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International audience; Five new chiral MnIII complexes [Mn((1R, 2R)-Salcy)N3]∞⋅CH3CN (1), [Mn((R,R)-Salcy)N3]∞ (2), [Mn((R,R)-Salcy)N3] (4), [Mn((R,R)-Salcy)(H2O)N3]⋅C4H8O (5) and [Mn((R,R)-Salcy)NCS] (6) have been synthesized and characterized by X-ray structural analysis and magnetic measurements (Salcy=N,N′-bis(salicylidene)-1,2-diaminocyclohexane. The four azido complexes have been obtained from the previously known [Mn((R,R)-Salcy)(CH3OH)N3] (3) by crystallization from various solvents. Compounds 1 and 2 are trans-μ-1,3-azide bridged coordination polymers. While 1 forms helical chains, the chain in 2 is formed via translation of a dimeric helicate repeat unit. Compound 3 is a methanol coordinated mononuclear azido complex which forms a 2D-network through H-bonding. Compounds 4 and 6 are phenoxo-bridged dimers without inversion center. Compound 5 is an aqua coordinated mononuclear azido complex, which forms a 1D-chain through O−H⋅⋅⋅N hydrogen bonding involving axial ligands. In all six compounds MnIII exhibits a characteristic Jahn−Teller elongation. The magnetic coupling in 1 and 2 leads to antiferromagnetic interaction along the chain (2 J=−11.6 cm−1 for 1 and –11.9 cm−1 for 2) through the μ-1,3-azide bridge. Compound 3 is weakly antiferromagnetic due to hydrogen bonding interactions in the lattice. The phenoxo dimers (4 and 6) do not have measurable exchange interaction, the low temperature susceptibility being influenced mainly by zero-field splitting.

Four new isostructural salts, [M(phen)3](I2Br)2·3CH2Cl2 where, M=Co (1), Ni (2), Cu (3), or Zn (4) have been synthesized by reacting the metal nitrates with 1,10–phenanthroline (phen) in presence of potassium bromide and iodine in a two phase procedure. The [Cu(phen)3]2+ coordination corresponds to tetragonally elongated octahedron while the other three are much more symmetrical. The pure Cu2+ complex as well as other salts doped with Cu2+ give hyperfine resolved EPR spectra in a wide temperature range showing dynamic Jahn–Teller distortion. The trihalide ion is nearly linear with bond distances in the range, I–I (2.786–2.833 A) and I–Br (2.759–2.794 A). Geometry optimization (DFT and MP2 methods) predicts a much more unsymmetrical “gas phase” structure for I2Br− ion. Calculated Raman frequencies are in reasonable agreement with observed values. Electronic spectral results show that the integrity of the trihalide ion is retained in solution. Three new isostructural compounds having the general formula [M(phen)3](I2Br)2 having nearly symmetrical I2Br− ion are synthesized and characterized.

Three three-dimensional coordination polymers,viz.poly[[diaqua-μ4-oxydiacetato-di-μ4-sulfato-dipraseodymium(III)] hemihydrate], [Pr2(C4H4O5)(SO4)2(H2O)2]·0.5H2O, (I), poly[[diaquadi-μ3-oxydiacetato-μ3-sulfato-dineodymium(III)] 1.32-hydrate], [Nd2(C4H4O5)2(SO4)(H2O)2]·1.32H2O, (II), and poly[[diaquadi-μ3-oxydiacetato-μ3-sulfato-disamarium(III)] 1.32-hydrate], [Sm2(C4H4O5)2(SO4)(H2O)2]·1.32H2O, (III), were obtained by hydrothermal reactions of the respective lanthanide oxides and ZnSO4with oxydiacetic acid (odaH2). The Nd3+and Sm3+compounds form isomorphous crystal structures in which the lanthanide cations are nine-coordinate, having a tricapped trigonal prismatic coordination. The Pr3+compound has an entirely different crystal structure in which two types of coordination polyhedra are observed,viz.nine-coordinate (trigonal prism) and ten-coordinate (bicapped square antiprism). The sulfate anions show various coordination modes, one of which has only rarely been observed crystallographically to date.

