Molybdenum Bisphosphonates with Cr(III) or Mn(III) Ions

The synthesis of Mo^VI bisphosphonates (BPs) complexes in the presence of a heterometallic element has been studied. Two different BPs have been used, the alendronate ligand, [O₃PC(C₃H₆NH₃)(O)PO₃]^4? (Ale) and a new BP derivative with a pyridine ring linked to the amino group, [O₃PC(C₃H₆NH₂CH₂C₅H₄N)(O)PO₃]^4? (AlePy). Three compounds have been isolated, a tetranuclear Mo^VI complex with Cr^III ions, (NH₄)₅[(Mo₂O₆)₂(O₃PC(C₃H₆NH₃)(O)PO₃)₂Cr]·11H₂O (Mo₄(Ale)₂Cr), its Mn^III analogue, (NH₄)_4.5Na_0.5[(Mo₂O₆)₂(O₃PC(C₃H₆NH₃)(O)PO₃)₂Mn]·9H₂O (Mo₄(Ale)₂Mn), and a cocrystal of two polyoxomolybdates, (NH₄)₁₀Na₃[(Mo₂O₆)₂(O₃PC(C₃H₆NH₂CH₂C₅H₄N)(O)PO₃)₂Cr]₂[CrMo₆(OH)₆O₁₈]·37H₂O ([Mo₄(AlePy)₂Cr]₂[CrMo₆]). In this latter compound an Anderson-type POM [CrMo₆(OH)₆O₁₈]^3? is sandwiched between two tetranuclear Mo^VI complexes with AlePy ligands. The protonated triply bridging oxygen atoms bound to the central Cr^III ion of the Anderson anion develop strong hydrogen bonding interactions with the oxygen atoms of the bisphosphonate complexes. The UV–Vis spectra confirm the coexistence in solution of both POMs. Cyclic voltammetry experiments have been performed, showing the reduction of the Mo centers. In strong contrast with the reported Mo^VI BP systems, the presence of trivalent cations in close proximity to the Mo^VI centers dramatically impact the potential solid-state photochromic properties of these compounds.     

Modular Molecules: Site‐Selective Metal Substitution,Photoreduction, and Chirality in Polyoxometalate Hybrids

The first members of a promising new family of hybrid amino acid–polyoxometalates have emerged from a search for modular functional molecules. Incorporation of glycine (Gly) or norleucine (Nle) ligands into an yttrium‐tungstoarsenate structural backbone, followed by crystallization with p‐methylbenzylammonium (p‐MeBzNH₃⁺) cations, affords (p‐MeBzNH₃)₆K₂(GlyH)[As^III₄(Y^IIIW^VI₃)W^VI₄₄Y^III₄O₁₅₉(Gly)₈‐ (H₂O)₁₄] ? 47 H₂O ( 1 ) and enantiomorphs (p‐MeBzNH₃)₁₅(NleH)₃ [As^III₄(Mo^V₂Mo^VI₂)W^VI₄₄Y^III₄O₁₆₀(Nle)₉(H₂O)₁₁][As^III₄(Mo^VI₂W^VI₂)‐ W^VI₄₄Y^III₄O₁₆₀(Nle)₉(H₂O)₁₁] (generically designated 2 : L ‐Nle, 2 a ; D ‐Nle, 2 b ). An intensive structural, spectroscopic, electrochemical, magnetochemical and theoretical investigation has allowed the elucidation of site‐selective metal substitution and photoreduction of the tetranuclear core of the hybrid polyanions. In the solid state, markedly different crystal packing is evident for the compounds, which indicates the role of noncovalent interactions involving the amino acid ligands. In solution, mass spectrometric and small‐angle X‐ray scattering studies confirm maintenance of the structure of the polyanions of 2 , while circular dichroism demonstrates that the chirality is also maintained. The combination of all of these features in a single modular family emphasizes the potential of such hybrid polyoxometalates to provide nanoscale molecular materials with tunable properties.     

