Abstract
Novel tridentate Schiff base ligand derived from the 2-aminobenzenthiol and 8-hydroxy-7-quinolinecarboxaldehyde (oxine) and its metal complexes have been prepared. The reaction of a solution of 7-(2,3-dihydro-1,3-benzothiazol- 2-yl)quinolin-8-ol (H2L) with di-and tetravalent transition metals have been studied chemically and biologically. The optimized bond lengths, bond angles and calculated the quantum chemical parameters for the ligand (H2L) [the cyclic form (A) and the Schiff base form (B)] were investigated. The complexes have been characterized by elemental analyses, IR spectra, thermal analyses and 1H-NMR spectroscopy. The spectral studies of the isolated complexes showed that the rearrangement of the benzothiazoline to the Schiff base had occurred. The data suggest that the Co(II) and Ni(II) complexes are binuclear and octahedral dimmers, while the rest are monomeric with square planar/ tetrahedral geometries. The ESR spectrum of the Cu(II) complex show axial type symmetry with gll > gâ´>2.0023, indicating dx2-y2 ground state with significant covalent bond character. Five doses were topically applied against the newly emerged adults of the red palm weevil Rhynchophorus ferrugineus. Percent of adult mortality was 98.2%, which occurred after adult treatment with the highest dose (2.2 mg/ml) of Ni(II) complex. The lowest mortality was 5.6% which obtained due to effect of oxine after adult was treated with dose of 0.25 mg/ml. Five doses were topically applied against the newly emerged adults of the stored product weevil, Sitophilus granaria. While the lower mortality, 5% caused due to effect of least dose, 0.15 mg/ml of the compound oxine.
Highlights
Schiff bases continue to occupy an important position as ligands in metal coordination chemistry even after almost a century since their discovery
Sulphur and nitrogen have long been used to increase the biological activity of organic moiety [1,2] and quinoline compounds have found applications in medicinal chemistry [3]
Reaction of 7-(2,3-dihydro-1,3-benzothiazol-2-yl)quinolin-8ol with metal ions: The complexes were prepared by methods similar to the reported in earlier publications [14,22,23,24] according to the following procedures: Scheme (1A)
Summary
Schiff bases continue to occupy an important position as ligands in metal coordination chemistry even after almost a century since their discovery. Reaction of 7-(2,3-dihydro-1,3-benzothiazol-2-yl)quinolin-8ol with metal ions: The complexes were prepared by methods similar to the reported in earlier publications [14,22,23,24] according to the following procedures: Scheme (1A) The selected geometrical structures of the investigated ligand (H2L) [cyclic form (A) and the Schiff base form (B)] were calculated by optimizing their bond lengths and bond angles and listed in Tables 1 and 2.
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