Laura Valencia

Synthesis and helical polymeric structure of a luminescent pendant-armed macrocyclic silver(I) complex with Ag–Ag interactions

An interesting 1D helical chain complex has been obtained with silver(I) nitrate and a tetrapyridyl pendant-armed macrocyclic ligand (L) in acetonitrile. The X-ray crystal structure of the complex, which has the formula ([Ag3L(NO3)](NO3)2·8H2O)∞, presents silver–silver interactions in an infinite spiral chain structure that is unprecedented in such pyridyl macrocyclic complexes. The structure forms a large cavity or channel that contains the silver(I) ions and presents face-to-face π,π-stacking between the pyridyl rings. The complex shows fluorescence in the solid state and acetonitrile solution at room temperature.

Synthesis and characterisation of silver, zinc and cadmium compounds with an N3O2 Schiff base macrocycle: the crystal and molecular structures of the silver(I) and cadmium(II) complexes

Abstract The metal-templated cyclocondensation of 2,6-diformylpyridine and 1,4-bis(2-aminophenoxy)butane in the presence of silver(I), zinc(II) and cadmium(II) salts gave the following di-imine macrocyclic complexes: [AgL](ClO4) (1), [ZnL](ClO4)2·2H2O (2), [ZnL](NO3)2 (3), [CdL(H2O)2](ClO4)2 (4) and [CdL(NO3)(CH3OH)](NO3) (5) (L=macrocyclic ligand). All compounds have been characterised by microanalysis, IR, conductivity measurements, MS-FAB and 1H NMR spectroscopic studies. Compounds 1, 4 and 5 were also studied by single-crystal X-ray diffraction.

Synthesis of a new tetra-cyanomethylated macrocyclic ligand with a nanotubular structure. X-Ray crystal structures of mono-, di-nuclear and polymeric metal complexes

A new pendant-armed macrocyclic ligand, L1, bearing four cyanomethyl pendant groups has been synthesized by N-alkylation of the tetraazamacrocyclic precursor L with bromoacetonitrile. The X-ray structural analysis of the ligand L1 shows the formation of tubular arrays, and reveals intra- and inter-molecular π-stacking interactions between the pyridyl groups of the macrocyclic backbone. Metal complexes of L1 have been synthesized and characterized by microanalysis, MS-FAB, conductivity measurements, IR, UV-Vis, 1H and 13C NMR spectroscopy and magnetic studies. Crystal structures of the ligand L1 as well as of the complexes [ZnL1](NO3)2·2H2O, [Ag2L1(NO3)2] and [Ag2L1](ClO4)2·4CH3CN have been determined by single crystal X-ray crystallography. Different macrocyclic disposition has been found in relation to the metal ion employed and even when different salts of the same metal are used. The X-ray studies show the presence of two metal atoms within the macrocyclic ligand in [Ag2L1(NO3)2] and [Ag2L1](ClO4)2·4CH3CN showing a monomeric and a polymeric nature respectively. The crystal structure of [ZnL1(NO3)2]·2H2O shows a mononuclear endomacrocyclic complex with the metal ion coordinated to the six nitrogen atoms in a distorted octahedral environment.

Magnetic Anisotropies in Rhombic Lanthanide(III) Complexes Do Not Conform to Bleaney’s Theory

We report a complete set of magnetic susceptibilities of lanthanide complexes with a macrocyclic ligand based on a 3,6,10,13-tetraaza-1,8(2,6)-dipyridinacyclotetradecaphane platform containing four hydroxyethyl pendant arms (L(1)). The [LnL(1)](3+) complexes are isostructural along the lanthanide series from Ce(3+) to Yb(3+), with the only structural change observed along the series being the monotonous shortening of the Ln-donor distances due to lanthanide contraction. The (1)H NMR spectra point to a D2 symmetry of the [LnL(1)](3+) complexes in aqueous solution, which provides a unique opportunity for analysis of the rhombic magnetic anisotropies with an unequivocal location of the magnetic axes. The contact contributions for the observed paramagnetic shifts have been estimated with density functional theory calculations on the [GdL(1)](3+) complex. Subsequently, the pseudocontact shifts could be factored out, thereby giving access to the axial and rhombic contributions of the magnetic susceptibility tensor. Our results show that the calculated magnetic anisotropies do not follow the trends predicted by Bleaneys theory, particularly in the case of Ho(3+) and Er(3+) complexes.

