Fe(bipy)(CN)(4)](-) as a versatile building block for the design of heterometallic systems: synthesis, crystal structure, and magnetic properties of PPh(4)[Fe(III)(bipy)(CN)(4)] x H(2)O, [[Fe(III)(bipy)(CN)(4)](2)M(II)(H(2)O)(4)] x 4H(2)O, and [[Fe(III)(bipy)(CN)(4)](2)Zn(II)] x 2H(2)O [bipy = 2,2'-Bipyridine; M = Mn and Zn

The new cyano complexes of formulas PPh(4)[Fe(III)(bipy)(CN)(4)] x H(2)O (1), [[Fe(III)(bipy)(CN)(4)](2)M(II)(H(2)O)(4)] x 4H(2)O with M = Mn (2) and Zn (3), and [[Fe(III)(bipy)(CN)(4)](2)Zn(II)] x 2H(2)O (4) [bipy = 2,2'-bipyridine and PPh(4) = tetraphenylphosphonium cation] have been synthesized and structurally characterized. The structure of complex 1 is made up of mononuclear [Fe(bipy)(CN)(4)](-) anions, tetraphenyphosphonium cations, and water molecules of crystallization. The iron(III) is hexacoordinated with two nitrogen atoms of a chelating bipy and four carbon atoms of four terminal cyanide groups, building a distorted octahedron around the metal atom. The structure of complexes 2 and 3 consists of neutral centrosymmetric [[Fe(III)(bipy)(CN)(4)](2)M(II)(H(2)O)(4)] heterotrinuclear units and crystallization water molecules. The [Fe(bipy)(CN)(4)](-) entity of 1 is present in 2 and 3 acting as a monodentate ligand toward M(H(2)O)(4) units [M = Mn(II) (2) and Zn(II) (3)] through one cyanide group, the other three cyanides remaining terminal. Four water molecules and two cyanide nitrogen atoms from two [Fe(bipy)(CN)(4)](-) units in trans positions build a distorted octahedron surrounding Mn(II) (2) and Zn(II) (3). The structure of the [Fe(phen)(CN)(4)](-) complex ligand in 2 and 3 is close to that of the one in 1. The intramolecular Fe-M distances are 5.126(1) and 5.018(1) A in 2 and 3, respectively. 4 exhibits a neutral one-dimensional polymeric structure containing two types of [Fe(bipy)(CN)(4)](-) units acting as bismonodentate (Fe(1)) and trismonodentate (Fe(2)) ligands versus the divalent zinc cations through two cis-cyanide (Fe(1)) and three fac-cyanide (Fe(2)) groups. The environment of the iron atoms in 4 is distorted octahedral as in 1-3, whereas the zinc atom is pentacoordinated with five cyanide nitrogen atoms, describing a very distorted square pyramid. The iron-zinc separations across the single bridging cyanides are 5.013(1) and 5.142(1) A at Fe(1) and 5.028(1), 5.076(1), and 5.176(1) A at Fe(2). The magnetic properties of 1-3 have been investigated in the temperature range 2.0-300 K. 1 is a low-spin iron(III) complex with an important orbital contribution. The magnetic properties of 3 correspond to the sum of two magnetically isolated spin triplets, the antiferromagnetic coupling between the low-spin iron(III) centers through the -CN-Zn-NC- bridging skeleton (iron-iron separation larger than 10 A) being very weak. More interestingly, 2 exhibits a significant intramolecular antiferromagnetic interaction between the central spin sextet and peripheral spin doublets, leading to a low-lying spin quartet.     

Hydrothermal syntheses,crystal structures,and properties of two-dimensional homo- and heterometallic cyanide-bridged complexes: [Cu2(CN)2(bpym)] and [Fe(bipy)2(CN)4Cu2] (bpym = 2,2'-bipyrimidine,bipy = 2,2'-bipyridine)

The hydrothermal reaction of K(3)[Fe(CN)(6)], CuCl(2), and 2,2'-bipyridine (bipy) resulted in the formation of a 2D cyanide-bridged heterobimetallic Fe(II)-Cu(I) complex, [Fe(bipy)(2)(CN)(4)Cu(2)], 1. Working in the same conditions, but using 2,2'-bipyrimidine (bpym) instead of bipy and methanol as solvent, we obtained the homometallic Cu(I) complex [Cu(2)(CN)(2)(bpym)](2), 2. The structure of 1 consists of cyanide-bridged Fe(II)-Cu(I) layers, constructed from alternately fused 6 (Fe(2)Cu(4)) and 10 (Fe(2)Cu(8)) metal-membered centrosymmetric rings, in which copper(I) and iron(II) ions exhibit distorted trigonal planar and octahedral cooordination environments, respectively. The formation of 1 can be explained by assuming that, under high pressure and temperature, iron(III) and copper(II) ions are reduced with the simultaneous and/or subsequent substitution of four cyanide ligands by two bipy molecules in the ferricyanide anions. It is interesting to note that 1 is the first cyanide-bridged heterobimetallic complex prepared by solvothermal methods. The structure of 2 consists of neutral 2D honeycomb layers constructed from fused Cu(6)(CN)(4)(bpym)(2) rings, in which copper(I) atoms exhibit distorted tetrahedral geometry. The isolation of 1 and 2, by using K(3)[Fe(CN)(6)] as starting material, demonstrates that hydrothermal chemistry can be used not only to prepare homometallic materials but also to prepare cyanide-bridged bimetallic materials. The temperature dependence of chi(M)T and M?ssbauer measurements for 1 reveal the existence of a high spin <--> low spin equilibrium involving the Fe(II) ions.     

