A mixed‐valence manganese(III)–manganese(IV) di‐μ‐oxo complex, [(cyclam)MnO]2(ClO4)2(NO3)

The title dinuclear di‐μ‐oxo‐bis­[(1,4,8,11‐tetra­aza­cyclo­tetra­decane‐κ⁴N)­manganese(III,IV)] diperchlorate nitrate complex, [Mn₂O₂(C₁₀H₂₄N₄)₂](ClO₄)₂(NO₃) or [(cyclam)Mn­O]₂(ClO₄)₂(NO₃), was self‐assembled by the reaction of Mn²⁺ with 1,4,8,11‐tetra­aza­cyclo­tetra­decane in aqueous media. The structure of this compound consists of a centrosymmetric binuclear [(cyclam)MnO]³⁺ unit, two perchlorate anions and one nitrate anion. While the low‐temperature electron paramagnetic resonance spectra show a typical 16‐line signal for a di‐μ‐oxo Mn^III/Mn^IV dimer, the magnetic susceptibility studies also confirm a characteristic antiferromagnetic coupling between the electronic spins of the Mn^IV and Mn^III ions.     

A novel one‐dimensional complex: catena‐poly­[[manganese(III)‐di‐μ‐2‐[(2‐hydroxy­ethyl)­imino­methyl]­phenolato‐κ2O1,N:κO2;κO2:κ2O1] chloride]

In the title one‐dimensional complex, {[Mn^III(C₉H₁₀NO₂)₂]Cl}_n, the Schiff base ligand 2‐[(2‐hydroxy­ethyl)­imino­methyl]­phenolate (Hsae⁻) functions as both a bridging and a chelating ligand. The Mn^III ion is six‐coordinated by two N and four O atoms from four different Hsae⁻ ligands, yielding a distorted MnO₄N₂ octahedral environment. Each [Mn^III(Hsae)₂]⁺ cationic unit has the Mn atom on an inversion centre and each [Mn^III(Hsae)₂]⁺ cation lies about another inversion centre. The chain‐like complex is further extended into a three‐dimensional network structure through Cl⋯H—O hydrogen bonds and C—H⋯π contacts involving the Hsae⁻ rings.     

A binuclear manganese(II) complex,deca­aqua(μ‐1,2,4,5‐benzene­tetra­carboxyl­ato‐O1:O4)­di­manganese(II) hydrate

In the title Mn^II complex, [Mn₂(C₁₀H₂O₈)(H₂O)₁₀]·H₂O, two independent binuclear mol­ecules bridged by the 1,2,4,5‐benzene­tetra­carboxyl anion exist in a unit cell, with each anion lying about an inversion centre. One of the Mn—O_water distances [2.2922 (13) Å] is significantly longer than the Mn^II—O_water distances reported so far for Mn^II complexes and very close to the Mn—O_water distances found in the axial direction of Mn^III complexes.     

Kinetics and mechanism of oxidation of 2‐mercaptosuccinic acid by bis(μ‐oxo)‐ manganese(III,IV)‐cyclam complex in aqueous medium: Influence of externally added copper(II)

Kinetic studies on the oxidation of 2‐mercaptosuccinic acid by dinuclear [Mn₂^III/IV(μ‐O)₂(cyclam)₂](ClO₄)₃] ( 1 ) (abbreviated as Mn^III–Mn^IV) (cyclam = 1,4,8,11‐tetraaza‐cyclotetradecane) have been carried out in aqueous medium in the pH range of 4.0–6.0, in the presence of acetate buffer at 30°C by UV–vis spectrophotometry. In the pH region, two species of complex 1 (Mn^III–Mn^IV and Mn^III–Mn^IVH, the later being μ‐O protonated form) were found to be kinetically significant. The first‐order dependence of the rate of the reactions on [Thiol] both in presence and absence of externally added copper(II) ions, first‐order dependence on [Cu²⁺] and a decrease of rate of the reactions with increase in pH have been rationalized by suitable sequence of reactions. Protonation of μ‐O bridge of 1 is evidenced by the perchloric acid catalyzed decomposition of 1 to mononuclear Mn(III) and Mn(IV) complex observed by UV–vis and EPR spectroscopy. The kinetic features have been rationalized considering Cu(RSH) as the reactive intermediate. EPR spectroscopy lends support for this. The formation of a hydrogen bonded outer‐sphere adduct between the reductant and the complex in the lower pH range prior to electron transfer reactions is most likely to occur. © 2004 Wiley Periodicals, Inc. Int J Chem Kinet 36: 170–177 2004     

