Metal-Metal Charge Transfer Properties of a Series of Trinuclear Fe2 Ru and Corresponding Pentanuclear Fe2 Ru2 Ag Cyanido-Bridged Complexes

A series of trimetallic cyanidometal-bridged compounds [Men Cp(dppe)FeII -(μ-NC)-RuII (MeOpy)4 -(μ-CN)-FeII (dppe)CpMen ] - [PF6 ]2 (N[PF6 ]2 , n=0, N =1; n=1, N=2; n=3, N=3; Cp=cyclopentadiene, dppe=1,2-bis(diphenylphosphino)ethane, MeOpy=4-methoxypyridine) and their one- and two-electron oxidized compounds N3+ and N4+ were synthesized and characterized. Meanwhile, a series of corresponding linear cyanido-bridged pentanuclear compounds [Men Cp(dppe)FeIII -(μ-NC)-RuII (MeOpy)4 -(μ-NC)-AgI -(μ-CN)-RuII (MeOpy)4 -(μ-CN)-FeIII (dppe)CpMen ][BF4 ]5 (M[BF4 ]5 , n=0, M=4; n=1, M=5; n=3, M=6) were also obtained and well characterized. The investigations suggest that in the trinuclear system there exists remote interaction between the two Fe centers, but no significant interactions exist across the central silver unit between the metals on the two sides of the silver center in the pentanuclear system. In both the trinuclear N4+ and the pentanuclear M5+ complexes, there exists the neighboring RuII →FeIII MM'CT transitions, and the MM'CT energy in the corresponding trinuclear system is higher than those in the pentanuclear system in which no remote metal-metal interaction occurs. Meanwhile, as the substituted methyl groups on the cyclopentadiene increases, the redox potential of the ruthenium in the trinuclear N4+ series increases, but that in the pentanuclear M5+ complexes decreases.

Syntheses, Structures, and Magnetic Properties of Three Cyano-Bridged FeII-MoIII Single-Molecule Magnets

Three new cyano-bridged FeII-MoIII complexes assembled from the [MoIII(CN)7]4- unit, FeII ions, and three pentadentate N3O2 ligands, namely {[Fe2H3(dapab)2][Mo(CN)6]}n·2H2O·3.5MeCN (1), [Fe(H2dapb)(H2O)][Fe(Hdapb)(H2O)][Mo(CN)6]·4H2O·3MeCN (2), and [Fe(H2dapba)(H2O)]2[Mo(CN)7]·6H2O (3) (H2dapab = 2,6-diacetylpyridine bis(2-aminobenzoylhydrazone), H2dapb = 2,6-diacetylpyridine bis(benzoylhydrazone), H2dapba = 2,6-diacetylpyridine bis(4-aminobenzoylhydrazone)), have been synthesized and characterized. Single-crystal structure analyses suggest that complex 1 contains a one-dimensional (1D) chain structure where two FeII ions are bridged by the in situ generated [MoIII(CN)6]3- unit through two trans-cyanide groups into trinuclear Fe2IIMoIII clusters that are further linked by the amino of the ligand into an infinite chain. Complexes 2 and 3 are cyano-bridged Fe2IIMoIII trinuclear clusters with two FeII ions connected by the [MoIII(CN)6]3- and [MoIII(CN)7]4- units, respectively. Direct current magnetic studies confirmed the ferromagnetic interactions between the cyano-bridged FeII and MoIII centers and significant easy-axis magnetic anisotropy for all three complexes. Furthermore, complexes 1-3 exhibit slow magnetic relaxation under a zero dc field, with relaxation barriers of 42.3, 21.6, and 14.4 K, respectively, making them the first examples of cyano-bridged FeII-MoIII single-molecule magnets.

