Trends in spectral parameters and nephelauxetic ratio values for some lanthanoid(III) tyrosine complexes. Part-III

Department of Chemistry, Dr. H. S. Gour University, Sagar-470 003, India E-mail : snl222@yahoo.co.in /tiwari_rashmi_chem@yahoo.com Manuscript received 20 August 2003. revised 9 March 2004, accepted 11 May 2004 Electronic spectral studies of [Ln(III).L] complexes, where, Ln = Pr, Nd and Er with tyrosine (tyr) have been undertaken with a view to evaluate the oscillator strengths (fJO), Judd-Ofelt parameters (τλ), inter-electronic repulsion Racah parameters (δEK) and nephelauxetic ratios (δE3/δE1). Studies have been performed at five different pH values to examine the pH dependence of the spectral parameters. The metal-ligand bonding pattern has been studied in the light of changes in τλ and nephelauxetic ratio values. The [Ln(Ill). tyr] interaction shows a drift from ionic to partial covalent nature