Aquachloro[N,N′‐ethylenebis(salicylideneiminato)]manganese(III)

The title compound, aqua­chloro{2,2′‐[1,2‐ethanediyl­bis­(nitrilo­methyl­idyne)]­diphenolato‐κ⁴O,N,N′,O′}manganese(III),[MnCl(C₁₆H₁₄N₂O₂)(H₂O)], is a neutral manganese(III) complex with a pseudo‐octahedral metal centre. The equatorial plane comprises the four donor atoms of the tetradentate Schiff base ligand [Mn—O 1.886 (4) and 1.893 (4) Å, and Mn—N 1.978 (5) and 1.982 (5) Å], with a water mol­ecule [Mn—O 2.383 (4) Å] and a Cl^? ligand [Mn—Cl 2.4680 (16) Å] completing the coordination sphere. The distorted geometry is highlighted by the marked displacement of the Mn^III ion out of the least‐squares plane of the four Schiff base donor atoms by 0.165 (2) Å. These monomeric Mn^III centres are then linked into a polymeric array via hydrogen bonds between the coordinated water mol­ecule and the phenolic O‐atom donors of an adjacent Mn^III centre [O—H?O 2.789 (5) and 2.881 (5) Å].     

Cyano­cobalt(III) complexes of penta‐ and tetra­dentate‐coordinated macrocyclic hexa­amines

The pendent‐arm macrocyclic hexa­amine trans‐6,13‐dimethyl‐1,4,8,11‐tetra­aza­cyclo­tetra­decane‐6,13‐diamine (L) may coordinate in tetra‐, penta‐ or hexa­dentate modes, depending on the metal ion and the synthetic procedure. We report here the crystal structures of two pseudo‐octa­hedral cobalt(III) complexes of L, namely sodium trans‐cyano­(trans‐6,13‐dimethyl‐1,4,8,11‐tetra­aza­cyclo­tetra­decane‐6,13‐diamine)cobalt(III) triperchlorate, Na[Co(CN)(C₁₃H₃₀N₆)](ClO₄)₃ or Na{trans‐[CoL(CN)]}(ClO₄)₃, (I), where L is coordinated as a penta­dentate ligand, and trans‐dicyano­(trans‐6,13‐dimethyl‐1,4,8,11‐tetra­aza­cyclo­tetra­decane‐6,13‐diamine)cobalt(III) trans‐dicyano­(trans‐6,13‐dimethyl‐1,4,8,11‐tetra­aza­cyclo­tetra­decane‐6,13‐diaminium)cobalt(III) tetra­perchlorate tetra­hydrate, [Co(CN)₂(C₁₄H₃₂N₆)][Co(CN)₂(C₁₄H₃₀N₆)](ClO₄)₄·4H₂O or trans‐[CoL(CN)₂]trans‐[Co(H₂L)(CN)₂](ClO₄)₄·4H₂O, (II), where the ligand binds in a tetra­dentate mode, with the remaining coordination sites being filled by C‐­bound cyano ligands. In (I), the secondary amine Co—N bond lengths lie within the range 1.944 (3)–1.969 (3) Å, while the trans influence of the cyano ligand lengthens the Co—N bond length of the coordinated primary amine [Co—N = 1.986 (3) Å]. The Co—CN bond length is 1.899 (3) Å. The complex cations in (II) are each located on centres of symmetry. The Co—N bond lengths in both cations are somewhat longer than in (I) and span a narrow range [1.972 (3)–1.982 (3) Å]. The two independent Co—CN bond lengths are similar [1.918 (4) and 1.926 (4) Å] but significantly longer than in the structure of (I), again a consequence of the trans influence of each cyano ligand.     

catena‐Poly[[diaquamanganese(II)]‐di‐μ‐1,1,3,3‐tetracyano‐2‐ethoxypropenido‐κ4N1:N3]

