Cyanide-Bridged Mn(III)−Fe(III) Bimetallic Complexes Based on the Pentacyano(1-methylimidazole)ferrate(III) Building Block: Structure and Magnetic Characterizations

[MII(H2dapsc)]-[Cr(CN)6] (M = Mn, Co) Chain and Trimer Complexes: Synthesis, Crystal Structure, Non-Covalent Interactions and Magnetic Properties

Four new heterometallic complexes combining [M^II(H₂dapsc)]²⁺ cations with the chelating H₂dapsc {2,6-diacetylpyridine-bis(semicarbazone)} Schiff base ligand and [Cr(CN)₆]^3- anion were synthesized: {[M^II(H₂dapsc)]Cr^III(CN)₆K(H₂O)_2.5(EtOH)_0.5}_n·1.2n(H₂O), M = Mn (1) and Co (2), {[Mn(H₂dapsc)]₂Cr(CN)₆(H₂O)₂}Cl·H₂O (3) and {[Co(H₂dapsc)]₂Cr(CN)₆(H₂O)₂}Cl·2EtOH·3H₂O (4). In all the compounds, M(II) centers are seven-coordinated by N₃O₂ atoms of H₂dapsc in the equatorial plane and N or O atoms of two apical -CN/water ligands. Crystals 1 and 2 are isostructural and contain infinite negatively charged chains of alternating [M^II(H₂dapsc)]²⁺ and [Cr^III(CN)₆]^3- units linked by CN-bridges. Compounds 3 and 4 consist of centrosymmetric positively charged trimers in which two [M^II(H₂dapsc)]²⁺ cations are bound through one [Cr^III(CN)₆]^3- anion. All structures are regulated by π-stacking of coplanar H₂dapsc moieties as well as by an extensive net of hydrogen bonding. Adjacent chains in 1 and 2 interact also by coordination bonds via a pair of K⁺ ions. The compounds containing Mn^II (1, 3) and Co^II (2, 4) show a significant difference in magnetic properties. The ac magnetic measurements revealed that complexes 1 and 3 behave as a spin glass and a field-induced single-molecule magnet, respectively, while 2 and 4 do not exhibit slow magnetic relaxation in zero and non-zero dc fields. The relationship between magnetic properties and non-covalent interactions in the structures 1-4 was traced.

Heterotrimetallic Ni2Ln2Fe3 chain complexes based on [Fe(1-CH3im)(CN)5]2

Two phenoxo- and cyanido-bridged one-dimensional complexes Ni^II₂Gd^III₂Fe^III₃ (1) and Ni^II₂Dy^III₂Fe^III₃ (2) have been prepared. They are the first pentacyanidoferrite-bridged heterotrimetallic complexes. Magnetic studies reveal that overall ferromagnetic interactions are present in complexes 1 and 2, and complex 2 shows single-molecule magnet (SMM) behaviour with an energy barrier of 14.8 K.

Slow Magnetic Relaxation, Antiferromagnetic Ordering, and Metamagnetism in MnII (H2 dapsc)-FeIII (CN)6 Chain Complex with Highly Anisotropic Fe-CN-Mn Spin Coupling

Reactions of [Mn(H₂ dapsc)Cl₂ ]⋅H₂ O (dapsc=2,6- diacetylpyridine bis(semicarbazone)) with K₃ [Fe(CN)₆ ] and (PPh₄ )₃ [Fe(CN)₆ ] lead to the formation of the chain polymeric complex {[Mn(H₂ dapsc)][Fe(CN)₆ ][K(H₂ O)_3.5 ]}_n ⋅1.5n H₂ O (1) and the discrete pentanuclear complex {[Mn(H₂ dapsc)]₃ [Fe(CN)₆ ]₂ (H₂ O)₂ }⋅4 CH₃ OH⋅3.4 H₂ O (2), respectively. In the crystal structure of 1 the high-spin [Mn^II (H₂ dapsc)]²⁺ cations and low-spin hexacyanoferrate(III) anions are assembled into alternating heterometallic cyano-bridged chains. The K⁺ ions are located between the chains and are coordinated by oxygen atoms of the H₂ dapsc ligand and water molecules. The magnetic structure of 1 is built from ferrimagnetic chains, which are antiferromagnetically coupled. The complex exhibits metamagnetism and frequency-dependent ac magnetic susceptibility, indicating single-chain magnetic behavior with a Mydosh-parameter φ=0.12 and an effective energy barrier (U_eff /k_B ) of 36.0 K with τ₀ =2.34×10^-11  s for the spin relaxation. Detailed theoretical analysis showed highly anisotropic intra-chain spin coupling between [Fe^III (CN)₆ ]^3- and [Mn^II (H₂ dapsc)]²⁺ units resulting from orbital degeneracy and unquenched orbital momentum of [Fe^III (CN)₆ ]^3- complexes. The origin of the metamagnetic transition is discussed in terms of strong magnetic anisotropy and weak AF interchain spin coupling.

