Coordination behavior of new bis(tridentate ONO, ONS and ONN) donor hydrazones towards some transition metal ions: Synthesis, spectral, thermal, antimicrobial and antitumor studies

Abstract

Three new hydrazone ligands, H2L1, H2L2 and H4L3, were prepared by condensation of 4,6-bis(1-hydrazonoethyl)benzene-1,3-diol with furan-2-carboxaldehyde, thiophene-2-carboxaldehyde and 1H-pyrrole-2-carboxaldehyde, respectively. The ligands reacted with copper(II), nickel(II), cobalt(II), zinc(II), cadmium(II) and dioxouranium(VI) ions to yield binuclear complexes formulated as [(L)M2(OAc)2(H2O)n(EtOH)m]·xH2O·yEtOH where L = L1 or L2; M = Cu, Ni, Co, Zn or Cd; n = nil, 1 or 4; m, x and y = nil or 1, [(H2L2)Cd2(OAc)4(H2O)2]·EtOH, [(L)(UO2)2(OAc)2(H2O)2Y2]·nH2O where L = L1 or L2; Y = nil or H2O; n = 2.5 or 7, [(L3)M2(H2O)6]·nH2O where M = Cu or Zn; n = 1 or 6, [(L3)(UO2)2(H2O)4]·2.5H2O and dimeric complexes; [(L1)2Ni2]·3H2O and [(H2L3)2M2]·nH2O where M = Ni or Co; n = 1.5 or 3. The ligands and their metal complexes were characterized by elemental analyses, IR, 1H and 13C NMR, electronic, ESR and mass spectra, conductivity, magnetic susceptibility measurements and powder XRD as well as thermal analysis. The coordinating sites are phenolic oxygens, azomethine nitrogens and the hetero O/N/S atoms. Octahedral, tetrahedral and square planar geometrical arrangements are proposed for metal complexes whilst the uranium ion is hepta- or octa-coordinated. The kinetics of the thermal decomposition for some metal complexes were studied and their thermodynamic parameters were calculated using Coats-Redfern method. The antimicrobial activity of the ligands and their complexes was screened. The antitumor activity of the ligands and their complexes was tested on Ehrlich Ascites Carcinoma. Copper(II) complexes showed promising IC50 values, which are comparable to that of cisplatin.