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International audience; Four new copper complexes, viz. [Cu(2-aminopyridine)(N3)2(H2O)2]n (1), [Cu3(3-aminopyridine)2(N3)6]n (2), [Cu(3-aminopyridine)(N3)22]n (3), and [Cu(4-aminopyridine)2(N3)2]n (4), have been synthesized with isomeric aminopyridines, viz. 2-aminopyridine (2-ap), 3-aminopyridine (3-ap), and 4-aminopyridine (4-ap), to probe the role of ligand and reactant molar ratios in directing the polynuclear assemblage and the associated magnetic properties. Ligand geometry is quite influential as can be seen through the versatile structures formed, viz. a hydrogen bonded layer of [small mu ]-1,1 azide bridged Cu dimers in 1; a network of two different types of dimers (Cu1-Cu2 & Cu3-Cu3[prime or minute]) involving [small mu ]-1,1; [small mu ]-1,3; [small mu ]-1,1,3; & [small mu ]-1,1,3,3 azide bridges in 2; a ladder structure in which [small mu ]-1,1 azide bridges form the rungs and [small mu ]-1,3 azide bridges form the rails of the ladder in 3; and a 1-D polymer chain involving [small mu ]-1,1 azide bridges in 4. Consistent with the bridge geometry, compounds 1 & 2 display ferromagnetic interactions, while 3 & 4 display antiferromagnetic interactions. The rather unexpected antiferromagnetic interactions in 3, in spite of [small mu ]-1,1 azide bridged rungs may be due to the crossover near the bridge angle. The ferromagnetic interactions in 1 and 2 are supported by DFT calculations.

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.

[Cu(en)(phen)2]+ is crystallized along with two phenanthroline and eight lattice water molecules either as a chloride or a nitrate salt. The cation has almost identical structural and spectral properties which correspond to a tetragonally elongated octahedral geometry with the en ligand in the equatorial plane. EPR parameters reveal a slight rhombicity in the coordination polyhedron. Even though both compounds have the same composition (except for the anions), the hydrogen bond networks involving the lattice water molecules and anions are quite different in the two compounds. There are also extensive π-stacking interactions involving the phenanthroline molecules, both coordinated and non-coordinated. The non-bonding interactions have a major directing role in the crystallization of the tris-chelate cation. The analogous mixed ligand complex of 2,2-bipyridine could not be crystallized.

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.

The Schiff base ligands, N,N′-bis(2-hydroxyacetophenone)-1,2-diaminoethane (acphenH2) and N,N′-bis(2-hydroxyacetophenone)-1,3-diaminopropane (acphpnH2), prepared in situ were used to synthesise two new Mn(III) complexes which were characterised by crystallography and variable temperature magnetic measurements. [Mn(acphen)NCS]2 is a phenoxo-bridged dimeric compound with the thiocyanate coordinating in the usual bent mode (Mn–N–C angle, 152°) and is weakly antiferromagnetic. Since there are no significant inter-dimer contacts in the crystal, the low temperature magnetic behaviour is influenced by single ion zero-field splitting. Exact diagonalisation of the spin Hamiltonian was performed to derive the following parameters: J = −0.7 cm−1, D = −0.6 cm−1. Mn(acphpn)(H2O)NCS is monomeric with an unusual linearly coordinated thiocyanate (Mn–N–C angle, 178°). Two lattice water molecules link the Mn(III) complex molecules through hydrogen bonds to form one-dimensional chains in the crystal. Magnetic exchange along the chain makes this compound also weakly antiferromagnetic with J ∼ –2 cm−1.

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.

Two new mixed ligand complexes of copper(II) with acetylacetonate (acac), 2,2′-bipyridine (bpy) and 1,10-phenanthroline (phen) belonging to the class of cytotoxic and antineoplastic compounds known as CASIOPEINAS® were synthesized and structurally characterized. Crystals of both complexes [Cu(acac)(bpy)(H2O)]NO3 · H2O (1), [Cu(acac)(phen)Br] (2) contain square pyramidal Cu(II) complex species. In frozen solution both compounds give well resolved EPR spectra with very similar parameters.

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

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.

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.

Dimeric [Mn(salpn)NCS] 2 (1) and polymeric [Mn(salpn)NCS] n (2) are formed by the reaction of Mn(CH 3 CO 2 ) 2 . 4H 2 0, the schiff base, and thiocyanate. The formation of the two polymorphic forms is solvent and temperature dependent. 1: orthorhombic, space group Pbca, with a = 12.573(2) A, b = 13.970(7) A, c = 18.891(9) A, and Z = 8. 2: orthorhombic, space group Pna2 1 , with a = 12.5277(14) A, b = 11.576(2) A, c = 11.513(2) A, and Z= 4. The dimers in 1 are held together by weak noncovalent S...π (phenyl) interactions leading to a chain along the a-axis. Each monomeric unit of the polymer in 2 is related to its adjacent ones by a 2-fold screw axis leading to a helix along the c-axis. The exchange coupling is nondetectable in the dimer. The magnetic susceptibility of the helical chain fits a classical chain law with J = -3.2 cm - 1 and shows a weak ferromagnetic ordering below 7 K due to spin canting effects.