Synthesis, Structures, and Magnetism of Four One-Dimensional Complexes Using [Ni(CN)4]2- and Macrocyclic Metal Complexes

Four one-dimensional complexes, denoted as [NiL₁][Ni(CN)₄] (1), [CuL₁][Ni(CN)₄] (2), [NiL₂][Ni(CN)₄]·2H₂O (3), and [CuL₂][Ni(CN)₄]·2H₂O (4) (L₁ = 1,8-dimethyl-1,3,6,8,10,13-hexaaza-cyclotetradecane; L₂ = 1,8-dipropyl-1,3,6,8,10,13-hexaazacyclotetradecane) were synthesized by reacting nickel/copper macrocyclic complexes with K₂[Ni(CN)₄]. Subsequently, the synthesized complexes were characterized using elemental analysis, infrared spectroscopy analysis, thermogravimetric analysis, and X-ray powder diffraction. Single-crystal structure analysis revealed that the Ni(II)/Cu(II) atoms were coordinated by two nitrogen atoms from [Ni(CN)₄]^2- with four nitrogen atoms from a macrocyclic ligand, forming a six-coordinated octahedral coordination geometry. Nickel/copper macrocyclic complexes were bridged by [Ni(CN)₄]^2- to construct one-dimensional chain structures in 1-4. The characterization results showed that the four complexes obeyed the Curie-Weiss law with a weak antiferromagnetic exchange coupling.

Site Selectivity for the Spin States and Spin Crossover in Undecanuclear Heterometallic Cyanido-Bridged Clusters

Polynuclear molecular clusters offer an opportunity to design new hierarchical switchable materials with collective properties, based on variation of the chemical composition, size, shapes, and overall building blocks organization. In this study, we rationally designed and constructed an unprecedented series of cyanido-bridged nanoclusters realizing new undecanuclear topology: Fe^II[Fe^II(bzbpen)]₆[W^V(CN)₈]₂[W^IV(CN)₈]₂·18MeOH (1), Na^I[Co^II(bzbpen)]₆[W^V(CN)₈]₃[W^IV(CN)₈]·28MeOH (2), Na^I[Ni^II(bzbpen)]₆[W^V(CN)₈]₃[W^IV(CN)₈]·27MeOH (3), and Co^II[Co^II(R/S-pabh)₂]₆[W^V(CN)₈]₂[W^IV(CN)₈]₂·26MeOH [4R and 4S; bzbpen = N¹,N²-dibenzyl-N¹,N²-bis(pyridin-2-ylmethyl)ethane-1,2-diamine; R/S-pabh = (R/S)-N-(1-naphthyl)-1-(pyridin-2-yl)methanimine], of size up to 11 nm³, ca. 2.0 × 2.2 × 2.5 nm (1-3) and ca. 1.4 × 2.5 × 2.5 nm (4). 1, 2, and 4 exhibit site selectivity for the spin states and spin transition related to the structural speciation based on subtle exogenous and endogenous effects imposed on similar but distinguishable 3d metal-ion-coordination moieties. 1 exhibits a mid-temperature-range spin-crossover (SCO) behavior that is more advanced than the previously reported SCO clusters based on octacyanidometallates and an onset of SCO behavior close to room temperature. The latter feature is also present in 2 and 4, which suggests the emergence of Co^II-centered SCO not observed in previous bimetallic cyanido-bridged Co^II-W^V/IV systems. In addition, reversible switching of the SCO behavior in 1 via a single-crystal-to-single-crystal transformation during desolvation was also documented.

Interplay of Anisotropic Exchange Interactions and Single-Ion Anisotropy in Single-Chain Magnets Built from Ru/Os Cyanidometallates(III) and Mn(III) Complex

Two novel 1D heterobimetallic compounds {[Mn^III(SB²⁺)M^III(CN)₆]·4H₂O}_n (SB²⁺ = N,N'-ethylenebis(5-trimethylammoniomethylsalicylideneiminate) based on orbitally degenerate cyanidometallates [Os^III(CN)₆]^3- (1) and [Ru^III(CN)₆]^3- (2) and Mn^III Schiff base complex were synthesized and characterized structurally and magnetically. Their crystal structures consist of electrically neutral, well-isolated chains composed of alternating [M^III(CN)₆]^3- anions and square planar [Mn^III(SB²⁺)]³⁺ cations bridged by cyanide groups. These -ion magnetic anisotropy of Mn^III centers. These results indicate that the presence of compounds exhibit single-chain magnet (SCM) behavior with the energy barriers of Δτ₁/k_B = 73 K, Δτ₂/k_B = 41.5 K (1) and Δτ₁/k_B = 51 K, Δτ₂ = 27 K (2). Blocking temperatures of T_B = 2.8, 2.1 K and magnetic hysteresis with coercive fields (at 1.8 K) of 8000, 1600 Oe were found for 1 and 2, respectively. Theoretical analysis of the magnetic data reveals that their single-chain magnet behavior is a product of a complicated interplay of extremely anisotropic triaxial exchange interactions in M^III(4d/5d)-CN-Mn^III fragments: -J_xS_M^xS_Mn^x-J_yS_M^yS_Mn^y-J_zS_M^zS_Mn^z, with opposite sign of exchange parameters J_x = -22, J_y = +28, J_z = -26 cm^-1 and J_x = -18, J_y = +20, J_z = -18 cm^-1 in 1 and 2, respectively) and single orbitally degenerate [Os^III(CN)₆]^3- and [Ru^III(CN)₆]^3- spin units with unquenched orbital angular momentum in the chain compounds 1 and 2 leads to a peculiar regime of slow magnetic relaxation, which is beyond the scope of the conventional Glaubers's 1D Ising model and anisotropic Heisenberg model.

