Crystal-field analysis for d8 ions at D4h symmetry sites: Electronic states in trans-NiCl2(H2O)4 complex

The polarized absorption spectra of trans-NiCl2(H2O)4 complex were measured by Bussière et al. [Coord. Chem. Rev. 219–221 (2001) 509–543] at low-temperature. Using the experimental spectroscopic data, semiempirical calculations of the crystal-field levels of trans-NiCl2(H2O)4 chromophore are carried out, based on the Racah theory. We used idealized D4h point group symmetry to analyse the observed crystalline-field splitting of this chromophore. As a result, Racah and crystal-field parameters have been reliably obtained. A good agreement between the theoretical and experimental energy levels of trans-NiCl2(H2O)4 complex has been obtained. The region of 3T1g/1Eg(Oh) bands is of great interest and it is useful to use the tetragonal symmetry to understand the features of this spectral region.