Abstract
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
Highlights
In recent year, agricultural plant diseases and insect pests are becoming more severe in the world [1,2,3,4]
The past literature works concerning nematode problems have indicated that some Schiff bases and their metal complexes act as active nematicidal agents [7, 8]
The infrared spectra and thermal analysis proved that presence of water molecules in the composition of the complexes
Summary
Agricultural plant diseases and insect pests are becoming more severe in the world [1,2,3,4]. Plant parasitic nematodes are the main pathogens on most fiber crops, horticultural, food and vegetable crops and without adequate control; they cause loss of yield and quality. Nematode Meloidogyne species is known to attack almost all types of plants and cause considerable damage [6]. The past literature works concerning nematode problems have indicated that some Schiff bases and their metal complexes act as active nematicidal agents [7, 8]. Tetradentate Schiff bases containing nitrogen and oxygen donor atoms are well known for their coordination with various metal ions, forming stable compounds and make significant contributions to biological systems [12,13,14]
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