The crystal structure of the title compound, [Mn(C₉H₅N₄O)₂(H₂O)₂], conventionally denoted Mn(EtO‐TCA)₂(H₂O)₂, where EtO‐TCA is 2‐ethoxy‐1,1,3,3‐tetra­cyano­propenide, is described. The EtO‐TCA anions bridge Mn^II centers through one of the nitrile N atoms of each of their two di­cyano­methanide groups, thus forming dibridged chains along ab. These chains are linked into two‐dimensional sheets through hydrogen bonding. The seven‐atom bridge, which results in a long Mn⃛Mn intrachain interaction [9.0044 (4) Å], as well as the large interchain separations [8.3288 (4) and 8.5220 (4) Å] prohibit long‐range magnetic ordering down to temperatures as low as 1.55 K.     

A dodeca­nuclear manganese(II,III) complex of penta­erythritol

The mol­ecule of the title compound, tetra‐μ₂‐acetato‐diaquadi‐μ₂‐chloro‐tetra­chloro­tetra­kis[μ₄‐3‐hydroxy‐2,2‐bis­(oxido­meth­yl)propanol­ato]­tetra­methanoldi‐μ₃‐methanolato‐di‐μ₅‐oxo‐octa­manganese(II)­tetra­manganese(III), [Mn₄^IIIMn₈^II(CH₃O)₂(C₂H₃O₂)₄(C₅H₉O₄)₄Cl₆O₂(CH₄O)₄(H₂O)₂], displays a centre of symmetry. The structure of the {Mn₄^IIIMn₈^IIO₁₈Cl₂}¹⁰⁻ core is composed of three layers and features two oxo ligands binding in a rare μ₅‐mode.     

cis‐Dinitrito(1,4,8,11‐tetra­aza­cyclo­tetra­decane‐κ4N)­chromium(III) nitrite

In the title compound, [Cr(ONO)₂(cyclam)]NO₂ (cyclam is 1,4,8,11‐tetra­aza­cyclo­tetra­decane, C₁₀H₂₄N₂), the complex cation is located on a twofold symmetry axis. The central Cr atom has a distorted octahedral coordination, involving two Cr—O bonds, with the monodentate nitrite O atoms adopting a cis configuration, and four Cr—N bonds. The mean Cr—N and Cr—O distances are 2.0895 (14) and 1.9698 (14) Å.     

Poly[bis(N‐methylformamide)tetra‐μ‐thiocyanato‐manganese(II)mercury(II)]

The title complex, [MnHg(NCS)₄(C₂H₅NO)₂]_n, consists of slightly distorted MnN₄O₂ octa­hedra and HgS₄ tetra­hedra. Each Mn^II cation is bound to four N atoms of the NCS groups and two O atoms of the N‐methyl­formamide (NMF) ligands in a cis configuration. Each Hg^II cation is coordinated to four S atoms of NCS groups. Each pair of Mn^II and Hg^II cations is connected by an –NCS– bridge, forming an infinite three‐dimensional –Mn—NCS—Hg– network.     

A novel bridged asymmetric binuclear manganese(II) complex with DTPB [DTPB is 1,1,4,7,7‐pentakis(1H‐benz­imidazol‐2‐yl­methyl)‐1,4,7‐tri­aza­heptane]

The crystal structure of the title compound, tetra­chloro­[μ‐1,1,4,7,7‐pentakis(1H‐benzimidazol‐2‐yl­methyl)‐1,4,7‐tri­azaheptane]­dimanganese(II) methanol pentasolvate tetrahydrate, [Mn₂Cl₄(C₄₄H₄₃N₁₃)]·5CH₄O·4H₂O, contains an ­asymmetric dinuclear Mn^II–DTPB [DTPB is 1,1,4,7,7‐pentakis(1H‐benzimidazol‐2‐yl­methyl)‐1,4,7‐tri­aza­heptane] complex with an intra‐ligand bridging group (–NCH₂CH₂N–), as well as several solvate mol­ecules (methanol and water). Both Mn^II cations have similar distorted octahedral coordination geometries. One Mn^II cation is coordinated by a Cl⁻ anion and five N atoms from the ligand, and the other is coordinated by three Cl⁻ anions and three N atoms of the same ligand. The Mn⋯Mn distance is 7.94 Å. A Cl⋯H—O⋯H—O⋯H—N hydrogen‐bond chain is also observed, connecting the two parts of the complex.     

