Alejandro Macías

Synthesis and characterisation of four novel NxOy-Schiff-base macrocyclic ligands and their metal complexes

Macrocyclic Schiff-bases, L1 and L2, and bis-macrocyclic ligands, L3 and L4, have been prepared by [1 + 1] and [2 + 1] cyclocondensation of 1,7-bis(2′-formylphenyl)-1,4,7-trioxaheptane or 2,6-bis(2-formylphenoxymethyl)pyridine with 2,6-bis(o-aminophenoxymethyl)pyridine or 1,2,4,5-tetraaminebenzene · 4HCl, respectively. The related YIII, MII (M=Co, Ni, Zn, Cd or Pb) and LnIII nitrate or perchlorate complexes have been synthesised following a template procedure, demonstrating the effectiveness of these metal ions to promote the assembly of these four symmetric Schiff-base macrocycles. The complexes were characterised by elemental analyses, molar conductivity, mass spectrometry, i.r., u.v.–vis, and 1H-n.m.r spectroscopy.

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 Characterization of Some Metal Complexes with New Nitrogen–Oxygen Donor Macrocyclic Ligands – X‐ray Crystal Structures of a 26‐Membered Reduced Monoprotonated Macrocycle and a 20‐Membered Pendant‐Arm Schiff‐Base Macrocyclic Cadmium(II) Complex

New series of macrocyclic Schiff-base lanthanide(III), yttrium(III), and cadmium(II) complexes, [M(1)]Xn (X = NO, M = Y, Ln = La–Yb except Pm and Dy; X = ClO, M = Cd, La, Ce, Pr, Sm, Gd, or Er) and [M(3)]Xn (X = NO, M = Dy; X = ClO, M = Er and Cd), have been prepared by cyclocondensation of O1,O7-bis(2-formylphenyl)-1,4,7-trioxaheptane with O1,O7-bis(2-aninyl)-1,4,7-trioxaheptane (1) or tris(2-aminoethyl)amine (3) in the presence of the appropriate metal salt as a template agent. The Schiff-base macrocycles 1 and 3 are also formed in the absence of a metal ion. Treatment of 1 with NaBH4 in methanol gives the diamine macrocycle 2. The reactions of LnIII, CdII, and YIII ions with 2 have also been investigated. The crystal structures of the monoprotonated ligand 2 and of the complex [Cd(3)](ClO4)2 have been determined by X-ray diffraction analysis.

Electrochemical synthesis of metal(II) complexes of schiff bases: the crystal structure of acetonitrile-bis{2-[(2-pyrrole)methylimino]-4,6-dimethylphenolato}zinc(II)

Abstract The electrochemical oxidation of anodic metals (Co, Ni, Cu, Zn and Cd) in acetonitrile solution containing a Schiff base (H2L) derived from H-pyrrole-2-carbaldehyde and a substituted o-aminophenol yielded the complexes M(HL)2 and acetonitrile-bis{2-[(2-pyrrole)methylimino]-4,6-dimethylphenolato}zinc(II). X-ray data show the latter to have a distorted bipyramidal coordination polyhedron that does not include the pyrrole nitrogen atoms

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.

The synthesis of zinc(II) complexes of 2-(2-mercaptophenyl)-iminophenol by electrochemical cleavage of a disulfide bond; the crystal structure of {(2, 2′-bipyridine)[2-(2-mercaptophenyl)iminophenoxy]}zinc(II)

Abstract The electrochemical oxidation of anodic zinc in an acetonitrile solution of the Schiff base derived from the required salicylaldehyde and bis-(2-aminophenyl)disulfide, L 2 H 2 , yields compounds having the formulation ZnL. When 1,10-phenanthroline (phen) or 2, 2′-bipyridine (bipy) is added to the electrolytic phase [ZnLphen] or [ZnLbipy] are obtained. The crystal structure of {2, 2′-bipyridine[2-(2-mercaptophenyl)]iminophenoxy}zinc(II) [ZnL 1 bipy] has been determined. The compound crystallises in the triclinic space group P 1(No. 1) with two molecules in the unit cell and cell constants a = 6.526(2), b = 11.686(3), c = 13.346(4)A; α = 107.72(2), β =92.08(2), γ = 91.79(2)°. The zinc atom has a distorted trigonal bipyramidal geometry. The IR and 1 H NMR spectra of complexes are discussed and related to the structure.

Comparative structural study of dimethyl(pyridine-2-thiolato)thallium(III) and dimethylbis(pyridine-2-thiolato)tin(IV)

The crystal structures of the [TlMe2L] and [SnMe2L2](L = pyridine-2-thiolate) have been determined. Dimethyl(pyridine-2-thiolato)thallium(III) crystallizes in the monoclinic space group P21/n(no 14) with a= 8.169(1), b= 13.214(1), c= 8.876(2)A, β= 104.61 (1)°, and Z= 4. Refinement converged to R= 0.047 for 1 531 independent observed reflections. The thallium atom co-ordinates to the two methyl carbons [Tl–C 2.159(8) and 2.199(8)A], to the pyridine nitrogen [Tl–N 2.494(7)A], and to two sulphur atoms [Tl–S 3.160(3) and 2.870(2)A]. Dimethylbis(pyridine-2-thiolato)tin(IV) crystallizes in the monoclinic space group P21/m(no 11) with a= 6.664(5), b= 17.342(5), c= 6.943(3)A, β= 112.53(5)°, and Z= 2. Refinement converged to R= 0.038 for 1 105 independent observed reflections. The tin atom co-ordinates to the two methyl carbons [Sn–C 2.133(9)A], the two pyridine nitrogens [Sn–N 2.702(5)A], and the two sulphur atoms [Sn–S 2.487(2)A]. The structural characteristics of the free ligand are compared with those of the co-ordination compounds, and the mass and 13C n.m.r. spectra of the two complexes are compared.

The crystal structure of dichlorobis(imidazole)dimethyltin(IV)

Abstract The structure of dichlorobis(imidazole)dimethyltin(IV) has been determined by X-ray diffraction. The crystal consists of discrete trans -Me 2 SnCl 2 (HIm) 2 units with the metal atom octahedrally coordinated to two Cl atoms (SnCl, 2.5955(7) A; ClSnCl, 180°), two methyl carbons (SnC, 2.110(3) A; CSnC, 180°), and two imidazole groups (SnN, 2.312(2) A; NSnN, 180°). The imidazole ligands are bound to the metal through their pyridine-like nitrogen atom, and intermolecularly hydrogen-bonded to the chlorine atoms.

Complexes of lead(II) and lanthanide(III) ions with two novel 26-membered-imine and -amine macrocycles derived from 2,6-bis(2-formylphenoxymethyl)pyridine☆

Abstract acrocyclic Schiff-base lanthanide(III) complexes, [LnL1] [X]3 (X = NO3, Ln = La, Ce, Pr, Ce, Pr, Nd, Sm, Eu, Gd Tb, Ho, Er, Tm, Yb or Lu: X = ClO4, Ln = La, Ce, Pr, Nd, Sm, Eu, Tb, Dy or Er) and the complex [PbL1] [ClO4]2 have been prepared by cyclocondensation of 2,6-bis(2-formylphenoxymethyl)pyridine and 1,5-bis(2-aminophenoxyl)-3-oxapentane in the presence of the appropriate metal salt as a template agent. The Schiff-base macrocycle L1 is also formed in the absence of the metal ion. Treatment of L1 with NaBH4 in methanol gave the di-amine macrocycle L2. The reactions of lanthanide(III) ions with L2 were also investigated.

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.