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A series of lanthanide dinuclear complexes and chains incorporating two derivatives of cinnamic acid (2-methoxycinnamic acid and 3-methoxycinnamic acid) have been synthesized and characterized by elemental analyses, Infra-Red Spectroscopy, X-ray diffraction, photoluminescence and magnetic measurements. The use of the 2-methoxycinnamic ligand enables the synthesis of two dinuclear complexes (Eu3+ (1), Tb3+ (2)), while the presence of 3-methoxycinnamic acid induces the formation of one-dimensional coordination polymers (Eu3+ (3), Gd3+ (4)). Investigations of the magnetic properties reveals a field-induced slow relaxation of the magnetization for the gadolinium analogue 4, whereas the characteristic Eu3+ luminescence is observed for the europium-based materials 1 and 3.

International audience; The present study deals with the synthesis and characterization by single-crystal X-ray analysis and IR spectroscopy of two new Copper (II) complexes with bidentate Schiff base ligand [N'-(propan-2-ylidene) thiophene-2-carbohydrazide] (HL). Depending on the copper salt used in the synthesis, a mononuclear or doubly chloro bridged dinuclear Copper (II) complexes of respective formula [Cu(L) 2 ] (1) and [Cu 2 (μ-Cl) 2 (HL) 2 Cl 2 ] (2) have been obtained. Magnetic study of complex 2 indicates the presence of weak antiferromagnetic interactions between the metal centers. To determine the antioxidant properties of both complexes, the ABTS radical scavenging and the reduction of copper (II)-neocuproine [Cu(II)-Nc] (CUPRAC) methods were used; 1 was more efficient than 2, for the two antioxidants assays. Lastly, Anti AChE activity method has been used to estimate in vitro anti-Alzheimer effect of 1 and 2 both of which show a potent AChE inhibition.

Two novel tridentate Schiff-base ligands containing carboxylate groups were obtained from the condensation of 3-amino-4-hydroxybenzoic acid with either acetylacetone (H3L1) or salicylaldehyde (H3L2). H3L1 reacted with copper(II) acetate and pyridine (strongly coordinating solvent) to afford the C1 complex, while reaction of H3L2 with nickel(II) acetate and pyridine afforded two types of complexes C2 and C3. The two ligands and their metal complexes were fully characterized by elemental analysis, XRD and spectroscopic analysis. Upon its fully deprotonated state, (L1)3− coordinates in a keto-enamine fashion and acts as a ditopic binder through an ONO tridentate donor system and an O monodentate donor system (carboxylate). Upon its doubly deprotonated state, (HL2)2− ligand acts either as monotopic tridentate binder (i.e. enol-imine form with an ONO donor system that lead to complex C2) or as a ditopic ligand (ONO tridentate and O monodentate donor systems to afford complex C3). The molecular structure of all the compounds were determined by single crystal X-ray diffraction studies and revealed several important characteristics. In complex C1, the Cu(II) cations are five-coordinated with a slightly distorted square pyramidal geometry, while in C2 and C3 complexes, the Ni(II) ions are four and six–coordinated with a square planar and a slightly distorted octahedral geometry, respectively. Following this structural investigation, the antioxidant activities of the free ligands and their metal complexes were then investigated and demonstrated interesting antioxidant features especially for H3L2 and complex C3. Lastly, temperature dependent magnetic susceptibility measurements showed the presence of ferromagnetic interactions in C1 mediated through the phenoxido bridges.

The authors thank the University of Montpellier, CNRS,MESRS (Algeria) for financial support and PAC of ICGM formagnetic measurements.; International audience; We report an investigation on the synthesis, structure and magnetic properties of a series of heteroleptic Zn2+/Ln3+ complexes of the general formula [ZnLClLn(o-van)(H2O)(NO3)]·H2O (H2L = N,N′-bis(3-methoxysalicylidene)-1,2-diaminoethane; o-van = o-vanillinate; Ln = Tb (1), Dy (2), Er (3)). All the compounds exhibit a slow relaxation of their magnetization and the dysprosium analogue shows one of the highest anisotropic barriers for ZnDy complexes.

