Syntheses, structures and magnetic properties of a family of one-dimensional M(Ⅱ)-lanthanide(Ⅲ) (M =Ni(Ⅱ) and Zn(Ⅱ)) coordination polymers

A series of 1D nickel(Ⅱ)/zinc(Ⅱ)-lanthanide(Ⅲ) coordination polymers, [M(μ-L)2Ln(NO3)3]n· solvents (HL =bis(2-pyridylcarbonyl)amine; M = Ni, Ln = Gd (1 · NiGd), Tb (2· NiTb), Dy (3· NiDy), Ho (4· NiHo), Y (5· NiY);M = Zn, Ln =Gd (6· ZnGd), Tb (7· ZnTb), Dy (8· ZnDy), Ho (9· ZnHo); solvents = H2O or H2O-ethanol), was synthesized and characterized. All of the complexes are isostructural at 293 K and crystallize in the orthorhombic space group Fddd. Magnetic measurements were performed on 1-9, where weak ferromagnetic interaction is found in 1 · NiGd, ferromagnetic interaction in 2·NiTb and 3·NiDy, and antiferromagnetic interaction in 4· NiHo. A remarkable dc magnetic field dependence of ac susceptibilities was found in this series of complexes.     

Cyano-bridged pentanuclear Fe(III)3M(II)2 (M = Ni, Co, Fe) clusters: synthesis, structures, and magnetic properties

The reactions of [M(II)(Tpm(Me))(H2O)3]2+ (M = Ni, Co, Fe; Tpm(Me) = tris(3,5-dimethyl-1-pyrazoyl)methane) with [Bu4N][(Tp)Fe(III)(CN)3] (Bu4N+ = tetrabutylammonium cation; Tp = tris(pyrazolyl)hydroborate) in MeCN-Et2O afford three pentanuclear cyano-bridged clusters, [(Tp)3(Tpm(Me))2Fe(III)3M(II)2(CN)9]ClO4.15H2O (M = Ni, 1; M = Co, 2) and [(Tp)3(Tpm(Me))2Fe(III)3Fe(II)2(CN)9]BF4.15H2O (3). Single-crystal X-ray analyses reveal that they show the same trigonal bipyramidal structure featuring a D3h-symmetry core, in which two opposing Tpm(Me)-ligated M(II) ions situated in the two apical positions are linked through cyanide bridges to an equatorial triangle of three Tp-ligated Fe(III) (S = 1/2) centers. Magnetic studies for complex 1 show ferromagnetic coupling giving an S = 7/2 ground state and an appreciable magnetic anisotropy with a negative D(7/2) value equal to -0.79 cm(-1). Complex 2 shows zero-field splitting parameters deducted from the magnetization data with D = -1.33 cm(-1) and g = 2.81. Antiferromagnetic interaction was observed in complex 3.     

Solid-state coordination chemistry: influences of (M(terpyridyl))(M = Fe(III), Cu(II), Ni(II)) subunits on molybdenum oxide structures

The hydrothermal reactions of Na2MoO4 x 2H2O and 2,2':6',2"-terpyridine with appropriate salts of Fe(II), Cu(II), and Zn(II) yield a variety of mixed metal oxide phases. The Cu(II) system affords the molecular cluster [Cu(terpy)MoO4].3H2O (MOXI-40 x 3H2O), as well as a one-dimensional material [Cu(terpy)Mo2O7](MOXI-41) which is constructed from (Mo4O14)4- clusters linked through (Cu(terpy))2+ units. In constrast, the Zn(II) phase of stoichiometry identical to that of MOXI-41, [Zn(terpy)Mo2O7](MOXI-42), exhibits a one-dimensional structure characterized by a (Mo2O7)n2n- chain decorated with peripheral (Zn(terpy))2+ subunits. The iron species [(Fe(terpy))2Mo4O12](MOXI-43) is also one-dimensional but exhibits [(Fe(terpy))2(MoO4)2]2+ rings linked through (MoO4)2- tetrahedra. A persistent structural motif which appears in MOXI-40, MOXI-41, and MOXI-43 is the [(M(terpy))2(MoO4)2]n cluster with a cyclic )(M2Mo2O4) core. In general, the secondary metal sites M(II, III) are effective bridging groups between molybdate subunits of varying degrees of aggregation. Furthermore, the ligands passivate the bimetallic oxide from spatial extension in two or three dimensions and provide a routine entree into low-dimensional structural types of the molybdenum oxide family of materials.     

