Complexation of zinc(II) and other divalent metal ions by the fluorophore 2-methyl-8-(toluene-p-sulfonamido)-6-quinolyloxyacetic acid in 50% aqueous ethanol

Rodopoulos, T.; Pittet, P.A.; Mahadevan, I.; Lincoln, S.; Ward, A.; Duckworth, P.; Kurucsev, T.; Hendrickson, K.; Forbes, I.; Zalewski, P.

Complexation of zinc(II) and other divalent metal ions by the fluorophore 2-methyl-8-(toluene-p-sulfonamido)-6-quinolyloxyacetic acid in 50% aqueous ethanol

1997

A potentiometric and fluorescence study of the complexation of divalent metal ions (M2+) by the fluorophore 2-methyl-8-(toluene-p-sulfonamido)-6-quinolyloxyacetic acid (H<inf>2</inf>L) in 50% (v/v) aqueous ethanol at 298.2 K and I = 0.10 mol dm-3 (NaClO<inf>4</inf>) showed that the [ML] and [ML<inf>2</inf>]2- complexes are characterised by log(β<inf>1</inf>/dm3 mol-1) and log(β<inf>2</inf>/dm6 mol-2) values of 8.12 ± 0.20 and 17.06 ± 0.11, respectively, when M2+ = Co2+ and corresponding values of < 8 and 15.73 ± 0.03 when M2+ = Ni2+, 11.96 ± 0.02 and 21.40 ± 0.03 when M2+ = Cu2+, 9.65 ± 0.02 and 19.11 ± 0.06 when M2+ = Zn2+ and 8.44 ± 0.50 and 15.38 ± 0.40 when M2+ = Cd2+. In the cobalt(II) system, [CoL<inf>3</inf>]4-, where log(β<inf>3</inf>/dm9 mol-3) = 25.56 ± 0.11, was also detected. The pK<inf>a</inf> values for H<inf>3</inf>L+ are 1.87 ± 0.10, 3.72 ± 0.03 and 10.01 ± 0.02. These data are discussed together with the fluorescence characteristics of HL-, [ZnL] and [ZnL<inf>2</inf>]2-.

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