f-f spectral studies of holmium(III) complexes

Holmium(III) mixed-ligand complexes containing ligands having oxygen and nitrogen donors have been spectrophotometrically investigated. The observed spectra in the visible region have been analysed to calculate covalency parameters (β, b� and δ), oscillator strengths and Judd-Ofelt parameters. The degree of covalency in the complexes increases with increase in coordination number. The hypersensitivity is correlated with the degree of covalency and number of coordinated ligands. The higher values of covalency parameters, oscillator strength and magnetic moment in the ten-coordinate HoIII is taken as evidence of participation of f-orbitals in bonding.

Synthesis and electron spin resonance study of a tetradentate copper(II) mercaptobenzaldimine complex

The X-band e.s.r, spectrum of a copper(II) Schiff-base complex, 2,2?- [ethylenebis(nitrilomethylidyne)]-bis(benzenethiolato-S,N)copper(II) (Cu(mben)), has been determined in frozen toluene-chloroform solutions. The complicated line shape has been simulated by a computer program incorporating symmetry around the copper lower than axial, together with a nitrogen hyperfine pattern calculated for two cis nitrogen atoms. The e.s.r parameters are compared with those obtained for two other thio Schiff-base chelates and with those for the salicylaldimine analogue, Cu(salen). Metal-ligand covalency parameters estimated from the e.s.r. parameters are discussed briefly.

TRANSFERRED HYPERFINE INTERACTIONS IN Fe(III) BIS-DITHIOCARBAMATO IODIDES

Parallel measurements of 129I and 57Fe Mössbauer spectra have been performed on four members of the class of FeIII bis-dithiocarbamato iodides. Three out of the four studied compounds are found to order magnetically at temperatures below 4 K. Hyperfine parameters for 57Fe and 129I have been determined by computer fits of the spectra in the paramagnetic and magnetically ordered regions. The 129I results have been used to calculate covalency parameters of the Fe-I bond.