Julio Latorre

Generalised syntheses of ordered mesoporous oxides: the atrane route

Abstract A new simple and versatile technique to obtain mesoporous oxides is presented. While implying surfactant-assisted formation of mesostructured intermediates, the original chemical contribution of this approach lies in the use of atrane complexes as precursors. Without prejudice to their inherent unstability in aqueous solution, the atranes show a marked inertness towards hydrolysis. Bringing kinetic factors into play, it becomes possible to control the processes involved in the formation of the surfactant–inorganic phase composite micelles, which constitute the elemental building blocks of the mesostructures. Independent of the starting compositional complexity, both the mesostructured intermediates and the final mesoporous materials are chemically homogeneous. The final ordered mesoporous materials are thermally stable and show unimodal porosity, as well as homogeneous microstructure and texture. Examples of materials synthesised on account of the versatility of this new method, including siliceous, non siliceous and mixed oxides, are presented and discussed.

Interactions of metal ions with two quinolone antimicrobial agents (cinoxacin and ciprofloxacin): Spectroscopic and X-ray structural characterization. Antibacterial studies

Several novel metal-quinolone compounds have been synthesized and characterized by analytical, spectroscopic and X-ray diffraction methods. The crystal structure of the four compounds, Na(2)[(Cd(Cx)3)(Cd(Cx)3(H2O))].12H2O, [Co(Cp)2(H2O)2].9H2O, [Zn(Cp)2(H2O)2].8H2O and [Cd(HCp)2(Cl)2].4H2O, is presented and discussed: HCx=1-ethyl-1,4-dihydro-4-oxo(1,3)-dioxolo(4,5-g)cinnoline-3-carboxylic acid and HCp=1-cyclopropyl-6-fluoro-1,4-dihydro-4-oxo-7-(1-piperazinyl)-3-quinoline carboxylic acid. In all these compounds the quinolone acts as a bidentate chelate ligand that binds through one carboxylate oxygen atom and the exocyclic carbonyl oxygen atom. Complexes of ciprofloxacin were screened for their activity against several bacteria, showing activity similar to that of the ligand. In addition, the number of bacteria killed after 3 h of incubation with the ligand, [Co(Cp)2(H2O)2].9H2O, Ni(Cp)2.10H2O and Cu(Cp)2.6H2O, was determined against S. aureus ATCC25923. There is a direct relationship between the growth rate and the lethal rate. Against growing bacteria, the ligand is the most bactericidal and Cu(Cp)2.6H2O is the less bactericidal. On the contrary, against non-dividing bacteria, the complexes were more bactericidal than the ligand, with Cu(Cp)(2).6H(2)O the most bactericidal compound.

COORDINATION BEHAVIOR OF SULFATHIAZOLE. CRYSTAL STRUCTURE OF CU(SULFATHIAZOLE) (PY)3CL SUPEROXIDE DISMUTASE ACTIVITY

Abstract The preparation, spectroscopic, magnetic properties, and crystal structure of [Cu(stzxpy) 3 Cl] (stz − stands for the deprotonated form of sulfathiazole, 4-amino-N-2-thiazolylbencenosulfonamide) are reported. Crystals are orthorhombic, space group Pbca, with cell constants a = 15.834(2), b = 17.512(4), and c = 18.79(2) A, and Z = 8. The structure was solved and refined to R = 0.041 (R W = 0.040). The structure consists of mononuclear units linked via hydrogen bonds to form the tridimensional pyramid. The geometry of CuN3N*NCl chromophore is distorted square-pyramid. The superoxide-dismutase mimetic activity of the compound is measured and compared with those of the SOD enzyme, the free drug, and other related sulfathiazole complexes.

