title: Nickel(II) meso-Hydroxyporphyrin Complexes Revisited: Palladium-Catalysed Synthesis, Electronic Structures of Derived Oxy Radicals, and Oxidative Coupling to a Dioxoporphodimethene Dyad.
abstract: We report the synthesis and characterisation of new examples of meso-hydroxynickel(II) porphyrins with 5,15-diphenyl and 10-phenyl-5,15-diphenyl/diaryl substitution. The OH group was introduced by using carbonate or hydroxide as nucleophile by using palladium/phosphine catalysis. The NiPor-OHs exist in solution in equilibrium with the corresponding oxy radicals NiPor-O.. The 15-phenyl group stabilises the radicals, so that the1H NMR spectra of {NiPor-OH} are extremely broad due to chemical exchange with the paramagnetic species. The radical concentration for the diphenylporphyrin analogue is only 1 %, and its NMR line-broadening was able to be studied by variable-temperature NMR spectroscopy. The EPR signals of NiPor-O.are consistent with somewhat delocalised porphyrinyloxy radicals, and the spin distributions calculated by using density functional theory match the EPR and NMR spectroscopic observations. Nickel(II) meso-hydroxy-10,20-diphenylporphyrin was oxidatively coupled to a dioxo-terminated porphodimethene dyad, the strongly red-shifted electronic spectrum of which was successfully modelled by using time-dependent DFT calculations.
authors.affiliation: School of Chemistry, Physics and Mechanical Engineering, Queensland University of Technology, GPO Box 2434, Brisbane, 4001, Australia.
authors.forename: Louisa J
authors.initials: LJ
authors.lastname: Esdaile
authors.affiliation: School of Chemistry, Physics and Mechanical Engineering, Queensland University of Technology, GPO Box 2434, Brisbane, 4001, Australia.
authors.forename: Llew
authors.initials: L
authors.lastname: Rintoul
authors.affiliation: School of Chemistry, Physics and Mechanical Engineering, Queensland University of Technology, GPO Box 2434, Brisbane, 4001, Australia.
authors.forename: Mean See
authors.initials: MS
authors.lastname: Goh
authors.affiliation: Institut de Chimie, Université de Strasbourg, 4 rue Blaise Pascal, BP 296 R8, 67008, Strasbourg Cedex, France.
authors.forename: Khalissa
authors.initials: K
authors.lastname: Merahi
authors.affiliation: Institut de Chimie, Université de Strasbourg, 4 rue Blaise Pascal, BP 296 R8, 67008, Strasbourg Cedex, France.
authors.forename: Nathalie
authors.initials: N
authors.lastname: Parizel
authors.affiliation: School of Chemistry, Physics and Mechanical Engineering, Queensland University of Technology, GPO Box 2434, Brisbane, 4001, Australia.
authors.forename: R Mark
authors.initials: RM
authors.lastname: Wellard
authors.affiliation: Institut de Chimie, Université de Strasbourg, 4 rue Blaise Pascal, BP 296 R8, 67008, Strasbourg Cedex, France.
authors.forename: Sylvie
authors.initials: S
authors.lastname: Choua
authors.affiliation: School of Chemistry, Physics and Mechanical Engineering, Queensland University of Technology, GPO Box 2434, Brisbane, 4001, Australia. d.arnold@qut.edu.au.
authors.forename: Dennis P
authors.initials: DP
authors.lastname: Arnold
keywords: EPR spectroscopy; NMR spectroscopy; density functional calculations; porphyrinoids; radicals