Cyanide-bridged Fe(III)-Co(II) bis double zigzag chains with a slow relaxation of the magnetisation

Reaction of [Fe(III)(bipy)(CN)4]- with fully solvated M(II) cations [M = Co (1) and Mn (2)] produces the isostructural bis double zigzag chains [[Fe(III)(bipy)(CN)4]2M(II)(H2O)] x MeCN x (1/2)H2O; 1 exhibits intrachain ferromagnetic and interchain antiferromagnetic couplings, slow magnetic relaxation and hysteresis effects.     

4,2-Ribbon like ferromagnetic cyano-bridged Fe(III)2Ni(II) chains: a magneto-structural study

The low-spin iron(III) complex AsPh(4)[Fe(III)(bpy)(CN)(4)].CH(3)CN (1) [AsPh(4) = tetraphenylarsonium cation] and the heterobimetallic chains [{Fe(III)(L)(CN)(4)}(2)Ni(II)(H(2)O)(2)].4H(2)O with L = bpy (2) and phen (3) [bpy = 2,2'-bipyridine and phen = 1,10-phenanthroline] have been prepared and their structures determined by X-ray diffraction methods. The structure of 1 consists of mononuclear [Fe(bpy)(CN)(4)](-) anions, tetraphenylarsonium cations and acetonitrile molecules of crystallization. The iron(III) is hexacoordinated with two nitrogen atoms of the bidentate bpy and four carbon atoms of four terminal cyanide groups building a distorted octahedral surrounding around the metal atom. 2 and 3 are isomorphous compounds whose structure is made up of neutral 4,2-ribbon like bimetallic chains of formula [{Fe(III)(L)(CN)(4)}(2)Ni(II)(H(2)O)(2)] where the [Fe(III)(L)(CN)(4)](-) unit acts as a bis-monodentate bridging ligand toward the trans-diaquanickel(II) units through two of its four cyanide groups in cis positions. The chains exhibit two orientations in the unit cell and they interact with each other through hydrogen bonds involving the coordination and crystallization water molecules together with the uncoordinated cyanide nitrogen atoms of the [Fe(L)(CN)(4)](-) units. Compounds 2 and 3 behave as ferromagnetic Fe(III)(2)Ni(II) chains which interact ferromagnetically at very low temperatures in the case of 2, whereas metamagnetic-like behaviour is observed for with a critical field (H(c)) around 200 G. For H > H(c) the ferromagnetic Fe(III)(2)Ni(II) chains of 3 exhibit a frequency dependence of the out-of-phase ac susceptibility signal at T < 3.5 K.     

mer-[Fe(pcq)(CN)3]-: a novel cyanide-containing building block and its application to assembling cyanide-bridged trinuclear FeIII2MnII complexes [pcq- = 8-(pyridine-2-carboxamido)quinoline anion

A new cyanide-containing building block K[Fe(pcq)(CN)(3)] [1; pcq(-) = 8-(pyridine-2-carboxamido)quinoline anion] containing a low-spin Fe(III) center with three cyanide groups in a meridional arrangement has been successfully designed and synthesized. Three cyanide-bridged trinuclear Fe(III)(2)Mn(II) complexes, [Fe(pcq)(CN)(3)](2)[Mn(CH(3)OH)(2)(H(2)O)(2)].2H(2)O (2), [Fe(pcq)(CN)(3)](2)[Mn(bipy)(2)].CH(3)OH.2H(2)O (3), and [Fe(pcq)(CN)(3)](2)[Mn(phen)(2)].CH(3)OH.2H(2)O (4), have been synthesized and structurally characterized. The magnetic susceptibilities of the three heterometallic complexes have been investigated.     