Eightfold Electrophilic Methylation of Octacyanotungstate [W(CN)8]4-/3-: Preparation of Homoleptic, Eight-Coordinate Methyl Isocyanide Complexes [W(CNMe)8]4+/5

Homoleptic eightfold coordinated methyl isocyanide complexes of W(IV) and W(V) have been prepared for the first time. The reaction of [NBu₄]₄[W(CN)₈] with methyl triflate (MeOTf) gives [W(CNMe)₈][OTf]₄. The even stronger methylating mixture of methyl fluoride (MeF) and arsenic pentafluoride (AsF₅) in liquid sulfur dioxide (SO₂) is able to fully alkylate both [NBu₄]₄[W(CN)₈] and [NBu₄]₃[W(CN)₈]. The paramagnetic octakis(methyl isocyanide)tungsten(V) complex [W(CNMe)₈][AsF₆]₅ is thermally highly unstable above -30 °C. All compounds have been characterized via single-crystal X-ray diffraction and IR, Raman, and NMR or EPR spectroscopy.

Ferromagnetic Archimedean polyhedra {Fe24M18} (M = Fe, Ni, and Mn) with tunable electron configurations

Three symmetric nanocages {Fe24M18} that mimic the Archimedean polyhedra, namely pseudo-rhombicuboctahedron, were synthesized. Their electron configurations depend highly on the changes of metal ions and the deprotonation of auxiliary ligands.

X-ray Structure and Magnetic Properties of Heterobimetallic Chains Based on the Use of an Octacyanidodicobalt(III) Complex as Metalloligand

The assembly of [Co2III(μ-2,5-dpp)(CN)8]2− anions and [MII(CH3OH)2(DMSO)2]2+ cations resulted into the formation of two heterobimetallic 1D coordination polymers of formula [MII(CH3OH)2(DMSO)2(μ-NC)2Co2III(μ-2,5-dpp)(CN)6]n·4nCH3OH [M = CoII (1)/FeII (2) and 2,5-dpp = 2,5-bis(2-pyridyl)pyrazine. The [Co2III(μ-2,5-dpp)(CN)8]2− metalloligand coordinates the paramagnetic [MII(CH3OH)2(DMSO)2]2+ complex cations, in a bis-monodentate fashion, to give rise to neutral heterobimetallic chains. Cryomagnetic dc (1.9–300 K) and ac (2.0–13 K) magnetic measurements for 1 and 2 show the presence of Co(II)HS (1) and Fe(II)HS (2) ions (HS – high-spin), respectively, with D values of +53.7(5) (1) and −5.1(3) cm−1 (2) and slow magnetic relaxation for 1, this compound being a new example of SIM with transversal magnetic anisotropy. Low-temperature Q-band EPR study of 1 confirms that D value is positive, which reveals the occurrence of a strong asymmetry in the g-tensors and allows a rough estimation of the E/D ratio, whereas 2 is EPR silent. Theoretical calculations by CASSCF/NEVPT2 on 1 and 2 support the results from magnetometry and EPR. The analysis of the ac magnetic measurements of 1 shows that the relaxation of M takes place in the ground state under external magnetic dc fields through dominant Raman and direct spin-phonon processes.

