1-D polymers with alternate Cu2 and Ln2 units (Ln = Gd, Er, Y) and carboxylate linkages

Three isostructural Cu 2Ln 2 1-D polymers [Cu 2Ln 2L 10(H 2O) 4.3H 2O] n where Ln = Gd ( 1), Er ( 2), and Y ( 3) and HL= trans-2-butenoic acid, were synthesized and characterized by X-ray crystallography, electron paramagnetic resonance, and magnetic measurements. Pairs of alternate Cu 2 and Ln 2 dinuclear units are combined into a linear array by a set of one covalent eta (2):eta (1):mu 2 carboxylate oxygen and two H bonds, at Cu...Ln distances of ca. 4.5 A. These units exhibit four eta (1):eta (1):mu 2 and two eta (2):eta (1):mu 2 carboxylate bridges, respectively. Magnetic measurements between 2 and 300 K, fields B 0 = mu 0 H between 0 and 9 T, and electron paramagnetic resonance (EPR) measurements at the X-band and room temperature are reported. The magnetic susceptibilities indicate bulk antiferromagnetic behavior of the three compounds at low temperatures. Magnetization and EPR data for 1 and 3 allowed evaluation of the exchange couplings between both Cu and Gd ions in their dinuclear units and between Cu and Gd neighbor ions in the spin chains. The data for the isolated Cu 2 units in 3 yield g || = 2.350 and g [symbol: see text] = 2.054, J Cu-Cu = -338 (3) cm (-1) for the exchange coupling [ H ex(1,2) = - J 1-2 S1 x S2], and D 0 = -0.342 (0.003) cm (-1) and E 0 = 0.003 (0.001) cm (-1) for the zero-field-splitting parameters of the triplet state arising from anisotropic spin-spin interactions. Considering tetranuclear blocks Gd-Cu-Cu-Gd in 1, with the parameters for the Cu 2 unit obtained for 3, we evaluated ferromagnetic interactions between Cu and Gd neighbors, J Cu-Gd = 13.0 (0.1) cm (-1), and between Gd ions in the Gd 2 units, J Gd-Gd = 0.25 (0.02) cm (-1), with g Gd = 1.991. The bulk antiferromagnetic behavior of 1 is a consequence of the antiferromagnetic coupling between Cu ions and of the magnitude, |J Cu-Gd|, of the Cu-Gd exchange coupling. Compound 2 displays a susceptibility peak at 15 K that may be interpreted as the combined result from antiferromagnetic couplings between Er (III) ions in Er 2 units and their coupling with the Cu 2 units.     

Two polymeric structures with a benzene-1,2,4,5-tetracarboxylate ligand acting in μ2- and μ4-bridging modes

catena-Poly[[tetraaquabis(1H-pyrazole-κN²)nickel(II)] [[diaquabis(1H-pyrazole-κN²)nickel(II)]-μ-benzene-1,2,4,5-tetracarboxylato-κ²O¹:O⁴] tetrahydrate], {[Ni(C₃H₄N₂)₂(H₂O)₄][Ni(C₁₀H₂O₈)(C₃H₄N₂)₂(H₂O)₂]·4H₂O}_n, (I), and poly[[(μ₄-benzene-1,2,4,5-tetracarboxylato-κ⁴O¹:O²:O⁴:O⁵)octakis(1H-pyrazole-κN²)dicobalt(II)] tetrahydrate], {[Co₂(C₁₀H₂O₈)(C₃H₄N₂)₈]·4H₂O}_n, (II), are polymeric compounds crystallizing in the space group P, with two independent metallic cations and one benzene-1,2,4,5-tetracarboxylate (btc) anion, each lying on symmetry centres. Individual coordination polyhedra are regular and the main differences are in the way the btc anion binds [μ₂ in (I) and μ₄ in (II)], promoting a `chain-like' one-dimensional structure in (I) and a `sieve-like' two-dimensional motif in (II).     

