAla)(H2O)3]NO3 (2); tri aqua 3-hydroxy-2-((2-hydroxybenzylidene)amino)propanoic acid U(VI) nitrate, [UO2(SalSer)(H2O)3]NO3 (3); tri aqua 2-((2-hydroxybenzylidene)amino)-3-methylbutanoic acid U(VI) nitrate, [UO2(SalVal)(H2O)3]NO3 (4), and tri aqua 2-((2-hydroxybenzylidene)amino)-4-(methylthio)butanoic acid U(VI) nitrate, [UO2(SalMet)(H2O)3]NO3 (5). The characterization of the complexes was performed by electrospray mass spectroscopy, ultraviolet-visible spectroscopy, Fourier transform infrared spectroscopy, nuclear magnetic resonance, fluorescence spectroscopy, and thermal analysis. The complexes are electrolytes (1 : 1) having a molar ratio M : L = 1 : 1, except 1, which is a nonelectrolyte with a molar ratio M : L = 1 : 2. The fluorescence intensity of the complexes is more intense than uncomplexed uranyl, except 1 and 5. High fluorescence of the uranyl SalAla complex (2) was used to assess complexes–DNA interaction based on fluorescence quenching assay. The interaction of 2 with DNA was assessed by measuring the relative fluorescence quenching of the complex when nucleic acids were added.