Guest-Dependent Pressure-Induced Spin Crossover in FeII 4 [MIV (CN)8 ]2 (M=Mo, W) Cluster-Based Material Showing Persistent Solvent-Driven Structural Transformations

Discrete molecular species that can perform certain functions in response to multiple external stimuli constitute a special class of multifunctional molecular materials called smart molecules. Herein, cyanido-bridged coordination clusters {[Fe^II (2-pyrpy)₂ ]₄ [M^IV (CN)₈ ]₂ }⋅4 MeOH⋅6 H₂ O (M=Mo (1 solv), M=W (2 solv) and 2-pyrpy=2-(1-pyrazolyl)pyridine are presented, which show persistent solvent driven single-crystal-to-single-crystal transformations upon sorption/desorption of water and methanol molecules. Three full desolvation-resolvation cycles with the concomitant change of the host molecules do not damage the single crystals. More importantly, the Fe₄ M₂ molecules constitute a unique example where the presence of the guests directly affects the pressure-induced thermal spin crossover (SCO) phenomenon occurring at the Fe^II centres. The hydrated phases show a partial SCO with approximately two out-of-four Fe^II centres undergoing a gradual thermal SCO at 1 GPa, while in the anhydrous form the pressure-induced SCO effect is almost quenched with only 15 % of the Fe^II centres undergoing high-spin to low-spin transition at 1 GPa.

Isolation and Structural Characterization of Eightfold Protonated Octacyanometalates [M(CNH)8 ]4+ (M=MoIV , WIV ) from Superacids

Octacyanometalates K₄[Mo(CN)₈] and K₄[W(CN)₈] are completely protonated in superacidic mixtures of anhydrous hydrogen fluoride and antimony pentafluoride. The resulting hydrogen isocyanide complexes [Mo(CNH)₈]⁴⁺ [SbF₆]⁻₄ and [W(CNH)₈]⁴⁺ [SbF₆]⁻₄ are the first examples of eight‐coordinate homoleptic metal complexes containing hydrogen isocyanide (CNH) ligands. The complexes were crystallographically characterized, revealing hydrogen‐bonded networks with short N⋅⋅⋅H⋅⋅⋅F contacts. Low‐temperature NMR measurements in HF confirmed rapid proton exchange even at −40 °C. Upon protonation, ν(C≡N) increases of about 50 cm⁻¹ which is in agreement with DFT calculations.

Smart Ligands for Efficient 3d-, 4d- and 5d-Metal Single-Molecule Magnets and Single-Ion Magnets

There has been a renaissance in the interdisciplinary field of Molecular Magnetism since ~2000, due to the discovery of the impressive properties and potential applications of d- and f-metal Single-Molecule Magnets (SMMs) and Single-Ion Magnets (SIMs) or Monometallic Single-Molecule Magnets. One of the consequences of this discovery has been an explosive growth in synthetic molecular inorganic and organometallic chemistry. In SMM and SIM chemistry, inorganic and organic ligands play a decisive role, sometimes equally important to that of the magnetic metal ion(s). In SMM chemistry, bridging ligands that propagate strong ferromagnetic exchange interactions between the metal ions resulting in large spin ground states, well isolated from excited states, are preferable; however, antiferromagnetic coupling can also lead to SMM behavior. In SIM chemistry, ligands that create a strong axial crystal field are highly desirable for metal ions with oblate electron density, e.g., TbIII and DyIII, whereas equatorial crystal fields lead to SMM behavior in complexes based on metal ions with prolate electron density, e.g., ErIII. In this review, we have attempted to highlight the use of few, efficient ligands in the chemistry of transition-metal SMMs and SIMs, through selected examples. The content of the review is purely chemical and it is assumed that the reader has a good knowledge of synthetic, structural and physical inorganic chemistry, as well as of the properties of SIMs and SMMs and the techniques of their study. The ligands that will be discussed are the azide ion, the cyanido group, the tris(trimethylsilyl)methanide, the cyclopentanienido group, soft (based on the Hard-Soft Acid-Base model) ligands, metallacrowns combined with click chemistry, deprotonated aliphatic diols, and the family of 2-pyridyl ketoximes, including some of its elaborate derivatives. The rationale behind the selection of the ligands will be emphasized.