Two octacyanomolybdate(IV)-M(II) (M = Mn,Co) bimetallic assemblies: Crystal structures and magnetic properties

Two cyano-bridged bimetallic complexes {[M₂(H₂O)₄Mo(CN)₈] · 4H₂O} _n [M = Mn (I) and Co (II)] have been synthesized and structurally characterized. The single-crystal X-ray analyses reveal that these two compounds have three-dimensional structures, and cell parameters are similar in a tetragonal system with space group I $ \bar 4 $ \bar 4 . In the both complexes, each [Mo(CN)₈]⁴⁻ building block is linked with M²⁺ [M = Mn and Co] ions through its eight CN ligands. Each M²⁺ center is connected to four Mo units forming a three-dimensional framework. In addition, magnetic studies of these complexes have been presented.     

Synthesis and magnetic properties of 3-D [Ru(II/III)(2)(O(2)CMe)(4)](3)[M(III)(CN)(6)] (M = Cr,Fe, Co)

Three-dimensional network structures of [Ru(II/III)(2)(O(2)CMe)(4)](3)[M(III)(CN)(6)] (M = Cr, Fe, Co) composition have been formed and their magnetic properties characterized. [Ru(II/III)(2)(O(2)CMe)(4)](3)[M(III)(CN)(6)] (M = Cr, Fe, Co) have nu(CN) IR absorptions at 2138, 2116, and 2125 cm(-1) and have body-centered unit cells (a = 13.34, 13.30, and 13.10 A, respectively) with -M-Ctbd1;N-Ru=Ru-Ntbd1;C-M- linkages along all three Cartesian axes. [Ru(II/III)(2)(O(2)CMe)(4)](3)[Cr(III)(CN)(6)] magnetically orders as a ferrimagnet (T(c) = 33 K) and has an unusual constricted hysteresis loop.     

New cyanide-bridged Mn(III)-M(III) heterometallic dinuclear complexes constructed from [M(III)(AA)(CN)4]- building blocks (M = Cr and Fe): synthesis, crystal structures and magnetic properties

Three Mn(III)-M(III) (M = Cr and Fe) dinuclear complexes have been obtained by assembling [Mn(III)(SB)(H(2)O)](+) and [M(III)(AA)(CN)(4)](-) ions, where SB is the dianion of the Schiff-base resulting from the condensation of 3-methoxysalicylaldehyde with ethylenediamine (3-MeOsalen(2-)) or 1,2-cyclohexanediamine (3-MeOsalcyen(2-)): [Mn(3-MeOsalen)(H(2)O)(μ-NC)Cr(bipy)(CN)(3)]·2H(2)O (1), [Mn(3-MeOsalen)(H(2)O)(μ-NC)Cr(ampy)(CN)(3)][Mn(3-MeOsalen)(H(2)O)(2)]ClO(4)·2H(2)O (2) and [Mn(3-MeOsalcyen)(H(2)O)(μ-NC)Fe(bpym)(CN)(3)]·3H(2)O (3) (bipy = 2,2'-bipyridine, ampy = 2-aminomethylpyridine and bpym = 2,2'-bipyrimidine). The [M(AA)(CN)(4)](-) unit in 1-3 acts as a monodentate ligand towards the manganese(III) ion through one of its four cyanide groups. The manganese(III) ion in 1-3 exhibits an elongated octahedral stereochemistry with the tetradentate SB building the equatorial plane and a water molecule and a cyanide-nitrogen atom filling the axial positions. Remarkably, the neutral mononuclear complex [Mn(3-MeOsalen)(H(2)O)(2)]ClO(4) co-crystallizes with the heterobimetallic unit in 2. The values of the Mn(III)-M(III) distance across the bridging cyanide are 5.228 (1), 5.505 (2) and 5.265 ? (3). The packing of the neutral heterobimetallic units in the crystal is governed by the self-complementarity of the [Mn(SB)(H(2)O)](+) moieties, which interact each other through hydrogen bonds established between the aqua ligand from one fragment with the set of phenolate- and methoxy-oxygens from the adjacent one. The magnetic properties of the three complexes have been investigated in the temperature range 1.9-300 K. Weak antiferromagnetic interactions between the Mn(III) and M(III) ions across the cyanido bridge were found: J(MnM) = -5.6 (1), -0.63 (2) and -2.4 cm(-1) (3) the Hamiltonian being defined as H = -JS(Mn)·S(M). Theoretical calculations based on density functional theory (DFT) have been used to substantiate both the nature and magnitude of the exchange interactions observed and also to analyze the dependence of the magnetic coupling on the structural parameters within the Mn(III)-N-C-M(III) motif in 1-3.     

