title: Comparison of the SOD-like activity of hexacoordinate Mn(II), Fe(II) and Ni(II) complexes having isoindoline-based ligands.
abstract: Recently, a series of Fe(II) complexes have been published by our group with 3N-donor 1,3-bis(2'-Ar-imino)isoindoline ligands containing various Ar-groups (pyridyl, 4-methylpyridyl, thiazolyl, benzimidazolyl and N-methylbenzimidazolyl). The superoxide scavenging activity of the compounds showed correlation with the Fe(III)/Fe(II) redox potentials. Analogous, electroneutral chelate complexes with Mn(II) and Ni(II) in 2:1 ligand:metal composition are reported here. Each Mn(II) complex exhibits one reversible redox wave that is assigned as the Mn(III)/Mn(II) redox transition. The E(1/2) spans a 180 mV range from -98 (Ar=3-methylpyridyl) to 82 mV (Ar=thiazolyl) vs. the Fc(+)/Fc depending on the Ar-sidearm. The SOD-like (SOD=superoxide dismutase)activity of all complexes was determined according to the McCord-Fridovich method. The Mn(II) isoindolinates have IC(50) values - determined with 50 μM cytochrome c Fe(III) - that range from (3.22±0.39)×10(-6) (Ar=benzimidazolyl) to (10.80±0.54)×10(-6) M (Ar=N-methylbenzimidazolyl). In contrast with the Fe(II) complexes, the IC(50) concentrations show no significant dependence on the E(1/2) values in this narrow potential range emphasizing that the redox potential is not the governing factor in the Mn(II)-containing scavengers. The analogous Ni(II) compounds show no redox transitions in the thermodynamically relevant potential range (-0.40 to 0.65 V vs. SCE) and accordingly, their superoxide scavenging activity (if any) is below the detection level.
authors.affiliation: Department of Chemistry, University of Pannonia, Veszprém, Hungary.
authors.forename: József S
authors.initials: JS
authors.lastname: Pap
authors.forename: Balázs
authors.initials: B
authors.lastname: Kripli
authors.forename: Tünde
authors.initials: T
authors.lastname: Váradi
authors.forename: Michel
authors.initials: M
authors.lastname: Giorgi
authors.forename: József
authors.initials: J
authors.lastname: Kaizer
authors.forename: Gábor
authors.initials: G
authors.lastname: Speier
mesh_terms: D002614:Chelating Agents / Q000138:chemical synthesis / Q000737:chemistry*; D056831:Coordination Complexes / Q000138:chemical synthesis* / Q000737:chemistry; D018360:Crystallography, X-Ray; D005296:Ferrous Compounds / Q000737:chemistry*; D007211:Indoles / Q000737:chemistry*; D008024:Ligands; D008345:Manganese / Q000737:chemistry*; D008958:Models, Molecular; D009532:Nickel / Q000737:chemistry*; D010084:Oxidation-Reduction; D013482:Superoxide Dismutase / Q000737:chemistry* / Q000378:metabolism; D013816:Thermodynamics
chemical_list: D002614:Chelating Agents; D056831:Coordination Complexes; D005296:Ferrous Compounds; D007211:Indoles; D008024:Ligands; D008345:Manganese; C057812:indoline; D009532:Nickel; D013482:Superoxide Dismutase