Cyano‐Bridged MnIII?MIII Single‐Chain Magnets with MIII=CoIII,FeIII, MnIII,and CrIII

A series of isostructural cyano‐bridged Mn^III(h.s.)–M^III(l.s.) alternating chains, [Mn^III(5‐TMAMsalen)M^III(CN)₆] ? 4H₂O (5‐TMAMsalen^2?=N,N′‐ethylenebis(5‐trimethylammoniomethylsalicylideneiminate), Mn^III(h.s.)=high‐spin Mn^III, M^III(l.s.)=low‐spin Co^III, Mn? Co ; Fe^III, Mn? Fe ; Mn^III, Mn? Mn ; Cr^III, Mn? Cr ) was synthesized by assembling [Mn^III(5‐TMAMsalen)]³⁺ and [M^III(CN)₆]^3?. The chains present in the four compounds, which crystallize in the monoclinic space group C2/c, are composed of an [‐Mn^III‐NC‐M^III‐CN‐] repeating motif, for which the ‐NC‐M^III‐CN‐ motif is provided by the [M^III(CN)₆]^3? moiety adopting a trans bridging mode between [Mn^III(5‐TMAMsalen)]³⁺ cations. The Mn^III and M^III ions occupy special crystallographic positions: a C₂ axis and an inversion center, respectively, forming a highly symmetrical chain with only one kind of cyano bridge. The Jahn–Teller axis of the Mn^III(h.s.) ion is perpendicular to the N₂O₂ plane formed by the 5‐TMAMsalen tetradentate ligand. These Jahn–Teller axes are all perfectly aligned along the unique chain direction without a bending angle, although the chains are corrugated with an Mn‐N_axis‐C angle of about 144°. In the crystal structures, the chains are well separated with the nearest inter‐chain M???M distance being relatively large at 9 Å due to steric hindrance of the bulky trimethylammoniomethyl groups of the 5‐TMAMsalen ligand. The magnetic properties of these compounds have been thoroughly studied. Mn? Fe and Mn? Mn display intra‐chain ferromagnetic interactions, whereas Mn? Cr is characterized by an antiferromagnetic exchange that induces a ferrimagnetic spin arrangement along the chain. Detailed analyses of both static and dynamic magnetic properties have demonstrated without ambiguity the single‐chain magnet (SCM) behavior of these three systems, whereas Mn? Co is merely paramagnetic with S_Mn=2 and D/k_B=?5.3 K (D being a zero‐field splitting parameter). At low temperatures, the Mn? M compounds with M=Fe, Mn, and Cr display remarkably large M versus H hysteresis loops for applied magnetic fields along the easy magnetic direction that corresponds to the chain direction. The temperature dependence of the associated relaxation time for this series of compounds systematically exhibits a crossover between two Arrhenius laws corresponding to infinite‐chain and finite‐chain regimes for the SCM behavior. These isostructural hetero‐spin SCMs offer a unique series of alternating [‐Mn‐NC‐M‐CN‐] chains, enabling physicists to test theoretical SCM models between the Ising and Heisenberg limits.     

Accelerated Oxygen Atom Transfer and C−H Bond Oxygenation by Remote Redox Changes in Fe3Mn‐Iodosobenzene Adducts

We report the synthesis, characterization, and reactivity of [LFe₃(PhPz)₃OMn(^sPhIO)][OTf]_x ( 3 : x =2; 4 : x =3), where 4 is one of very few examples of iodosobenzene–metal adducts characterized by X‐ray crystallography. Access to these rare heterometallic clusters enabled differentiation of the metal centers involved in oxygen atom transfer (Mn) or redox modulation (Fe). Specifically, ⁵⁷Fe Mössbauer and X‐ray absorption spectroscopy provided unique insights into how changes in oxidation state ( Fe^III ₂ Fe^IIMn^II vs. Fe^III ₃ Mn^II ) influence oxygen atom transfer in tetranuclear Fe₃Mn clusters. In particular, a one‐electron redox change at a distal metal site leads to a change in oxygen atom transfer reactivity by ca. two orders of magnitude.     