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.

Three examples of Cu(II) complexes with dafone, Cu(dafone)2Br2 (1), [Cu(dafone)2(H2O)2](NO3)2 (2) and [Cu(dafone)2(H2O)2](ClO4)2 (3) have been synthesized and characterized structurally and spectroscopically. All complexes show unsymmetric chelation of dafone with one Cu—N bond being much longer than the other. Powder diffuse reflectance spectra have been recorded for 1, 2 and the known complex, Cu(dafone)2Cl2 (4) and correlated with the molecular g-values for this relatively new type of Cu(II) chromophore. Compounds 1 and 2 were found to be sensitive to grinding leading to additional EPR signals for 1 and changes in the X-ray powder diffraction patterns.

Treatment of an aqueous solution of copper(II) acetate, dafone, and KI with I2 in CH2Cl2 leads to the formation of Cu(dafone)3I12 (1). 1 crystallizes in the orthorhombic system, space group Pbcn, with a = 22.902(4) A, b = 11.104(2) A, c = 18.992(7) A, and Z = 4. Cu(dafone)32+ is the first tris chelate of dafone and is stabilized by a channel-forming network of planar I122- ions. Temperature dependence of the EPR spectrum indicates fluxionality of the cation.

Reaction of AgNO3 with excess 2-(aminomethyl)pyridine (amp) in water led to the crystallization of Ag(amp)NO3 (1). Nearly linear coordination of silver (I) by pyyridine-N and amino-N from two different amp molecules results in a polymeric chain structure of 1. The packing is stabilized by ring-ring stacking interactions between two inversion-related polymer chains. Oxidation of 1 with (NH4)2S2O8 resulted in an orange solution from which a magnetically dilute AgII complex was crystallized by the addition of NH4PF6. It gave a well-resolved EPR spectrum and is formulated as silver(II) picolinate co-crystallized with NH4PF6.

Non-bonded interactions stabilise a normal Ag(dmp)NO3 molecule and a highly distorted [Ag2(dmp)2NO3]+ in the crystal of Ag(dmp)NO3 · 2H2O. The structure consists of two complex molecules, a mononuclear Ag(dmp)NO3 and NO3 bridged dinuclear cation [Ag2(dmp)2NO3]+ . The coordination around Ag in Ag(dmp)NO3 is of a regular 3+1 type while the dinuclear cation has a highly distorted geometry. The ring-ring stacking, CH3-CH3 interactions and C-H · O H-bonding stabilise the two complex molecules.

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.

1477-9226; An end-on azido bridged MnIII coordination chain polymer [Mn(5-Clsalpn)N3]n (complex 1) and its dimeric polymorph, [Mn(5-Clsalpn)N3]2 (complex 2), where 5-Clsalpn is N,N[prime or minute]-bis(5-chlorosalicylidene)-1,3-diaminopropane, were prepared. Complex 1, which is obtained as two concomitant polymorphs (1a and 1b) with nearly identical molecular structures but different crystal packing, has [small mu ]-1,1(end-on) azido bridges. This single atom bridge is unsymmetrical and leads to a -1 cm-1 antiferromagnetic interaction among MnIII centers of the one-dimensional coordination polymer. MnIII anisotropy is manifested through Jahn-Teller elongation along the N(azido)-Mn-N(azido) axis, and results in single-chain magnet behavior. The phenoxo-bridged dimer (complex 2) has terminal azido ligands and a ferromagnetic interaction is mediated by the unsymmetrical bis-phenoxo bridge. MnIII anisotropy is manifested through Jahn-Teller elongation along an N-Mn-O axis, and results in single molecule magnet behavior. The dimers are organized into a two-dimensional network structure via ClCl and ClH-phenyl interactions which are also ferromagnetic.

[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 mixed valence Mn(III, IV) complexes, [Mn2O2L4]X3 with L=2,2-bipyridine or 1,10-phenanthroline and X=ClO 4 − or PF 6 − undergo partial ligand displacement reactions giving rise to the new compounds [Mn2O2L3A2]X3 with A=N, N-dimethylformamide or pyridine. The substitution is believed to take place at the labiled 4, Mn(III) centre. The substituted complexes have more deeply trapped valencies based on their electronic spectral characteristics. The EPR spectra are found to be essentially unaffected by ligand substitutions. Computer simulations of frozen solutions as well as polycrystalline spectra of the PF 6 − salts showing hyperfine splittings are presented. All the complexes evolve oxygen from water when present as a solid phase in contact with an aqueous solution containing Ce4+ions. The oxygen-evolving solution is found to contain MnO 4 − ions.

The reaction of (NH4)2Ce(NO3)6 and CaCl2 with dipicH2 resulted in the title compound (1). 1 crystallizes in the triclinic system, space group P1, with a = 11.234(2) A, b = 12.719(4) A, c = 16.142(4) A, α = 95.63(2)°, β = 103.73(2)°, γ = 113.83(2)°, and Z = 2. The structure consists of Ce(dipic)32- and Ca(dipicH2)(OH2)32+ ions linked by carboxylate groups forming an infinite linear chain having alternating tricapped trigonal prismatic and square antiprismatic polyhedra.

