Spectroscopically labelled hydroxylamino-triazine (BHT) siderophores toward the quantification of iron(<sc>iii</sc>), vanadium(<sc>v</sc>) and uranium(<sc>vi</sc>) hard metal ions

Based on the strong binding properties of hydroxylamino-1,3,5-triazine (BHT) for hard metal ions, a novel spectroscopically labelled triazine-hydroxylaminato ligand, N,N '-(6-(9H-carbazol-9-yl)-1,3,5-triazine-2,4-diyl)bis(N-methylhydroxylamine) (H(2)cbht), was synthesized. Reaction of H(2)cbht with Fe-III, V-V and U-VI resulted in the synthesis of [(UO2)-O-VI(cbht)(DMF)(MeOH)], 1, (PPh4)(2)([(UO2)-O-VI(Hcbht)(2)]<middle dot>2[(UO2)-O-VI(Hcbht)(cbht)]), 2, (PPh4)(2)[((UO2)-O-VI)(3)(mu-cbht)(2)(cbht)(2)], 3, Na[(VO2)-O-V(cbht)], 4, and (PPh4)[Fe-III(cbht)(2)], 5. The complexes were characterized by X-ray crystallography showing strong chelation of the metal ions with the BHT chelating moiety H(2)cbht. The DMSO/DMF solutions of the complexes were characterized by NMR, UV-vis and electrochemistry, confirming the high affinity of H(2)cbht for Fe-III, V-V or U-VI. The luminescence properties of the carbazole group were retained in the BHT adduct of the H(2)cbht ligand. Interaction of the metal ions with H(2)cbht resulted in quenching of the luminescence of H(2)cbht. Stern-Volmer plots of luminescence vs. concentration of the metal ions are linear and suitable for the determination of the concentration of metal ions in nM range concentrations. Benesi-Hildebrand plots show that the metal-to-ligand ratio is 1 : 1 while the formation of the metal complexes exhibits high association constants.