Structural Disorder in High-Spin {CoII9WV6} (Core)-[Pyridine N-Oxides] (Shell) Architectures

The combinations of Co(II), octacyanidotungstate(V), and monodentate pyridine N-oxide (pyNO) or 4-phenylpyridine N-oxide (4-phpyNO) led to crystallization of novel crystalline phases {Co^II[Co^II₈(pyNO)₁₂(MeOH)₁₂][W^V(CN)₈]₆} (1) and {Co^II[Co^II₈(4-phpyNO)₇(MeOH)₁₇][W^V(CN)₈]₆}·7MeOH·(4-phpyNO)₃ (2). In both architectures, metal-cyanide clusters are coordinated by N-oxide ligands in a simple monodentate manner to give the spherical objects of over 1 nm core diameter and about 2.2 nm (1) and 3 nm (2) of the total diameter, terminated with the aromatic rings. The supramolecular architecture is dominated by dense and rich π-π interaction systems. Both structures are characterized by a significant structural disorder in ligand shell, described with the suitable probability models. For 1, the π-π interactions between the pyNO ligands attached to the same metal centers are suggested for the first time. In 2, 4-phpyNO acts as monodentate ligand and as the crystallization molecule. Magnetic studies indicate the high-spin ground state due to the ferromagnetic interactions Co(II)-W(V) through the cyanido bridges. Due to the high symmetry of the clusters, no signature of slow magnetic relaxation was observed. The characterization is completed by solid-state IR and UV-Vis-NIR spectroscopy. The conditions for the stable M₉M'₆-based crystals formation are synthetically discussed in terms of the type of capping ligands: monodentate, bridging, and chelating. The potential of the related polynuclear forms toward the magnetism-based functional properties is critically indicated.

Bulky ligands shape the separation between the large spin carriers to condition field-induced slow magnetic relaxation

Crystal engineering of magnetic relaxation in supramolecular networks based on almost isotropic cyanido-bridged {Mn9[W(CN)8]6L8(solv)8} clusters decorated by bulky 4,4'-di-tert-butyl-2,2'-bipyridine (But2bpy) and 4,7-diphenyl-1,10-phenanthroline (Ph2phen) ligands is presented. The three new compounds {MnII9[WV(CN)8]6(But2bpy)8(MeOH)8}·Pri2O·13MeOH (1), {MnII9[WV(CN)8]6(But2bpy)8(MeOH)6(H2O)2}·4Pri2O·2H2O (1a), and {MnII9[WV(CN)8]6(Ph2phen)8(MeOH)8}·29MeOH·6H2O (2) were characterized structurally and magnetically. Compound 1 exhibits unequivocal domination of repulsive intercluster contacts operating between the side But groups leading to intercluster distances exceeding 10 Å in all three dimensions. Compound 1a reveals a 1-dimensional (1D) supramolecular chain structure with very close intercluster distances of 6.7 Å realized through the direct W-CNHO-Mn hydrogen bonds along the chain, further isolated by the above repulsive ButBut synthons. Compound 2 shows significant separation in all three directions with the intercluster distances close to 10, 12 and 13.5 Å. However, in contrast to 1, these separations are accompanied by indirect hydrogen bond arrays and local π-π interactions of potential to assist in the transfer of weak magnetic interactions. The dc magnetic data show the signature of S = 39/2 in the ground state, which is typical in this group of compounds. The high-spin clusters are accompanied by different intercluster interactions, illustrated by the effective zJ' values of +0.010 cm-1 (1), +0.008 cm-1 (1a) and +0.001 cm-1 (2). The low temperature ac susceptibility measurements revealed a temperature- and field-dependent magnetic relaxation time for all 1, 1a and 2 compounds (τ1, τ1a-fast, and τ2-fast in the range 10-3-10-4 s). In contrast and only in the case of 1a and 2, an additional temperature independent slow process was detected (τ1a-slow and τ2-slow located between 0.1 s and 1 s). The magnetic relaxations were correlated with the obtained supramolecular networks, indicating the significant role of dipolar fields, weak non-covalent interactions, hydrogen bonds and π-π interactions.

