OPTICAL-PROPERTIES OF NI[T-BU(2)P(O)NR](2) - A PARAMAGNETIC D(8) COMPLEX WITH PLANAR STRUCTURE

The title complexes of Ni(II) with trans-planar structure are paramagn etic because they have a triplet ground state (R=i-propyl, green isome r of c-hexyl) or there is another electronic level closely located abo ve the singlet ground state which is available by thermal energy kT (R =t-butyl). Angular overlap model (AOM) calculations are able to interp ret these ground states as well as the ligand field spectra measured f rom the crystals in the near-IR and visible region. For this the model must be extended considering metal ion s-d orbital mixing for a NiN2O 2 chromophore. A fitting of absorption peaks to theoretical transition energies supplies AOM parameters e sigma, e pi and e(sd sigma) of lig ands with oxygen and nitrogen donor atoms which compare well to parame ter values of other ligands of similar nature, as far as these are kno wn.