M(III)Dy(III)3 (M = Fe(III), Co(III)) complexes: three-blade propellers exhibiting slow relaxation of magnetization

[Dy(III)(HBpz(3))(2)](2+) moieties (HBpz(3)(-) = hydrotris(pyrazolyl)borate) and a 3d transition-metal ion (Fe(III) or Co(III)) have been rationally assembled using an dithiooxalato dianion ligand into 3d-4f [MDy(3)(HBpz(3))(6)(dto)(3)]·4CH(3)CN·2CH(2)Cl(2) (M = Fe (1), Co (2) complexes. Single-crystal X-ray studies reveal that three eight-coordinated Dy(III) centers in a square antiprismatic coordination environment are connecting to a central octahedral trivalent Fe or Co ion forming a propeller-type complex. The dynamics of the magnetization in the two isostructural compounds, modulated by the nature of the central M(III) metal ion, are remarkably different despite their analogous direct current (dc) magnetic properties. The slow relaxation of the magnetization observed for 2 mainly originates from isolated Dy ions, since a diamagnetic Co(III) metal ion links the magnetic Dy(III) ions. In the case of 1, the magnetic interaction between S = 1/2 Fe(III) ion and the three Dy(III) magnetic centers, although weak, generates a complex energy spectrum of magnetic states with low-lying excited states that induce a smaller energy gap than for 2 and thus a faster relaxation of the magnetization.     

Cyano-bridged bimetallic assemblies from hexacyanometalate, [M(CN)6](3-) (M = Mn(III) and Fe(III)), and [M(N4-macrocycle)]2+ (M=Fe(III), Ni(II) and Zn(II)) building blocks. Syntheses, multidimensional structures, and magnetic properties

