title: Synthesis, characterization, and physicochemical properties of manganese(III) and manganese(V)-oxo corrolazines.
abstract: The structural and physicochemical properties of the manganese-corrolazine (Cz) complexes (TBP8Cz)Mn(V)O (1) and (TBP8Cz)Mn(III) (2) (TBP = p-tert-butylphenyl) have been determined. Recrystallization of 2 from toluene/MeOH resulted in the crystal structure of (TBP8Cz)Mn(III)(CH3OH) (2 x MeOH). The packing diagram of 2 x MeOH reveals hydrogen bonds between MeOH axial ligands and meso N atoms of adjacent molecules. Solution binding studies of 2 with different axial ligands (Cl-, Et3PO, and Ph3PO) reveal strong binding, corroborating the preference of the Mn(III) ion for a five-coordinate environment. High-frequency and field electron paramagnetic resonance (HFEPR) spectroscopy of solid 2 x MeOH shows that 2 x MeOH is best described as a high-spin (S = 2) Mn(III) complex with zero-field splitting parameters typical of corroles. Structural information on 1 was obtained through an X-ray absorption near-edge structure (XANES)/extended X-ray absorption fine structure (EXAFS) study and compared to XANES/EXAFS data for 2 x MeOH. The XANES data for 1 shows an intense pre-edge transition characteristic of a high-valent metal-oxo species, and a best fit of the EXAFS data gives a short Mn-O bond distance of 1.56 A, confirming the structure of the metal-oxo unit in 1. Detailed spectroelectrochemical studies of 1 and 2 were performed revealing multiple reversible redox processes for both complexes, including a relatively low potential for the Mn(V) --> Mn(IV) process in 1 (near 0.0 V vs saturated calomel reference electrode). Chemical reduction of 1 results in the formation of a Mn(III)Mn(IV)(mu-O) dimer as characterized by electron paramagnetic resonance spectroscopy.
authors.affiliation: Department of Chemistry, Johns Hopkins University, 3400 North Charles Street, Baltimore, Maryland 21218, USA.
authors.forename: David E
authors.initials: DE
authors.lastname: Lansky
authors.forename: Beaven
authors.initials: B
authors.lastname: Mandimutsira
authors.forename: Bobby
authors.initials: B
authors.lastname: Ramdhanie
authors.forename: Maria
authors.initials: M
authors.lastname: Clausén
authors.forename: James
authors.initials: J
authors.lastname: Penner-Hahn
authors.forename: S A
authors.initials: SA
authors.lastname: Zvyagin
authors.forename: Joshua
authors.initials: J
authors.lastname: Telser
authors.forename: J
authors.initials: J
authors.lastname: Krzystek
authors.forename: Riqiang
authors.initials: R
authors.lastname: Zhan
authors.forename: Zhongping
authors.initials: Z
authors.lastname: Ou
authors.forename: Karl M
authors.initials: KM
authors.lastname: Kadish
authors.forename: Lev
authors.initials: L
authors.lastname: Zakharov
authors.forename: Arnold L
authors.initials: AL
authors.lastname: Rheingold
authors.forename: David P
authors.initials: DP
authors.lastname: Goldberg
mesh_terms: D001665:Binding Sites; D002412:Cations; D004563:Electrochemistry; D004578:Electron Spin Resonance Spectroscopy; D008024:Ligands; D008345:Manganese / Q000737:chemistry*; D008665:Metalloporphyrins / Q000138:chemical synthesis*; D008956:Models, Chemical; D010084:Oxidation-Reduction; D010100:Oxygen / Q000737:chemistry*; D013052:Spectrometry, X-Ray Emission
chemical_list: D002412:Cations; D008024:Ligands; D008665:Metalloporphyrins; D008345:Manganese; D010100:Oxygen