Three Mn(III,III) complexes containing dibenzoylmethane (dbm), Mn 2 (OMe) 2 (dbm) 2 (ClH 2 CCOO) 2 ( 1 ), Mn 2 (OMe) 2 (dbm) 2 (Cl 2 HCCOO) 2 ( 2 ) and Mn 2 (OMe) 2 (dbm) 2 (Cl 3 CCOO) 2 ( 3 ) were synthesized. Crystal structure determination and magnetic characterization were done for 2 . The Mn⋯Mn distance in complex 2 is 2.865 A. It exhibits antiferromagnetic coupling with exchange parameter | J | = 20.4 cm −1 ( H = −2 JS A S B ). All three complexes, though insoluble in common solvents, catalyse the disproportionation of hydrogen peroxide when dispersed on silica gel with turnover numbers ∼150–300. DFT simulations showed that bridging moieties have remarkable effect on intermetallic distances in dimanganese(III,III) complexes.

Reaction of pyridine-2,6-dicarboxylic acid (dipicH2) with ammonium ceric nitrate and Cu(II) salts yielded three heterometallic compounds all of which contain [Ce(dipic)3]2− linked to aquo-Cu(II) complex units. Part of the Ce(IV) gets reduced by solvent during the reaction leading to [(Ce(dipic)3Ce(H2O)8)2Cu(H2O)4][Ce(dipic)3]2·12H2O (1). Other lanthanide(III) ions could take the place of Ce(III) as demonstrated by the preparation of [(Ce(dipic)3La(H2O)8)2Cu(H2O)4][Ce(dipic)3]2·12H2O (4), which is isomorphous with compound 1. [Ce(dipic)3Cu(H2O)4]·8H2O (2) is a one-dimensional coordination polymer in which two types of aquo-Cu(II) complex units which differ in the orientation of the tetragonal axis alternate along the chain. The central Cu(H2O)22+ unit in the trinuclear anion of [Cu(H2O)6][Ce(dipic)3Cu(H2O)2Ce(dipic)3]·8H2O (3) is chelated by two carboxylate groups in trans positions in off-axis mode. In all the four complexes, the Cu(II) centres are magnetically isolated leading well-resolved EPR spectra in polycrystalline samples.

Three new phenoxo-bridged dimeric compounds of MnIII with tetradentate Schiff bases (salpnH2, salmenH2 and acphpnH2) and pseudohalide ligands have been synthesized and characterized by crystallography and dc and ac magnetic measurements. Mn(salpn)NCO (1) and Mn(salmen)N3 (2) exhibit intra-dimer ferromagnetic exchange (J = 0.42(2) cm−1 for 1, J = 0.58(1) cm−1 for 2, H ˆ = - 2 J S ˆ 1 S ˆ 2 ). The χmT product of 1 continuously increases upon lowering temperature, reaching a value of 10.01 cm3 mol−1 K at 1.98 K. In the case of 2, the χmT product reaches a maximum value of 7.85 cm3 mol−1 K at 5.82 K and decreases upon further cooling to a value of 6.34 cm3 mol–1 K at 2 K, indicating the operation of inter-dimer antiferromagnetic interactions. Frequency dependence of ac magnetic susceptibility shows single-molecule-magnetic (SMM) behavior in the temperature range 2–10 K for both compounds. In sharp contrast, Mn(acphpn)N3 (3) exhibits antiferromagnetic exchange interactions. salpnH2 = N,N′-bis(salicylidene)-1,3-diaminopropane, salmenH2 = N,N′-bis(salicylidene)-1,2-diaminopropane and acphpnH2 = N,N′-bis(2-hydroxyacetophenone)-1,3-diaminopropane.

Two complexes of silver(I) with 4,5-diazafluoren-9-one (dafone) which are the first examples of Ag-dafone complexes were synthesized and structurally characterized. Crystals of [Ag(dafone)2]NO3 · H2O (1) contain two strictly planar four-coordinate Ag(I) complexes. The silver coordination polyhedron in [Ag2(4,4′-bpy)(dafone)4]BF4 (2) is a highly distorted tetrahedron. Its crystal structure is built by a two-fold interpenetration of identical porous networks. The unusual coordination in the two compounds (planar four-coordinate d10 ion in 1, chelation with two long Ag–N bonds in 2 and low bond valence sums in both complexes) is in part due to the large chelate bite of dafone, and in part due to the stacking and other intermolecular interactions influencing the coordination geometry of Ag(I). This was further probed through molecular simulation of [Ag(N–N)2]+ complexes using DFT calculations.