Potentiometric and spectroscopic studies of transition-metal ions complexes with a quinolone derivative (cinoxacin). Crystal structures of new Cu(II) and Ni(II) cinoxacin complexes

Abstract The interaction of cobalt(II), nickel(II), copper(II), and zinc(II) with Cinoxacin (HCx = 1-ethyl-1,4-dihydro-4-oxo(1,3)dioxolo(4,5-g)cinnoline-3-carboxylic acid), a 4-quinolone derivative, has been studied at metal/ligand ratios of 1:1-1:3 by means of pH-metric, spectrophotometric, and ESR methods. The formation constants have been determined and the stereochemistry for the metal ions in the species present in aqueous solutions (at 37 ± 0.1°C and I = 0.1 mol dm −3 NaCl) is discussed. In all the studied systems, complexes with different stoichiometric ratios, in which cinoxacin acts both as neutral and deprotonated ligand, are formed. The anomalous sequence of the stepwise stability constants observed for cobalt(II) and nickel(II) systems suggests changes in stereochemistry when CoCx 2 and NiCx 2 are formed. For zinc(II) this change has to be still more pronounced since a [ZnCx] + species has not been detected. For the Cu(II) system the sequence in the stepwise stability constants indicates the preferential formation of the [CuCx] + monocomplex. The crystal and molecular structure of new Cu(II) and Ni(II) complexes of cinoxacin have been investigated. The metal ion in [Cu(Cx) 2 H 2 O]·3H 2 O is five-coordinated and the complex crystallizes in the triclinic P 1 space group with a = 10.620(1), b = 11.358(1), c = 12.440(2) A , α = 78.25(1), β = 80.24(1), γ = 63.34(1)°, and Z = 2 . The complex [Ni(Cx) 2 -(DMSO) 2 ]·4H 2 O contains six-coordinated Ni(II) and crystallizes in the triclinic P 1 space group with a = 8.866(3), b = 9.141(1), c = 11.580(1) A , α = 69.301(9), β = 82.17(2), γ = 75.86(2)°, and Z = 1 .

Superoxide dismutase activity of ternary copper complexes of sulfathiazole and imidazole derivatives. Synthesis and properties of [CuL2(R-Him)2] [HL=4-amino-N-(thiazol-2-yl)benzenesulfonamide, R-Him=4-methylimidazole, 4,4-dimethylimidazoline or 1,2-dimethylimidazole]. Crystal structure of [CuL2(4,4-dimethylimidazoline)2]

Abstract New ternary copper(II) complexes of sulfathiazole (4-amino-N-(thiazol-2-yl)benzenesulfonamide)(HL) and methyl imidazole derivatives have been synthesised and characterised. The crystal structure of the complex [CuL2(4,4-dmHim)2] (1) [4,4-dmHim=4,4-dimethylimidazoline] has been determined. The copper centre has a quasi regular square planar environment with Cu-nitrogen bond lengths ranging from 1.952 to 2.010 A. From the spectroscopic properties of the complexes [CuL2(1,2-dmHim)2] (2) [1,2-dmHim=1,2-dimethylimidazole] and [CuL2(4-mHim)2] (3) [4-mHim=4-methylimidazole] a distorted tetragonal octahedral geometry is deduced. The compounds showed SOD mimetic activity in fact, a low concentration of the complexes catalyses the dismutation of superoxide at biological pH. This SOD activity is correlated with their structural properties. Using Extended Huckel Molecular Orbital Calculations the one-electron energy levels of the CuN4 chromophore in complex 1 are reported and correlated with the data of the CuN6 and CuN5 chromophores of the previously reported [CuL2(Him)2]·MeOH and [CuL2(mim)2]·H2O compounds. In addition, the influence of the geometry distortion on the composition and energy of the molecular orbitals is described using idealised models.

Nanoparticulated Silicas with Bimodal Porosity : Chemical Control of the Pore Sizes

Nanoparticulated bimodal porous silicas (NBSs) with pore systems structured at two length scales (meso- and large-meso-/macropores) have been prepared through a one-pot surfactant-assisted procedure by using a simple template agent and starting from silicon atrane complexes as hydrolytic inorganic precursors. The final bulk materials are constructed by an aggregation of pseudospherical mesoporous primary nanoparticles process, over the course of which the interparticle (textural) large pore system is generated. A fine-tuning of the procedural variables allows not only an adjustment of the processes of nucleation and growth of the primary nanoparticles but also a modulation of their subsequent aggregation. In this way, we achieve good control of the porosity of both the intra- and interparticle pore systems by managing independent variables. We analyze in particular the regulating role played by two physicochemical variables: the critical micelar concentration (cmc) of the surfactant and the dielectric constant of the reaction medium.