Construction of Two High‐Nuclear 3d‐4d Heterometallic Cluster Organic Frameworks by Introducing a Bifunctional Tripodal Alcohol as a Structure‐Directing Agent

Two unique heterometallic cluster organic frameworks, [Cd₄Mn^III₄Mn^II₆(Tri)₄(CH₃COO)₁₄(μ₄‐O)₂(μ₃‐O)₂(H₂O)₂] Cd(H₂O)₂?9 H₂O ( 1 ) and Cu[Cd₅Cu₆(Tri)₄(CH₃COO)₉(H₂O)₄]₂(CH₃COO)₃?24 H₂O ( 2 ) (H₃Tri=2‐(hydroxymethyl)‐2‐(pyridine‐4‐yl)‐1,3‐propanediol), have been successfully prepared by employing a bifunctional tripodal alcohol ligand as a structure‐directing agent. Crystal structure analyses reveal that 1 represents a rare example of frameworks constructed from Cd?Mn heterometallic chains, and 2 is the first heterometallic MOF based on highest‐nuclear Cd?Cu heterometallic cluster building blocks. Furthermore, the magnetic properties and gas adsorption abilities of 1 and 2 were systematically studied.     

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.     

X-ray photoelectron spectra of heterometallic 3<Emphasis Type="Italic">d</Emphasis>-metal carboxylate complexes

The electronic structure and magnetic states in the heterometallic hexanuclear complex Mn₄^IIFe₂^III (μ₄-O)₂(Piv)₁₀ · MeCN₄ have been studied by X-ray photoelectron spectroscopy (XPS). The substitution of two Mn atoms for two Fe atoms in the hexanuclear complex was found to have an effect on the patterns of iron and manganese X-ray photoelectron spectra. XPS data are evidence of the high-spin paramagnetic state of Mn^II and Fe^III atoms, as well as of the ligand-metal charge transfer upon complex formation. In the heteroatomic complex, the degree of bond covalence increased for both the manganese and iron atoms. The results obtained are in good agreement with X-ray diffraction data.     

The Electron Transfer Series [MoIII(bpy)3]n (n=3+, 2+, 1+, 0, 1−), and the Dinuclear Species [{MoIIICl(Mebpy)2}2(μ2‐O)]Cl2 and [{MoIV(tpy.)2}2(μ2‐MoO4)](PF6)2⋅4 MeCN

The electronic structures of the five members of the electron transfer series [Mo(bpy)₃]ⁿ (n=3+, 2+, 1+, 0, 1?) are determined through a combination of techniques: electro‐ and magnetochemistry, UV/Vis and EPR spectroscopies, and X‐ray crystallography. The mono‐ and dication are prepared and isolated as PF₆ salts for the first time. It is shown that all species contain a central Mo^III ion (4d³). The successive one‐electron reductions/oxidations within the series are all ligand‐based, involving neutral (bpy⁰), the π‐radical anion (bpy^.)^1?, and the diamagnetic dianion (bpy^2?)^2?: [Mo^III(bpy⁰)₃]³⁺ (S=3/2), [Mo^III(bpy^.)(bpy⁰)₂]²⁺ (S=1), [Mo^III(bpy^.)₂(bpy⁰)]¹⁺ (S=1/2), [Mo^III(bpy^.)₃] (S=0), and [Mo^III(bpy^.)₂(bpy^2?)]^1? (S=1/2). The previously described diamagnetic dication “[Mo^II(bpy⁰)₃](BF₄)₂” is proposed to be a diamagnetic dinuclear species [{Mo(bpy)₃}₂(μ₂‐O)](BF₄)₄. Two new polynuclear complexes are prepared and structurally characterized: [{Mo^IIICl(^Mebpy⁰)₂}₂(μ₂‐O)]Cl₂ and [{Mo^IV(tpy^.)₂}₂(μ₂‐Mo^VIO₄)](PF₆)₂?4 MeCN.     