Cyanide-Bridged Fe(III)-Cu(II) Complexes: Jahn-Teller Isomerism and Its Influence on the Magnetic Properties

We report here the synthesis and characterization of four dinuclear cyanide-bridged Fe(III)-Cu(II) complexes, based on a tetra- or a pentadentate bispidine ligand (L(1) or L(2), respectively; bispidines are 3,7-diazabiyclo[3.3.1]nonane derivatives) coordinated to the Cu(II) center, and a tridentate bipyridineamide (bpca) coordinated to the low-spin Fe(III) site, with cyanide groups completing the two coordination spheres, one of them bridging between the two metal ions. The four structurally characterized complexes [{Fe(bpca)(CN)(3)}{Cu(L(1)·H(2)O)}]BF(4), [{Fe(bpca)(CN)(3)}{Cu(L(2))}][Fe(bpca)(CN)(3)]·5H(2)O, [{Fe(bpca)(CN)(3)}{Cu(L(2)·MeOH)}]PF(6)·MeOH·H(2)O, and [{Fe(bpca)(CN)(3)}{Cu(L(2))}]PF(6)·2H(2)O belong to different structural isomers. The most important differences are structurally and electronically enforced (direction of the pseudo-Jahn-Teller mode) strong or weak interactions of the copper(II) center with the cyanide bridge. The related strength of the magnetic coupling of the two centers is analyzed with a combination of experimental magnetic, electron paramagnetic resonance (EPR), electronic spectroscopic data together with a ligand-field theory- and density functional theory (DFT)-based analysis.     

Fe(Phen)(CN)4]-: a versatile building block for the design of heterometallic systems. Crystal structures and magnetic properties of PPh4[Fe(Phen)(CN)4]*2H2O and [[Fe(Phen)(CN)4]2M(H2O)2]*4H2O [Phen = 1,10-phenanthroline; M = Mn(II) and Zn(II)

The mononuclear PPh4[Fe(phen)(CN)4]*2H2O (1) complex and the cyanide-bridged bimetallic [[Fe(phen)(CN)4]2M(H2O)2]*4H2O compounds [M = Mn(II) (2) and Zn(II) (3); phen = 1,10-phenanthroline; PPh4 = tetraphenylphosphonium cation] have been synthesized and structurally and magnetically characterized. Complex 1 crystallizes in the monoclinic system, space group P2(1)/c, with a = 9.364(4) A, b = 27.472(5) A, c = 14.301(3) A, beta = 97.68(2) degrees, and Z = 4. Complexes 2 and 3 are isostructural and they crystallize in the monoclinic system, space group P2(1)/n, with a = 7.5292(4) A, b = 15.6000(10) A, c = 15.4081(9) A, beta = 93.552(2) degrees, and Z = 2 for 2 and a = 7.440(1) A, b = 15.569(3) A, c = 15.344(6) A, beta = 93.63(2) degrees, and Z = 2 for 3. The structure of complex 1 is made up of mononuclear [Fe(phen)(CN)4]- anions, tetraphenyphosphonium cations, and water molecules of crystallization. The iron(III) is hexacoordinate with two nitrogen atoms of a chelating phen (2.018(6) and 2.021(6) A for Fe-N) and four carbon atoms of four terminal cyanide groups (Fe-C bond lengths varying in the range 1.906(8)-1.95(1) A) building a distorted octahedron around the metal atom. The structure of complexes 2 and 3 consists of neutral double zigzag chains of formula [[Fe(phen)(CN)4]2M(H2O)2] and crystallization water molecules. The [Fe(phen)(CN)4]- entity of 1 is present in 2 and 3 acting as a bridging ligand toward M(H2O)2 units [M = Mn(II) (2) and Zn(II) (3)] through two cyanide groups in cis positions, the other two cyanide remaining terminal. Two water molecules in trans positions and four cyanide-nitrogen atoms from four [Fe(phen)(CN)4]- units build a distorted octahedral surrounding Mn(II) (2) and Zn(II) (3). The M-O bond lengths are 2.185(3) (2) and 2.105(3) A (3), whereas the M-N bond distances vary in the ranges 2.210(3)-2.258(3) A (2) and 2.112(3)-2.186(3) A (3). The structure of the [Fe(phen)(CN)4]- complex ligand in 2 and 3 is as in 1. The shorter intrachain Fe-M distances through bridging cyano are 5.245(5) and 5.208(5) A in 2 and 5.187(1) and 5.132(1) A in 3. The magnetic properties of 1-3 have been investigated in the temperature range 2.0-300 K. Complex 1 is a low-spin iron(III) complex with an appreciable orbital contribution. The magnetic properties of 3 correspond to the sum of two magnetically isolated spin triplets, the magnetic coupling between the low-spin iron(III) centers through the -CN-Zn-NC- bridging skeleton (iron-iron separation larger than 10.2 A) being negligible. More interestingly, 2 exhibits one-dimensional ferrimagnetic behavior due to the noncompensation of the local interacting spins (S(Mn) = 5/2 and S(Fe) = 1/2) which interact antiferromagnetically through bridging cyano groups. A comparison between the magnetic properties of the isostructural compounds 2 and 3 allow us to check the antiferromagnetic coupling in 2.     