Reaction of nickel chloride with acetylacetone bis(salicylhydrazone) (L) (prepared in situ by condensation of acetylacetone with salicylhydrazide) in methanol results in the formation of air-sensitive nickel (II) complex of symmetrical tetradentate Schiff base [NiII(L)] (1). Air oxidation of 1 leads to the formation of dinuclear species [NiII(L-L)NiII] (2) where the ligand (L-L)4– is formed by oxidative C-C coupling at the central methylene group of the acetylacetone fragment of (L)2–. The same reaction in methanol/pyridine solution leads to oxidative C-N coupling forming a mesoionic [NiII(L-Py)](3). The use of Nickel acetylacetonate in methanol/pyridine or DMSO solution under aerobic conditions provide [NiII(L-O)(py)2](4), [NiII(L-O)(DMSO)2](5). In this case, the ligand (L)2– is partially oxidized to form (L-O) which is formed by oxidation of the central methylene group. The molecular structure of 1–5 have been determined by X-ray crystallography. The first three complexes 1, 2 and 3 have a square-planar geometry, while, 4 and 5 adopt octahedral geometry. In vitro antioxidant activities of compounds 1, 4 and 5 were evaluated against DPPH radical and hydrogen peroxide and were compared with standard antioxidant, ascorbic acid. Our results reveal that the three compounds exhibit excellent radical scavenging activities. DFT calculations have been performed on complexes 1–5 using the BP86 and B3LYP functionals to provide a complete rationalization of their structures and to describe their electronic structures elucidating the fundamental spin state and the Metal-Ligand interaction type.

We report here the synthesis and investigation into the magnetic properties of a luminescent trinuclear Zn2Dy Schiff-base complex that exhibits a zero-field single-molecule magnet behaviour. Magneto-structural correlation confirms that the axial crystal-field is generated by the phenoxide moieties while the characteristic Dy3+-based luminescence is observed.

Discrete and extended architectures based on the association of lanthanide ions with two derivatives of cinnamic acid (2-methoxycinnamic acid and 3-methoxycinnamic acid) have been synthesized and characterized by IR spectroscopy, elemental analyses, X-ray diffraction and magnetic measurements. The use of the 2-methoxycinnamic ligand enables the synthesis of a series of dinuclear complexes (Ce3+ (1), Nd3+ (2), Gd3+ (3), Dy3+ (4)), while the presence of 3-methoxycinnamic acid induces the formation of one-dimensional coordination polymers (Ce3+ (5), Nd3+ (6), Dy3+ (7)). Investigations of the magnetic properties of the complexes reveal that they all exhibit field-induced slow relaxation of the magnetisation, mainly induced by Raman and direct relaxation processes.

Two new complexes [MnIII(HL)2(acac)] and [MnII(HL)2]n have been obtained by reacting manganese(III) acetylacetonate monohydrate or manganese(II) chloride monohydrate with 2-salicylichydrazono-1,3-dithiolane ligand (H2L). Both compounds have been fully characterized by spectroscopic methods and single crystal X-ray diffraction. In the solid state, the molecular packing are described and discussed in term of weak H-bonds and short contacts. The unprecedented bridging coordination mode of this ligand lead to the first 2-salicylichydrazono-1,3-dithiolane-bridged coordination polymer [MnII(HL)2]n. The EPR spectrum of this compound was obtained with g ≈ 2.07, corresponding to a manganese ion (+II) in octahedral high-spin coordination sphere. The MnII complex exhibit paramagnetic behavior corresponding to quasi-isolated metal centers.