Synthesis, crystal structures and magnetic characterisation of two 2p–3d metallic coordination polymers

The coordination polymers {Mg[Fe(L)(CN)5]}n·0.5nH2O and {MgCu2(CH3COO)6}n [L = bis( N-imidazolyl)methane] have been synthesised. X-ray diffraction revealed that {Mg[Fe(L)(CN)5]}n·0.5nH2O has a one-dimensional neutral chain structure consisting of alternating [Mg(L)2(H2O)2)]2+ species and [Fe(L)(CN)5]2– building blocks, which can be further linked into a three-dimensional supramolecular structure by inter-chain p–p interactions. {MgCu2(CH3COO)6}n has a three-dimensional network with the [MgCu2(CH3COO)6] unit as neutral core extended by Mg–O bonds. Magnetic susceptibility studies on {MgCu2(CH3COO)6}n revealed antiferromagnetic interactions between adjacent Cu(II) ions.

Cyanide-bridged heterobimetallic magnetic complexes based on metalloporphyrinate and tricyanometalate building blocks

Three novel cyanide-bridged metalloporphyrinate complexes were synthesized and characterized, and their magnetic properties have also been systematically investigated.

Assembly of cyanometalate-functionalized phosphotungstates with magnetic properties and bifunctional electrocatalytic activities

Two cyanometalate-functionalized Dawson type phosphotungstates with a “Netherlands windmills” shape have been prepared under conventional reaction conditions. Their magnetic properties and electrocatalytic activity were investigated.

Synthesis, crystal structures and magnetic properties of mer-cyanideiron(iii)-based 1D heterobimetallic cyanide-bridged chiral coordination polymers

Two pairs of 1D cyanide-bridged heterometallic chiral enantiomer complexes have been synthesized, structurally characterized and magnetically investigated.

Single-molecule magnet engineering: building-block approaches

Tailoring the specific magnetic properties of any material relies on the topological control of the constituent metal ion building blocks. Although this general approach does not seem to be easily applied to traditional inorganic bulk magnets, coordination chemistry offers a unique tool to delicately tune, for instance, the properties of molecules that behave as "magnets", the so-called single-molecule magnets (SMMs). Although many interesting SMMs have been prepared by a more or less serendipitous approach, the assembly of predesigned, isolatable molecular entities into higher nuclearity complexes constitutes an elegant and fascinating strategy. This Feature article focuses on the use of building blocks or modules (both terms being used indiscriminately) to direct the structure, and therefore also the magnetic properties, of metal ion complexes exhibiting SMM behaviour.

The supramolecular interaction mediated chiral 1D cyanide-bridged metamagnet: synthesis, crystal structures and magnetic properties

Two cyanide-bridged enantiopure one-dimensional single chain complexes, [Mn((R,R)-Salcy)Fe(pcq)(CN)3]2n·1.5nDMF (1) and [Mn((S,S)-Salcy)Fe(pcq)(CN)3]2n·1.5nDMF (2), have been synthesized and structurally characterized. Systematically magnetic investigations show the antiferromagnetic coupling between the cyanide-bridged Mn(III)-Fe(III) centers and the interesting metamagnetic behavior at about 5.0 K resulted from the intermolecular π-π interaction.

A new series of cyanide-bridged heterobimetallic FeIII–FeIII/MnIII/CuII one-dimensional complexes: synthesis, crystal structures, and magnetic properties

Four new cyanide-bridged Fe^III–Fe^III/Mn^III/Cu^II one-dimensional complexes have been assembled using K[Fe(bpdBrb)(CN)₂]·2H₂O (1) as building blocks, and structurally characterized and magnetically investigated.

Syntheses, crystal structures, MMCT and magnetic properties of four one-dimensional cyanide-bridged complexes comprised of MII–CN–FeIII (M = Fe, Ru, Os)

Four 1D cyanide-bridged complexes [cis-M^II(L)₂(CN)₂Fe^III(salen)](PF₆) (3–6) have been synthesized, of which 3 and 4 are Class II mixed-valence complexes.

