MnII Compounds Research Articles

Trinuclear manganese and zinc clusters and a dinuclear manganese complex with multiple oxo-bridges: Syntheses, structures, and magnetic properties of the MnII compounds and luminescent property of the ZnII complex

Two trinuclear clusters [Mn3(L1)2] (1) and [Zn3(L1)2] (2) have been prepared from the reactions of Mn(CH3COO)2·4H2O and Zn(CH3COO)2·4H2O, respectively, with a hydroxy-rich Schiff-base ligand H3L1 (H3L1 = 2-{[bis(2-hydroxy-3-methoxybenzyl)(amino-ethyl)amino]methyl}phenol). One dinuclear compound [Mn2(HL2)Cl2] (3) was synthesized from the treatment of MnCl2·4H2O with another hydroxy-rich Schiff base ligand H3L2 (H3L2 = 2-{[bis(2-hydroxy-3-methoxybenzyl)(amino-ethyl)amino]ethyl}phenol). Complexes 1–3 were characterized by single-crystal X-ray diffraction analysis. The structural analyses indicated that complexes 1 and 2 are isostructural and contain linear MnII–MnII–MnII and ZnII–ZnII–ZnII cores. In compounds 1–3, the metal centers are doubly bridged by phenoxido groups of the ligands. Variable temperature magnetic measurements of 1 and 3 revealed the presence of antiferromagnetic intramolecular couplings, and the magnetic susceptibility data are consistent with S = 5/2 of the MnII ions. The luminescent property of compound 2 was investigated. The 3d10 zinc compound 2 exhibited strong luminescence with λmax = 491 nm (for λex = 418 nm).

Reactive Solubilization of Heterometallic Clusters by Treatment of (TrBi3 )2- Anions (Tr=Ga, In, Tl) with [Mn{N(SiMe3 )2 }2

Lowering the charge of Zintl anions by (element-)organic substituents allows their use as sources of (semi)metal nanostructures in common organic solvents, as realized for group 15 anions or Ge9 4- and Sn9 4- . We developed a new strategy for other anions, using low-coordinate 3d metal complexes as electrophiles. [K(crypt-222)]+ salts of (TrBi3 )2- anions dissolved in situ in Et2 O and/or THF when reacted with [Mn(hmds)2 ]. Work-up afforded soluble [K(crypt-222)]+ salts of [{(hmds)2 Mn}2 (TlBi3 )]2- (in 1), [{(hmds)2 Mn}2 (Bi2 )]2- (in 2), and [{(hmds)Mn}4 (Bi2 )2 ]2- (in 3) (crypt-222=4,7,13,16,21,24-hexaoxa-1,10-diazabicyclo[8.8.8]hexacosane; Tr=Ga, In, Tl; hmds=N(SiMe3 )2 ), representing rare cases of Zintl clusters with open-shell metal atoms. 1 comprises the first coordination compound of the (TlBi3 )2- anion, 2 features a diamond-shaped {Pn2 M2 } unit, and 3 is a mixed-valent MnI /MnII compound. The uncommon electronic structures in 1-3 and magnetic coupling were studied by comprehensive DFT calculations.

Three-Dimensional Supramolecular Architectures with MnII Ions Assembled from Hydrogen Bonding Interactions: Crystal Structures and Antiferromagnetic Properties.

