Abstract
Many new complexes of tri- and tetra- valent lanthanide ions and divalent calcium with Schiff bases have been synthesised and their properties investigated by chemical analysis, infra-red, visible, and ultra-violet absorption spectroscopy, X-ray powder diffraction studies, and molar conductance and magnetic susceptibility measurements. The Schiff bases, which were mainly derivatives of sali-cylaldehyde and primary amines, formed complexes in two ways. In the first, the phenolic hydrogen atoms were un -ionised and the base behaved as a neutral ligand whilst in the second, the base reacted in the usual way as an anion. For the trivalent metal ions, complexes of the following types were obtained:- 1. Ln(L)Cl[3]. nH[2]O and La(Hsal-ane)Cl[3]. [2]EtOH. (Ln=Ce,La; n=1 and 2; L=NN'-ethylenebis(salicylideneimine) (H[2]salen) and NN'-1,3-propylenebis(salicylideneimine) (H[2]sal-1,3pn); N-salicylideneaniline (Hsal-ane); EtOH-ethanol). 2. Ln[2](L)[3]X[6]. nH[2]O. 3. Ln(L)[2]X[3]. nH[2]O and La(Hsal-ane)[2](NO[3])[3]. 2EtOH. 4. Ln(L)[3]X[3]. nH[2]O, (Ln=La,Ce,Pr,Nd,Sm,Gd,Ho,Yb; X=Cl-,Br-,NO[3-]; L=H[2]salen, H[2]sal-1,3pn, NN'-1,2-propylenebis(salicylideneimine) (H2sal-1,2pn), NN'-1,6-hexylenebis(salicylideneimine) (H[2]sal-1,6hex), and Hsal-ane ; n=0 - 2). A few exceptions are discussed in detail in Chapter 2. New series of complexes with tetravalent cerium with ionised and un-ionised Schiff bases of formulae below have been synthesised:- 5. Ce(L')2, 6. Ce(L)2(NO3)4. H2O (L' = the ionised Schiff bases: NN' -1,2-propylenebis(salicylideneiminate) (sal-1,2pn), NN'-1,3-propylenebis(salicylideneiminate) (sal-1,3pn), NN'-ethylenebis(3-inethoxysalicylideneiminate) (3-methoxy-salen), NN'-ethylenebis(5-nitrosalicylideneiminate) (5-nitrosalen), NN'-1,2-propylenebis(5-nitrosalicylideneiminate) (5-nitrosal-1,2pn), NN'-1,3-propylenebis(5-nitrosalicylideneiminate) (5-nitrosal-1,3pn) and L=H2salen, H2sal-1,2pn, H2sal-1,3pn and H2sal-1,6hex). Calcium complexes of the types shown below have been isolated:- 7. Ca(L)X2. nsolvent, 8. Ca(L)2X2. nsolvent (n=0 - 2; solvent = H2O or ethanol; L=H2salen, H2sal-1,2pn, H2sal-1,3pn, and H2sal-1,6hex and X=Cl- and NO3-). On the basis of the infra-red spectroscopy it was concluded that the un-ionised ligands behave as bidentate species with coordination taking place through the azomethine nitrogen atoms and not through the phenolic oxygen atoms. The ionised bases behave as tetra-dentate ligands in the well-established manner. There is evidence for coordinated nitrate in all the lanthanide nitrato- complexes. Far infra-red spectroscopy has shown the presence of the coordinated halide in some of the lanthanide complexes. The coordination numbers of a series of neodymium(III) Schiff base complexes have been deduced through the hypersensitive transitions observed in the visible region of the absorption spectrum by comparison with the spectra of complexes of known structure. The coordination numbers of the lanthanide complexes are probably 8 or 9 in the halide complexes and between 10 and 12 for the nitrates. The calcium complexes may have coordination numbers between 4 and 6. Furthermore, the X-ray powder photography has shown the complexes to be true compounds and not simple mixtures. Isomorphism was found in some cases for the trivalent lanthanum and neodymium complexes. The conclusions were consistent with those obtained from the other measurements.