A hexaaza macrocyclic ligand containing acetohydrazide pendants for Ln(III) complexation in aqueous solution. Solid-state and solution structures and DFT calculations

Lanthanide complexes of a hexaaza macrocyclic ligand containing acetohydrazide pendants (L) have been synthesised (Ln = La-Er, except Pm), and structural studies have been carried out both in the solid state and in aqueous solution. Attempts to isolate the complexes of the heaviest Ln(iii) ions (Ln = Tm-Lu) were unsuccessful. The crystal structures of the ligand and its lanthanum complex have been determined by single-crystal X-ray crystallography. The X-ray crystal structure of [La(L)](3+) shows the metal ion being ten-coordinate, with the acetohydrazide pendants situated alternatively above and below the plane of the macrocycle. The two five membered chelate rings formed by the ethylenediamine moieties adopt (deltadelta) [or (lambdalambda)] conformations. The [Ln(L)](3+) complexes have been characterised by means of density-functional theory (DFT) calculations (B3LYP model). The structures obtained from these theoretical calculations are in very good agreement with the experimental solution structures, as obtained from paramagnetic NMR measurements on the Ce(iii), Pr(III), Nd(III) and Eu(III) complexes. The complexes adopt in aqueous solution a D(2) structure with the ligand adopting a (deltadelta) [or (lambdalambda)] conformation.

Synthesis of perchlorate metal complexes with a new tetrapyridyl pendant armed macrocyclic ligand

Abstract A new pendant-armed macrocyclic ligand, L1, bearing four pyridyl pendant groups has been synthesized by N-alkylation of the tetraazamacrocyclic precursor L with picolyl chloride hydrochloride. Metal complexes of L1 using hydrated perchlorate salts of transition and post-transition metal ions have been synthesized and characterized by microanalysis, MS FAB, conductivity measurements, IR, UV–Vis, 1H and 13C NMR spectroscopy and magnetic studies. When Ni(II) or Cd(II) perchlorate salts are used 1:1 metal complexes are obtained, whereas with Co(II) or Ag(I) salts the 2:1 metal:ligand complexes are obtained. Nevertheless when Cu(II) or Zn(II) salts are employed 1:1 and 2:1 complexes are obtained depending on the stoichiometry of the reaction. Crystal structures of the ligand L1 as well as of the complexes [NiL1](ClO4)2·2H2O, [CuL1](ClO4)2·2H2O, [Cu2L1(CH3CN)2](ClO4)4·2CH3CN, [ZnL1](ClO4)2·4H2O, [CdL1](ClO4)2·2CH3CN and [Ag2L1](ClO4)2·2CH3CN have been determined. The X ray studies show the presence of two metal atoms within the cavity of the macrocyclic ligand in [Ag2L1](ClO4)2·2CH3CN, whilst in [Cu2L1](ClO4)4·4CH3CN the copper atoms are coordinated exocyclically to the nitrogen atoms from the pendant arms of the ligand. The crystal structures of [NiL1](ClO4)2·2H2O, [CuL1](ClO4)2·2H2O, [ZnL1](ClO4)2·4H2O and [CdL1](ClO4)2·2CH3CN show mononuclear endomacrocyclic complexes with the metal ion coordinated to six nitrogen atoms in a distorted octahedral environment.

Lanthanide(III) complexes of two oxaazadiamine macrocyclic ligands derived from 2,6-diformylpyridine: the crystal structures of a reduced macrocyclic ligand and the corresponding diprotonated macrocycle

Abstract New macrocyclic lanthanide(III) complexes were obtained with two oxaazadiamine macrocycles derived from 2,6-diformylpyridine: (i) mononuclear complexes of an 18-membered sexidentate N3O3 macrocyclic (L1) derived from 1,5-bis(2-aminophenoxy)-3-oxapnetate; (ii) mononuclear complexes of a 16-membered pentadentate N3O2 macrocycle (L2) derived from 1,3-bis(2-aminophenoxy)propane. The complexes were characterized by elemental analysis, molar conductivity, mass spectrometry, IR and 1H NMR spectroscopy, thermogravimetry and magnetic measurements. The crystal structures of the L2 macrocycle and the corresponding diprotonated ligand are also reported.

