Synthesis and characterization of the binuclear complex di-µ-oxo-bis[N,N′-bis(2-methylpyridyl)ethane-1,2-diamine]dimanganese(III,IV)perchlorate trihydrate,[(bispicen)MnO]₂(ClO₄)₃·3H₂O

Abstract

The title complex, a new binuclear di-p-oxo complex of manganese-(111) and -(Iv) with a single tetradentate ligand in place of the previously reported bidentate bpy or phen ligands, has been synthesised and characterised by X-ray crysta I I og rap h y and cyclic vo Ita m met ry.

Synthesis, Structure, Electronic, Redox, and Magnetic Properties of a New Mixed-Valent Mn-Oxo Cluster: [Mn2III,IVO2(N,Nbispicen)2]3+ (N,Nbispicen =N,N-bis(2-pyridylmethyl)-1,2-diaminoethane)

“…(1) 177 The difference between the average MnϪN(axial ligand) distances around both Mn ions reflects the asymmetry in electron distribution between the two Mn ions. [6] Here the value is 0.230 Å , which is comparable to that found for [ Figure 2 in the form of the χ M T versus T plot. was generated by the best fit parameters given in the text χ M T decreases from 0.64 cm 3 mol Ϫ1 K at 292 K to a plateau at 0.38 cm 3 mol Ϫ1 K around 60 K. This is characteristic of an antiferromagnetic coupling between the electronic spins of the Mn(III) and Mn(IV) ions which produces a spin S ϭ 1/2 ground state.…”

“…The MnϪMn distance is 2.646(2) Å , which is comparable to the value found in dimanganese(III,IV)-di-µ-oxo complexes previously reported. [6] [12] An antibonding molecular orbital which is half occupied for the Mn(III) ion and empty for the Mn(IV) ion results fom the interaction of the d z 2 orbital with the σ orbitals of the axial pyridine N2 atom and the axial primary amino-group N4 atom. In previous studies it has been found that the average axial Mn(III) primary amine distance is 2.276 Å [9] 2 ] 3ϩ is 2.233 Å .…”

“…Magnetic properties were determined and show that the ground state is a spin doublet. This can be quantitatively interpreted by antiferromagnetic coupling between a Mn(III) high spin and a Mn(IV) (J = Ϫ316 cm Ϫ1 [4] Similar complexes using linear tetradentate ligands like N,NЈ-bis(2-pyridylmethyl)-1,2-diaminoethane (bispicen) [6] have been prepared in order to study their redox properties in relation to their structures. [7] We report herein the synthesis and characterization of a new dinuclear mixed-valence di-µ-oxo manganese complex with the tetradentate ligand N,N-bis(2-pyridylmethyl)-1,2-diaminoethane (N,Nbispicen), an isomer of bispicen which presents a tertiary amino group as well as a primary amino group instead of the two secondary amino groups in bispicen.…”

Water Oxidation Catalyzed by a Dinuclear Mn Complex: A Functional Model for the Oxygen‐Evolving Center of Photosystem II

“…It is likely that during the 3!4 reaction step the carboxylate arms are concomitantly displaced to accommodate the two m-oxo ligands. Thus, an arrangement similar to other, known bis(moxo)-dimanganese complexes of linear N 4 bispicen-based [11] ligands (Mn···Mn = 2.7 ) [12][13][14] is achieved. The anticipated facile oxidation of 3 (oxidase activity) can be invoked to explain the slightly different curve shape in the first evolution step (the front of the peak shows a spike, which indicates an initial rapid reduction in O 2 concentration).…”

Chemical Modeling of the Oxygen-Evolving Center in Plants. Synthesis, Structure, and Electronic and Redox Properties of a New Mixed Valence Mn−Oxo Cluster: [Mn2III,IVO2(bisimMe2en)2]3+ (bisimMe2en = N,N‘-Dimethyl-N,N‘-bis(imidazol-4-ylmethyl)ethane-1,2-diamine). EPR Detection of an Imidazole Radical Induced by UV Irradiation at Low Temperature

“…Then the sample was immediately put into an EPR tube and frozen quickly to 77 K. UV irradiation was done at 77 K with a 1000 W Hg/Xe lamp (Oriel). 16 In other systems, the Mn-Mn axis is not an axis of symmetry, and the distances around each Mn atoms can be inequivalent as in [Mn 2 O 2 (TPA) 2 ] 3+ where the distances are Mn III -N ax ) 2.260 Å, 2.206 Å and Mn IV -N ax ) 2.012 Å, 2.014 Å. the Mn-Mn axis is a C 2 axis.…”