A new H‐bonded (H2O)38 water cluster was identified in a mixed‐valent cerium dipicolinate complex [CeIV(dipic)3CeIII(H2O)8][CeIV(dipic)3CeIII(H2O)7CeIV(dipic)3] · 20H2O (dipicH2=dipicolinic acid). Such a large cluster built around an inversion centre and occupying 20% of the unit cell volume is supported by the bulky acceptor rich complex ions in the crystal lattice. The compound crystallises in the triclinic crystal system with space group P1¯ and unit cell parameters; a=16.5285(9) A, b=17.1905(10) A, c=19.5220(11) A, α=76.0440(10)°, β=79.0180(10)°, γ=65.6370(10)°, V=4877.7(5) A3.

Cationic metal complexes of dipicolinic acid (dipicH2) are stabilized by [Ce(dipic)3]2− ions in the three isomorphous crystals [M(dipicH2)(OH2)3][Ce(dipic)3] · 3H2O (M = Ni, 1; Cu, 2; Zn, 3). Magnetic dilution provided by the bulky anions leads to well-resolved EPR spectra in polycrystalline samples of 2. The cations have 4+2 coordination, the carbonyl atom of the carboxylic acid groups coordinating weakly from trans positions. In the case of 2 this steric distortion is augmented by Jahn–Teller distortion. All the three structures are satisfactorily modelled by calculations based on density functional theory (DFT). The switch of the Jahn–Teller axis upon deprotonation of the complex, leading to the neutral species Cu(dipic)(H2O)3, is also reproduced by DFT. Electronic transition energies as well as the g-tensor component of the d9 complex obtained are in good agreement with experiment. However, the calculated hyperfine coupling constants are in error. DFT also fails to satisfactorily account for the electronic transition in the d8 ion in 1.

Construction and characterization of metal–organic frameworks (MOFs) continue to attract much attention owing to their potential to produce solid-state materials with useful properties. Heterometallic compounds formed from lanthanides and transition-metal ions are of interest because of their magnetic properties, especially because some of them behave as single-molecule magnets. Though much work has been done with lanthanides and copper, there are only a few coordination networks with lanthanide(III) and manganese(II) centers. Oxydiacetic acid (O(CH2CO2H)2, odaH2), a multidentate ligand with five coordination sites, forms a number of MOF structures with lanthanides and transition-metal ions as well as 3d–4f composites. Herein, we report the synthesis, structure, and magnetic properties of [{Mn(H2O)6}{MnGd(oda)3}2]·6H2O (1), which is the first cubic gadolinium–manganese 3D MOF with a ferromagnetic interaction. Compound 1 was obtained as colorless cubes by slow evaporation of an aqueous solution containing the metal salts and odaH2 at pH 6–7. The crystal structure consists of a novel anionic 3D cubic network formed with [Gd(oda)3] 3 and Mn as building blocks. Gd is nine-coordinate with a distorted tricapped trigonal-prismatic geometry formed by the coordination of three oxygen (two carboxylate and one alkoxo) atoms from each oda ligand. The octahedral coordination sphere of Mn is formed by six free carboxylate oxygen atoms from six neighboring [Gd(oda)3] 3 units (Figure 1). [Gd(oda)3] 3 unit is surrounded by six Mn units and vice-versa, creating a cubic lattice with voids in the structure (Figure 2). As shown in Figure 3, the metal-only lattice permits only one type of channel. However the carbon atoms of the oda ligand project into these channels, alternatively narrowing and broadening it, resulting in two types of cavities. The bigger cavity is

The title compound, [Fe2O(SO4)2(C10H8N2)4], crystallizes as two different hydrates, viz. 11H2O, (I), and 15H2O, (II). The complex is binuclear, in which the two FeIII atoms are coordinated in an octahedral geometry to four N atoms from the two bipyridine ligands, to one O atom from the sulfate ion and to an oxide ion on a twofold axis, which acts as a bridge between the symmetry-related units. The Fe...Fe separation is 3.556 (4) A and the Fe-O-Fe angle is 161.6 (2) degrees in (I); the corresponding values are 3.544 (1) A and 165.8 (2) degrees in (II). In (II), one of the O atoms of the sulfate ion is disordered over two positions. In both compounds, the solvent water molecules form slightly different one-dimensional hydrogen-bonded networks which pass along the c axis of the unit cell. In (I), three solvent water molecules and, in (II), one solvent water molecule, are situated on the twofold axis. In both (I) and (II), the central O atom of the metal complex lies on a twofold axis.