Reactions between [M(N(4)-macrocycle)](2+) (M = Zn(II) and Ni(II); macrocycle ligands are either CTH = d,l-5,5,7,12,12,14-hexamethyl-1,4,8,11-tetraazacyclotetradecane or cyclam = 1,4, 8, 11-tetrazaazaciclotetradecane) and [M(CN)(6)](3-) (M = Fe(III) and Mn(III)) give rise to cyano-bridged assemblies with 1D linear chain and 2D honeycomblike structures. The magnetic measurements on the 1D linear chain complex [Fe(cyclam)][Fe(CN)(6)].6H(2)O 1 points out its metamagnetic behavior, where the ferromagnetic interaction operates within the chain and the antiferromagnetic one between chains. The Neel temperature, T(N), is 5.5 K and the critical field at 2 K is 1 T. The unexpected ferromagnetic intrachain interaction can be rationalized on the basis of the axially elongated octahedral geometry of the low spin Fe(III) ion of the [Fe(cyclam)](3+) unit. The isostructural substitution of [Fe(CN)(6)](3-) by [Mn(CN)(6)](3-) in the previously reported complex [Ni(cyclam)](3)[Fe(CN)(6)](2).12H(2)O 2 leads to [Ni(cyclam)](3)[Mn(CN)(6)](2).16 H(2)O 3, which exhibits a corrugated 2D honeycomblike structure and a metamagnetic behavior with T(N) = 16 K and a critical field of 1 T. In the ferromagnetic phase (H > 1 T) this compound shows a very important coercitive field of 2900 G at 2 K. Compound [Ni(CTH)](3)[Fe(CN)(6)](2).13H(2)O 4, C(60)H(116)Fe(2)N(24)Ni(3)O(13), monoclinic, A 2/n, a = 20.462(7), b = 16.292(4), c = 27.262(7) A, beta = 101.29(4) degrees, Z = 4, also has a corrugated 2D honeycomblike structure and a ferromagnetic intralayer interaction, but, in contrast to 2 and 3, does not exhibit any magnetic ordering. This fact is likely due to the increase of the interlayer separation in this compound. ([Zn(cyclam)Fe(CN)(6)Zn(cyclam)] [Zn(cyclam)Fe(CN)(6)].22H(2)O.EtOH) 5, C(44)H(122)Fe(2)N(24)O(23)Zn(3), monoclinic, A 2/n, a = 14.5474(11), b = 37.056(2), c = 14.7173(13) A, beta = 93.94(1) degrees, Z = 4, presents an unique structure made of anionic linear chains containing alternating [Zn(cyclam)](2+) and [Fe(CN)(6)](3)(-) units and cationic trinuclear units [Zn(cyclam)Fe(CN)(6)Zn(cyclam)](+). Their magnetic properties agree well with those expected for two [Fe(CN)(6)](3-) units with spin-orbit coupling effect of the low spin iron(III) ions.     

Synthesis and photophysical properties of new Ln(III) (Ln = Eu(III), Gd(III), or Tb(III)) complexes of 1-amidino-O-methylurea

Three new solid lanthanide(III) complexes, [Ln(1-AMUH)₃] · (NO₃)₃ (1-AMUH = 1-amidino-O-methylurea; Ln = Eu(III), Gd(III), or Tb(III)) were synthesised and characterised by elemental analysis, infrared spectra, magnetic moment measurement, and electron paramagnetic resonance (EPR) spectra for Gd(III) complex. The formation of lanthanide(III) complexes is confirmed by the spectroscopic studies. The photophysical properties of Gd(III), Eu(III), and Tb(III) complexes in solid state were investigated. The Tb(III) complex exhibits the strongest green emission at 543 nm and the Eu(III) complex shows a red emission at 615 nm while the Gd(III) complex shows a weak emission band at 303 nm. Under excitation with UV light, these complexes exhibited an emission characteristic of central metal ions. The powder EPR spectrum of the Gd(III) complex at 300 K exhibits a single broad band with g = 2.025. The bi-exponential nature of the decay lifetime curve is observed in the Eu(III) and Tb(III) complexes. The results reveal them to have potential as luminescent materials.     

Syntheses, structures, and properties of trinuclear complexes [M(bpca)(2)(M'(hfac)(2))(2)], constructed with the complexed bridging ligand [M(bpca)(2)] [M, M' = Ni(II), Mn(II); Cu(II), Mn(II); Fe(II), Mn(II); Ni(II), Fe(II); and Fe(II), Fe(II); Hbpca = Bis(2-pyridylcarbonyl)amine, Hhfac = Hexafluoroacetylacetone

