title: Valence tautomerism and macrocycle ruffling in nickel(III) porphyrins.
abstract: Nonlocal density functional calculations with full geometry optimization have been carried out on the low-lying electronic states of oxidized nickel porphyrins. For [NiIII(P)(Py)2]+, the ground state corresponds to a t2g6(z2)1 configuration and the t2g6(x2-y2)1 configuration is 0.43 eV higher in energy. In contrast, the ground state of [NiIII(P)(CN)2]- corresponds to a t2g6(x2-y2)1 configuration, the t2g6(z2)1 configuration being 0.96 eV higher in energy. The results are consistent with EPR spectroscopic results on the TPP analogs of these complexes. For [Ni(P)(Py)2]+, the a2u- and a1u-type Ni(II) porphyrin cation radical states are higher in energy by 0.63 and 1.23 eV, respectively, relative to the t2g6(z2)1 Ni(III) ground state. The Ni-N(Porphyrin) distance is significantly shorter in [NiIII(P)(Py)2]+ (196 pm) than in [NiIII(P)(CN)2]- (206 pm), which is consistent with the ruffled and planar macrocycle conformations, respectively, in the two complexes.
authors.affiliation: Institute of Chemistry, University of Tromsø, Norway. abhik@chem.uit.no
authors.forename: A
authors.initials: A
authors.lastname: Ghosh
authors.forename: T
authors.initials: T
authors.lastname: Wondimagegn
authors.forename: E
authors.initials: E
authors.lastname: Gonzalez
authors.forename: I
authors.initials: I
authors.lastname: Halvorsen
mesh_terms: D004578:Electron Spin Resonance Spectroscopy; D004583:Electrons; D007536:Isomerism; D008665:Metalloporphyrins / Q000737:chemistry*; D008958:Models, Molecular; D008968:Molecular Conformation; D015394:Molecular Structure; D009532:Nickel / Q000737:chemistry*; D011789:Quantum Theory
chemical_list: D008665:Metalloporphyrins; D009532:Nickel