Synthesis, structures, and magnetic properties of a series of cyano-bridged Fe-Mn bimetallic complexes

The preparation and crystal structures of five cyano-bridged Fe-Mn complexes, [(bipy)2Fe(II)(CN)2Mn(II)(bipy)2]2(ClO4)4 (1), [(bipy)2Fe(II)(CN)2Mn(II)(DMF)3(H2O)]2(ClO4)4 (2), {[(Tp)Fe(III)(CN)3]2Mn(II)(DMF)2(H2O)}2 (3), {[(Tp)Fe(III)(CN)3]2Mn(II)(DMF)2}n (4), and Na2[Mn(II)Fe(II)(CN)6] (5) (bipy = 2,2'-bipyridine, Tp = tris(pyrazolyl)hydroborate), are reported here. Compounds 1-4 contain the basic Fe2(CN)4Mn2 square building units, of which 1-3 show the motif of discrete molecular squares of Fe2(CN)4Mn2 and 4 possesses a 1D double-zigzag chain-like structure, while compound 5 is a 3D cubic framework analogous to that of Prussian blue. Compounds 1 and 2 show weak ferromagnetic interactions between two Mn(II) ions through the bent -NC-Fe(II)-CN- bridges. Compound 3 shows weak antiferromagnetic coupling between the Fe(III) and Mn(II) ions, while compound 4 displays a metamagnetic-like behavior with TN = 5.2 K and Hc = 10.5 kOe. Compound 5 exhibits a ferromagnetic ordering with Tc= 3.5 K, coercive field, Hc, = 330 G, and a remnant magnetization of 503 cm3 Oe mol(-1).     

Nuclearity controlled cyanide-bridged bimetallic CrIII-MnII compounds: synthesis, crystal structures, magnetic properties and theoretical calculations

The preparation, X-ray crystallography and magnetic investigation of the compounds PPh4[Cr(bipy)(CN)4].2 CH3CN.H2O (1) (mononuclear), [[Cr(bipy)(CN)4]2Mn-(H2O)4].4H2O (2) (trinuclear), [[Cr(bipy)(CN)4]2Mn(H2O)2] (3) (chain) and [[Cr(bipy)(CN)4]2Mn(H2O)].H2O.CH3CN (4) (double chain) [bipy=2,2'-bipyridine; PPh4 (+)=tetraphenylphosphonium] are described herein. The [Cr(bipy)(CN)4]- unit act either as a monodentate (2) or bis-monodentate (3) ligand toward the manganese atom through one (2) or two (3) of its four cyanide groups. The manganese atom is six-coordinate with two (2) or four (3) cyanide nitrogens and four (2) or two (3) water molecules building a distorted octahedral environment. In 4, two chains of 3 are pillared through interchain Mn-N-C-Cr links which replace one of the two trans-coordinated water molecules at the manganese atom to afford a double chain structure where bis- and tris-monodenate coordination modes of [Cr(bipy)(CN)4]- coexist. The magnetic properties of 1-4 were investigated in the temperature range 1.9-300 K. A Curie law behaviour for a magnetically isolated spin quartet is observed for 1. A significant antiferromagnetic interaction between CrIII and MnII through the single cyanide bridge [J=-6.2 cm(-1), the Hamiltonian being defined as H=-J(SCr1.SMn+SCr2.SMn] occurs in 2 leading to a low-lying spin doublet which is fully populated at T <5 K. A metamagnetic behaviour is observed for 3 and 4 [the values of the critical field Hc being ca. 3000 (3) and 1500 Oe (4)] which is associated to the occurrence of weak interchain antiferromagnetic interactions between ferrimagnetic Cr2III MnII chains. The analysis of the exchange pathways in 2-4 through DFT type calculations together with the magnetic bevaviour simulation using the quantum Monte Carlo methodology provided a good understanding of their magnetic properties.     

mer-[Fe III(bpca)(CN)3]-: a new low-spin iron(III) complex to build heterometallic ladder-like chains

The novel mononuclear complex PPh(4)-mer-[Fe(III)(bpca)(3)(CN)(3)].H(2)O (1) [PPh(4)(+) = tetraphenylphosphonium cation and bpca = bis(2-pyridylcarbonyl)amidate anion] and ladder-like chain compound [[Fe(III)(bpca)(micro-CN)(3)Mn(II)(H(2)O)(3)] [Fe(III)(bpca)(CN)(3)]].3H(2)O (2) have been prepared and characterized by X-ray diffraction analysis. Compound 1 is a low-spin iron(III) compound with three cyanide ligands in mer arrangement and a tridentate N-donor ligand building a distorted octahedral environment around the iron atom. Compound 2 is an ionic salt made up of cationic ladder-like chains [[Fe(III)(bpca)(micro-CN)(3)Mn(II)(H(2)O)(3)]](+) and uncoordinated anions [Fe(III)(bpca)(3)(CN)(3)](-). The magnetic properties of 2 correspond to those of a ferrimagnetic chain with significant intrachain antiferromagnetic coupling between the low-spin iron(III) centers and the high-spin manganese(II) cations. This compound exhibits ferrimagnetic ordering below 2.0 K.     

