Coordination compounds of Cu (II), Y (III), Zr (IV) and La (III) with the tetradentate Schiff base (H 2 L) obtained through the condensation of pphenylenediamine with salicylaldehyde under reflux conditions. The complexes were characterized by elemental analysis, magnetic susceptibility, molar conductance and also, with various spectroscopic techniques such as 1 H NMR, UV-Vis., IR and XRD techniques. Electrolytic nature of complexes was ascertained by molar conductance values. In these four complexes, the ligand chelates act in a tetradentate manner via azomethine nitrogen and oxygen atoms of phenolic groups. Electronic spectroscopic data are in agreement with an octahedral geometrical structure. Thermal degradation analyses in nitrogen gas were used to investigate the number and location of water molecules. The chemical formulae of metal complexes were confirmed by microanalytical data. The activation thermodynamic parameters, such as, E * , ΔH * , ΔS * and ΔG * were calculated from the DTG curves using Coats Redfern (CR) andHorowitz-Metzeger (HM) methods at n = 1 or n ≠ 1. Nematicidal activities indicate that the ligand exhibit greater activity when compared to its complexes. In addition metal complexes displayed good moderate nematicidal activities.

A series of Co(II), Cu(II), Y(III), Zr(IV), La(III), and U(VI) complexes derived from 2-(2-hydroxybenzylidinemine)-benzoic acid (L) ligand were synthesized. The mode of bonding of L and the structure of its metal complexes were investigated using different analytical and spectral tools (FT-IR, UV-Vis, 1 H NMR, mass, and XRD). The ligand chelated with the metal ions as a neutral bidentate through oxygen and azomethine nitrogen atoms. All metal complexes adopted octahedral geometry with characteristic color for metal ions. The results of magnetic moment measurements supported paramagnetic for some complexes (Co(II) and Cu(II)) and diamagnetic phenomena for the other complexes. The thermal decomposition of the ligand along with its metal complexes was explained. The molar conductance values of all complexes in (DMF) were found in the range 154.50 to 250.20 S cm 2 mol −1 at room temperature. The activation thermodynamic parameters, such as E*, ΔH*, ΔS* and ΔG*, were calculated from the DTG curves using Coats-Redfern (CR) and Horowitz-Metzeger (HM) methods at n = 1 or n 6 ¼ 1.The nematicidal activity of the synthesized L and their metal complexes was screened. K E Y W O R D S

ABSTRACT. Cobalt(II), copper(II), yttrium(III), zirconium(IV), lanthanum(III) and uranium(VI) complexes of 1,4-di(2-hydroxybenzylidene)thiosemicarbazide (H2L) were prepared and characterized. The proposed structures were determined from their elemental analyses, molar conductivities, magnetic moment, IR, Proton NMR, UV-Vis., mass spectra, X-ray diffraction and thermal analyses measurements. The high conductance data supply evidence for the electrolytic nature of the complexes. The changes in the selected bands in IR of Schiff base ligand upon coordination showed that Schiff base exhibits as a neutral tetradentate manner with oxygen and nitrogen donor sites. The complexes are thermally steady at room temperature and break up to two or three steps. The kinetic and thermodynamic parameters of complexes have been determined by using Coats-Redfern and Horowitz-Metzeger methods at n=1 and n≠1 and values suggest more ordered activated complex formation. The calculated bond length and force constant, F(U=O), in the uranyl complex are 1.744 Å and 664.886 Nm-1. The nematicidal activity of free Schiff base and all complexes were investigated and showed a low inhibition percentage (%I) of complexes compared with H2L.                     KEY WORDS: Schiff base, IR, Thermal, XRD, Nematicidal activity   Bull. Chem. Soc. Ethiop. 2021, 35(2), 315-335. DOI: https://dx.doi.org/10.4314/bcse.v35i2.8

ABSTRACT. A series of metal complexes [Co(HL)2(H2O)2]Cl2.5H2O (A), [Cu(HL)2](CH3COO)2.2H2O (B), [Y(HL)2]Cl3.2H2O (C), [ZrO(HL)2H2O]Cl2.H2O (D), [La(HL)2(H2O)2]Cl3.5H2O (E) and [UO2(HL)2](CH3COO)2 (F) were prepared. The structures of the compounds in solid state were detected by micro analytical, Fourier transform IR, 1H NMR, UV-Vis, mass, X-ray diffraction spectra, molar conductivity, magnetic susceptibility measurements and TG/DTG analysis. The IR spectral data point out that the ligand behaves as tridentate in nature with Cu(II), Y(III), U(VI) and bidentate with Co(II), Zr(IV) and La(III) metal ions. The conductivity values showed that the complexes found as electrolytes and the XRD models of the complexes indicated crystalline nature. The thermodynamic parameters of compounds have been detected using Coats-Redfern and Horowitz-Metzeger methods at n = 1 and n ≠ 1 and values point out more ordered activated complex formation. The nematicidal efficacy of compounds was assessed.                     KEY WORDS: Schiff base, Spectroscopic analysis, Thermal analysis, XRD, Nematicidal   Bull. Chem. Soc. Ethiop. 2021, 35(2), 381-397. DOI: https://dx.doi.org/10.4314/bcse.v35i2.12

ABSTRACT. Some new solid complexes [CrCl3(L)3]⋅6H2O, [FeCl3(L)3]⋅6H2O and [Cu(CH3COO)2(L)3]⋅2H2Ohave been synthesized quantitatively by the interactions of 2-methyl-quinazolinone (L) with CrCl3.6H2O, FeCl3.6H2O and Cu(CH3COO)2.2H2O in a mixture of an ethanol-bidistilled water (1:1), at 60 °C. They were characterized by melting point, molar conductivity, magnetic moment, elemental analysis, infrared spectra and thermal analyses. The results supported the formation of the complexes and indicated that the ligand reacted as a monodentate ligand bound to the metal ion through the oxygen atom. The antifungal activity of the free ligand and their metal complexes were evaluated against several species, such as Fusarium solani, Rizoctonia solani, Sclortium rolfsii and Botryodiplodia and they showed a good antifungal activity to some selected fungal strain as compared with free ligand.