Reaction between Ag(I) salts and the three isomers of (aminomethyl)pyridines, viz., 2-amp, 3-amp, and 4-amp, lead to either discrete or polymeric (1-D and 2-D) structures influenced by anions and closed shell Ag.Ag contacts. Characterization data for Ag(2-amp)BF(4) (1) follow: monoclinic, space group C2/c, with a = 16.788(2) A, b = 11.5719(6) A, c = 11.3864(7) A, beta = 123.671(8) degrees, and Z = 8. For Ag(2)(2-amp)(3)(PF(6))(2) (2): monoclinic, space group P2(1)/a, with a = 10.029(7) A, b = 20.291(12) A, c = 13.907(6) A, beta = 95.38(5) degrees, and Z = 4. For Ag(2)(3-amp)(3)(PF(6))(2) (4): triclinic, space group P1, with a = 10.4482(7) A, b = 11.1468(9) A, c = 12.2720(11) A, alpha = 81.018(7) degrees, beta = 80.668(6) degrees, gamma = 80.977(6) degrees, and Z = 2. For Ag(4-amp)BF(4).0.75CH(3)CN (5): orthorhombic, space group C222(1), with a = 9.272(2) A, b = 16.164(12) A, c = 27.851(2) A, and Z = 8. For Ag(4-amp)PF(6) (6): monoclinic, space group P2(1)/m, with a = 5.2089(7) A, b = 14.3950(17) A, c = 7.0149(14) A, beta = 96.538(14) degrees, and Z = 2. While Ag(I) is 2-coordinate in 1, 5 and 6, it shows 3-coordination in 2 and 4. Compound 1 consists of a 1-D polymeric cation chain with interchain Ag...Ag contacts and the anions sitting on the edges of the chains. The dication in 2 is held in the form of a circular helicate by closed shell Ag...Ag interactions. Compound 4 generates a 2-D network with channels big enough to accommodate the anions. Compound 5 is a 2-D chiral network of chains connected by Ag...Ag contacts. Compound 6 shows a simple 1-D chain structure with an alternating arrangement of cationic chains and anions.

The crystal and molecular structures of [Mn(phen)-(OH2)Cl3] (1) and [Mn(acac)2(OH2)2]ClO4·2H2O (2) were determined. A comparison is made of the Jahn-Teller distortion in these compounds with those observed in other manganese(III) complexes with monodentate axial ligands.

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 trinuclear manganese complex [Mn(3)O(4)(phen)(4)(H(2)O)(2)](NO(3))(4).2.5H(2)O, 1 (where, phen = 1,10-phenanthroline), has been synthesized by the Ce(IV) oxidation of a concentrated solution of manganese(II) acetate and phen in 1.6 N nitric acid. The complex crystallizes in the triclinic space group Ponemacr; with a = 10.700(2) Å, b = 12.643(3) Å, c = 20.509(4) Å, alpha = 78.37(3) degrees, beta = 83.12(3) degrees, gamma = 82.50(3) degrees, and Z = 2. The structure was solved by direct methods and refined by least-squares techniques to the conventional R (R(w)) factors of 0.055 (0.076) based on 4609 unique reflections with F(o)/= 6.0sigma(F(o)). The structure of the cation consists of an oxo-bridged Mn(3)O(4)(4+) core, with the geometry of the manganese atoms being octahedral. The coordination polyhedron of one of the manganese atoms (Mn(1)) consists of twomgr; oxo ligands and two pairs of nitrogen atoms of two phen moieties, whereas that of each of the remaining two manganese atoms consists of threemgr;-oxo ligands, two nitrogen atoms of a phen moiety, and the oxygen atom of a water molecule. The complex represents the second example for water coordination to manganese(IV) centers in complexes with a Mn(3)O(4)(4+) core. Optical spectra in ligand buffer (pH 4.5) reveal complete conversion of the complex into a Mn(III)Mn(IV) species. The observed room-temperature (298 K) magnetic moment of 3.75mgr;(B) indicates the presence of strong antiferromagnetic coupling in the complex.

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

Mise en evidence d'une delocalisation etendue incluant l'ion nitrate. Evaluation des parametres de liaison en utilisant les parametres RPE et les energies de transition electronique. Comparaison des stabilites redox des complexes d'argent et de cuivre

The electronic structure of the manganese complex of the Schiff base, 3,5-di-tert-butyl-1,2-quinone-1-(2-oxo-3,5-di-tert-butyl-3,6-cyclohexadiene)imin radical (SQ-N-BQ; monoanionic form = Cat-N-BQ; dianionic form = Cat-N-SQ) is re-examined on the basis of single-crystal EPR studies on Mn/Zn(Cat-N-BQ) 2 . It is shown that both possibilities, viz. Mn(Cat-N-BQ) 2 (low-spin Mn 2+ ) and Mn(Cat-N-SQ) 2 (Mn 4+ , strongly antiferromagnetically coupled with two S = 1 2 ligands) can have an anisotropic manganese hyperfine coupling, albeit for different reasons.