Two novel cocrystal MnII compounds were successfully synthesized. The composition of two kinds crystals correspond to [Mn(hfac)2La2·Mn(hfac)2La(H2O)·Mn(hfac)2(H2O)2] (1) and [Mn(hfac)2Lb2·Mn(hfac)2(H2O)2·0.5(C6H14)] (2) [La = 1,3-bis(1′-oxyl-3′-oxido-4′,4′,5′,5′-tetramethyl-4,5-dihydro-1H-imidazol-2-y1)benzene; Lb = 1-(1′-oxyl-4′,4′,5′,5′-tetramethylimidazolin-2-yl)-3-(1′-oxyl-3′-oxo-4′,4′,5′,5′-tetramethylimidazolin-2-yl)benzene; hfac = hexafluoroacetylacetonato). Surprisingly, the compounds were not polymeric or clusters but, more interestingly, different ratio biradical–metal coordination compound cocrystals. The extensive intramolecular H-bonds are the cause of formation of the cocrystal structures by assembly in the two manganese(II) derivatives; and another factor is the halogen bonds between CF3 of hfac groups. Furthermore, three-dimensional supramolecular architectures were formed. The magnetic susceptibility of both compounds showed strong antiferromagnetic interactions involving the coordinated radical unit and the metal and lesser contribution from ferromagnetic interactions between the radical units. For compound 1, a good fit was obtained for gMn = 2.08, grad = 2.00 (fixed), J1 = −294.3 cm–1, J2 = 6.2 cm–1 and J3 = 10.8 cm–1. A reasonable fit for compound 2 was obtained for gMn = 2.04, grad = 2.00 (fixed), J1′ = −273.4 cm–1 and J2′ = 8.6 cm–1.

Incorporation of Manganese Complexes within Hybrid Resol-Silica and Carbon-Silica Nanoparticles.

The incorporation of a luminescent probe into a nano-vector is one of the approaches used to design chemosensors and nanocargos for drug delivery and theranostics. The location of the nano-vector can be followed using fluorescence spectroscopy together with the change of environment that affects the fluorescence properties. The ligand 9-anthracene carboxylate is proposed in this study as a luminescent probe to locate two types of manganese complexes inside three series of porous nanoparticles of different composition: resol-silica, carbon-silica and pure silica. The manganese complexes are a tetranuclear MnIII cluster [MnIII4(μ-O)2(μ-AntCO2)6(bpy)2(ClO4)2] with a butterfly core, and a MnII dinuclear complex [{MnII(bpy)(AntCO2)}2(μ-AntCO2)2(μ-OH2)]. The magnetic measurements indicate that both complexes are present as dinuclear entities when incorporated inside the particles. Both the Mn complexes and the nanoparticles are luminescent. However, when the metal complexes are introduced into the nanoparticles, the luminescent properties of both are altered. The study of the fluorescence of the nanoparticles’ suspensions and of the supernatants shows that MnII compounds seem to be more retained inside the particles than MnIII compounds. The resol-silica nanoparticles with MnII complexes inside is the material that presents the lowest complex leaching in ethanol.

Crystal structure, synthesis and thermal properties of tetra-kis-(4-benzoyl-pyridine-κN)bis-(iso-thio-cyanato-κN)iron(II).

The asymmetric unit of the title compound, [Fe(NCS)2(C12H9NO)4], consists of an FeII ion that is located on a centre of inversion, as well as two 4-benzoyl-pyridine ligands and one thio-cyanate anion in general positions. The FeII ions are coordinated by two N-terminal-bonded thio-cyanate anions and four 4-benzoyl-pyridine ligands into discrete complexes with a slightly distorted octa-hedral geometry. These complexes are further linked by weak C-H⋯O hydrogen bonds into chains running along the c-axis direction. Upon heating, this complex loses half of the 4-benzoyl-pyridine ligands and transforms into a compound with the composition Fe(NCS)2(4-benzoyl-pyridine)2, that might be isotypic to the corresponding MnII compound and for which the structure is unknown.

Catalytic Behaviors of CoII and MnII Compounds Bearing α-Diimine Ligands for Oxidative Polymerization or Drying Oils

The oxidative polymerization of linseed oil was investigated comparing the classical catalysts cobalt(II) 2-ethylhexanoate and manganese(II) 2-ethylhexanoate and their derivatives modified by the presence of chelating nitrogen ligands, i.e., 2,2'-bipyridyl, 2-(acetyl-2,6-diisopropylphenylimine)-pyridine and [N-(2,6-diisopropylphenyl)imine]acenaphthoquinone. The suitable stoichiometries between the two precursor complexes with the three ligands were determined by UV-visible spectroscopy. All complexes were characterized by infrared spectroscopy, and one complex was characterized also by X-ray diffraction. The apparent kinetic constants of oxidative polymerization of linseed oil was determined, for each catalytic system, via the periodic measurements of the oil viscosity during the oxidation reaction. The results indicated that the modifications of the classical two complexes with the chelating nitrogen ligands improved the catalytic efficiency at least to the manganese complex.

