ELECTRONIC SPECTRAL STUDIES ON LANTHANIDE(III) IN MIXED-METAL ENVIRONMENTS OF THE TYPE [LN(III)CENTER-DOT-DTPA-CENTER-DOT-M(II)] - LN(III) = PR, ND, SM, DY, ER, TM AND M(II) = MN, FE, CO, NI, CU, ZN

Electronic spectral studies of lanthanides (Ln) in mixed metal environ ments of the type [Ln(III).DTPA.M(II)] (where Ln(III)=Pr, Nd, Sm, Dy, Er, Tm; and M(II)=Mn, Fe, Co, Ni, Cu and Zn) in aqueous phase at contr olled pH (similar to 4.00) have been carried out in order to evaluate electronic spectral parameters, viz: (i) oscillator strength (f(JO)), (ii) Judd-Ofelt parameters (T-lambda), (iii) interelectronic repulsion (Racah) parameters (delta E-k) and (iv) nephelauxetic ratio (delta E- 3/delta E-1) values in mixed metal environments and to examine their v ariations as a result of insertion of M(II) (3d transition metal) ions in a [Ln.DTPA] environment. Octadentate DTPA has been used as a bridg ing ligand between two elemental moieties, viz: Ln(III) and M(II). The electronic spectral parameters (f(JO)), (T-lambda) and (delta E-3/del ta E-1) values show marked dependence on the nature of M(II) ions inse rted in [Ln.DTPA] complex with a general sequence of Mn<Fe<Co<Ni<Cu>Zn indicating an allowed dependence of the spectral parameters on the na ture of the M(ill) ion. The variations in the spectral parameters have been discussed in light of partial covalency, symmetry around the Ln( III) cation and the degree of delocalisation of the 4f shell. J quantu m number dependency of the electronic spectral parameters has also bee n discussed. (C) 1998 Elsevier Science S.A.