Synthesis,structure, and properties of polynuclear molybdenum(v,vi) oxomethoxides with magnesium

General conditions for the formation of heterometallic clusters by the simultaneous methanolysis of MoCl₅ and MgCl₂ were determined. The resultant alkalinity of the reaction solution, the Mg/Mo molar ratio, and the presence of traces of water are key factors responsible for the composition and structure of the mixed magnesium molybdenum methoxides that formed. The new decanuclear mixed-valence Mo^V,VI Mg oxomethoxide [Mo^V ₄O₄(μ₃-O)₂(μ₂-O)₂Mo^VI ₂-O₄(OMe)₂Mg₄(MeOH)₆(μ₃-OMe)₆(μ₂-OMe)₈] (1) was synthesized by the reaction of lowernuclearity magnesium molybdenum oxoalkoxide complexes: NaMo^V of the complex Na(MeOH)Mo^V ₂O₂(μ₂-OMe)₃(OMe)₄ (2) and MgMo^VI of the complex [Mo^VIO₂Mg(MeOH)₂-(OMe)₄]₂ (3). The molecular structure of 1 was determined by X-ray diffraction.     

Modele de nitrogenase. activite de complexes molybdenecysteine dans la reduction de l'acetylene

The complex Mo₂O₄(cys)₂^2? disproportionates nito Mo^VI and Mo^III at a _pH higher than 9. Under our experimental conditions, the reduction of acetylene by molybdenum-cystéine complexes does only occur after addition of naBH₄·Mo^III; the molybdenum(III) species seems to be responsible for this activity.     

A 1,2,4‐Triazole‐based Polynuclear Mixed‐valence MnIIMnIII Complex: Synthesis,Characterization, and Magnetic Property

A mixed‐valence Mn complex {[Mn^IIMn^III(HL)₂(4,4′‐bpy)(H₂O)₂] · (ClO₄)(DMF)₃(4,4′‐bpy)_0.5}_n ( 1 ) [H₂L = 3‐(2‐phenol)‐5‐(pyridin‐2‐yl)‐1,2,4‐triazole] was synthesized and characterized by X‐ray single‐crystal structure analysis and magnetic susceptibility. Single‐crystal X‐ray analysis revealed that complex 1 has a dinuclear core, in which adjacent central Mn^III atoms are linked by 4,4′‐bipyridine to form an infinite one‐dimensional (1D) molecular configuration. According to the Mn surrounding bond lengths and bond valence sum (BVS) calculations, we demonstrated that the Mn atom coordinated to the pyridine N atoms is in the +2 oxidation state, while another Mn atom coordinated to the phenolic oxygen atoms is in the +3 oxidation state. Magnetic susceptibility data of the complex 1 indicate that the ferromagnetic interaction dominates in this complex.     

