ELECTRONIC-STRUCTURE AND SPECTROSCOPY OF NICKEL(II), PALLADIUM(II), AND PLATINUM(II) ACETYLACETONATE COMPLEXES

The electronic structure and optical spectra of Ni(acac)2 and Pd(acaC)2 have been investigated using the semiemperical INDO/S-SCF-CI (ZINDO) algorithm. The results of the electronic structure calculations are in good agreement with those of previous ab initio calculations for these complexes. Increasing the atomic number of the metal is found to increase the metal-ligand covalency, to increase the separation of the two highest occupied and two lowest unoccupied, ligand-localized (pi and pi*) molecular orbitals, and to decrease the separation between the highest occupied and lowest unoccupied molecular orbitals. The effects of electronic relaxation (due to Coulomb and exchange integrals) and configuration interaction on the calculated energies of singlet-singlet transitions are analyzed using Platt diagrams to illustrate the origin of the d-->d transitions, observed for Ni(acac)2 but not for Pd(acaC)2 or Pt(acaC)2, and the increasing complexity of the ultraviolet portion of the spectrum with increasing atomic number. Thus the ZINDO calculations provide the basis for the first detailed rationalization of the complex optical spectra of the group 10(II) beta-diketonates.