A solution of the previously known 1-D coordination polymer, made up of alternating [Ce(dipic)3]2− and [Sr(dipicH2)(OH2)3]2+ polyhedra takes up additional Ce4+ and Sr2+ ions leading to the double stranded hetero-metallic squarate chain. The transformation can be reversed by adding excess dipicH2. The crystal structure and thermal decomposition study of the new squarate chain polymer is reported. The analogous Ca compound does not undergo this transformation.

The crystal structure of Ce(dipic)2(H2O)3·4H2O reveals an unusual hydrogen-bonded water octamer. The centrosymmetric octamer is built by bridging two water molecules to the chair form of a water hexamer. The structure, predicted to be unstable relative to other octameric structures, is stabilized by hydrogen bonding with the carboxylate groups lining the cavity in the host crystal. The water cluster is removed by heating at 100 °C but can be reassembled by exposing the dehydrated form to an atmosphere saturated with water vapor.

Reaction of dipicolinic acid with ammonium ceric nitrate and barium chloride produces, by self-assembly, three coordination polymers having similar stoichiometry but very different network structures. The structure of Ba(dipicH2)(OH2)4Ce(dipic)3 · 4.6H2O (1) is built up of 1-D alternating chains of nine-coordinate Ce and Ba polyhedra, each having tricapped trigonal prismatic geometry. The structure of Ba(OH2)6Ce(dipic)3 (2), wherein a chain of nine-coordinate aquo-Ba polyhedra is threaded through the channel formed by a trigonal arrangement of the Ce ( dipic ) 3 2 - anions, is analogous to that of SrCl2 · 6H2O · Ba(OH2)4Ce(dipic)3 · 2H2O (3), a polymorph of 2 (formally its hydrate isomer), exhibits a layered network in which Ce and Ba coordination polyhedra are linked by dipic ligands to form a corrugated sheet structure and may be considered as a metal–organic analog of the PbO lattice.

Bis­[(2-pyridyl­methyl)­ammonio]silver(I) trinitrate, [Ag(C6H9N2)2](NO3)3, (I), and bis{bis­[(4-pyridyl­methyl)­ammonio]silver(I)} hexakis­(perchlorate) dihydrate, [Ag(C6H9N2)2]2(ClO4)6·2H2O, (II), are rare examples of complexes with cationic ligands. In (I), the Ag+ cation has a T-shaped [2+1] coordination involving the pyridine N atoms and a nitrate O atom, while in (II) there are three independent two-coordinate Ag complex cations (two with the Ag atoms on independent inversion centres) and disordered ClO4− ions. The crystal structures reveal the role of hydrogen bonding in stabilizing these complexes.

Crystal structures of the three isomeric compounds Ag(2-amp)ClO4 (1), Ag(3-amp)ClO4 (2), and Ag(4-amp)ClO4 (3) reveal different packing arrangements of one-dimensional (1-D) infinite chain coordination polymers, formed in each case by the coordination of Ag to the pyridine N and amino N atoms from two different ligand molecules. 1: triclinic, space group P1, with a = 7.672(6) A, b = 11.1401(11) A, c = 11.322(4) A, α = 91.207(14)°, β = 105.52(4)°, γ = 90.48(2)°, and Z = 2. 2: monoclinic, space group P21/c, with a = 8.345(4) A, b = 8.6748(7) A, c = 26.056(9) A, β = 97.96(4)°, and Z = 4. 3: hexagonal, space group P6522, with a = 9.3154(11) A, c = 39.313(5) A, and Z = 12. 1 consists of zigzag chains, while 2 is made up of triple helical chains generating a tunnel space large enough to hold half the anions inside it. 3 has a highly symmetrical arrangement of 12 crystallographically equivalent chains held by weak Ag···Ag bonds. The crystal packing of the 1-D polymers in this case may be described in terms o...

