Synthesis and structural characterization of zinc(II) and cobalt(II) complexes based on multidentate hydrazone ligands

Abstract

Two multidentate Schiff base ligands containing a hydrazone unit have been synthesized and investigated for zinc(II) and cobalt(II) coordination chemistry. The reactions of the 4-pyridyl derived hydrazone ligand HL1 with zinc(II) or cobalt(II) salts gave three mononuclear complexes that were structurally characterized by X-ray diffraction analysis. The results revealed that the ligand could adopt different coordination modes when various counter anions were employed. While in the case that zinc dichloride was used as a metal salt a neutral mononuclear mono-ligand complex was formed, the deprotonation of hydrazone occurred when zinc(II) or cobalt(II) nitrate were present and two new isostructural mononuclear bis-ligand complexes were isolated. Modification of the hydrazone ligand with oxygen donors was found to have a significant impact on the ligand reactivity, and a similar reaction of H 2 L2 with cobalt(II) nitrate gave a protonated product of H 2 L2 without the incorporation of cobalt(II), which features a one-dimensional hydrogen-bonded network in the solid state.

Synthesis, Characterization, Catalytic Activity, and DFT Calculations of Zn(II) Hydrazone Complexes

“…The complex 1 shows slightly greater degree of trigonal distortion from ideal square-based pyramidal configuration, in comparison with the other five-coordinate Zn(II) complexes with N -heteroaromaticmonohydrazones of Girard’s T reagent and pseudohalide or halide ligand (N 3 − , NCO − , NCS − or Cl − ) as monodentate for which the calculated τ values are in the range 0.31–0.34 (complexes 3 – 6 , Table S1 in the Supplementary Materials ) [ 8 , 9 , 10 ]. The τ values for complexes 1 , 3 – 6 fit into the range of values obtained for related Zn(II)complexes [ 36 , 37 , 38 , 39 , 40 ] (complexes 7 – 15 , Table S1 in the Supplementary Materials ). The Zn(II) ion in 1 is more strongly bound to the imine nitrogen atom of the ligand L 1 than to the 1,3-thiazole nitrogen, as indicated by the Zn1–N2, 2.058(2) Å and Zn1–N1, 2.212(2) Å bond lengths ( Table 2 ).…”

New Tridentate Hydrazone Metal Complexes Derived from 2-Hydroxy-4-Methoxyacetophenone and some Acid Hydrazides: Synthesis, Characterization and Antibacterial Activity Evaluation

“…Aroyl hydrazones are quite interesting ligands as they present a combination of donor sites, such as amide oxygen atom, imine nitrogen atom of the hydrazone moiety and an additional donor site (usually N or O) provided from the aldehyde or ketone forming them. Hydrazones have interesting ligation properties due to the presence of these several coordination sites, hence they display versatility in metal coordination (Li et al, 2016 ;Singh et al, 2015). The mode of coordination depends on the nature of the central metal atom, the pH of the medium, the nature of the substituents and also on the position of the hydrazone group relative to other moieties.…”

Synthesis, Spectroscopic Characterization And Antimicrobial Evaluation of Novel Nitrogen Containing Metal Complexes

“…Schiff bases are azomethine group (C=N) containing compounds which were first announced by Hugo Schiff in 1864 and synthesized by condensation of the primary amine with carbonyl compound [1]. Schiff bases remain the most extensively utilized organic compounds [2][3][4][5][6][7] and it has potential sites, such as nitrogen and other electron donors; it may be related to their stability, uses and applications in numerous scientific areas [1,2,4,5,[8][9][10]. For long periods of time, coordination chemistry of Schiff base ligands has been the topic of great interest.…”

“…For long periods of time, coordination chemistry of Schiff base ligands has been the topic of great interest. These compounds are able to form coordination bonds with many metal ions via azomethine group (C=N) and other electron donor groups, so they have been used for the synthesis of metal complexes due to their easy formation and strong ability to bind with metal ions [4][5][6][7][10][11][12][13] and their ability to form stable complexes to use as model compounds in service of biologically important species [12][13][14] where the nitrogen atom of azomethine group may be participated in the formation of constituents and interferes in normal cell processes so the (C=N) bond in azomethine derivatives is essential for biological activities [1,15] as antitumor, antimicrobial agents (antifungal, antibacterial, antiviral and antiparasitic agents) and other biological performances [15]. These compounds have also played a great role in the chemistry development [2,3,5,6,11,16].…”

“…Much interest has been focused on the hydrazone complexes to exhibit the coordinative behavior-microbial activity relationship and to their antiparasitic, fungicidal and bactericidal properties [8,20]. And this is because the strong ability of hydrazone part in chelating metal ions [7,8], whereas hydrazone contain two nitrogen atoms of different nature are associated and a C=N that is conjugated with alone pair of the terminal nitrogen atom [19]. The hydrazides and their derivatives are very important ligands and have attracted considerable attention recently, due to their several biological activities.…”