Spectroscopically labelled hydroxylamino-triazine (BHT) siderophores toward the quantification of iron(), vanadium() and uranium() 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-(9 H -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 [U VI O 2 (cbht)(DMF)(MeOH)], 1 , (PPh 4 ) 2 ([U VI O 2 (Hcbht) 2 ]·2[U VI O 2 (Hcbht)(cbht)]), 2 , (PPh 4 ) 2 [(U VI O 2 ) 3 (μ-cbht) 2 (cbht) 2 ], 3 , Na[V V O 2 (cbht)], 4 , and (PPh 4 )[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. The first BHT luminescent siderophore-type ligand has been prepared. Coordination of the selective ligand with hard metal ions, Fe III , V V and U VI , quenches the emitted light permitting the quantification of metal ions at nM concentrations.