Tetra­aqua­bis(5‐carb­oxy‐2‐nitro­benzo­ato‐κO)manganese(II) dihydrate: a metal–water chain complex containing cyclic water tetra­mers

In the title complex, [Mn(C₈H₄NO₆)₂(H₂O)₄]·2H₂O, cyclic water tetra­mers forming one‐dimensional metal–water chains have been observed. The water clusters are trapped by the co‐­operative association of coordination inter­actions and hydrogen bonds. The Mn^II ion resides on a center of symmetry and is in an octa­hedral coordination environment comprising two O atoms from two 5‐carboxy‐2‐nitrobenzoate ligands and four O atoms from water mol­ecules.     

catena‐Poly[[aqua­bis(1H‐benzimidazole‐κN3)manganese(II)]‐μ‐adipato]

In the title polymeric complex, [Mn(C₆H₈O₄)(C₇H₆N₂)₂(H₂O)]_n, the Mn^II atom is surrounded by two adipate dianions, two benzimidazole mol­ecules and one coordinated water mol­ecule. The Mn atoms and coordinated water mol­ecule are located on a twofold axis, and the bridging adipate ligand is located on an inversion center. The adipate dianions bridge neighboring Mn^II atoms to form polymeric chains. Each Mn^II atom is seven‐coordinate, the longest Mn—O bond length being 2.5356 (16) Å.     

Syntheses,Structures and Magnetic Properties of Two Mixed‐Valent Disc‐like Hepta‐nuclear Compounds of [FeIIFeIII6(tea)6](ClO4)2 and [MnII3MnIII4(nmdea)6(N3)6]·CH3OH (tea = N(CH2CH2O)33−, nmdea = CH3N(CH2CH2O)22−)

Two mixed‐valent disc‐like hepta‐nuclear compounds of [Fe^IIFe^III₆(tea)₆](ClO₄)₂ ( 1Fe , tea = N(CH₂CH₂O)₃^3?) and [Mn^II₃Mn^III₄(nmdea)₆(N₃)₆]·CH₃OH ( 2Mn , nmdea = CH₃N(CH₂CH₂O)₂^2?) have been synthesized by the reaction of Fe(ClO₄)₂·6H₂O with triethanolamine (H₃tea) for the former and reaction of Mn(ClO₄)₂·6H₂O with diethanolamine (H₂nmdea) and NaN₃ for the later, respectively. 1Fe has the cationic cluster with a planar [Fe^IIFe^III₆] core consisting of one central Fe^II and six rim Fe^III atoms in hexagonal arrangement. The Fe ions are linked by the oxo‐bridges from the alcohol arms in the manner of edge‐sharing of their coordination octahedra. 2Mn is a neutral cluster with a [Mn^II₃Mn^III₄] core possessing one central Mn^II atom surrounded by six rim Mn ions, two Mn^II and four Mn^III. The structure is similar to 1Fe but involves six terminal azido ligands, each coordinate one rim Mn ion. 1Fe showed dominant antiferromagnetic interaction within the cluster and long‐range ordering at 2.7 K. The cluster probably has a ground state of low spin of S = 5/2 or 4/2. The long‐range ordering is weak ferromagnetic, showing small hysteresis with a remnant magnetization of 0.3 Nβ and a coercive field of 40 Oe. Moreover, the isofield of lines 1Fe are far from superposition, indicating the presence of significant zero–field splitting. Ferromagnetic interactions are dominant in 2Mn . An intermediate spin ground state 25/2 is observed at low field. In high field of 50 kOe, the energetically lowest state is given by the m_s = 31/2 component of the S = 31/2 multiplet due to the Zeeman effect. Despite of the large ground state, no single‐molecule magnet behavior was found above 2 K.     