Structural and magnetic properties of heptacoordinated MnII complexes containing a 15-membered pyridine-based macrocycle and halido/pseudohalido axial coligands

Heptacoordinated MnII compounds with a pentadentate 15-membered pyridine-based macrocycle and two axially coordinated halido/pseudohalido coligands, having a monomeric or polymeric composition, were investigated.

Alternating chains with the new J1J2J3J1⋯ sequence in a three-dimensional MnII complex

A three-dimensional carboxylate-bridged MnII compound [Mn6(tci)4(H2O)3]·7H2O}n (1) (tci=tris(2-carboxyethyl) isocyanurate) have been synthesized. The structure contains unique manganese chains in which the MnII ions are alternatively bridged by carboxylate groups in different coordination modes. The first example of such alternating Mn chain shows Mn1–(COO)3–Mn2–(COO)2–Mn3–(COO)3–Mn1–(COO)3–Mn2-sequence arranged as J1J2J3J1S⋯ mode. Magnetic susceptibility measurement reveals an antiferromagnetism behavior derived from the topology of the chain. There is no suitable analytical expression for determining the exchange parameters in a 1-D Heisenberg ferrimagnet consisting of alternating interactions J1J2J3J1⋯. The best way to fit the magnetic behavior of these complexes is to proceed by using a Hamiltonian that corresponds to a 12-membered of S=5/2 with 4 fragments repeating the sequence J1J2J3. The fit was performed by means of the computer program MAGPACK. The fitting for the observed magnetic data gives J1=−2.31cm−1, J2=−1.60cm−1, J3=−3.10cm−1, zJ′=−0.03cm−1 and g=1.98, with R=7.2×10−3.

Magnetic coupling and slow relaxation of magnetization in chain-based Mn(II), Co(II), and Ni(II) coordination frameworks.

Three isomorphous coordination polymers based on the chain with triple (μ-1,1-N3)(μ-1,3-COO)2 bridges have been synthesized from a new zwitterionic dicarboxylate ligand [L(-) = 1-(4-carboxylatobenzyl)pyridinium-4-carboxylate]. They are of formula [M(L)(N3)]n·3nH2O [M = Mn(II), Co(II), and Ni(II)]. In these compounds, the mixed-bridge chains are linked into 2D coordination networks by the N-benzylpyridinium spacers. The magnetic properties depend strongly on the nature of the metal center. The magnetic coupling through (μ-1,1-N3)(μ-1,3-COO)2 is antiferromagnetic in the Mn(II) compound but ferromagnetic in the Co(II) and Ni(II) analogues. Magnetostructural analyses indicate that the magnitude of the magnetic coupling can be correlated to the M-N-M angle of the azide bridge and the average M-O-C-O torsion angle of the carboxylate bridge. As the values of these parameters increase, the antiferromagnetic coupling for Mn(II) decreases while the ferromagnetic coupling for Co(II) increases. With strong magnetic anisotropy, the Co(II) compound behaves as a single-chain magnet showing hysteresis and Glauber-type slow dynamics probably in the infinite-chain region, with Δ(τ)/k = 86 K, Δ(ξ)/k = 26 K, and Δ(A)/k = 34 K. With weaker anisotropy, the Ni(II) species shows slow relaxation of magnetization at much lower temperature.