Homo‐ and Heterovalent Polynuclear Cerium and Cerium/Manganese Aggregates

Reactions of Ce^III(NO₃)₃?6 H₂O or (NH₄)₂[Ce^IV(NO₃)₆] with Mn‐containing starting materials result in seven novel polynuclear Ce or Ce/Mn complexes with pivalato (^tBuCO ) and, in most cases, auxiliary N,O‐ or N,O,O‐donor ligands. With nuclearities ranging from 6–14, the compounds present aesthetically pleasing structures. Complexes [Ce^IV₆(μ₃‐O)₄(μ₃‐OH)₄(μ‐O₂C^tBu)₁₂] ( 1 ), [Ce^IV₆Mn^III₄(μ₄‐O)₄(μ₃‐O)₄(O₂C^tBu)₁₂(ea)₄(OAc)₄]?4 H₂O?4 MeCN (ea^?=2‐aminoethanolato; 2 ), [Ce^IV₆Mn^III₈(μ₄‐O)₄(μ₃‐O)₈(pye)₄(O₂C^tBu)₁₈]₂[Ce^IV₆(μ₃‐O)₄(μ₃‐OH)₄(O₂C^tBu)₁₀(NO₃)₄] [Ce^III(NO₃)₅(H₂O)]?21 MeCN (pye^?=pyridine‐2‐ethanolato; 3 ), and [Ce^IV₆Ce^III₂Mn^III₂(μ₄‐O)₄(μ₃‐O)₄(^tbdea)₂(O₂C^tBu)₁₂(NO₃)₂(OAc)₂]?4 CH₂Cl₂ (^tbdea^2?=2,2′‐(tert‐butylimino]bis[ethanolato]; 4 ) all contain structures based on an octahedral {Ce^IV₆(μ₃‐O)₈} core, in which many of the O‐atoms are either protonated to give (μ₃‐OH)^? hydroxo ligands or coordinate to further metal centers (Mn^III or Ce^III) to give interstitial (μ₄‐O)^2? oxo bridges. The decanuclear complex [Ce^IV₈Ce^IIIMn^III(μ₄‐O)₃(μ₃‐O)₃(μ₃‐OH)₂(μ‐OH)(bdea)₄(O₂C^tBu)_9.5(NO₃)_3.5(OAc)₂]?1.5 MeCN (bdea^2?=2,2′‐(butylimino]bis[ethanolato]; 5 ) contains a rather compact Ce^IV₇ core with the Ce^III and Mn^III centers well‐separated from each other on the periphery. The aggregate in [Ce^IV₄Mn^IV₂(μ₃‐O)₄(bdea)₂(O₂C^tBu)₁₀(NO₃)₂]?4 MeCN ( 6 ) is based on a quasi‐planar {Mn^IV₂Ce^IV₄(μ₃‐O)₄} core made up of four edge‐sharing {Mn^IVCe^IV₂(μ₃‐O)} or {Ce^IV₃(μ₃‐O)} triangles. The structure of [Ce^IV₃Mn^IV₄Mn^III(μ₄‐O)₂(μ₃‐O)₇(O₂C^tBu)₁₂(NO₃)(furan)]?6 H₂O ( 7 ?6 H₂O) can be considered as {Mn^IV₂Ce^IV₂O₄} and distorted {Mn^IV₂Mn^IIICe^IVO₄} cubane units linked through a central (μ₄‐O) bridge. The Ce₆Mn₈ equals the highest nuclearity yet reported for a heterometallic Ce/Mn aggregate. In contrast to most of the previously reported heterometallic Ce/Mn systems, which contain only Ce^IV and either Mn^IV or Mn^III, some of the aggregates presented here show mixed valency, either Mn^IV/Mn^III (see 7 ) or Ce^IV/Ce^III (see 4 and 5 ). Interestingly, some of the compounds, including the heterovalent Ce^IV/Ce^III 4 , could be obtained from either Ce^III(NO₃)₃?6 H₂O or (NH₄)₂[Ce^IV(NO₃)₆] as starting material.     

Cube‐like 12‐MC‐4 and Offset Stacked 10‐MC‐3 Metallacrowns: Synthesis,Structure, and Magnetic Properties

Two complexes [Mn^III₄(naphthsao)₄(naphthsaoH)₄] ( 1 ) and [Fe^III₆O₂(naphthsao)₄(O₂CPh)₆] ( 2 ) [naphthsao = 1‐(1‐hydroxy‐naphthalen‐2‐yl)ethanone oxime] were obtained through the reactions of naphthsao ligand and MnCl₂ · 4H₂O or FeCl₃ · 6H₂O in the presence of triethylamine (Et₃N). Their structures were determined by X‐ray single crystal diffraction, elemental analysis, and IR spectra. Complex 1 displays 12‐MC‐4 metallacrown structural type with cube‐like configuration and 2 shows an offset stacked 10‐MC‐3 structural type with the ring connectivity containing Fe–O–C–O–Fe–O–N–Fe–O–N. Magnetic susceptibility measurement reveals the ferromagnetic interactions and field‐induced slow relaxation of the magnetization for 1 , whereas out‐of‐phase signal is not observed for 2 .     