Structural, MALDI-TOF-MS, magnetic and spectroscopic studies of new dinuclear copper(II), cobalt(II) and zinc(II) complexes containing a biomimicking μ-OH bridge.

The Py(2)N(4)S(2) octadentate coordinating ligand afforded dinuclear cobalt, copper and zinc complexes and the corresponding mixed metal compounds. The overall geometry and bonding modes have been deduced on the basis of elemental analysis data, MALDI-TOF-MS, IR, UV-vis and EPR spectroscopies, single-crystal X-Ray diffraction, conductivity and magnetic susceptibility measurements. In the copper and zinc complexes, a μ-hydroxo bridge links the two metal ions. In both cases, the coordination geometry is distorted octahedral. Magnetic and EPR data reveal weakly antiferromagnetic high spin Co(II) ions, compatible with a dinuclear structure. The magnetic characterization of the dinuclear Cu(II) compound indicates a ferromagnetically coupled dimer with weak antiferromagnetic intermolecular interactions. The intra-dimer ferromagnetic behaviour was unexpected for a Cu(II) dimer with such μ-hydroxo bridging topology. We discuss the influence on the magnetic properties of non-covalent interactions between the bridging moiety and the lattice free water molecules.

Synthesis and characterisation of cobalt, nickel, zinc and cadmium compounds with a pyridine-derived N3O2 macrocycle: Crystal and molecular structures of the macrocyclic ligand and Co(II), Ni(II) and Zn(II) complexes

Abstract The interaction of Co(II), Ni(II), Zn(II) and Cd(II) with L, a macrocycle containing an N 3 O 2 -donor set, has been investigated. The X-ray crystal structures of L, [Co L (NO 3 ) 2 ] ( 1 ), [Ni L (NO 3 ) 2 ] ( 2 ) and [Zn L (H 2 O)(CH 3 CN)](ClO 4 ) 2 ( 5 ) have been determined. The metal atoms in the complexes are coordinated in an endomacrocyclic fashion with the Co and Ni atoms in six-coordinate environments comprised of the ligand N 3 -donor set and two nitrate ions, one monodentate and the other bidentate, giving a distorted octahedral geometry at the metal. In the Zn complex the metal is in a five-coordinate environment comprised of the ligand N 3 -donor set, a water molecule and an acetonitrile molecule, giving a trigonal bipyramidal geometry around the metal.

Synthesis and characterization of a series of transition metal complexes with a new symmetrical polyoxaaza macroacyclic Schiff base ligand: X-ray crystal structure of cobalt(II) and nickel(II) complexes and their antibacterial properties

A new symmetrical [N4O2] hexadentate Schiff base ligand, (E)-N-(pyridin-2-ylmethylene)-2-(3-(2-((E)-pyridin-2-lmethyleneamino)phenoxy)naphthalen-2-yloxy)benzenamine, abbreviated to L, and its complexes of Ni(II), Cu(II), Zn(II), Co(II), Cd(II) and Mn(II) have been synthesized in the presence of metal ions. The complexes were structurally characterized by elemental analyses, IR, UV-Vis, NMR and molar conductivity. The crystal structures of two complexes, [NiL(ONO2)2]·2H2O and [CoLCl2]CH3OH·0.5H2O, have been determined by a single crystal X-ray diffraction study. In these complexes, the ligand is coordinated in a neutral form via pyridine and azomethine nitrogen atoms. The metal ions complete their six coordination with two coordinated nitrate or chloride ions, forming a distorted octahedral geometry. The synthesized compounds have antibacterial activity against the three Gram-positive bacteria: Enterococcus faecalis, Bacillus cereus and Staphylococcus epid and also against the three Gram-negative bacteria: Citrobacter freundii, Enterobacter aerogenes and Salmonella typhi. The activity data show that the complexes are more potent antibacterials than the parent Schiff base.