Two structurally significant polyiodides have been synthesized as salts of manganese(II) trischelates and characterized by three-dimensional X-ray crystallographic data. The complex, [Mn(phen)3](I3)2 (1), where phen = 1,10-phenanthroline, crystallizes in the hexagonal space group R 3 with 6 mononuclear cations in a cell of dimensions, a = b = 16.456(3) A; c = 25.864(4) A. The structure has been refined to the final R1 (wR2) values of 0.0365 (0.0782) based on 1981 (F ≥ 4σF) observed independent reflections. The structure of the [Mn(phen)3]2+ cation is unexceptional, whereas there are two types of symmetric I3− ions with I–I distances of 2.828(1) and 2.912(1) A. The longer I3− ions and the trischelate cations form layers of hexagonal network, while the shorter I3− ions are present as linkages between the layers in the crystal. The complex, [Mn(bpy)3](I3)1.5(I8)0.25 (2), where bpy = 2,2′-bipyridine, crystallizes in the monoclinic space group C2/c with 8 mononuclear cations in a cell of dimensions, a = 29.321(1) A; b = 12.9177(4) A; c = 23.2863(8) A; β = 120.950(2)°. The structure has been refined to the final R1 (wR2) values of 0.0536 (0.1310) based on 4192 (F ≥ 4σF) observed independent reflections. The structure consists of [Mn(bpy)3]2+ cations, two types of I3− ions, and infinite linear polyiodide chains of the composition, (I82−)n. Powder diffuse reflectance spectra measured for the complexes are similar exhibiting features at 23.0, 20.8, 18.5 and 17.2 kK, and are characteristic of the presence of I3− ions. Room temperature magnetic susceptibility measurements gave the magnetic moments of 5.85 and 6.05 μB for 1 and 2, respectively; the values are consistent with the expected spin-only magnetic moment for high-spin d5 manganese(II) complexes. Single crystal EPR spectral measurements with the applied field aligned parallel to the trigonal or pseudo-trigonal symmetry axis of the molecules gave zero-field splitting (D) values of 0.154 cm−1 (g = 2.06) and 0.066 cm−1 (g = 2.03) for 1 and 2, respectively. A comparison of the conductivities of the complexes in a single crystal form reveals a higher anisotropic conductivity for 2, which is attributed to the presence of linear polyiodide chains.

1099-0682; A tetranuclear CuII complex, Cu4(dafone)4(N3)8 (1, dafone = 4,5-diazafluoren-9-one) is described. The propensity of dafone to chelate through one short and one long bond is readily accommodated by the tendency of CuII to undergo Jahn-Teller elongation in its six-coordinate complexes. The crystal structure of 1 consists of two distortion isomers of the tetranuclear complex molecule. In each isomer, there are four μ1,1-azido bridges and two μ1,1,1-azido bridges as well as two terminally coordinated azide ions. The isomers, both of which are centrosymmetric, differ in the way the Jahn-Teller axes of the different CuII sites are aligned. Magnetic susceptibility measurements show an overall ferromagnetic interaction, which could be fitted with a two parameter model (J1 = 22.8 cm-1, J3 = -8.2 cm-1). The magnetic interaction was modelled by using DFT calculations, which showed that the two isomers are magnetically quite different; one is a ferromagnetically coupled tetramer, and the other may be viewed as two ferromagnetic dimers. The X-band EPR spectra are in broad agreement with this model.

[DafoneH 2 ][(CuCl 3 H 2 O)HCl (dafone=4,5-diazafluoren-9-one) crystallizes in the monoclinic space group P2 1 /c with a=14.585(2) A, b=14.143(7) A, c=7.076(6) A, β=91.3(2) o , and Z=4. The crystal contains the unusual chromophore [(CuCl 3 H 2 O)Cl] 2- showing coordinated water and a semicoordinate Cl - . Moderately strong antiferromagnetic exchange (J=-72.8 K, with H ex =-2JS 1 S 2 ) is present. The exchange pathway appears to be via an H-bond involving H 2 O and Cl - of inversion-related molecules