Geometry and electronic structure of a heterometallic cluster Mo<Subscript>2</Subscript>Mg<Subscript>2</Subscript> in different oxidation states of Mo: a DFT study

Reduction of tetranuclear heterometallic complex Mo₂Mg₂ was simulated using the B3LYP and PBE density functional methods. The results of geometry calculations of the initial complex [Mo^VIO₂Mg(MeOH)₂(OMe)₄]₂ and a partially reduced Mo^V complex are in good agreement with experimental data. The reduced Mo^III complex is characterized by a decrease in the binding energy of aqua ligands. Structural rearrangement of the complex with release of a coordination position at the Mo atoms requires small energy expenditure. One can assume that the reduction of the polynuclear complex causes overcrowding of its coordination sphere, which favors formation of dinitrogen complexes. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 441–457, March, 2008.     

Synthesis, structures, and magnetic properties of carboxylate-bridged trinuclear complexes based on low-spin manganese(III)/iron(III) building blocks

Four linear trinuclear transition metal complexes have been prepared and characterized. The complexes [M^II(MeOH)₄][Fe^III(L)₂]₂·2MeOH (M = Fe (1) or Ni (2)), [Co^II(EtOH)₂(H₂O)₂][Fe^III(L)₂]₂·2EtOH (3), and [Mn^II(phen)₂][Mn^III(L)₂]₂·4MeOH (4) (H₂L = ((2-carboxyphenyl)azo)-benzaldoxime, phen = 1,10-phenanthroline) possesses a similar syn–anti carboxylate-bridged structure. The terminal Fe(III) or Mn(III) ions are low spin, and the central M(II) ions are high spin. Magnetic measurements show that antiferromagnetic interactions were present between the adjacent metal ions via the syn–anti carboxylate bridges. The antiferromagnetic coupling between low-spin Fe(III) and Ni(II) is unusual, which has been tentatively assigned to the structural distortion of Fe(III).     

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.     

trans‐Bis(cyano‐κC)(1,4,8,11‐tetraazacyclotetradecane‐κ4N)manganese(III) perchlorate,a low‐spin manganese(III) complex

The crystal structure of the low‐spin (S = 1) Mn^III complex [Mn(CN)₂(C₁₀H₂₄N₄)]ClO₄, or trans‐[Mn(CN)₂(cyclam)](ClO₄) (cyclam is the tetradentate amine ligand 1,4,8,11‐tetra­aza­cyclo­tetra­decane), is reported. The structural parameters in the Mn(cyclam) moiety are found to be insensitive to both the spin and the oxidation state of the Mn ion. The difference between high‐ and low‐spin Mn^III complexes is that a pronounced tetragonal elongation of the coordination octahedron occurs in high‐spin complexes and a slight tetragonal compression is seen in low‐spin complexes, as in the title complex.     

A new 1-D chain based on the trivacant monocapped Keggin arsenomolybdate and the copper complex linker: synthesis,crystal structure,and ESI-MS analyses

A new organic–inorganic hybrid (H₂en)₂[[Cu(en)₂]As^IIIAs^VMo^VI₉O₃₄]·6H₂O (1), containing a 1-D helical chain based on the trivacant monocapped Keggin arsenomolybdate and the copper complex linker {[Cu(en)₂][As^IIIAs^VMo^VI₉O₃₄]}_n^4n? (en = ethylenediamine), has been synthesized and characterized by IR spectra, TG analyses, single-crystal X-ray diffraction, and high-resolution electrospray ionization mass spectrometry (ESI-MS). Large voids are observed and a 1-D chain containing repeated (H₂O)₈ water units from lattice water molecules is formed along the a axis in the crystal structure. The high-resolution ESI-MS shows that the intact framework [Cu(en)₂][As^IIIAs^VMo^VI₉O₃₄]^4? exists in solution.     