Manganese compounds with phthalate and terephthalate ligands: Synthesis, crystal structure, magnetic properties and catalase activity

The reactivity of carboxybenzoic acids substituted in ortho, meta and para positions (phthalic, isophthalic and terephthalic acids) has been explored. These acids have been used for the synthesis of dinuclear MnIII and polynuclear MnII compounds, obtaining unexpected results. From all the reactions, one dinuclear MnIII compound, [{Mn(H2O)(phen)}2(μ-2-COOHC6H4COO)2(μ-O)](ClO4)2 (1), one mixed valence compound, [{Mn(phen)2}2(μ-O)2](NO3)3 (2), and four MnII compounds, [{Mn(H2O)(phen)2}2(μ-4-COOC6H4COO)](NO3)2 (3), [Mn3(μ-4-COOC6H4COO)3(bpy)2]n (4), [{Mn(phen)2}2(μ-2-COOHC6H4COO)2](ClO4)2 (5) and [Mn(μ-2-COOC6H4COO)(H2O)2(phen)]n (6), (phen=1,10-phenanthroline, bpy=2,2′-bipyridine) have been obtained and characterised by X-ray diffraction, showing different coordination modes for the carboxylate ligand: a bidentate bridge in a syn−syn, syn–anti or anti–anti mode, a bis-monodentate bridge and a bis-bidentate bridge. The six compounds show antiferromagnetic coupling, with magnetic interaction constants of −3.7 and −332.5cm−1 for the dinuclear MnIII (1) and MnIIIMnIV (2) compounds and −0.04, −4.5, −1.5 and −0.55cm−1 for MnII compounds 4–6. Each MnII compound shows a different EPR spectrum at 4K, which has been simulated including the ZFS parameters. The catalase activity of the compounds with phthalate and terephthalate ligands has been studied, the former being less active than the latter.

Novel MnII coordination compounds constructed from benzoate and various bipyridyl ligands: Magnetic property and catalytic activity

Three new MnII-benzoates coordination polymers containing various bipyridyl ligands (3,3′-dipicoylamine (3), 3-methylisoquinoline (4), and 4,4′-dithiopyridine (5)) and a [Mn6(O2CPh)10(μ4-OH)2(CH3OH)3(H2O)]·1.5(C4H4N2) cluster (1) have prepared and their structures were determined. The bipyridyl ligands can act as bridging ligands to produce 1-D or 2-D polymeric compounds. The pyrazine produced a Mn6 cluster molecule, and 3-methylisoquinoline did a benzoate-bridged 1-D MnII compound. The Mn6 cluster (1) and 1-D MnII compounds (3) and (4) show antiferromagnetic property. The compounds 1, 3, and 4 have catalyzed efficiently the transesterification of a variety of esters, while 5 has displayed a very slow conversion. The thermal stabilities of these complexes were also examined.

Spin delocalization in the molecular manganese tetra-helicate cluster: [Mn3L4](ClO4)2(H2O)2

The magnetic properties of the compound [Mn3L4](C1O4)2(H2O)2 revealed that it is a rare trinuclear MnII compound showing ferromagnetic interactions and a possible anisotropic behaviour. Here we report preliminary magnetic susceptibility measurements and spin density determinations at the Mn and O atoms to elucidate the magnetic interaction model and the possible anomalous anisotropic magnetic behaviour reported previously for this compound, that it is confirmed to be inexistent.

An Unusual (10,3)‐d MOF Material with Nanoscale Helical Cavities and Multifunctionality

AbstractThe MnII and CuII compounds of 3‐(2‐pyridyl)‐5,6‐diphenyl‐1,2,4‐triazine‐4,4′‐disulfonic acid (H2pdtd) were synthesized and systematically characterized. The metal‐organic framework (MOF) [Mn2(pdtd)2(H2O)4]n·5nH2O (1) was constructed by a solvothermal method preformed at 140 °C with methanol as the solvent, while [Cu(pdtd)(H2O)4]·H2O (2) was obtained by conventional solution chemistry conducted at 80 °C. Crystallographic analysis revealed that 1 has an acentric structure in which the MnII centers are linked via sulfonate groups and chelating nitrogen atoms within the pdtd ligands to give a rare noninterpenetrating (10,3)‐d framework with permanent helical cavities. Consequently, 1 exhibits nonlinear optical (NLO) activity, significant CO2 sorption, and magnetic coupling. In contrast, 2 is a mononuclear complex with coordinated water and lacks functional properties.

