Synthesis, Crystal Structures, and Magnetic Properties of Mixed-Valent Tetranuclear Complexes with Y-Shaped MnII2MnIII2 Core

Abstract

Tetranuclear Mn II 2 Mn III 2 complexes with 1,3-bis(5-bromo-3-metoxysalicylidenaminomethyl)-2-propanol (H 3 bmsap) and 1,3-bis(5-chloro-3-methoxysalicylidenaminomethyl)-2-propanol (H 3 cmsap), [Mn 4 (bmsap) 2 (CH 3 CO 2 ) 3 (CH 3 O)] (3) and [Mn 4 (cmsap) 2 (CH 3 CO 2 ) 3 (CH 3 O)] (4), were synthesized and characterized by elemental analysis, infrared and diffused reflectance spectra and variable-temperature magnetic susceptibility measurements in the 2-300 K range. The crystal structures of 3 and 4 revealed a Y-shaped tetranuclear manganese cluster formed by the two Schiff-base ligands, three kinds of acetato ligands (bidentate, syn-anti-bridging, and syn-syn-bridging), and µ-methoxido ligand. The magnetic data showed the magnetic interactions among the four manganese atoms are antiferromagnetic as a whole within the tetranuclear cluster.

Crystal Structure of μ-Oxido-μ-phenolato-bridged Dinuclear Manganese(III) Complex of Schiff-base Ligand with Bromido Coordination

“…Manganese complexes are interesting compounds because of their diversity in the molecular structures and relevance to redox manganese enzymes, such as manganese catalase and an oxygen evolving complex of photosystem II. [1][2][3][4][5][6][7][8][9][10][11] Recently, we reported on the crystal structure of the dinuclear manganese(III) complex with a Schiff-base ligand having three phenolate donor atoms: 2-(5-nitro-2-hydroxyphenyl)-1,3-bis(2-(5-nitro-2-hydroxybenzylidene amino) ethyl)imidazolidine (H3LNO2), [(C2H5)3NH][Mn2(μ-LNO2)(μ-O)Cl2]•2THF; each manganese atom is coordinated by a phenolato-oxygen, imino-and imidazolidine-nitrogen atoms of LNO2 3in a meridional fashion and a chlorido ligand and the two manganese atoms are bridged by the third phenolato-oxygen atom of LNO2 3and a μ-oxido oxygen atom to form a distorted octahedral geometry. 11 It is interesting that a chlorido ligand is coordinated to a manganese atom in this complex, because the chloride and bromide ions are known to be an effective factor in the oxygen evolution activity of photosystem II.…”

Crystal Structure of a μ-Phenolato-μ-oxido-bridged Dinuclear Manganese(III) Complex with Dinucleating Schiff-base Ligand Having Three Phenolate Groups

“…Manganese complexes have been studied by many researchers because of their diversity in metal oxidation numbers, coordination geometries, and molecular structures, having relevance to the presence of manganese ions at the active sites in redox enzymes, such as manganese catalases. [1][2][3][4][5][6][7] Previously, we reported unique dinuclear copper(II) complexes with a Schiffbase ligand having three phenolate donor atoms: 2-(5-chloro-2hydroxyphenyl)-1,3-bis(2-(5-chloro-2-hydroxybenzylideneamino)ethyl)imidazolidine (H3LCl), [Cu2(μ-LCl)(μ-CH3CO2)]•CH3CN• H2O and [Cu2(μ-LCl)(μ-C6H5CO2)]•H2O, where each copper atom is coordinated by phenolato-oxygen, imino-and imidazolidine-nitrogen atoms of LCl 3in a meridional fashion and the two copper atoms are bridged by the third phenolatooxygen of LCl 3and a μ-carboxylato group to form a squarepyramidal geometry. 8,9 As far as we know, there are no reports on a manganese complex with this type of Schiff-base ligands having three phenolate donor atoms.…”

“…2,3 The charge balance and a bond valence sum calculation supported the Mn(III) state. 5,11 In the crystal, the protonated triethylammonium ion is hydrogen-bonded to the oxido-oxygen atom (O7) Prime denotes the symmetry code: (x, 1/2-y, z).…”

Dinuclear Manganese(III) Complex with a Schiff-base Having a Di-μ-acetato-μ-alkoxido-bridged Core

“…1 So far, mononuclear, dinuclear, tetranuclear, and polynuclear manganese complexes with dinucleating Schiff-base ligands having a bridging alkoxido-oxygen, 1,3-bis(salicylideneamino)-2-propanol (H3sap) and its substituent derivatives, have appeared in the literature. [2][3][4][5][6][7][8] In this study, we isolated a new dinuclear manganese complex with 1,3-bis(3-methoxysalicylideneamino)-2-propanol (H3msap) and determined the crystal structure, which shows a dinuclear core with one alkoxido-oxygen and two-μ-acetato bridges, as shown in Fig. 1.…”

“…The spectrum shows a very broad feature typical for this kind of manganese(III) complexes, containing the main band at around 432 nm, assigned to the LMCT band of phenolato-oxygen to manganese(III) with hidden d-d transition bands at around 520, 650, and 870 nm. 3,7,8…”