Three lanthanide complexes derived from itaconic acid and 2,2′‐bipyridine

The structures of three new polymeric lanthanide complexes, poly[[bis(2,2′‐bipyridine)‐μ₄‐itaconato‐di‐μ₃‐itaconato‐digadolinium(III)] tetrahydrate], {[Gd₂(C₅H₄O₄)₃(C₁₀H₈N₂)₂]·4H₂O}_n, (I), poly[diaqua(2,2′‐bipyridine)di‐μ₃‐itaconato‐μ₂‐itaconato‐digadolinium(III)], [Gd₂(C₅H₄O₄)₃(C₁₀H₈N₂)(H₂O)₂]_n, (II), and poly[[bis(2,2′‐bipyridine)‐μ₄‐itaconato‐di‐μ₃‐itaconato‐diholmium(III)] dihydrate], {[Ho₂(C₅H₄O₄)₃(C₁₀H₈N₂)₂]·2H₂O}_n, (III), have been solved from twinned specimens. Compound (I) presents a two‐dimensional polymeric structure parallel to (011) built up around two independent nine‐coordinated Gd centres displaying similar GdO₇N₂ environments, with both N‐donor atoms in each provided by a chelating 2,2′‐bipyridine (bpy) unit. The coordinating O atoms are from three different itaconate (ita) anions (itaconic acid is 2‐methylidenebutanedioic acid). Compound (II) also presents two independent Gd centres (one ten‐ and the other eight‐coordinated), but the overall formula and individual coordinations are different from those of (I). The chemical unit is in this case completed by one bpy ligand, three ita anions (one of them displaying a new, hitherto unreported, μ₃‐O,O′:O′,O′′:O′′′ binding mode) and two aqua ligands. The whole structure is built up around a twofold rotation axis passing through both cations, as well as through the centre of the bpy ligand and one of the ita anions, thus making only half of the chemical unit independent. Finally, compound (III) presents a single independent Ho centre, a bpy unit and one and a half ita anions (one of them bisected by a twofold rotation axis) in the asymmetric unit, plus two (disordered) nonbonded solvent water molecules. In compounds (II) and (III), those ita anions bisected by a symmetry element incompatible with the internal symmetry of the ligand exhibit disorder in the C=CH₂ group.     

Bottom and top AF/FM interfaces of NiFe/FeMn/NiFe trilayers

X-ray reflectivity analyses were performed in the Si/WTi (7 nm)/NiFe (30 nm)/FeMn (13 nm)/NiFe (10 nm)/WTi (7 nm) exchange-biased system prepared by magnetron sputtering under three different argon working pressures. Layer-by-layer analyses were realized in order to obtain the interfacial roughness parameters quantitatively. For a fixed argon pressure, the root-mean-square roughness (including the atomic grading) of the upper (FeMn/NiFe) interface are greater than that for the lower one in all studied samples. Argon working pressure also has severe influence over the NiFe/FeMn interfaces, being more pronounced at the upper interfaces.     

Single Crystal XRD Structure Determination and Analysis of Bis(2,9-Dimethyl-1,10-Phenanthroline-κ2N,N′)(Sulfato-κ2O,O′)Nickel(II), Hydrate (NiNeo2SO4·H2O; Neo: 2,9-Dimethyl-1,10-Phenanthroline)

Abstract  

The title compound is monomeric with a Ni(II) hexacoordinated center. The coordination sphere is formed with four nitrogens from two neocuproine molecules and two oxygens from a sulfate ion that acts as a bidentate ligand. A water molecule completes the formula with an important role in the stabilization of the structure through the formation of O_W–H···O_S bridges, in which it acts as a donor and interactions of the type C_ar–H···O_W and C_Met–H···O_W, where it is an acceptor group (W: water; S: sulfate; ar: arene; Met: methyl). The compound is monoclinic, space group P2₁ /c with a = 14.4829(4) ?, b = 14.4563(4) ?, c = 12.1559(3) ?, β = 94.407(1)°, V = 2,537.55(12) ?³ and Z = 4. The structure was solved by direct methods with a conventional R (on F) = 0.0359 for 4841 reflexions with Fo > 4σ(Fo). Three levels of super-structural hierarchy can be identified in the crystal construction: (1) the primary structure corresponding to the molecular skeletons of their building blocks, the isolated complex itself and the water molecule, (2) an 1D supramolecular array that form chains through a non-covalent polymerization via interactions O_W–H···O_S, C_ar–H···O_W, C_ar–H···O_S and C_Met–H···O_W and (3) finally the 3D macroscopic conglomerate formed through inter-chains interactions C_ar–H···O_W, C_ar–H···O_S, C_Met–H···ar and offset stacked arene–arene.     