Heterometallic 3d-4d coordination polymers assembled from trans-[RuIII(L)(CN)2]- tectons and 3d cations

Five new cyanido-bridged heterometallic coordination polymers have been obtained by reacting PPh4[RuIII(salpn)(CN)2]·H2O (1) and AsPh4[RuIII(valen)(CN)2]·8.5H2O (2) (H2salpn and H2valen being Schiff-base proligands resulting from the condensation reaction of salicylaldehyde with 1,3-propanediamine and, respectively, o-vanillin with 1,2-ethanediamine) with divalent transition metal perchlorate salts: ∞1[{RuIII(salpn)(CN)2}3{MII(DMF)3}2](ClO4)·4DMF (MII = Mn, 3; Co, 4) and ∞2[{RuIII(valen)(CN)2}4{MII(DMF)3}2{MII(DMF)4}](ClO4)2·4DMF (MII = Mn, 5; Co, 6; Ni, 7), respectively. The dicyanido species, trans-[Ru(salpn)(CN)2]- and trans-[Ru(valen)(CN)2]-, act as metalloligands with the 3d metal ions. Compounds 3 and 4 are isostructural one-dimensional (1D) coordination polymers with a ladder topology. Each MII ion is hexacoordinated by three cyanido groups arising from three {Ru(salpn)(CN)2} units and by the oxygen atoms from three DMF molecules, which are coordinated at meridional positions. Compounds 5-7 are also isostructural, their structures consisting of 2D networks with a herringbone topology. The magnetic susceptibility measurements of these 1D and 2D systems reveal the presence of dominating RuIII-MII antiferromagnetic (AF) interactions in compounds 3, 4, 5 and 6, while ferromagnetic RuIII-NiII interactions are observed in 7. All these compounds stay in their paramagnetic state down to 1.8 K except compound 4 which possesses a 3D ordered AF ground state.

Two three-dimensional [MoIII(CN)7]4−-based magnets showing new topologies and ferrimagnetic ordering below 80 K

Two 3D [Mo^III(CN)₇]⁴⁻-based magnets with new topologies and ferrimagnetic ordering below 80 K have been prepared using different amides as auxiliary ligands.

A heterotrimetallic synthetic approach in versatile functionalization of nanosized {MxCu13–xW7}3+ and {M1Cu8W6} (M = Co, Ni, Mn, Fe) metal–cyanide magnetic clusters

The addition of 3d metal heteroatom into Cu^II(Me₃tacn)[W(CN)₈]ⁿ⁻ cluster system governs its structural and magnetic features.

Syntheses, structures, and magnetic properties of three new MnII-[MoIII(CN)7]4- molecular magnets

By reaction of K4[MoIII(CN)7]·2H2O, Mn(ClO4)2·6H2O and bidentate chelating ligands, three new cyano-bridged compounds, namely Mn2(3-pypz)(H2O)(CH3CN)[Mo(CN)7] (1), Mn2(1-pypz)(H2O)(CH3CN)[Mo(CN)7] (2) and Mn2(pyim)(H2O)(CH3CN)[Mo(CN)7] (3) (3-pypz = 2-(1H-pyrazol-3-yl)pyridine, 1-pypz = 2-(1H-pyrazol-1-yl)pyridine, pyim = 2-(1H-imidazol-2-yl)pyridine), have been synthesized and characterized structurally and magnetically. Single crystal X-ray analyses revealed that although the chelating ligands are different, compounds 1 to 3 are isomorphous and crystallize in the same monoclinic space group C2/m. Connected by the bridging cyano groups, one crystallographically unique [Mo(CN)7]4- unit and three crystallographically unique MnII ions of different coordination environments form similar three-dimensional frameworks, which have a four-nodal 3,4,4,7-connecting topological net with a vertex symbol of {43}{44·62}2{410·611}. Magnetic measurements revealed that compounds 1-3 display long-range magnetic ordering with critical temperatures of 64, 66 and 62 K, respectively. These compounds are rare examples of a small number of chelating co-ligand coordinated [Mo(CN)7]4--based magnetic materials. Specifically, the bidentate chelating ligands were successfully introduced into the heptacyanomolybdate system for the first time.

A new Mo(iv) complex with the pentadentate (N3O2) Schiff-base ligand: the first non-cyanide pentagonal-bipyramidal paramagnetic 4d complex

A heptacoordinate complex [Mo^IV(DAPBH)Cl₂] (H₂DAPBH is 1,1'-(pyridine-2,6-diyl)bis(ethan-1-yl-1-ylidene)dibenzohydrazine) has been synthesized and characterized structurally and magnetically. It exhibits a slightly distorted pentagonal bipyramidal geometry and reveals paramagnetic behaviour resulting from two unpaired electrons (S = 1) with large positive zero-field splitting (D = +50 cm^-1) and pronounced temperature-independent paramagnetism.

