Comparison of chelating ability of NO-, NS-, ONS-, and ONO-type Schiff base derivatives and their stability constants of Bis-complexes with copper(II)

Kaynakça (1)

1. 1a 26 14 Ref. 10 21 57 Ref. 10 90 35 Ref. 10 38 ± 0.03 9.46 ± 0.08 84 ± 0.03 This work 1b 29 ± 0.03 9.38 ± 0.09 68 ± 0.03 This work 1c 05 ± 0.03 9.75 ± 0.08 80 ± 0.02 This work 1d 45 22 Ref. 10 22 56 Ref. 10 95 35 Ref. 10 18 ± 0.01 9.21 ± 0.06 39 ± 0.03 This work 1e - 32 34 Ref. 8 94 ± 0.02 9.16 ± 0.03 11.33 ± 0.08 20.45 ± 0.06 24.43 ± 0.07 This work 1f - 19 40 Ref. 7 46 46 Ref. 9 28 62 11 Ref. 10 11 73 25 Ref. 10 01 61 30 Ref. 10 47 ± 0.04 8.07 ± 0.01 10.76 ± 0.08 18.83 ± 0.07 23.29 ± 0.07 This work 2a 83 ± 0.03 15 ± 0.08 99 ± 0.03 This work 2b 75 ± 0.03 69 ± 0.07 44 ± 0.03 This work 2c 43 ± 0.03 9.15 ± 0.02 58 ± 0.02 This work 2d 07 ± 0.01 9.28 ± 0.02 34 ± 0.03 This work 2e 35 ± 0.02 9.74 ± 0.03 09 ± 0.06 This work 3a 41 25 Ref. 7 58 13 Ref. 8 37 77 Ref. 6 36 ± 0.04 6.09 ± 0.09 9.11 ± 0.01 19 ± 0.04 19.55 ± 0.03 This work 12 Ref. 5 3b 38 ± 0.04 6.54 ± 0.09 10.12 ± 0.04 16.66 ± 0.04 20.03 ± 0.04 This work mM + lL + hH M m L l H h (3) β mlh = [M m L l H h ] [M ] m [L] l [H] h, (4) where M is Cu(II) ion, L is ligand, and H is proton, and m, l, and h are the respective stoichiometric coefficients. The potentiometric data for the Cu(II) – L 2 systems indicate that there is a significant tendency toward the formation of ML 2 species. Cu(II) ion complexes were formed by releasing 2 of the hydrogen ions from the fully protonated form of the ligands. 11 Compounds 1e and 1f serve as tridentate ligands by the coordinating of imino, phenolic –OH and –SH groups with Cu(II) ion. The others (1a, 1b, 1c, 1d, 2a, 2b, 2c, 2d, 2e, 3a, and 3b) serve as bidentate ligands. Thus, the stability constants of Cu(II) complexes of 1e and 1f are higher than those of the others. Coordination numbers of a central atom can change to 6 or 4 depending on the ligand structures in the complex formation. For example, the coordination number of Cu(II) ion was observed as 4 against all studied ligands except 1e and 1f in this study. Therefore, tetrahedral complexes were obtained. On the other hand, the coordination number of Cu(II) ion was 6 against 1e and 1f, because they are tridentate ligands. The molecular structures of 4- and 6-coordinated complexes of copper with 1a and 1f are given in Figure 3a and 3b. Figure 3. Molecular structures of 4- and 6-coordinated complexes of Cu(II) with 1a and 1f (a) Cu(II)–1a 2 (b) Cu(II)–1f 2 Complexes having 6 coordination numbers form an octahedral structure and they can be formulated as MX 2, where MX 2 is a structure of bis-complex, M is Cu(II) ion, and