Fe(bpym)(CN)4]-: a new building block for designing single-chain magnets

We herein present the preparation, crystal structure, magnetic properties, and theoretical study of new heterobimetallic chains of formula {[Fe(III)(bpym)(CN4)]2M(II)(H2O)2}.6H2O [bpym = 2,2'-bipyrimidine; M = Zn (2), Co (3), Cu (4), and Mn (5)] which are obtained by using the building block PPh4[Fe(bpym)(CN)4].H2O (1) (PPh4+= tetraphenylphosphonium) as a ligand toward the fully solvated MII ions. The structure of complex 1 contains mononuclear [Fe(bpym)(CN)4]- anions. Compounds 2-5 are isostructural 4,2-ribbonlike bimetallic chains where the [Fe(bpym)(CN)4]- unit acts as a bis-monodenate ligand through two of its four cyanide ligands toward the M atom. Water hexamer clusters (4) and regular alternating fused six- and four-membered water rings with two dangling water molecules (2, 3, and 5) are trapped between the cyanide-bridged 4,2-ribbonlike chains. 1 and 2 behave as magnetically isolated low-spin iron(III) centers. 3 behaves as a single-chain magnet (SCM) with intrachain ferromagnetic coupling, slow magnetic relaxation, hysteresis effects, and frequency-dependent ac signals at T < 7 K). As expected for a thermally activated process, the nucleation field (Hn) in 3 increases with decreasing T and increasing v. Below 1.0 K, Hn becomes temperature independent but remains strongly sweep rate dependent. In this temperature range, the reversal of the magnetization may be induced by a quantum nucleation of a domain wall that then propagates due to the applied field. 4 and 5 are ferro- and ferrimagnetic chains respectively, with metamagnetic-like behavior (4). DFT-type calculations and QMC methodology provided a good understanding of the magnetic properties of 3-5.     

An S = 2 cyanide-bridged trinuclear Fe(III)2Ni(II) single-molecule magnet

Treatment of [NEt4][(pzTp)Fe(III)(CN)3] (1) with Ni(II)(OTf)2 (OTf = trifluoromethanesulfonate) and 1,5,8,12-tetraazadodecane (L) affords {[(pzTp)Fe(III)(CN)3]2[Ni(II)L]} x 1/2MeOH (2), while 2,2'-bipyridine (bipy) affords {[(pzTp)Fe(III)(CN)3]2[Ni(II)(bipy)2]} x 2 H2O (3). Magnetic measurements indicate that 2 and 3 have S = 2 ground states and that 3 exhibits slow relaxation of the magnetization above 2 K.     

Assembly of azido- or cyano-bridged binuclear complexes containing the bulky [Mn(phen)2]2+ building block: syntheses, crystal structures, and magnetic properties

Two new cyano-bridged heterobinuclear complexes, [Mn(II)(phen)2Cl][Fe(III)(bpb)(CN)2] x 0.5CH3CH2OH x 1.5H2O (1) and [Mn(II)(phen)2Cl][Cr(III)(bpb)(CN)2] x 2H2O (2) [phen = 1,10-phenanthroline; bpb(2-) = 1,2-bis(pyridine-2-carboxamido)benzenate], and four novel azido-bridged Mn(II) dimeric complexes, [Mn2(phen)4(mu(1,1)-N3)2][M(III)(bpb)(CN)2]2 x H2O [M = Fe (3), Cr (4), Co (5)] and [Mn2(phen)4(mu(1,3)-N3)(N3)2]BPh4 x 0.5H2O (6), have been synthesized and characterized by single-crystal X-ray diffraction analysis and magnetic studies. Complexes 1 and 2 comprise [Mn(phen)2Cl]+ and [M(bpb)(CN)2]- units connected by one cyano ligand of [M(bpb)(CN)2]-. Complexes 3-5 are doubly end-on (EO) azido-bridged Mn(II) binuclear complexes with two [M(bpb)(CN)2]- molecules acting as charge-compensating anions. However, the Mn(II) ions in complex 6 are linked by a single end-to-end (EE) azido bridging ligand with one large free BPh4(-) group as the charge-balancing anion. The magnetic coupling between Mn(II) and Fe(III) or Cr(III) in complexes 1 and 2 was found to be antiferromagnetic with J(MnFe) = -2.68(3) cm(-1) and J(MnCr) = -4.55(1) cm(-1) on the basis of the Hamiltonian H = -JS(Mn)S(M) (M = Fe or Cr). The magnetic interactions between two Mn(II) ions in 3-5 are ferromagnetic in nature with the magnetic coupling constants of 1.15(3), 1.05(2), and 1.27(2) cm(-1) (H = -JS(Mn1)S(Mn2)), respectively. The single EE azido-bridged dimeric complex 6 manifests antiferromagnetic interaction with J = -2.29(4) cm(-1) (H = -JS(Mn1)S(Mn2)). Magneto-structural correlationship on the EO azido-bridged Mn(II) dimers has been investigated.     