Halogen⋯halogen interactions in the self-assembly of one-dimensional 2,2′-bipyrimidine-based CuIIReIV systems

Two one-dimensional Cu^IIRe^IV coordination polymers of the general formula {[Re^IVCl₄(μ-bpym)Cu^IIX₂]·solvent}_n [where bpym = 2,2′-bipyrimidine, X = Cl (1) and Br (2), and solvent = H₂O (1) and CHCl₃ (2)] have been prepared and characterised structurally and magnetically.

2D and 3D mixed MII/CuIImetal–organic frameworks (M = Ca and Sr) withN,N′-2,6-pyridinebis(oxamate) and oxalate: preparation and magneto-structural study

Heterobimetallic coordination polymers with either antiferro- of ferromagnetic interactions are described herein.

Design of 3d–4f molecular squares through the [Fe{(HB(pz)3)}(CN)3]− metalloligand

A new series of cyanido-bridged {FeIII2LnIII2} heterobimetallic molecular squares [Ln = La (1), Gd (2), Tb (3) and Dy (4)] has been prepared and magneto-structurally investigated.

Modulation of the FeII spin crossover effect in the pentadecanuclear {Fe9[M(CN)8]6} (M = Re, W) clusters by facial coordination of tridentate polyamine ligands

N,N,N-tridentate ligands coordinated to {Fe₉[M(CN)₈]₆} (M = Re, W) induce the spin crossover on the external Fe sites of the cluster.

Synthesis, crystal structure and magnetic properties of a cyanide-bridged heterometallic {CoIIMnIII} chain

The assembly reaction between the low-spin [Co^II(dmphen)(CN)₃]^- metalloligand and the [Mn^III(salen)(H₂O)]⁺ complex cation yielded the one-dimensional compound {[Mn^III(salen)(μ-NC)₂Co^II(dmphen)(CN)]·2H₂O}_n (1), which behaves as a ferrimagnetic chain, the intrachain magnetic coupling being J = -1.71(1) cm^-1.

Ligand dependent topology and spontaneous resolution in high-spin cyano-bridged Ni3W2 clusters

Two high-spin pentanuclear NiW clusters with diimine blocking ligands have been obtained: {[Ni(4,4'-MeObpy)2]3[W(CN)8]2}·12H2O (1) and {[Ni(phen)2(H2O)][Ni(phen)2]2[W(CN)8]2}·7H2O (2) (4,4'-MeObpy = 4,4'-dimethoxy-2,2'-bipyridine, phen = 1,10-phenanthroline). Despite the similarity of the building blocks and synthetic conditions the compounds show different topologies of the cluster core: 1 is a trigonal bipyramid while 2 is a decorated square. Both cluster structures are chiral with either ΔΔΔ or ΛΛΛ configuration around all three Ni centres. In 1 spontaneous resolution occurs and it crystallises in the P212121 space group forming a conglomerate containing both types of enantiomorphic crystals. 1Δ and 1Λ are the first pair of enantiomorphic structures of cyano-bridged clusters of trigonal bipyramidal topology obtained with achiral bidentate blocking ligands. 2 crystallises as a racemic compound in a centrosymmetric space group P1[combining macron] with both enantiomers present in the structure. 2 is an exceptional square-motif containing structure with an identical stereoconfiguration of all complex cations within one cluster. Ferromagnetic interactions are present in both clusters resulting in the ground spin state S = 4.

The Heptacyanotungstate(IV) Anion: A New 5 d Transition-Metal Member of the Rare Heptacyanometallate Family of Anions

The heptacyanotungstate(IV) anion was isolated in the salt (n-Bu4 N)3 [W(IV) (CN)7 ] (1) from the reduction of (n-Bu4 N)3 [W(V) (CN)8 ] with concomitant loss of one cyanide ligand. The anion in 1 adopts a slightly distorted pentagonal bipyramidal geometry with an average W-C distance of 2.169 Å. The spectroscopic and magnetic properties are described.