Structural Study and Solution Integrity of Dioxomolybdenum(VI) Complexes with Tridentate Schiff Base and Azole Ligands

Four new molybdenum complexes [Mo^VIO₂(L¹)(Him)] ( 1 ), [Mo^VIO₂(L¹)(3‐MepzH] ( 2 ), [Mo^VIO₂(L²)(3‐MepzH)] ( 3 ), and [(Mo^VIO₂)₂(μ‐L³)(MeOH)₂] ( 4 ) were synthesized and characterized by IR, NMR, ESI‐MS, and single‐crystal structure analysis [H₂L¹ = 2‐(salicylideneamino)‐2‐methyl‐1‐propanol, H₂L² = 2‐(3‐methoxysalicylideneamino)‐2‐methyl‐1‐propanol, H₄L³ = 1, 7‐bis(salicylidene)dihydrazide malonic acid, Him = imidazole and 3‐MepzH = 3‐methylpyrazole]. In all four structures the molybdenum atom has a distorted octahedral coordination with the three meridional donor atoms from the Schiff base di‐ or tetraanion (L^{1, 2})^2—/(L³)^4— and one oxo group occupying the sites of the equatorial plane. The other oxo group and the azole or methanol molecule occupy the apical sites. In 1—3 two centrosymmetrically related molecules form a hydrogen‐bonded pair through the (azole)N‐H···O(alkoxo) interaction. Additional crystal packing appears to be controlled mostly by π stacking between the aromatic rings of the salicyl moiety. ESI‐MS investigations reveal that the integrity of complexes 1—4 is largely retained in methanol solution. At the same time evidence is provided that di‐ to tetranuclear oligomers of formula [{Mo^VIO₂(L)}_x] and [{Mo^VIO₂(L)}_x(3‐MepzH)] with L = L¹, L², x = 2, 3, 4 are present simultaneously with 2 and 3 in methanol solution, respectively the tetranuclear species [{(Mo^VIO₂)₂(L³)}₂] with 4 .     

Hexanuclear and Tetranuclear Mn/Ln clusters using 2‐(hydroxymethyl)pyridine: Synthesis,structures and magnetic properties

Reactions of manganese benzoate dihydrate and lanthanide nitrate hexahydrate with 2‐(hydroxymethyl)pyridine (hmpH) as ligand in the mixture solutions of acetonitrile and ethanol according to different molar ratios of NEt₃ generated two kinds of Mn‐Ln compounds [Mn^III₄La^III₂(O)₂(hmp)₇(PhCO₂)₂(NO₃)₅] ·5H₂O ( 1 ) and [Mn^III₂Gd^III₂(hmp)₆(PhCO₂)₄(NO₃)₂] ·3CH₃CN·3C₂H₅OH·2H₂O ( 2 ). By comparison of the two compounds, there exist considerable effects of reaction alkalinity on the structures and magnetic properties of products. Compound 1 possesses a core of [Mn^III₄La^III₂(μ ₄‐O)(μ ₃‐O)(μ ₃‐OR)(μ ₂‐O)₇]²⁻, which comprises three face‐sharing defected cubane units. The core topology represents a new core type of Mn‐Ln clusters. Compound 2 has a planar‐butterfly structure. The solid‐state dc magnetic susceptibility analyses indicate the antiferromagnetic interactions within compound 1 and ferromagnetic interactions within compound 2 . Compound 1 has an S  = 0 ground state, while compound 2 possesses an S  = 11 ground state, fitting of the dc data for the tetranuclear Mn₂Gd₂ with the Magpack program gives parameters of J _Mn‐Mn  = 3.11 cm⁻¹, J _Mn‐Gd  = 0.02 cm^—1 and g  = 1.96.