Structural and photophysical properties of coordination networks combining [Ru(Bpym)(CN)4]2- or [[Ru(CN)4]2(mu-bpym)]4- anions (bpym = 2,2'-bipyrimidine) with lanthanide(III) cations: sensitized near-infrared luminescence from Yb(III), Nd(III), and Er(III) following Ru-to-lanthanide energy transfer

Reaction of the cyanoruthenate anions [Ru(bpym)(CN)4]2- and [[Ru(CN)4]2(mu-bpym)]4- (bpym = 2,2'-bipyrimidine) with lanthanide(III) salts resulted in the crystallization of coordination networks based on Ru-CN-Ln bridges. Four types of structure were obtained: [Ru(bpym)(CN)4][Ln(NO3)(H2O)5] (Ru-Ln; Ln = Sm, Nd, and Gd) are one-dimensional helical chains; [Ru(bpym)(CN)4]2[Ln(NO3)(H2O)2][Ln(NO3)(0.5)(H2O)(5.5)](NO3)(0.5).5.5H2O (Ru-Ln; Ln = Er and Yb) are two-dimensional sheets containing cross-linked chains based on Ru2Ln2(mu-CN)4 diamond units, which are linked into one-dimensional chains via shared Ru atoms; [[Ru(CN)4]2(mu-bpym)][Ln(NO3)(H2O)5]2.3H2O (Ru2-Ln; Ln = Nd and Sm) are one-dimensional ladders with parallel Ln-NC-Ru-CN-Ln-NC strands connected by the bipyrimidine "cross pieces" acting as rungs on the ladder; and [[Ru(CN)4]2(mu-bpym)][Ln(H2O)6](0.5)[Ln(H2O)4](NO3)(0.5).nH2O (Ru2-Ln; Ln = Eu, Gd, and Yb; n = 8.5, 8.5, and 8, respectively) are three-dimensional networks in which two-dimensional sheets of Ru2Ln2(mu-CN)4 diamonds are connected via cyanide bridges to Ln(III) ions between the layers. Whereas Ru-Gd shows weak triplet metal-to-ligand charge-transfer (3MLCT) luminescence in the solid state from the Ru-bipyrimidine chromophore, in Ru-Nd, Ru-Er, and Ru-Yb, the Ru-based emission is quenched, and all of these show, instead, sensitized lanthanide-based near-IR luminescence following a Ru --> Ln energy transfer. Similarly, Ru2-Nd and Ru2-Yb show lanthanide-based near-IR emission following excitation of the Ru-bipyrimidine chromophore. Time-resolved luminescence measurements suggest that the Ru --> Ln energy-transfer rate is faster (when Ln = Yb and Er) than in related complexes based on the [Ru(bipy)(CN)4]2- chromophore, because the lower energy of the Ru-bpym 3MLCT provides better spectroscopic overlap with the low-energy f-f states of Yb(III) and Er(III). In every case, the lanthanide-based luminescence is relatively short-lived as a result of the CN oscillations in the lattice.     

Slow relaxation of the magnetization in a 4,2-wavelike Fe(III)2Co(II) heterobimetallic chain

The reaction of the low-spin iron(III) complex [Fe(dmbpy)(CN)(4)](-) (1) with fully solvated cobalt(II) ions affords the cyanide-bridged heterobimetallic chain {[Fe(III)(dmbpy)(CN)(4)](2)Co(II)(H(2)O)(2)}(n) · 4nH(2)O (2), which exhibits intrachain ferromagnetic coupling and double slow relaxation of the magnetization.     

Lanthanide-3d cyanometalate chains Ln(III)-M(III) (Ln=Pr, Nd, Sm, Eu, Gd, Tb; M=Fe) with the tridentate ligand 2,4,6-tri(2-pyridyl)-1,3,5-triazine (tptz): evidence of ferromagnetic interactions for the Sm(III)-M(III) compounds (M=Fe, Cr)

