Synthesis, structure and electrochemical behaviour of Na, MgII, MnII, ZnII, CdII and NiII complexes of 3-(2-carboxyphenylhydrazone)pentane-2,4-dione

Mononuclear manganese(II) [Mn(κO-HL)2(CH3OH)4] (4), nickel(II) [Ni(κ2O, κN-L)(H2O)3] (5), cadmium(II) [Cd(κ2O-HL)2(CH3OH)3] (7), tetranuclear zinc(II) [Zn4(μ-OH)2(1κO:2κO-HL)4(κO-HL)2(H2O)4] (6) and polynuclear aqua sodium(I) [Na(H2O)2(μ-H2O)2]n(HL)n (2) and magnesium(II) [Mg(OH)(H2O)(μ-H2O)2]n(HL)n (3) complexes were synthesized using 3-(2-carboxyphenyl-hydrazone)pentane-2,4-dione (H2L, 1) as a ligand precursor. The complexes were characterized by single crystal X-ray diffraction, elemental analysis, IR, 1H and 13C NMR (for 2, 3, 6 and 7) spectroscopies. Mono- or dianionic deprotonated derivatives of H2L display different coordination modes and lead to topologies and nuclearities of the complexes depending on metal ions and conditions used for the syntheses. Extensive intermolecular H-bonds form supramolecular arrangements in 1D chains (4 and 6), 1D chains of the organic anion and 2D networks of the metal-aqua aggregates (2 and 3), 2D networks (7) or even 3D frameworks (5). Electrochemical studies, by cyclic voltammetry and controlled potential electrolysis, show ligand centred redox processes as corroborated by theoretical DFT calculations in terms of LUMO and HOMO compositions.

Graphical abstract3-(2-carboxyphenylhydrazone)pentane-2,4-dione is a valuable ligand leading to a variety of complexes with different coordination modes and nuclearities.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Na, MgII, MnII, ZnII, CdII and NiII complexes with 3-(2-carboxyphenylhydrazone)pentane-2,4-dione. ► Ligand coordinates in bi-, tri- and tetradentate mode depending on the metal ion. ► Different topologies and nuclearities of the complexes are depending on metal ion.