Five trinuclear complexes [M(bpca)(2)(M'(hfac)(2))(2)] (where MM'(2) = NiMn(2), CuMn(2), FeMn(2), NiFe(2), and FeFe(2); Hbpca = bis(2-pyridylcarbonyl)amine; and Hhfac = hexafluoroacetylacetone) were synthesized almost quantitatively by the reaction of [M(bpca)(2)] and [M'(hfac)(2)] in 1:2 molar ratio, and their structures and magnetic properties were investigated. Three complexes, with M' = Mn, crystallize in the same space group, Pna2(1), whereas two complexes, with M' = Fe, crystallize in P4(1), and complexes within each set are isostructural to one another. In all complexes, [M(bpca)(2)] acts as a bis-bidentate bridging ligand to form a linear trinuclear complex in which three metal ions are arranged in the manner M'-M-M'. The central metal ion is in a strong ligand field created by the N(6) donor set, and hence the Fe(II) in the [Fe(bpca)(2)] moiety is in a low-spin state. The terminal metal ions (M') are surrounded by O(6) donor sets with a moderate ligand field, which leads to the high-spin configuration of Fe(II). Three metal ions in all complexes are almost collinear, and metal-metal distances are ca. 5.5 A. The magnetic behavior of NiMn(2) and NiFe(2) shows a weak ferromagnetic interaction between the central Ni(II) ion and the terminal Mn(II) or Fe(II) ions. In these complexes, sigma-spin orbitals of the central Ni(II) ion and those of terminal metal ions have different symmetry about a 2-fold rotation axis through the Ni-N(amide)-M'(terminal) atoms, and this results in orthogonality between the neighboring sigma-spin orbitals and thus ferromagnetic interactions.     

Isomorphous replacement of M(II) ions in M(II)-Gd(III) dimers (M(II) = Cu(II), Mn(II), Ni(II), Co(II), Zn(II)): magnetic studies of the products

Complexes [M(II)Gd(III){pyCO(OEt)pyC(OH)(OEt)py}?](ClO?)?·EtOH [M(II) = Cu(II) (1), Mn(II) (2), Ni(II) (3), Co(II) (4) and Zn(II) (5)] crystallize in the monoclinic Cc space group and contain one hexacoordinate M(II) ion and one enneacoordinate Gd(III) ion, bridged by three {pyCO(OEt)pyC(OH)(OEt)py}? ligands. Magnetic susceptibility measurements indicate a ferromagnetic interaction for 1 and antiferromagnetic interactions for 2-4. Using the ? = -J?(Gd(III))?(M(II)) spin Hamiltonian formalism, fits to the magnetic susceptibility data yielded J values of +0.32 cm?1 for 1, -1.7 cm?1 for 2, and -0.22 cm?1 for 3. In complex 4, the orbital contributions of Co(II) precluded the determination of the magnetic coupling. The complex follows the Curie-Weiss law with θ = -2.07 K (-1.44 cm?1).     

Magnetic nanosized {M(II)24}-wheel-based (M = Co, Ni) coordination polymers

Two 3D coordination polymers, [Co(24)(OH)(12)(SO(4))(12)(ip)(6)(DMSO)(18)(H(2)O)(6)]·(DMSO)(6)(EtOH)(6)(H(2)O)(36) (1·guests, ip = isophthalate) and [Ni(24)(OH)(12)(SO(4))(12)(ip)(6)(DMSO)(12)(H(2)O)(12)]·(DMSO)(6)(EtOH)(6)(H(2)O)(20) (2·guests), constructed with nanosized tetraicosanuclear Co(II) and Ni(II) wheels are solvothermally synthesized. Both complexes show intra- and interwheel dominant antiferromagnetic interactions.     

Cyano-bridged Mn(III)-M(III) single-chain magnets with M(III)=Co(III), Fe(III), Mn(III), and Cr(III)

A series of isostructural cyano-bridged Mn(III)(h.s.)-M(III)(l.s.) alternating chains, [Mn(III)(5-TMAMsalen)M(III)(CN)(6)]?4H(2)O (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 C(2) 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 N(2)O(2) 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?? 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.     

Fe(III), Co(II,III), and Ni(II) phenanthrolinate peroxodisulfates

Complexes with the compositions [Fe(Phen)₃]₂(S₂O₈)₃ · 2H₂O, [Co(Phen)₃]₂(S₂O₈)₃ · 8H₂O, Co(Phen)₂S₂O₈ · 3H₂O, and [Ni(Phen)₂(H₂O)₂]S₂O₈ were synthesized and studied by spectroscopic, X-ray powder diffraction, and TG methods.     

