Optical properties of Ni[ tbu 2P(O)NR] 2: A paramagnetic d 8 complex with planar structure

Abstract

The title complexes of Ni(II) with trans-planar structure are paramagnetic because they have a triplet ground state (R = i-propyl, green isomer of c-hexyl) or there is another electronic level closely located above the singlet ground state which is available by thermal energy kT (R = t-butyl). Angular overlap model (AOM) calculations are able to interpret these ground states as well as the ligand field spectra measured from 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 NiN 2O 2; chromophore. A fitting of absorption peaks to theoretical transition energies supplies AOM parameters e σ, e π and e sdσ of ligands with oxygen and nitrogen donor atoms which compare well to parameter values of other ligands of similar nature, as far as these are known.