A series of cyanide-bridged chain mixed Fe(III)/Ln(III) (Ln=Pr, Nd, Sm, Eu, Gd, Tb) complexes with the tridentate ligand 2,4,6-tri(2-pyridyl)-1,3,5-triazine (tptz) used as a capping group has been prepared. Reactions of tptz and LnCl3 with K3Fe(CN)6 yield a family of air-stable 1-D compounds {[Pr(tptz)(H2O)4Fe(CN)6].8H2O}infinity, {[Nd(tptz)(H2O)4Fe(CN)6].8H2O}infinity, {[Sm(tptz)(H2O)4Fe(CN)6].8H2O}, {[Eu(tptz)(H2O)4Fe(CN)6].6H2O}infinity, {[Gd(tptz)(H2O)4Fe(CN)6].6H2O}infinity, and {[Tb(tptz)(H2O)4Fe(CN)6].8H2O}infinity. Temperature dependent magnetic susceptibility studies of reveal that in , the Sm(III) and Fe(III) ions are ferromagnetically coupled with 3-D ordering occurring below 3.5 K. The appearance of the frequency dependent out-of-phase signal is explained in terms of an ordering with a spin glass-like behavior. To compare the magnetic behavior of with related compounds, {[Sm(tptz)(H2O)4Co(CN)6].8H2O}infinity and {[La(tptz)(DMF)(H2O)3Fe(CN)6].5H2O}infinity, {[Sm(tmphen)(DMF)3(H2O)Fe(CN)6].2H2O}infinity, {[Sm(tmphen)2(H2O)2Fe(CN)6].MeOH.13H2O}infinity and {[Sm(tmphen)2(H2O)2Cr(CN)6].MeOH.9H2O}infinity with 3,4,7,8-tetramethyl-1,10-phenanthroline (tmphen) were also prepared.     

3d-Metal derivatives of the [Cu(I)(SO3)4]7- ion: structure and magnetism

The Cu(SO(3))(4)(7-) anion, which consists of a tetrahedrally coordinated Cu(I) centre coordinated to four sulfur atoms, is able to act as a multidentate ligand in discrete and infinite supramolecular species. The slow oxidation of an aqueous solution of Na(7)Cu(SO(3))(4) yields a mixed oxidation state, 2D network of composition Na(5){[Cu(II)(H(2)O)][Cu(I)(SO(3))(4)]}·6H(2)O. The addition of Cu(II) and 2,2'-bipyridine to an aqueous Na(7)Cu(SO(3))(4) solution leads to the formation of a pentanuclear complex of composition {[Cu(II)(H(2)O)(bipy)](4)[Cu(I)(SO(3))(4)]}(+); a combination of hydrogen bonding and π-π stacking interactions leads to the generation of infinite parallel channels that are occupied by disordered nitrate anions and water molecules. A pair of Cu(SO(3))(4)(7-) anions each act as a tridentate ligand towards a single Mn(II) centre when Mn(II) ions are combined with an excess of Cu(SO(3))(4)(7-). An anionic pentanuclear complex of composition {[Cu(I)(SO(3))(4)](2)[Fe(III)(H(2)O)](3)(O)} is formed when Fe(II) is added to a Cu(+)/SO(3)(2-) solution. Hydrated ferrous [Fe(H(2)O)(6)(2+)] and sodium ions act as counterions for the complexes and are responsible for the formation of an extensive hydrogen bond network within the crystal. Magnetic susceptibility studies over the temperature range 2-300 K show that weak ferromagnetic coupling occurs within the Cu(II) containing chains of Na(5){[Cu(II)(H(2)O)][Cu(I)(SO(3))(4)]}·6H(2)O, while zero coupling exists in the pentanuclear cluster {[Cu(II)(H(2)O)(bipy)](4)[Cu(I)(SO(3))(4)]}(NO(3))·H(2)O. Weak Mn(II)-O-S-O-Mn(II) antiferromagnetic coupling occurs in Na(H(2)O)(6){[Cu(I)(SO(3))(4)][Mn(II)(H(2)O)(2)](3)}, the latter formed when Mn was in excess during synthesis. The compound, Na(3)(H(2)O)(6)[Fe(II)(H(2)O)(6)](2){[Cu(I)(SO(3))(4)](2)[Fe(III)(H(2)O)](3)(O)}·H(2)O, contained trace magnetic impurities that affected the expected magnetic behaviour.     

Syntheses, structures, and magnetic properties of cyano-bridged heterobimetallic complexes based on [Fe(bpca)(CN)3]-