Controlled association of single-molecule magnets (SMMs) into coordination networks: towards a new generation of magnetic materials

The field of molecular magnetism has rapidly expanded since the discovery of single-molecule magnets (SMMs) at the beginning of the 1990s. Numerous SMMs have been studied and a broad community currently works on these systems to improve their magnetic characteristics. However, it has also become an important strategy to diversify a part of our research activity toward the organization of these magnetic molecules in order to move closer to future applications. One of the possible ways is to utilize SMMs as molecular building blocks and assemble them with the help of coordination chemistry. This strategy presents a significant challenge since the intrinsic magnetic properties of the parent SMMs can be modified, which consequently also provides a unique opportunity to investigate new behaviours at the frontier between SMMs and classical bulk magnets. Furthermore, the design of systems with "enhanced" SMM properties or magnet behaviour is theoretically possible by choosing coordinating linkers that could favour an effective ferromagnetic arrangement of the SMMs. In this perspective article, we will give an overview of the known networks based on SMMs with an emphasis on the synthetic strategies, magnetic properties, and finally possible routes to a new generation of molecular magnetic materials.

Syntheses, structures, and magnetic properties of low-dimensional heterometallic complexes based on the versatile building block [(Tp)Cr(CN)3]-

Using the tricyano precursor (Bu(4)N)[(Tp)Cr(CN)(3)] (Bu(4)N(+) = tetrabutylammonium cation; Tp = tris(pyrazolyl)hydroborate), a pentanuclear heterometallic cluster [(Tp)(2)Cr(2)(CN)(6)Cu(3)(Me(3)tacn)(3)][(Tp)Cr(CN)(3)](ClO(4))(3)·5H(2)O (1, Me(3)tacn = N,N',N'-trimethyl-1,4,7-triazacyclononane), three tetranuclear heterometallic clusters [(Tp)(2)Cr(2)(CN)(6)Cu(2)(L(OEt))(2)]·2.5CH(3)CN (2, L(OEt) = [(Cp)Co(P(O)(OEt)(2))(3)], Cp = cyclopentadiene), [(Tp)(2)Cr(2)(CN)(6)Mn(2)(L(OEt))(2)]·4H(2)O (3), and [(Tp)(2)Cr(2)(CN)(6)Mn(2)(phen)(4)](ClO(4))(2) (4, phen = phenanthroline), and a one-dimensional (1D) chain polymer [(Tp)(2)Cr(2)(CN)(6)Mn(bpy)](n) (5, bpy = 2,2'-bipyridine) have been synthesized and structurally characterized. Complex 1 shows a trigonal bipyramidal geometry in which [(Tp)Cr(CN)(3)](-) units occupy the apical positions and are linked through cyanide to [Cu(Me(3)tacn)](2+) units situated in the equatorial plane. Complexes 2-4 show similar square structures, where Cr(III) and M(II) (M = Cu(II) or Mn(II)) ions are alternatively located on the rectangle corners. Complex 5 consists of a 4,2-ribbon-like bimetallic chain. Ferromagnetic interactions between Cr(III) and Cu(II) ions bridged by cyanides are observed in complexes 1 and 2. Antiferromagnetic interactions are presented between Cr(III) and Mn(II) ions bridged by cyanides in complexes 3-5. Complex 5 shows metamagnetic behavior with a critical field of about 22.5 kOe at 1.8 K.

Synthesis, structure, and magnetic properties of three 1D chain complexes based on high-spin metal-cyanide clusters: [Mn(III)6M(III)] (M = Cr, Fe, Co)

On the basis of high-spin metal-cyanide clusters of Mn(III)(6)M(III) (M = Cr, Fe, Co), three one-dimensional (1D) chain complexes, [Mn(salen)](6)[Cr(CN)(6)](2)·6CH(3)OH·H(2)O (1), [Mn(5-CH(3))salen)](6)[Fe(CN)(6)](2)·2CH(3)CN·10H(2)O (2), and [Mn(5-CH(3))salen)](6)[Co(CN)(6)](2)·2CH(3)CN·10H(2)O (3) [salen = N,N'-ethylenebis(salicylideneiminato) dianion], have been synthesized and characterized structurally as well as magnetically. Complexes 2 and 3 are isomorphic but slightly different from complex 1. All three complexes contain a 1D chain structure which is comprised of alternating high-spin metal-cyanide clusters of [Mn(6)M](3+) and a bridging group [M(CN)(6)](3-) in the trans mode. Furthermore, the three complexes all exhibit extended 3D supramolecular networks originating from short intermolecular contacts. Magnetic investigation indicates that the coupling mechanisms are intrachain antiferromagnetic interactions for 1 and ferromagnetic interactions for 2, respectively. Complex 3 is a magnetic dilute system due to the diamagnetic nature of Co(III). Further magnetic investigations show that complexes 1 and 2 are dominated by the 3D antiferromagnetic ordering with T(N) = 7.2 K for 1 and 9.5 K for 2. It is worth noting that the weak frequency-dependent phenomenon of AC susceptibilities was observed in the low-temperature region in both 1 and 2, suggesting the presence of slow magnetic relaxations.