Assembly,crystal structures,and luminescent properties of three new thiocyanate-bridging mercury(II) coordination polymers

Two ligands, 2-{5,5-dimethyl-3-[2-(pyridin-3-yl)-ethenyl]cyclohex-2-enylidene}propanedinitrile (L1) and 2-{5,5-dimethyl-3-[2-(pyridin-2-yl)-ethenyl]cyclohex-2-enylidene}propanedinitrile (L2), were synthesized. By reaction of mercury thiocyanate with L1 and L2, respectively, coordination polymers [Hg(L1)(μ_1,3-SCN)₂]_n (1), [Hg(L1)₂(μ_1,3-SCN)₂]_n (2), and [Hg(L2)(μ_1,3-SCN)(SCN)]_n (3) with different structures and topologies were obtained. In 1, the thiocyanate shows μ_1,3-SCN bridging coordination, and adjacent Hg(II) ions are bridged by two μ_1,3-SCN ions to form an infinite chain with the remaining position of five-coordinate Hg(II) occupied by L1. In 2, the thiocyanate has the same coordination as 1. However, Hg(II) has octahedral coordination with two L1 involved in coordination. An unusual feature of 3 is the presence of two types of thiocyanates, one has a S-terminal ligand and the other has a μ_1,3-SCN bridge. The mercury(II) in 3 is four-coordinated by L2 and three thiocyanates. Luminescent properties and thermal stabilities of 1–3 were studied.     

Synthesis, Crystal Structure and Fluorescent Property of d-f Heterodinuclear Eu(III)-M(II) (M=Cd(II), Ni(II)) Cryptates.

The design of ligands capable of forming stable and strong luminescent Eu3+ complexes is a theme of great interest . Because such complexes have potential use as luminescent molecular label for biological study1 and luminescent materials for lasers2. The cryptates have good thermodynamic stability and kinetic inertness toward metal dissociation. The pioneer studies on lanthanide polyaza-cryptates containing three 2, 2'-bipyridines and their N-oxides have been presented by J. M. Lehn, and c…     

Structures and magnetic properties of ferromagnetic coupling 2D Ln-M heterometallic coordination polymers (Ln = Ho, Er; M = Mn, Zn)

Four new heterometallic coordination polymers have been successfully synthesized, namely, {[Ho(2)(HCAM)(6)Mn(3)(H(2)O)(12)].17.5H(2)O}(n) (1), {[Er(2)(HCAM)(6)Mn(3)(H(2)O)(12)].17.5H(2)O}(n) (2), {[Ho(2)(HCAM)(6)Zn(3)(H(2)O)(12)].26H(2)O}(n) (3), and {[Er(2)(HCAM)(6)Zn(3)(H(2)O)(12)].26H(2)O}(n) (4) (H(3)CAM = chelidamic acid). X-ray crystallographic studies reveal that coordination polymers 1-4 are isostructural and crystallized in the rhombohedral crystal system, space group R3. These compounds comprise a 2D honeycomb-type framework. A 2D water sheet is first found in 3 and 4, which exhibits a novel topological motif. The magnetic results for 1-4 show that ferromagnetic interactions take place between the Ho(3+)/Er(3+) and Mn(2+) ions within 1 and 2.     

Synthesis, crystal structures, and magnetic properties of a new family of heterometallic cyanide-bridged Fe(III)2M(II)2 (M=Mn, Ni, and Co) square complexes

