Two novel cyanide-bridged bimetallic magnetic chains derived from manganese(III) Schiff bases and hexacyanochromate(III) building blocks

A rare isostructural series of 3d-4f cyanido-bridged heterometallic squares obtained by assembling [FeIII{HB(pz)3}(CN)3]- and LnIII ions: synthesis, X-ray structure and cryomagnetic study

A new series of cyanido-bridged {Fe^IIILn^III}₂ neutral molecular squares of general formula [Fe{HB(pz)₃}(CN)(μ-CN)₂Ln(NO₃)₂(pyim)(Ph₃PO)]₂·2CH₃CN [Ln = Ce (1), Pr (2), Nd (3), Gd (4), Tb (5), Dy (6) and Er (7); {HB(pz)₃}^- = hydrotris(pyrazolyl)borate, pyim = 2-(1H-imidazol-2-yl)pyridine and Ph₃PO = triphenylphosphine oxide] were obtained by reacting the low-spin [Fe{HB(pz)₃}(CN)₃]^- species with the preformed [Ln^III(pyim)(NO₃)₂(pyim)(Ph₃PO)]⁺ complex anions (generated in situ by mixing the nitrate salt of each Ln(III) ion with pyim and Ph₃PO molecules). Single-crystal X-ray diffraction studies show that 1-7 are isostructural compounds that crystallize in the triclinic P1̄ space group. Their crystal structures consist of centrosymmetric cyanido-bridged {Fe^IIILn^III}₂ molecular squares where two [Fe{HB(pz)₃}(CN)₃]^- units adopt bis-monodentate coordination modes towards two [Ln^III(pyim)(NO₃)₂(pyim)(Ph₃PO)]⁺ moieties. The cis-oriented convergent sites from both low-spin Fe^III and Ln^III fragments form a quasi square-shaped molecule in which the 3d and 4f ions alternatively occupy the corners of the square. Both Fe^III ions show a distorted octahedral surrounding (C_3v symmetry), whereas the Ln^III ions exhibit a distorted muffin-like geometry (C_s symmetry) in 1-7. The intramolecular Fe^III⋯Ln^III distances across the two cyanido-bridges range from ca. 5.48/5.46 up to ca. 5.58/5.61 Å. The molecular squares in 1-7 are interlinked through hydrogen bonds, weak π⋯π stacking and very weak C-H⋯π type interactions into three-dimensional supramolecular networks. The analysis of the solid-state direct-current (dc) magnetic susceptibility data of 1-7 in the temperature range 1.9-300 K reveals the occurrence of weak intra- and intermolecular antiferromagnetic interactions. The small intramolecular antiferromagnetic couplings in 4 compare well with those previously reported for parent systems. Although the coexistence of the spin-orbit coupling (SOC) of the low-spin iron(III) and lanthanide(III) ions in the remaining compounds together with the ligand field effects mask the visualization and make difficult the evaluation of the possible magnetic interactions in them, we were able to do it through a SOC model applied on exact or effective Hamiltonians. Frequency-dependent alternating current magnetic susceptibility signals in the temperature range 2.0-9.0 K under zero and non-zero static fields were observed for 5-7 which indicate slow magnetic relaxation (SMM) behavior. The usual absence of χ''_M maxima moved us to estimate their energy barriers through ln(χ''_M/ χ'_M) vs. 1/T plots, obtaining values from 25 to 40 cm^-1.

Weak ferromagnetism derived from spin canting in an amido-bridged homochiral Mn(iii) 1-D coordination polymer

An amido-bridged homochiral one-dimensional (1D) Mn(iii) coordination polymer behaves as a weak ferromagnet arising from spin canting with a coercive field of 3.0 kOe.

The first 3D and trinuclear cyano-bridged FeIII–FeIII(CN)6 complexes: structure and magnetic characterizations

Crystal structures and magnetic properties of 3D cis-cyano-bridged and 2D trans-cyano-bridged trinuclear Fe^III–Fe^III(CN)₆ structures are reported.

Heterometallic complexes combining [MnIII(salpn)]+ and [Fe(CN)6]4− units as the products of reactions between [MnIII(salpn)(H2O)C(CN)3] and [Fe(CN)6]3−/4−

The tricyanomethanide ligand reduces Fe(iii) to Fe(ii) yielding the discrete and chain complexes.

Pressure induced transition from spin glass-like behavior to a metamagnet exhibiting weak ferromagnetism observed for decamethylferrocenium hexacyanobutadienide, [FeCp*2]˙+ [HCBD]˙-

The magnetic properties of [Fe(III)Cp*2]˙(+)[HCBD]˙(-) (Cp* = pentamethylcyclopentadienide; HCBD = hexacyanobutadienide, C4(CN)6) and [Fe(III)Cp*2]˙(+)[DDQ]˙(-) (DDQ = 2,3-dichloro-5,6-dicyanoquinonide) were measured at ambient and applied hydrostatic pressures up to 11.4 and 9.2 kbar, respectively. At ambient pressure [FeCp*2][HCBD] exhibits spin glass-like behavior with a freezing temperature, Tf, of 2.93 K from the peak in χ'(T) at 10 Hz, but magnetic ordering is not evident due to the lack of a remnant magnetization, bifurcation temperature, and hysteresis. Above 3.1 kbar, [FeCp*2][HCBD] magnetically orders as a metamagnet with an antiferromagnetic ground state with an ordering temperature, Tc, of 2.46 K determined from the Fisher specific heat, which increases linearly to 4.80 K at 11.4 kbar at a rate of 0.28 K kbar(-1). Upon application of pressure metamagnetic-like behavior with hysteresis indicative of a weak ferromagnet (canted antiferromagnet) was observed at and above 3.1 kbar, with a coercive field, Hcr, of 65 Oe, which increases exponentially to 795 Oe at 11.4 kbar. [FeCp*2]˙(+)[DDQ]˙(-) did not magnetically order above 2 K, and magnetic order was not observed up to 9.2 kbar. The pressure dependencies are reversible.

Synthesis, Crystal Structures and Magnetic Properties of Cyanide-bridged Trinuclear and Ion-pair Heterometallic Complexes

A cyanide-bridged, trinuclear, heterometallic Pd(II)–Mn(III) complex [{Mn(L)(H2O)}2{(μ-CN)2Pd(CN)2}] and an ion-pair complex [Co(Phen)2(H2O)2][Pd(CN)4]·MeOH have been synthesised (L = N,N-ethylene-bis(3-ethoxysalicylideneiminate; Phen = 1,10-phenanthroline). Single X-ray diffraction analysis reveals the neutral trinuclear complex is self-complementary through coordinated aqua ligands from one complex and the free O4 compartments from the neighbouring complex, thereby giving a 1D single chain supramolecular structure. The ion-pair complex forms a three-dimensional network via intermolecular O…H–N hydrogen bond interactions. Magnetic susceptibility studies show overall weak antiferromagnetic coupling between adjacent Mn(III) ions in the trimeric complex.

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.