Formation in solution, synthesis, and electrochemical study of oxalato complexes of N,N′-ethylenebis(salicylideneiminato)-chromium(III) and -iron(III): crystal structures of piperidinium [N,N′-ethylenebis(salicylideneiminato)](oxalato-O1O2)-chromate(III) and ferrate(III)

Two new mononuclear complexes of formula [Hpip][M(salen)(ox)][M = CrIII(1) or FeIII(2)] and the binuclear [Fe2(salen)2(ox)]·H2O, (3) where Hpip = piperidinium, salen =N,N′-ethylenebis(saIicylideneiminate), and ox = oxalate, have been synthesized. Compounds (1) and (2) are isostructural, monoclinic, space group P21/n, Z= 4, with a= 24.425(3), b= 6.847(1), c= 14.271(2)A, and β= 100.95(2)° for (1) and a= 24.363(4), b= 6.991(2), c= 14.105(3)A, and β= 98.76(2)°for (2). The structure of (1) was solved by direct methods whereas that of (2) was solved by isomorphous replacement from the co-ordinates of (1). Both structures consist of [M (salen)(ox)]– mononuclear anions and piperidinium cations. The presence of the bidentate oxalate ligand in both complexes forces the salen ligand to adopt the non-planar cis-β configuration. The metal ions exhibit distorted octahedral geometry with the two co-ordinated oxygen atoms of the oxalate ligand and an oxygen and a nitrogen atom from the salen defining the best equatorial plane. The remaining two co-ordinating atoms of the quadridentate Schiff base are bent away from the oxalate ligand. The stability constant of the complex [Cr(salen)(ox)]– as well as [Cr(salen)(H2O)2]++ ox2– [graphic omitted] [Cr(salen)(ox)]–(i), [Cr(salen)(H2O)2]+ [graphic omitted] [Cr(salen)(OH)(H2O)]+ H+(ii), [Cr(salen)(OH)(H2O)] [graphic omitted] [Cr(salen)(OH)2]–+ H+(iii) the acidity constants of the complex [Cr(salen)(H2O)2]+ have been determined by potentiometry in aqueous solution: log β1= 4.80 ± 0.03, pKa1= 7.54 ± 0.01, and pKa2= 10.47 ± 0.01 (25 °C, 0.1 mol dm3 NaNO3). Complexes (1) and (2) undergo one-electron reduction at a platinum electrode in dimethyl sulphoxide solution. The reduction process is totally irreversible due to an inner-sphere redox reaction in the case of CrIII and to the dissociation of the anionic oxalate ligand in the case of FeIII A reactivity scheme is proposed to explain their different electrochemical behaviour.

Large monolithic silica-based macrocellular foams with trimodal pore system

Silica-based materials with hierarchical pore systems at three different length scales (small mesopores-large mesopores-macropores) have been prepared through a nanotectonic approach by using mesoporous nanoparticles as building blocks; the resulting materials present a highly accessible foam-like architecture and can be prepared as large monoliths.

Biomimetic chitosan-mediated synthesis in heterogeneous phase of bulk and mesoporous silica nanoparticles

Both bulk and mesoporous silica nanoparticles can be obtained in the form of granular aggregates using chitosan flakes as additive under very soft biomimetic reaction conditions.

Synthesis of ruthenium(II) compounds with ortho-oxypyridinate ligands (hp). Crystal structure characterization of [Ru(η6-p-CH3C6H4CH(CH3)2)Cl(hp)]

Abstract The reaction of [Ru(η6-p-cymene)Cl2]2 (p-cymene = p-CH3C6H4CH(CH3)2) with Nahp in THF yields [Ru(η6]-p-cymene)Cl(hp)] (1). The crystal structure of (1) has been determined by X-ray methods. (1) crystallizes in the space group Pbca, with a = 16.629(2), b = 10.201(3), c = 17.752(2) A. The compound contains one coordinated arene group, one chlorine and one hp group in a chelating coordination mode. The reaction of (1) with Aghp yields [Ru(η6-p-cymene)(hp)2] (2). The 13C NMR spectrum at - 70°C is consistent with a structure Ru(η6-p-cymene)(η2-hp)(η1-hp). At room temperature a rapid interconvertion between the two hp ligands occurs according to the observed 1H and 13C NMR spectra.