Field‐Induced Slow Magnetic Relaxation in a Mononuclear Manganese(III)–Porphyrin Complex

We report on a novel manganese(III)–porphyrin complex with the formula [Mn^III(TPP)(3,5‐Me₂pyNO)₂]ClO₄?CH₃CN ( 2 ; 3,5‐Me₂pyNO=3,5‐dimethylpyridine N‐oxide, H₂TPP=5,10,15,20‐tetraphenylporphyrin), in which the Mn^III ion is six‐coordinate with two monodentate 3,5‐Me₂pyNO molecules and a tetradentate TPP ligand to build a tetragonally elongated octahedral geometry. The environment in 2 is responsible for the large and negative axial zero‐field splitting (D=?3.8 cm^?1), low rhombicity (E/|D|=0.04) of the high‐spin Mn^III ion, and, ultimately, for the observation of slow magnetic‐relaxation effects (E_a=15.5 cm^?1 at H=1000 G) in this rare example of a manganese‐based single‐ion magnet (SIM). Structural, magnetic, and electronic characterizations were carried out by means of single‐crystal diffraction studies, variable‐temperature direct‐ and alternating‐current measurements and high‐frequency and ‐field EPR spectroscopic analysis followed by quantum‐chemical calculations. Slow magnetic‐relaxation effects were also observed in the already known analogous compound [Mn^III(TPP)Cl] ( 1 ; E_a=10.5 cm^?1 at H=1000 G). The results obtained for 1 and 2 are compared and discussed herein.     

trans‐Bis(isothiocyanato‐κN)bis(methanol‐κO)bis[2,4,6‐tri(4‐pyridyl)‐1,3,5‐triazine‐κN2]manganese(II)

The title compound, [Mn(NCS)₂(C₁₈H₁₂N₆)₂(CH₄O)₂], con­tains a centrosymmetric octahedral Mn^II centre and three pairs of trans‐coordinating ligands. It is the first example of a mononuclear metal complex with the 2,4,6‐tri(4‐pyridyl)‐1,3,5‐triazine (tpt) ligand. Intermolecular π–π stacking of the planar tpt ligands, as well as hydrogen bonds between pyridyl N and methanol H atoms, results in the formation of a three‐dimensional network.     

One‐Dimensional Ferromagnetically Coupled Bimetallic Chains Constructed with trans‐[Ru(acac)2(CN)2]−: Syntheses,Structures, Magnetic Properties,and Density Functional Theoretical Study

Four cyano‐bridged 1D bimetallic polymers have been prepared by using the paramagnetic building block trans‐[Ru(acac)₂(CN)₂]^? (Hacac=acetylacetone): {[{Ni(tren)}{Ru(acac)₂(CN)₂}][ClO₄]?CH₃OH}_n ( 1 ) (tren=tris(2‐aminoethyl)amine), {[{Ni(cyclen)}{Ru(acac)₂(CN)₂}][ClO₄]? CH₃OH}_n ( 2 ) (cyclen=1,4,7,10‐tetraazacyclododecane), {[{Fe(salen)}{Ru(acac)₂(CN)₂}]}_n ( 3 ) (salen^2?=N,N′‐bis(salicylidene)‐o‐ethyldiamine dianion) and [{Mn(5,5′‐Me₂salen)}₂{Ru(acac)₂(CN)₂}][Ru(acac)₂(CN)₂]? 2 CH₃OH ( 4 ) (5,5′‐Me₂salen=N,N′‐bis(5,5′‐dimethylsalicylidene)‐o‐ethylenediimine). Compounds 1 and 2 are 1D, zigzagged NiRu chains that exhibit ferromagnetic coupling between Ni^II and Ru^III ions through cyano bridges with J=+1.92 cm^?1, z J′=?1.37 cm^?1, g=2.20 for 1 and J=+0.85 cm^?1, z J′=?0.16 cm^?1, g=2.24 for 2 . Compound 3 has a 1D linear chain structure that exhibits intrachain ferromagnetic coupling (J=+0.62 cm^?1, z J′=?0.09 cm^?1, g=2.08), but antiferromagnetic coupling occurs between FeRu chains, leading to metamagnetic behavior with T_N=2.6 K. In compound 4 , two Mn^III ions are coordinated to trans‐[Ru(acac)₂(CN)₂]^? to form trinuclear Mn₂Ru units, which are linked together by π–π stacking and weak Mn???O* interactions to form a 1D chain. Compound 4 shows slow magnetic relaxation below 3.0 K with ?=0.25, characteristic of superparamagnetic behavior. The Mn^III???Ru^III coupling constant (through cyano bridges) and the Mn^III???Mn^III coupling constant (between the trimers) are +0.87 and +0.24 cm^?1, respectively. Compound 4 is a novel single‐chain magnet built from Mn₂Ru trimers through noncovalent interactions. Density functional theory (DFT) combined with the broken symmetry state method was used to calculate the molecular magnetic orbitals and the magnetic exchange interactions between Ru^III and M (M=Ni^II, Fe^III, and Mn^III) ions. To explain the somewhat unexpected ferromagnetic coupling between low‐spin Ru^III and high‐spin Fe^III and Mn^III ions in compounds 3 and 4 , respectively, it is proposed that apart from the relative symmetries, the relative energies of the magnetic orbitals may also be important in determining the overall magnetic coupling in these bimetallic assemblies.     