Two new cyano-bridged one-dimensional heterobimetallic coordination polymers, [(bpca)(2)Fe(III)(2)(CN)(6)Cu(H(2)O)(2).1.5H(2)O](n)() (2) and [(bpca)Fe(III)(CN)(3)Cu(bpca)(H(2)O).H(2)O](n)() (3), and a trinuclear complex, [(bpca)(2)Fe(III)(2)(CN)(6)Mn(CH(3)OH)(2)(H(2)O)(2)].2H(2)O (4), have been synthesized using the tailored tricyanometalate precursor (Bu(4)N)[Fe(bpca)(CN)(3)].H(2)O (1) (Bu(4)N(+) = tetrabutylammonium cation; bpca = bis(2-pyridylcarbonyl)amidate anion) as a building block and structurally characterized. In complex 2, the Cu(II) ions are six-coordinated in an elongated distorted octahedral environment, and they are linked by distorted octahedrons of [Fe(bpca)(CN)(3)](-) to form 1D chain of squares. Complex 3 is an unexpected chiral heterobimetallic helical chain complex, in which the helical chain consists of the asymmetric unit of [(bpca)Fe(CN)(3)Cu(bpca)(H(2)O)]. In complex 4, there are two independent trinuclear clusters in one asymmetric unit, and the coordination modes of the two methanol and two water molecules coordinating to the central Mn(II) ion are different (cis and trans). Complex 2 shows metamagnetic behavior with a Neel temperature of T(N) = 2.2 K and a critical field of 250 Oe at 1.8 K, where the cyanides mediate the intrachain ferromagnetic coupling between the Cu(II) and Fe(III) ions. Complex 3 shows ferromagnetic coupling between Cu(II) and Fe(III) ions, the best-fit for chi(M)T versus T using a 1D alternating chain model leads to the parameters J(1) = 7.9(3) cm(-)(1), J(2) = 1.03(2) cm(-)(1), and g = 2.196(3). Complex 4 exhibits ferrimagnetic behavior caused by the noncompensation of the local interacting spins (S(Mn) = 5/2 and S(Fe) = 1/2) which interact antiferromagnetically through bridging cyano groups.     

Structural and photomagnetic studies of two compounds in the system Cu(2+)/Mo(CN8)(4-): from trinuclear molecule to infinite network

The syntheses and structural and physical characterization of the compounds [Cu(bipy)(2)](2)[Mo(CN)(8)].5H(2)O. CH(3)OH (1) with bipy = 2,2'-bipyridine and M(II)(2)[Mo(IV)(CN)(8)].xH(2)O (2 with M = Cu, x = 7.5; 3 with M = Mn, x = 9.5) are presented. 1 crystallizes in the triclinic space group P1; (a = 11.3006(4) A, b = 12.0886(5) A, c = 22.9589(9) A, alpha = 81.799(2) degrees, beta = 79.787(2) degrees, gamma = 62.873(2) degrees, Z = 2). The structure of 1 consists of neutral trinuclear molecules in which a central [Mo(CN8)](4-) anion is linked to two [Cu(bipy)2](2+) cations through two cyanide bridges. 2 crystallizes poorly, and hence, structural information has been obtained from the wide-angle X-ray scattering (WAXS) technique, by comparison with 3 and Fe(II)(2)(H(2)O)(4)[Mo(IV)(CN)(8)].4H(2)O whose X-ray structure has been previously solved. 2, 3, and Fe(II)(2)(H(2)O)(4)[Mo(IV)(CN)(8)].4H(2)O form extended networks with all the cyano groups acting as bridges. The magnetic properties have shown that 1 and 2 behave as paramagnets. Under irradiation with light, they exhibit important modifications of their magnetic properties, with the appearance at low temperature of magnetic interactions. For 1 the modifications are irreversible, whereas they are reversible for 2 after cycling in temperature. These photomagnetic effects are thought to be caused by the conversion of Mo(IV) (diamagnetic) to Mo(V)(paramagnetic) through a photooxidation mechanism for 1 and a photoinduced electron transfer in 2. These results have been correlated with the structural features.     

Compositions and structures of copper hexacyanoferrates(II) and (III): experimental results

The preparation, composition and structure of copper hexacyanoferrates have been investigated. Three methods were used: precipitation, local growth in an aqueous solution, and growth in a gel. Four compounds were obtained, either in powdered form or as single crystals: Cu(II)(2)Fe(II)(CN)(6) . xH(2)O, Cu(II)(3)[Fe(III)(CN)(6)](2) . xH(2)O, Na(2)Cu(II)Fe(II)(CN)(6) . 10H(2)O and K(2)Cu(II)Fe(II)(CN)(6). Powders of Cu(II)(2)Fe(II)(CN)(6) . xH(2)O and Cu(II)(3)[Fe(III) (CN)(6)](2) . xH(2)O are easily prepared by precipitation and can also be obtained by local growth. They crystallise generally with cubic symmetry, in space group Fm3m, and are structurally disordered. The mixed copper hexacyanoferrates of general formulae M(1)(2)Cu(II)Fe(II)(CN)(6) or M(I)Cu(II)Fe(III)(CN)(6) (here M(I) is Na, K) were not obtained by precipitation. The appropriate method was local growth for the preparation of powders of K(2)Cu(II)Fe(II)(CN)(6). Single crystals of Na(2)Cu(II)Fe(II)(CN)(6) were obtained by growth in a gel, and their study using single crystal X-ray diffraction revealed a new monoclinic structure.