Cyclic voltammetric and e.s.r. studies of a tetraaza 14-membered macrocyclic copper(II) complex derived from 3-salicylideneacetylacetone ando-phenylenediamine: stabilization and activation of unusual oxidation states

Abstract

A 14-membered macrocyclic Schiff base derived from 3-salicylideneacetylacetone and o-phenylenediamine acts as a tctradentate and strongly conjugated ligand to form a cationic solid complex with CuC12. U.v.-vis. and e.s.r. spectral data reveal a strong ligand to metal 7z-interaction in the square planar complex. C.v. data reveal that the title ligand is able to stabilize the copper(III) oxidation state more cffectivcly than comparable saturated or partially unsaturated macrocyclic ligands and confers a weaker tendency for reduction of copper(II) to copper(I) and copper(0). While the inclusion of a PPh 3 ligand suppresses the Cu ~ -, Cu j -, Cu u oxidation, imidazole and pyridinc strongly enhance the Cu ~I ~ Cu ~II oxidation ofthc complex.

Synthesis, spectral characterization, redox and antimicrobial activity of Schiff base transition metal(II) complexes derived from 4-aminoantipyrine and 3-salicylideneacetylacetone

“…The voltammogram shows three reduction peaks in the cathodic direction which are assigned as follows: Cu III → Cu II at Ep c = 0.882 V, Cu II → Cu I at Ep c = 0.123 V and Cu I → Cu 0 at Ep c = -0.471 V respectively and it shows two oxidation peaks in the anodic direction, one very strong absorption peak at Ep a = 0.041 V which is due to Cu 0 → Cu II and another peak observed at Ep a = 0.738 V is due to Cu II → Cu III . These values are similar to the values reported earlier 12 . The cathodic to anodic peak current ratio i pc /i pa ≈ 0.5 of the couple Cu III /Cu II indicates the quasi-reversible nature of the couple.…”

“…• C. The Knoevenagel condensate β-diketone (3-salicylideneacetyl-acetone) was synthesized according to the reported procedure [12]. The preparation of the Schiff base 3SDAP is shown in Scheme 1.…”

“…This process has been successfully applied to the non-symmetrical tetradentate Schiff base having the mixed donor sets N 2 O 2 . In our earlier studies,various N 2 O 2 and N 4 ligands derived from benzil, acetylacetone, acetoacetanilide with o-phenylenediamine and 4-aminoantipyrine have been reported [8][9][10][11][12]. In this paper the synthesis of new tetradentate N 2 O 2 donor type Schiff base and its bivalent metal complexes derived by the condensation of 4-aminoantipyrine (1-phenyl-2,3-dimethyl-4-amino-pyrazol-5-one) with 3-salicylidene-acetylacetone is described.…”

Antimicrobial, Antioxidant and DNA Interaction Studies of Water-soluble Complexes of Schiff Base Bearing Morpholine Moiety

“…The cyclic voltammogram for complexes (1-5) revealed that one electron reduction peak (E pc ) corresponding to M(II) to M(I) and oxidation peak (E pa ) corresponding to M(I) to M(II) [39] . The observed value of peak-to-peak separation (ΔE P ) for complexes (1)(2)(3)(4)(5) were in the range of 262-829 mV, which was larger than the Nernstian value (E Pa -E Pc ) (or) ΔE P =2.303RT/nF = 59/n mV, for the M(II)/M(I) redox couple revealed that this process was the best quasi-reversible.…”

Synthesis and Characterization of Zinc β-Diketonate Complex Extended to the Macromolecular Polymers

“…IR spectrum of 3 shows prominent absorptions at 3426 cm -1 (ascertains the presence of coordinated aqua ligands 23 ) and 1601 -1410 cm -1 (typical for metal b-diketonate complexes 24 -25 . IR spectroscopy can also be used to monitor the elimination of the aqua ligands in 3 by thermal treatment because the very characteristic vibrations of the aqua ligands continuously disappear with progress of the reaction 14,24 . The peaks at 1601, 1578, 1540, and 1508 are assigned to the keto-enol tautomerism chelating ring of  C=O and  C=C stretching vibrations 18 .…”