Georgina Pina-Luis

Solid Phase Synthesis of N-Alkyl-bis-o-aminobenzamides for Metal Ion Sensing Based on a Fluorescent Dansyl Platform

In this paper, we report the synthesis on Merrifields resin of alkyl-bis-o-aminobenzamides labeled with a fluorescent dansyl group for use in metal ion recognition. The influence of alkyl groups with different long chains (n = 1, 2, 4, 6) on the spectral fluorescence characteristics was studied. The sensing properties of the beads were evaluated by packing the resins into a flow-through cell for use in a FIA (flow injection analysis)format. Results demonstrated that for those materials with a longer alkyl chain, the fluorescence emission increased upon Li+, Na+, K+, Ca2+, and Mg2+ addition with a higher sensitivity for Mg2+. On the contrary,a fluorescence quenching was observed when Cu2+, Fe3+, or Zn2+ ions were added. The potential applicability of the sensing approach described in this paper for magnesium ions and the sensing response mechanism are outlined.

Solid-phase organic synthesis of sensing sorbent materials for copper and lead recovery

The synthesis of sorption materials for retention and/or preconcentration of species of clinical and environmental interest, such as metal ions, is an important area of contemporary research. We report herein the synthesis of different solid supports of anthracene-phosphine sulfide for Cu(II) and Pb(II) preconcentration. Sensing properties of these materials were also evaluated using a flow-through optosensing approach.

Quantum chemical calculations on the interaction between flavonol and functional monomers (methacrylic acid and 4-vinylpyridine) in molecularly imprinted polymers.

Quantum chemical calculations were performed to characterize the interaction of the flavonol molecule (FL) with methacrylic acid (MAA) and 4-vinylpyridine (4VPy) in the formation of imprinted polymers. The polarizable continuum model (PCM) was used to gain insight on the type of interaction between the reactant molecules under vacuum conditions and in the presence of different solvents. The effect of solvent on the pre-polymerization complex formation was evaluated through the stability energy, in which chloroform behaves as the best solvent for the synthesis of the imprinted polymers since it facilitates the reaction by lowering its degree of stabilization. The reactivity was analyzed in terms of the electrostatic surface potential (ESP) and Mulliken charge. By means of these results, it has been possible to determine two potential recognition sites for the interaction of the MAA monomer and one for the 4VPy in relation to the strength of interaction with FL. In this concern, the interaction of the system FL-MAA is stronger than FL-4VPy.

Novel naphthalimide–aminobenzamide dyads asOFF/ONfluorescent supramolecular receptors in metal ion binding

Abstract A series of novel naphthalimide–aminobenzamide (NAPIM-2ABZ) dyads 3 connected by different length polymethylene chains were synthesized and studied as fluorescent supramolecular receptors in metal ion binding. The photophysical properties were evaluated and compared with separated chromophores. The electronic absorption spectra of dyads 3 showed no interaction between chromophores in the ground state. The fluorescence quantum yields were lower in dyads 3 in comparison with N-propyl-2-aminobenzamide (8). The fluorescence quenching is attributed to a PET mechanism between fluorophores (from 2ABZ to NAPIM), which is dependent on the polymethylene chain length. In metal binding study was found a response towards transition metal ions such as Hg(II), Cu(II), Zn(II) and Ni(II). Dyad 3b presented selectivity towards Cu(II). The UV-vis, IR and 1H-NMR studies demonstrated the interaction with 2ABZ moiety in the ground state, and interestingly dyads with shorter polymethylene chains 3a (n = 0), 3b (n = 1) and 3c (n = 2) exhibited an OFF/ON fluorescence behaviour due to the PET inhibition and the quenching of 2ABZ fluorescence. Dyads 3d (n = 4) and 3e (n = 6) presented opposite response ON/OFF in the complex with metal ions evidencing the absence of PET in these dyads.

Photoinduced electron transfer in N,N-bis(pyridylmethyl)naphthalenediimides: study of their potential as pH chemosensors

Abstract The change in fluorescent properties of a series of N,N-bis(pyridylmethyl)naphthalenediimides (BIPy-NDIs) as function of pH were investigated. The naphthalenediimide dyes displayed OFF–ON pH sensing properties owing to photoinduced electron transfer in the pH range from 1.7 to 4.1. The fluorescence enhancement of the chemosensors studied is based on the hindering of photoinduced energy-electron transfer (PET) from pyridine ring to the naphthalene fluorophore by protonation. Moreover, using density functional theory theoretical calculations of molecular orbitals, it was verified that protonation nitrogen atom in pyridine ring inhibits the PET process. The best selective response for monitoring pH in the presence of different metal ions, was exhibited by BIPy-NDI 1B. In addition, 1B was applied for determination of pH in real samples of commercial vinegars. The results were consistent with those obtained by glass electrode method, indicating that the new probe could be a practical pH indicator in strongly acidic conditions.

Preparation of a Library of EDTA Amide x-Aminenaphthalene-y-sulfonic Acid Derivatives on Solid Phase and Their Fluorescence Behavior toward Transition Metals

In this work, we report the synthesis of a combinatorial library of 80 derivatives of EDTA amide x-aminenaphthalene-y-sulfonic acid on four different supports with variable length linker. The sensing fluorescence behavior of these materials for transitions metals was studied by packing the beads into a conventional flow-through cell in a continuous flow injection set up. The fluorescence emission response of these materials shows that sensors supported in Argopore (a) with the fluorescence moiety of 1-aminenaphthalene-4-sulfonic acid behaves like dosimeter for copper.