Three new transition metal complexes, [Cu(L-cyst)(dmbpy)(H 2 O)] ( 1 ), [Mn(dmbpy) 2 (N 3 )(Cl)] ( 2 ) and [Co(dmbpy) 3 ].[CoCl 4 ].Cl.7H 2 O ( 3 ) with (L-cyst = L-cysteic acid, dmbpy = 4,4’-dimethyl-2,2’-bipyridine, N 3 = azide) have been synthesized and characterized by elemental analysis, thermal analysis (DTA/TGA), IR spectroscopy and single crystal X-ray diffraction (XRD). In the complex 1 , the copper atoms are five-coordinated in a distorted square pyramidal site. It forms monomeric species, which are further connected into a three-dimensional supramolecular network through hydrogen bonding interactions. In the complex 2 , the manganese atoms have a distorted octahedral environment with four nitrogen atoms of the two dmbpy , one nitrogen atom provided from azide ligand, the coordination sphere being completed by a chlorine atom. ( 2 ) is also a monomeric complex and the molecular structure of compound 2 is stabilized by non standard weak C-H…Cl hydrogen-bonds. The asymmetric unit of the complex 3 is built of two cobalt-containing fragments: the cationic [Co II (dmbpy) 3 ] +2 and the anionic (Co II Cl 4 ) −2 groups. The molecular structure of compound 3 is stabilized by hydrogen bonds via O-H…O, O-H…Cl and C-H…Cl interactions. The thermal decompositions for 1 and 3 in the temperature range 30–1000 °C has revealed that the Cu complex decomposes in three steps whereas Co complex decomposes in four steps and transforms into the corresponding metal oxide.

We report the synthesis and molecular solid-state structures of five novel CoII and CoIII mononuclear complexes supported by the 2-salicyloylhydrazono-1,3-dithiolane (L1) and 2-salicyloylhydrazono-1,3-dithiane (L2) ligands. Moreover, one novel diamagnetic μ-oxo dinuclear CoIII complex [CoIII2(HL)4(μ-O)2] supported by the ligand L1 was stabilized and characterized. Crystal structure of the supporting ligand L2 was also determined.

Single crystals of new open-framework lanthanide sulphate nitrite La(NO2)(SO4)(H2O) has been synthesized, in the presence of 2,6-diformyl-4-chlorophenol. His structure has been determined by X-ray diffraction data: the complex crystallizes in the tetragonal system, space group P43, with a = 7.0028(2) (A), b = 7.0028(2) (A), c = 11.8341(4) A, V = 580.34(3) A3, Z = 4, D c = 3.582 Mg m−3. The three-dimensional (3D) framework of this compound is built up by the linkages of lanthanide atoms and the oxygen atoms of the sulphate $$ {\left( {{\text{SO}}^{{{\text{2}} - }}_{{\text{4}}} } \right)} $$ and nitrite $$ {\left( {{\text{NO}}^{ - }_{{\text{2}}} } \right)} $$ groups. The lanthanum atom is 9-fold coordinated. The structure is unfamiliar in lanthanide chemistry and this compound represents the first example of nitrite lanthanide sulphate complex. An unfamiliar structure in lanthanide chemistry represented by the first example of nitrite lanthanide sulphate complex is described.

Two polynuclear transition-metal complexes, [CoII3(cinna)6(phen)2] (1), [CuII2(cinna)2(phen)2(NO3)(H2O)]NO3·CH3OH (2), where cinna = trans-cinnamate, PhCH = CHCO2− and phen = 1,10-phenanthroline, have been synthesized and characterized by elemental analyses, infrared spectroscopy, single-crystal X-ray diffraction (XRD) and magnetic measurements. 1 contains two independent geometrical isomers of [Co3(cinna)6(phen)2], where the cobalt atoms form a linear spine bridged by carboxylate from cinnamate radiating perpendicular to it, the 1,10-phenanthroline chelating the ends. Weak C H···O hydrogen bonds in two directions generate a bidimensional network. 1 behaves as a paramagnet due to the absence of magnetic exchange between the trimers in the absence of chemical bonds between trimers. 2 contains a positively charged dimer of copper ions bridged to two cinnamate in syn–syn mode with two almost parallel phenanthroline molecules chelating the two copper ions, while a water molecule and one NO3− coordinate their axial positions. The dimer is described as a pincer molecule. Weak O H···O and C H···O hydrogen bonds and π–π stacking interactions are consistent with a description of a supramolecular assembly of dimers. The exchange coupling within the doubly-bridged copper atoms is antiferromagnetic (J = −153(1) K).