Synthesis and Electronic Structure of Reduced Bis(imino)pyridine Manganese Compounds

AbstractThe synthesis and electronic structure of reduced aryl‐substituted bis(imino)pyridine manganese compounds have been explored. Stirring a THF slurry of [(iPrPDI)MnCl2] {iPrPDI = 2,6‐(2,6‐iPr2–C6H3N=CMe)2C5H3N} with excess Na and catalytic (0.5 mol‐%) naphthalene furnished the bis(THF) compound [(iPrPDI)Mn(THF)2]. Performing the reduction with excess Na(Hg) in toluene furnished the bis(chelate) manganese compound [(iPrPDI)2Mn]. For both compounds, a combination of EPR spectroscopy, magnetic measurements and metrical parameters determined from X‐ray diffraction established high‐spin MnII compounds with reduced, redox‐active bis(imino)pyridine ligands. Substitution of the THF ligands with carbon monoxide yielded [(iPrPDI)Mn(CO)2], a low‐spin MnI, d6 compound with an experimentally observed bis(imino)pyridine‐centred radical. Oxidation and reduction of this compound furnished [(iPrPDI)Mn(CO)3]+ and [(iPrPDI)Mn(CO)2]–, respectively, and provided a series of three manganese carbonyl compounds over three oxidation states. Elucidation of the electronic structure of these compounds established that oxidation events within the series are ligand‐ rather than manganese‐based, most likely a result of the stable low‐spin MnI, d6 electron configuration imparted by the strong‐field carbonyl ligands.

ChemInform Abstract: A Planar {Mn19(OH)12}26+ Unit Incorporated in a 60‐Tungsto‐6‐silicate Polyanion.

AbstractThe new MnII compound (III) crystallizes in the triclinic space group P$\bar 1$ with Z = 1 (single crystal XRD).

Crystal Structure and Magnetic Properties of the Dinuclear MnII Compound [Mn2(bpy)4(2-ClC6H4COO)2](ClO4)2·2EtOH

The synthesis and crystal structure of the dinuclear manganese (II) compound [Mn2(bpy)4(2-ClC6H4COO)2](ClO4)2·2EtOH is described. The complex crystallizes in the monoclinic system, space group P21/n with a = 12.2067(18), b = 17.335(3), c = 13.706(3) A and β = 92.606(8)°. In this structure, two manganese ions are bridged by two 2-chlorobenzoate ligands in a syn–anti mode. The hexa-coordination of each manganese is completed by two 2,2′-bipyridine ligands. Two perchlorate anions and two molecules of ethanol complete the packing. In order to check the magnetic properties previously reported from a powder sample, new magnetic studies have been carried out from a crystal sample, obtaining J = −1.79 cm−1 and g = 2.00 (H = −JS 1 ·S 2 ). The X-ray crystal structure of the dinuclear MnII compound [Mn2(bpy)4(2-ClC6H4COO)2](ClO4)2·2EtOH has been determined and its magnetic properties studied.

Isomorphous tetrazolate MnII and CoII compounds built on Δ-chain showing different magnetic behaviors

As a continuation of the study on using the tetrazolate ligands to construct coordination polymers, two isomorphous 3D coordination polymers built on Δ-chain topological rod-shaped SBUs have been synthesized with formulae [M(2)(μ(3)-OH)L(1)L(2)](n) (5-amino-1H-tetrazole (HL(1)), 2,3-pyrazinedicarboxylic acid (H(2)L(2)) and different 3d spin carriers (M = Mn(II), 1 and Co(II), 2)). The SBU consists of corner-sharing [M(3)(μ(3)-OH)] isosceles triangle motifs with mixed multiple (μ(4)-tetrazolyl, μ(3)-OH, syn-syn carboxylate) bridges. The SBUs were further linked by syn-anti carboxylates to form the sra net. Spin-competing was observed in the Mn(II) compound, whereas the Co(II) compound exhibits spin-canting.