New heterobimetallic tetranuclear complexes of formula [Fe(III){B(pz)(4)}(CN)(2)(μ-CN)Mn(II)(bpy)(2)](2)(ClO(4))(2)·CH(3)CN (1), [Fe(III){HB(pz)(3)}(CN)(2)(μ-CN)Ni(II)(dmphen)(2)](2)(ClO(4))(2)·2CH(3)OH (2a), [Fe(III){B(pz)(4)}(CN)(2)(μ-CN)Ni(II)(dmphen)(2)](2)(ClO(4))(2)·2CH(3)OH (2b), [Fe(III){HB(pz)(3)}(CN)(2)(μ-CN)Co(II)(dmphen)(2)](2)(ClO(4))(2)·2CH(3)OH (3a), and [Fe(III){B(pz)(4)}(CN)(2)(μ-CN)Co(II)(dmphen)(2)](2)(ClO(4))(2)·2CH(3)OH (3b), [HB(pz)(3)(-) = hydrotris(1-pyrazolyl)borate, B(Pz)(4)(-) = tetrakis(1-pyrazolyl)borate, dmphen = 2,9-dimethyl-1,10-phenanthroline, bpy = 2,2'-bipyridine] have been synthesized and structurally and magnetically characterized. Complexes 1-3b have been prepared by following a rational route based on the self-assembly of the tricyanometalate precursor fac-[Fe(III)(L)(CN)(3)](-) (L = tridentate anionic ligand) and cationic preformed complexes [M(II)(L')(2)(H(2)O)(2)](2+) (L' = bidentate α-diimine type ligand), this last species having four blocked coordination sites and two labile ones located in cis positions. The structures of 1-3b consist of cationic tetranuclear Fe(III)(2)M(II)(2) square complexes [M = Mn (1), Ni (2a and 2b), Co (3a and 3b)] where corners are defined by the metal ions and the edges by the Fe-CN-M units. The charge is balanced by free perchlorate anions. The [Fe(L)(CN)(3)](-) complex in 1-3b acts as a ligand through two cyanide groups toward two divalent metal complexes. The magnetic properties of 1-3b have been investigated in the temperature range 2-300 K. A moderately strong antiferromagnetic interaction between the low-spin Fe(III) (S = 1/2) and high-spin Mn(II) (S = 5/2) ions has been found for 1 leading to an S = 4 ground state (J(1) = -6.2 and J(2) = -2.7 cm(-1)), whereas a moderately strong ferromagnetic interaction between the low-spin Fe(III) (S = 1/2) and high-spin Ni(II) (S = 1) and Co(II) (S = 3/2) ions has been found for complexes 2a-3b with S = 3 (2a and 2b) and S = 4 (3a and 3b) ground spin states [J(1) = +21.4 cm(-1) and J(2) = +19.4 cm(-1) (2a); J(1) = +17.0 cm(-1) and J(2) = +12.5 cm(-1) (2b); J(1) = +5.4 cm(-1) and J(2) = +11.1 cm(-1) (3a); J(1) = +8.1 cm(-1) and J(2) = +11.0 cm(-1) (3b)] [the exchange Hamiltonian being of the type H? = -J(S?(i)·S?(j))]. Density functional theory (DFT) calculations have been used to substantiate the nature and magnitude of the exchange magnetic coupling observed in 1-3b and also to analyze the dependence of the exchange magnetic coupling on the structural parameters of the Fe-C-N-M skeleton.     

Controlled aggregation of heterometallic nanoscale Cu12Ln6 clusters (Ln = Gd(III) or Nd(III)) into 2D coordination polymers

Discrete dinuclear and polymeric heterometallic copper(II)-lanthanide(III) complexes have been synthesized upon variation of pH and characterized by X-ray diffraction analysis. Reactions of the ligand Htza (tetrazole-1-acetic acid) with copper(II) and lanthanide(III) salts gave dinuclear [CuLn(tza)4(H2O)5Cl] complexes at the low pH of 3.5 and 2D heterometallic coordination polymers with high-nuclearity [{Cu2(OH)2}2{Cu12Ln6(mu3-OH)24(Cl)(1/2)(NO3)(1/2)(tza)12(H2O)18}](NO3)(9).8H2O (Ln = Gd or Nd) at a higher pH of 6.6. The acidity of the reaction solution can cause drastic changes in the structures of the products. In the dinuclear complexes, each pair of adjacent dinuclear molecules is linked through hydrogen bonds and pi-pi stacking interactions, and the whole structure is a hydrogen-bonded three-dimensional cubic net. In the coordination polymers, the connecting nodes are [Cu12Ln6] units, which are interconnected by [Cu2O2] units into two-dimensional structures. Magnetic studies exhibit the existence of weak exchange interactions between the Cu(II) and Ln(III) ions bridged by carboxylate and hydroxy ligands.