Guzmán Sánchez

Modified mesoporous silica nanoparticles as a reusable, selective chromogenic sensor for mercury(II) recognition

A new tripodal receptor and a novel dyed mesoporous material are presented. The presence of thioureas conjugated with azobenzene chromophores enables the selective colorimetric detection of mercury(II) cations in THF through a remarkable colour change from yellow to deep purple.

Bis(carbazolyl)ureas as selective receptors for the recognition of hydrogenpyrophosphate in aqueous media.

Recognition properties of the novel bis(carbazole) tris-ureidic-based receptors 1 and 2 toward different anions have been studied by (1)H NMR and absorption and emission spectroscopy, as well as by DFT calculations. Receptor 1, in which the two urea-functionalized arms are decorated with p-nitrophenyl rings, behaves as a highly selective chromogenic molecular probe for hydrogenpyrophosphate anion in a competitive medium (acetonitrile/water, 70/30). Receptor 2, bearing two urea arms decorated with photoactive pyrenyl rings, acts as a highly selective fluorescent molecular probe for hydrogenpyrophosphate anion in either acetonitrile or an aqueous mixture (acetonitrile/water, 85/15). Receptor 2 exhibits a dual monomer-excimer emission spectrum and undergoes a remarked ratiometry in acetonitrile in the presence of hydrogenpyrophosphate: the excimer band disappears, whereas the monomer band is slightly increased. However, in the aqueous mixture, a strong increase of the excimer emission band was observed, while the monomer emission bands remained almost unaffected. The resulting binding modes and spectroscopic features are explained by suitable structures of model complexes for both receptors. In such complexes, a peripheral cooperative effect was found, alleviating the excess of negative charge in the guest toward the outer surface of the host, as well as the required enlargement on its internal cavity.

Structure determination of di-μ-hydroxo-bis[(2-(2-pyridyl)phenyl-κ2N,C1)palladium(II)] by X-ray powder diffractometry

The title compound was synthesized in the form of a powder, and was studied by elemental analysis, IR spectroscopy, thermogravimetry and mass spectroscopy. Its crystal structure was then determined by X-ray powder diffractometry, using X-ray diffraction data collected in the reflection Bragg-Brentano geometry. The methodology followed in the present study to resolve the crystal structure consisted of peak indexing, then the use of the Monte-Carlo/parallel tempering search algorithm, and finally Rietveld refinement coupled with difference-Fourier synthesis. We found that the crystals are composed of monoclinic unit cells, with 1.5 molecules in the asymmetric unit and therefore six molecules per unit cell. In addition, we concluded that the complexes adopt a planar conformation, forming trimers created by groups of parallel molecules.

Thermal Study of [Pd(2-Phpy)Cl(L)] Complexes (L=pyridines and amines)

AbstractThe complex [Pd(2-Phpy)(µ-Cl)]2 reacts with pyridines (L=pyridine, α-picoline and γ-picoline), amines (L=isopropylamine, tert-butylamine) and ammonia to form the corresponding ortho-palladatedderivatives [Pd(2-Phpy)ClL]. The compounds have been characterized by C, H and Nanalyses and spectroscopic methods (IR and 1H and 13C NMR).TG, DTG and DSC studies of the complexes were carried out in dynamic nitrogen atmosphere. From DSC analyses the heats of decomposition were calculated. The kinetics ofthe first step of thermal decomposition were evaluated from TG data by isothermal methods for L=pyridine and isopropylamine. The activation energies obtained are in the range 90–100 kJ mol-1. The best fitting for data was observed for R2 and A1.5 kinetic models.

Highly sensitive and selective detection of the pyrophosphate anion biomarker under physiological conditions

A multidentate adsorbate having a bis(carbazolyl)urea unit, as a receptor for hydrogen pyrophosphate anions, and two cyclic bidentate alkyl disulfide groups, as linkers to gold surfaces, has been designed and synthesized. Self-assembled monolayers (SAMs) on gold of this adsorbate have been obtained and characterized showing a high robustness along with an extremely large sensitivity and selectivity for hydrogen pyrophosphate anions enabling to be used as a surface plasmon resonance (SPR) sensor for the detection of such anions at the ppt concentration level under physiological conditions.

Benzodipyrrole derivates as new ionophores for anion-selective electrodes: Improving potentiometric selectivity towards divalent anions

Two open substituted benzodipyrroles were tested as hydrogen-bond-forming anion ionophores for the development of anion-selective electrodes. These compounds were incorporated in plasticized polymeric membranes with different plasticizers, using different membrane compositions to explore their response towards several anions. The electrodes constructed with membranes containing 2-nitrophenyl octyl ether and a 0.5 molar ratio ionic additive/ionophore showed pronounced anti-Hofmeister behaviour, providing a significantly enhanced response towards the divalent anions sulfate, sulfite, thiosulfate and oxalate. The selected electrodes were also evaluated in terms of detection limits and selectivity. (1)H NMR experiments were carried out in an attempt to explain some aspects of the behaviour observed.

Anion Binding Studies on Receptors Derived from the Indolo[2,3-a]carbazole Scaffold Having Different Binding Cavity Sizes

The indolo[2,3-a]carbazole scaffold is a fused polyheteroaromatic system bearing two NH groups which suitably converge as hydrogen bond donor sites for the recognition of anions. A simple derivatisation of the indolocarbazole system at positions 1 and 10 with different functional groups, namely alcohols and amides, has contributed to modulate the anion binding selectivity and sensibility. A particularly good response has been obtained for the benzoate anion.