Water-compatible core–shell Ag@SiO2 molecularly imprinted particles for the controlled release of tetracycline

Silver nanoparticles coated with molecularly imprinted silica shell (Ag@SiO2-MIP) were synthesized, and their properties for the molecular recognition and the controlled delivery of tetracycline (TC) in aqueous environments were investigated. In this study, a synthesis protocol based in the entrapping of TC into silica particles with a core of silver nanoparticles (AgNPs) was developed. These particles were examined by transmission electron microscopy, scanning electron microscopy, energy dispersion spectroscopy, Fourier transform infrared spectroscopy, zeta potential and UV visible, and fluorescence spectroscopy. The as-prepared Ag@SiO2-MIP particles were evaluated for selective recognition of TC. The imprinted particles have higher TC binding ability as compared with corresponding non-imprinted particles and have high selectivity toward TC over other competitive antibiotics. The studies of release profiles of TC-loaded Ag@SiO2-MIP particles in aqueous solutions demonstrated a strong dependence with pH and temperature. The kinetic delivery of TC showed two types of release which includes initial burst release (low-affinity sites) and slow release (high-affinity sites). The amount of TC release from Ag@SiO2-MIP particles was lower at pH 2 (simulated gastric fluid) to pH 8 (simulated colonic fluid), which makes the proposed system a good candidate for TC oral administration. The excellent biocompatibility of the silica materials, the known bactericidal properties of the AgNPs, and the drug release results render the possibility of designing a new generation of TC delivery systems for controlled release.

Colorimetric and Fluorescent Determination of Fluoride Using a Novel Naphthalene Diimide Boronic Acid Derivative

ABSTRACT A new 1,4,5,8-naphthalene diimide functionalized with two 3-phenylboronic acid groups (1) was prepared and used as a selective sensor for fluoride. The proposed sensor is based on anion–π interactions between fluoride and naphthalene diimide core and the cooperative effect of boronic acid groups acting as Lewis acid anion receptors. The results show that the naphthalene diimide and boronic acid fragments participate in fluoride recognition. This modification significantly and positively affected the analytical response of the receptor. Interactions of 1 with fluoride were characterized by ultraviolet-visible, fluorescence, and nuclear magnetic resonance (NMR) spectroscopy. The influence of the boronic groups on the colorimetric and fluorescent properties was established by comparison with a non-functionalized aniline derivative. The sensor showed high selectivity in the presence of other anions. Colorimetric sensor 1 operated from 3.3 × 10−4 to 1.5 × 10−3 M with a detection limit of 3.6 × 10−4 M. The fluorescent sensor operated from 0 to 4 × 10−4 M allowing the measurement of 1.7 × 10−5 M. The results open the possibility of design and development of a new class of naphthalene diimide receptors based on cooperative effects.

A Novel and Highly Regioselective Synthesis of New Carbamoylcarboxylic Acids from Dianhydrides

A regioselective synthesis has been developed for the preparation of a series of N,N′-disubstituted 4,4′-carbonylbis(carbamoylbenzoic) acids and N,N′-disubstituted bis(carbamoyl) terephthalic acids by treatment of 3,3′,4,4′-benzophenonetetracarboxylic dianhydride (1) and 1,2,4,5-benzenetetracarboxylic dianhydride (2) with arylalkyl primary amines (A-N). The carbamoylcarboxylic acid derivatives were synthesized with good yield and high purity. The specific reaction conditions were established to obtain carbamoyl and carboxylic acid functionalities over the thermodynamically most favored imide group. Products derived from both anhydrides 1 and 2 were isolated as pure regioisomeric compounds under innovative experimental conditions. The chemo- and regioselectivity of products derived from dianhydrides were determined by NMR spectroscopy and confirmed by density functional theory (DFT). All products were characterized by NMR, FTIR, and MS.

NIR-Emitting Alloyed CdTeSe QDs and Organic Dye Assemblies: A Nontoxic, Stable, and Efficient FRET System

In the present work, we synthesize Near Infrared (NIR)-emitting alloyed mercaptopropionic acid (MPA)-capped CdTeSe quantum dots (QDs) in a single-step one-hour process, without the use of an inert atmosphere or any pyrophoric ligands. The quantum dots are water soluble, non-toxic, and highly photostable and have high quantum yields (QYs) up to 84%. The alloyed MPA-capped CdTeSe QDs exhibit a red-shifted emission, whose color can be tuned between visible and NIR regions (608–750 nm) by controlling the Te:Se molar ratio in the precursor mixtures and/or changing the time reaction. The MPA-capped QDs were characterized by UV-visible absorption spectroscopy, fluorescence spectroscopy, transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDS), and zeta potential measurements. Photostability studies were performed by irradiating the QDs with a high-power xenon lamp. The ternary MPA-CdTeSe QDs showed greater photostability than the corresponding binary MPA-CdTe QDs. We report the Förster resonance energy transfer (FRET) from the MPA-capped CdTeSe QDs as energy donors and Cyanine5 NHS-ester (Cy5) dye as an energy acceptor with efficiency (E) up to 95%. The distance between the QDs and dye (r), the Förster distance (R0), and the binding constant (K) are reported. Additionally, cytocompatibility and cell internalization experiments conducted on human cancer cells (HeLa) cells revealed that alloyed MPA-capped CdTeSe QDs are more cytocompatible than MPA-capped CdTe QDs and are capable of ordering homogeneously all over the cytoplasm, which allows their use as potential safe, green donors for biological FRET applications.