A μ1,1- or μ1,3-carboxylate bridge makes the difference in the magnetic properties of dinuclear MnII compounds

Six new dinuclear Mn(II) compounds with carboxylate bridges have been synthesized and characterized by X-ray diffraction: [{Mn(phen)(2)}(2)(μ-RC(6)H(4)COO)(2)](ClO(4))(2) with R = 2-Cl (1), 2-CH(3) (2), 3-Cl (3), 3-CH(3) (4), 4-Cl (5) and 4-CH(3) (6). Compounds 1 and 2 show two μ(1,3)-carboxylate bridges in a syn-anti mode while compounds 3-6 present a very uncommon coordination mode of the carboxylate ligand: the μ(1,1)-bridge. The magnetic properties of these compounds are very sensitive to the bridging mode of the carboxylate ligands. While compounds 1 and 2 (μ(1,3)-bridge) display antiferromagnetic interactions, with J values of -1.41 and -1.66 cm(-1), respectively, compounds 3-6 (μ(1,1)-bridge) show ferromagnetic interactions, with J values of 1.01, 0.98, 1.04 and 1.06 cm(-1), respectively. It is worth noting that compounds 3-6 are the first of their class to be magnetically characterized. The EPR spectra at 4 K for compounds with antiferromagnetic coupling (1 and 2) are more complex than those for compounds with a ferromagnetic interaction (3-6). Quite good simulations can be obtained with the ZFS parameters of the Mn(II) ion D(Mn) ~ 0.095 cm(-1) and E(Mn) ~ 0.025 cm(-1) for compounds 1 and 2 and D(Mn) ~ 0.060 cm(-1) and E(Mn) ~ 0.004 cm(-1) for compounds 3-6.

A two-step field-induced magnetic transition in spin-canted systems observed only for the CoIIcoordination polymer

Two isostructural 1D compounds {[M3(hpdc)2(H2O)6] 2H2O}n (M = Mn, Co; H3hpde = 2-hydroxypyrimidine-4,6-dicarboxylic acid) were synthesized by the in situ hydrothermal reactions of 2-chloropyrimidine-4,6-dicarboxylic acid with MCl2 (M = Mn, Co) and NaOH; the MnII compound shows spin-canted antiferromagnetism, whereas the CoII compound exhibits the coexistence of spin-canting and a two-step field-induced magnetic phase transition.

A Pulse Radiolysis Study of Catalytic Superoxide Radical Dismutation by a Manganese(II) Complex with an N‐Tripodal Ligand (Eur. J. Inorg. Chem. 14/2005)

AbstractThe cover picture shows an allegory of bioinorganic chemistry and biomimetic studies. Here, the metalloprotein (human Mn‐SOD, PDB‐code 1MSD) is posing for the painter. As a bioinorganic chemist, he is designing new molecules that would reproduce this protein activity; he is testing the activity of these molecules and deciphering mechanisms. Here, we show the structure of a small MnII complex that has been studied for its SOD‐like activity by pulsed radiolysis. In the painting, the UV/Vis trace of a multipulse experiment at 300 nm is shown, with successive spikes and plateaus. An overall increase in the absorbance of the successive plateaus is observed. The asterisks indicate irradiations. Simulations of the individual growth of the spikes, of the individual decrease down to the plateau and of the overall increase of the absorbance for the successive plateaus leads to the proposition of a mechanism. This is the triangular cycle shown in the painting, involving an {MnOO}6 adduct between MnII and superoxide. This label, {MnOO}6, is proposed by analogy with the nomenclature used for iron−nitroxide adducts. Each event indicated in the cycle has been proven. Moreover, this study shows unambiguously that the MnII compound displays a catalytic activity for superoxide dismutation. Details are presented in the article by J.‐P. Renault, C. Policar et al. on p. 2789 ff. In the original picture by Magritte, the inset in the lower right‐hand corner, is entitled “La clairvoyance” (clear‐sightedness) and was painted in 1936.