ISSN print edition: 0366-6352 ISSN electronic edition: 1336-9075 Registr. No.: MK SR 9/7 Published monthly

Electron spin resonance and optical spectral studies of a titanium(III) complex formed with nitrilotriacetic acid

P.I. Premović and L.S. Jovanović

Laboratory of Geochemistry, Department of Chemistry, Faculty of Science, University of Niš, Y U-J 8000 N iš

Abstract: On adding more than two moles of nitrilotriacetic acid (NTA) to a solution of Ti(III) at pH 4 to 10 containing 10-20 M tartaric acid, a solution is obtained that exhibits a rather sharp ESR absorption signal (g₀ = 1.963 +/- 0.001, the linewidth ∆H_p-p = (0.30 +/- 0.05) mT). A constant maximum signal level is observed under basic conditions: pH 4 to 10. Measurement of the integrated intensity of the maximum signal indicated that (90 +/- 10) % of Ti(III) is in the complex. The variation and mole ratio methods based on the measurement of the ESR signal and optical absorption maximum (at nu approximately = 14 000 cm-1), respectively, for determining the composition of this complex ion indicate that the concentration ratio Ti(III) to NTA is 1:2. The experimental g-tensor components (g_x = 1.946 +/- 0.001, g_y = 1.959 +/- 0.001, and g(z) = 1.997 +/- 0.001) derived from the frozen solution ESR spectrum of this Ti(NTA)₂ paramagnetic species are consistent with an axially elongated octahedral structure with an equatorial rhombic distortion through bidentate NTA ligands. Significant in-plane   σ and π  bonding is indicated in this octahedron of the D_2h symmetry. It is proposed that there is at least one axial hydroxide ligand.

Full paper in Portable Document Format: 454a433.pdf

Chemical Papers 45 (4) 433–448 (1991)