Mn 2 (μ-O) 2 (μ-OAc)(H 2 O) 2 (bipy) 2 ] (ClO 4 ) 3 .H 2 O crystallizes in the monoclinic system, space group P2 1 /n (No.14) with Z=4 and a=13.619(1) A, b=16213(2) A, c=16.266(1) A, and β=113.08 (1) o . The structure was solved by direct methods and refined to conventional agreement indices R=0.021 and R w =0.024 with 5159 unique reflections for which I>3σ (I). The structure consists of binuclear [Mn IV 2 (μ-O) 2 (μ-OAc)(H 2 O) 2 (bipy) 2 ] 3+ cation separated by ClO 4 - anions and a molecule of water of crystallization

A series of new heterometallic compounds containing cerium(IV) and lanthanide(III) with pyridine-2,6-dicarboxylic acid (dipicH(2)) have been synthesized. Depending on the Ln(III) ion and preparation conditions, we obtained four types of compounds. Type-I: one-dimensional coordination polymer, [Ln(dipicH)(H(2)O)(4)Ce(dipic)(3)].7H(2)O; Ln = La (1), Ce (2), or Pr (3). Type-II: ionic compound, [Ln(dipicH)(H(2)O)(6)][Ce(dipic)(3)].7H(2)O; Ln = Nd (4), Sm (5), Eu (6), Gd (7), or Dy (8). Type-III: octanuclear cluster incorporating a six-membered coordination ring, [Ln(H(2)O)(7)Ln(dipic)(H(2)O)(4)(Ce(dipic)(3))(2)](2).nH(2)O; Ln = La (9) n = 24, Ce (10) n = 24, Pr (11) n = 24, or Nd (12) n = 26. Type-IV: hexanuclear cluster incorporating a four-membered coordination ring, [(Ln(H(2)O)(5))(2)(Ce(dipic)(3))(4)(2H(+))].nH(2)O; Ln = Nd (13) n = 34, Sm (14) n = 26, Eu (15) n = 26, or Gd (16) n = 26. Crystal structures were determined for compounds 1-16. Tb and heavier lanthanides all form compounds isomorphous with Type-IV compounds. The observed structural variety is a consequence of the interplay of lanthanide contraction and kinetic effects involving water molecules, free as well as clusters, ranging in size from 6 to 26. A metal-centered luminescence sensitized by dipic ligand was observed in compounds containing Eu(III) and Dy(III) ions. Direct chelation, as opposed to bridging coordination, leads to enhanced luminescence. Resolved EPR spectra were observed for the Gd(III) compounds which are dependent on the coordination environment.

The crystal and molecular structure of Ag(dmbp)NO3, where dmbp=6,6′-dimethyl-2,2′-bipyridine, has been determined. The crystal consists of dimers formed by two symmetry-related molecules. Each dimeric unit is held together by (weak) Ag−Ag and heteroaromatic ring stacking interactions. Stacking interactions lead to a slipped stack arrangement of the dimers. The coordination around silver is very nearly planar (tetrahedral distortion angle=15°), with the nitrate ion acting as an unsymmetrical chelating ligand.

The Ce4+ oxidation of Mn2+ in acetic acid in the presence of 2,2?-bipyridine gives the unsymmetrical complex [Mn2O(OAc)2(H2O)(NO3)(bpy) 2](ClO4) � CH3COOH. The crystal structure of the complex shows the coordination of both nitrate and water to the metal ion. Each metal centre exhibits Jahn-Teller distortion and results in two types of Mn - OOAc bonds. The formation of different high-valent manganese complexes by Ce4+ oxidation under different conditions is discussed in the light of possible disproportionation and proton-coupled electron transfer reactions. The mode of (pseudo) Jahn-Teller distortion seen in manganese(III,III) complexes having the Mn2O(OAc)2+ 2 core is reviewed. Copyright ? 1996 Elsevier Science Ltd.

The crystal structure of Cu(dafone) 2 Cl 2 (dafone=4,5-diazafluoren-9-one) was determined (monoclinic, space group p2 1 /n with a=6.5911 (6) A, b=13.0712 (5) A, c=11.4813 (9) A, β=95.575 (4) o , and Z=2). This strucutre represents the first crystallographic example in a family of Cu(NN) 2 X 2 chromophores (NN=2,2'-bipyridine, 1, 10-phenanthroline, or bis(2-pyridyl)amine, and X is an anion) that has retained its octahedral coordination through trans ligation, in spite of the steric effects