Tetrakis[(4‐aminopyridinio)acetato‐κO]diaquamanganese(II) diper­chlorate

In the centrosymmetric title complex, [Mn(C₇H₈N₂O₂)₄(H₂O)₂](ClO₄)₂, the Mn^II ion is in an octahedral environment, with the equatorial plane being defined by the O atoms of four monodentate carboxyl­ate groups, and the octahedron being completed by two trans‐coordinated water mol­ecules. There are intramolecular hydrogen bonds between the coordinated water mol­ecules and the non‐coordinated O atoms of the carboxyl­ate groups. Hydrogen bonds between the amino groups and the carboxyl­ate groups of neighbouring mol­ecules generate a layered hydrogen‐bonded network.     

Diaqua­bis[5‐(pyrazin‐2‐yl‐κN1)‐1H‐tetra­zolato‐κN1]manganese(II) and diaqua­bis[5‐(pyrazin‐2‐yl‐κN1)‐1H‐tetra­zolato‐κN1]zinc(II)

The two new title complexes, [Mn(C₅H₃N₆)₂(H₂O)₂] and [Zn(C₅H₃N₆)₂(H₂O)₂], are isomorphous. In both compounds, the metal atom is located on an inversion center and is coordinated by four N atoms from two 5‐(pyrazin‐2‐yl)‐1H‐tetra­zolate anions in the basal plane and by two O atoms of water ligands in the apical positions to form a distorted octa­hedral geometry. Inter­molecular hydrogen‐bond inter­actions between the uncoordinated N atoms of the tetra­zolate anions and the H atoms of the water mol­ecules lead to the formation of a three‐dimensional network.     

Di­aqua­bis(1,10‐phenanthroline‐κ2N,N′)­manganese(II) thiodiglycolate bis(1,10‐phenanthroline‐κ2N,N′)(thiodiglycolato‐κ2O,O′)­manganese(II) tridecahydrate

The title compound, [Mn(C₁₂H₈N₂)₂(H₂O)₂](C₄H₄O₄S)·[Mn(C₄H₄O₄S)(C₁₂H₈N₂)₂]·13H₂O, contains one dianion of thio­diglycolic acid (tdga²⁻) and two independent man­ganese(II) moieties, viz. [Mn(phen)₂(H₂O)₂]²⁺ and [Mn(tdga)(phen)₂], where phen is 1,10‐phenanthroline. The Mn^II atoms are octahedrally coordinated by four N atoms of two bidentate phen ligands [Mn—N = 2.240 (2)–2.3222 (19) Å] and either two water O atoms or two tdga carboxyl O atoms [Mn—O = 2.1214 (17)–2.1512 (17) Å]. The tdga ligand chelates as an O,O′‐bidentate ligand, forming an eight‐membered ring with one Mn atom. The free tdga²⁻ dianion is hydrogen bonded to an [Mn(phen)₂(H₂O)₂]²⁺ ion, with O⋯O distances of 2.606 (2) and 2.649 (2) Å. The crystal structure is further stabilized by an extensive network of hydrogen bonds involving 13 water mol­ecules.