The new Mn ( HL ) 2 L 2 ′ complexes with 2-salicyloylhydrazono-1,3-dithiolane ligand (H2L) have been obtained with good yields (≈85%) by reacting manganese (II) acetate tetrahydrate or manganese (II) acetylacetonate with 2-salicyloylhydrazono-1,3-dithiolane ligand in DMF, THF or Py (L′). These compounds have been fully characterized by spectroscopic methods and single crystal X-ray diffraction. In the solid state, supramolecular networks are described and discussed in terms of weak H-bonds and short contacts. The new monomeric complexes will be considered as candidates to obtain polynuclear complexes.

A new chiral 3D metal-organic coordination polymer [Cd((S)-mal)] (mal = malic acid), has been solvothermally synthesized and characterized by elemental analysis, IR, TG and single crystal X-ray diffraction. Colorless crystals crystallize in the orthorhombic system, space group P212121, a = 6.804(1), b = 8.488(2), c = 9.997(3) A, V = 577.35 (2) A3, Z = 4 and R1 = 0.0298. The structure of the compound exhibits a chiral 3D covalent framework based on chiral bridging ligands, the coordination environment around the CdII is pentagonal bipyramidal.

The structure of the title compound, (C5H7N5)2[SnCl6]Cl2·4H2O, can be described as alternating layers of C5H7N52+ and [SnCl6]2− ions along the b axis, the SnIV atom lying on a twofold axis. The chloride ions are located between the organic entities, forming hydrogen bonds with the N atoms and water molecules. Layers of adeninium cations and hexa­chloro­stannate anions are linked by anion–cation, cation–water and water–water hydrogen bonds. This three-dimensional complex network of hydrogen bonds ensures the cohesion of the ionic structure.

The title compound, {[Co(C10H8N2)2(H2O)2](NO3)2·4H2O} n , (C10H8N2 = 4,4'-bipyridine = 4,4'-bpy) is a layered coordination polymer built up from a cationic square grid extending in (101) enclosing uncoordinating nitrate ions and water mol-ecules. The Co(II) ion has site symmetry 2 and one of the 4,4'-bpy ligands is generated by twofold symmetry [two N atoms and two C atoms lie on the rotation axis and the dihedral angle between the pyridine rings is 45.66 (5)°]. The other 4,4'-bpy ligand is generated by a crystallographic inversion center. The Co(II) ion exhibits a slightly distorted octa-hedral coordination geometry defined by two O atoms of two coordinating water mol-ecules and four N atoms from four bridging 4,4'-bpy ligands. The structure is consolidated by O-H⋯O, C-H⋯O and C-H⋯N hydrogen bonds.

The title compound, [Ni(C5H7O2)2(C5H5N)2]·2H2O, crystallizes with two half-molecules in the asymmetric unit. The NiIIion of each unique complex molecule lies on an inversion centre and has an octahedral coordination geometry. The crystal structure features weak O—H...O hydrogen bonds, which form chains running parallel to theaaxis.

The title compound, C14H9Cl2N, a derivative of benzo­quinoline, is a tricyclic planar nitro­gen heterocyclic system.

In the title complex, [Cu(C(9)H(7)N(2)O(2)S)(2)], the Cu(II) ion, located on an inversion center, adopts an N(2)O(2) square-planar coord-ination. The 2-(5-methyl-sulfanyl-1,3,4-oxadiazol-2-yl)phenolate ligand is chelated to the central Cu(II) ion in an N,O-bidentate manner.