Monodentate and bridging behaviour of the sulfur‐containing ligand 4′‐[4‐(methylsulfanyl)phenyl]‐4,2′:6′,4′′‐terpyridine in two discrete zinc(II) complexes with acetylacetonate

The Zn complexes bis(acetylacetonato‐κ²O,O′)bis{4′‐[4‐(methylsulfanyl)phenyl]‐4,2′:6′,4′′‐terpyridine‐κN¹}zinc(II), [Zn(C₅H₇O₂)₂(C₂₂H₁₇N₃S)₂], (I), and {μ‐4′‐[4‐(methylsulfanyl)phenyl]‐4,2′:6′,4′′‐terpyridine‐κ²N¹:N^1′′}bis[bis(acetylacetonato‐κ²O,O′)zinc(II)], [Zn₂(C₅H₇O₂)₄(C₂₂H₁₇N₃S)], (II), are discrete entities with different nuclearities. Compound (I) consists of two centrosymmetrically related monodentate 4′‐[4‐(methylsulfanyl)phenyl]‐4,2′:6′,4′′‐terpyridine (L1) ligands binding to one Zn^II atom sitting on an inversion centre and two centrosymmetrically related chelating acetylacetonate (acac) groups which bind via carbonyl O‐atom donors, giving an N₂O₄ octahedral environment for Zn^II. Compound (II), however, consists of a bis‐monodentate L1 ligand bridging two Zn^II atoms from two different Zn(acac)₂ fragments. Intra‐ and intermolecular interactions are weak, mainly of the C—H...π and π–π types, mediating similar layered structures. In contrast to related structures in the literature, sulfur‐mediated nonbonding interactions in (II) do not seem to have any significant influence on the supramolecular structure.     

Bis(2,2′:6′,2′′-ter­pyridine-κ3N)­manganese(II) tetra­thionate trihydrate

The structure of the title compound, [Mn(tpy)₂](S₄O₆)·3H₂O (tpy is 2,2′:6′,2′′-ter­pyridine, C₁₅H₁₁N₃), consists of monomeric [Mn(tpy)₂]²⁺ units embedded in a complex anionic network made up of tetra­thionate ions and hydration water mol­ecules connected via a complex hydrogen-bonding scheme.     

Bis­(acetato‐κ2O,O′)(2,9‐di­methyl‐1,10‐phenanthroline‐κ2N,N′)mercury(II) in two differently hydrated crystal forms

Two differently hydrated crystal forms of the title compound, viz. bis­(acetato‐κ²O,O′)(2,9‐di­methyl‐1,10‐phenanthroline‐κ²N,N′)­mercury(II), [Hg(C₂H₃O₂)₂(C₁₄H₁₂N₂)] or [HgAc₂(dmph)] [dmph is 2,3‐di­methyl‐1,10‐phenantroline (neocuproine) and Ac is acetate], (I), and tris­[bis­(acetato‐κ²O,O′)(2,9‐di­methyl‐1,10‐phenanthroline‐κ²N,N′)­mercury(II)] hexadecahydrate, [Hg(C₂H₃O₂)₂(C₁₄H₁₂N₂)]₃·16H₂O or [HgAc₂(dmph)]₃·16H₂O, (II), are presented. Both structures are composed of very simple monomeric units, which act as the building blocks of complex packing schemes stabilized by a diversity of π–π and hydrogen‐bonding interactions.