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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) (H2cbht), was synthesized. Reaction of H2cbht with FeIII, VV and UVI resulted in the synthesis of [UVIO2(cbht)(DMF)(MeOH)], 1, (PPh4)2([UVIO2(Hcbht)2]·2[UVIO2(Hcbht)(cbht)]), 2, (PPh4)2[(UVIO2)3(μ-cbht)2(cbht)2], 3, Na[VVO2(cbht)], 4, and (PPh4)[FeIII(cbht)2], 5. The complexes were characterized by X-ray crystallography showing strong chelation of the metal ions with the BHT chelating moiety H2cbht. The DMSO/DMF solutions of the complexes were characterized by NMR, UV-vis and electrochemistry, confirming the high affinity of H2cbht for FeIII, VV or UVI. The luminescence properties of the carbazole group were retained in the BHT adduct of the H2cbht ligand. Interaction of the metal ions with H2cbht resulted in quenching of the luminescence of H2cbht. 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. [ABSTRACT FROM AUTHOR]

The two-electron reductive activation of O 2 to O 2 2- is of particular interest to the scientific community mainly due to the use of peroxides as green oxidants and in powerful fuel cells. Despite of the great importance of vanadium(IV) species to activate the two-electron reductive activation of O 2 , the mechanism is still unclear. Reaction of V IV O 2+ species with the tridentate-planar N,N,N- carboxamide (ΗL) ligands in solution (CH 3 OH:H 2 O) under atmospheric O 2 , at room temperature, resulted in the quick formation of [V V (═O)(η 2 -O 2 )(κ 3 -L)(H 2 O)] and cis -[V V (═O) 2 (κ 3 -L)] compounds. Oxidation of the V IV O 2+ complexes with the sterically hindered tridentate-planar N,N,N- carboxamide ligands by atmospheric O 2 gave only cis -[V V (═O) 2 (κ 3 -L)] compounds. The mechanism of formation of [V V (═O)(η 2 -O 2 )(κ 3 -L)(H 2 O)] (I) and cis -[V V (═O) 2 (κ 3 -L)] (II) complexes vs time, from the interaction of [V IV (═O)(κ 3 -L)(Η 2 Ο) 2 ] + with atmospheric O 2 , was investigated with 51 V, 1 H NMR, UV-vis, cw-X-band EPR, and 18 labeling IR and resonance Raman spectroscopies revealing the formation of a stable intermediate ( 2 ). EPR, MS, and theoretical calculations of the mechanism of the formation of I and II revealed a pathway, through a binuclear [V Id ). EPR, MS, and theoretical calculations of the mechanism of the formation of I and II revealed a pathway, through a binuclear [V IV (═O)(κ 3 -L)(H 2 O)(η 1 ,η 1 -O 2 )V IV (═O)(κ 3 -L)(H 2 O)] 2+ intermediate. The results from cw-EPR, 1 H NMR spectroscopies, cyclic voltammetry, and the reactivity of the complexes [V IV (═O)(κ 3 -L)(Η 2 Ο) 2 ] + reduction fit better to an intermediate with a binuclear nature. Dynamic experiments in combination with computational calculations were undertaken to fully elucidate the mechanism of the O 2 reduction fit better to an intermediate with a binuclear nature. Dynamic experiments in combination with computational calculations were undertaken to fully elucidate the mechanism of the O 2 reduction to O 2 2- by [V IV (═O)(κ 3 -L)(Η 2 Ο) 2 ] + . The galvanic cell {Zn|V III ,V II || Id , [V IV O(κ 3 -L)(H 2 O) 2 ] + |O 2 |C(s)} was manufactured, demonstrating the important applicability of this new chemistry to Zn|H 2 O 2 fuel cells technology generating H 2 O 2 in situ from the atmospheric O 2 .