Asunción Muñoz

Solid Polymer Substrates and Coated Fibers Containing 2,4,6- Trinitrobenzene Motifs as Smart Labels for the Visual Detection of Biogenic Amine Vapors

Attempts to polymerize trinitrobenzene derivatives (TNB) have been fruitless so far. Accordingly, polymers containing TNB have not been exploited in spite of their envisaged potential applications. Here, we describe two ways for preparing polymers with TNB moieties thus overcoming the previously reported polymerization impairments. We also report on the exploitation of the materials, both obtained as tractable transparent films and coated fibers, as smart labels for the visual detection of amine vapors. More precisely, amines in the atmosphere surrounding the sensory materials diffuse into them reacting with the TNB motifs forming highly colored Meisenheimer complexes, giving rise to development of color and to the naked eye sensing phenomenon. This is the case of highly volatile amines, such as trimethylamine, produced in food spoilage, specifically in the deterioration of fish or meat, for which the color development of the smart labels can be used as a visual test for food freshness.

Forced Solid-State Interactions for the Selective “Turn-On” Fluorescence Sensing of Aluminum Ions in Water Using a Sensory Polymer Substrate

Selective and sensitive solid sensory substrates for detecting Al(III) in pure water are reported. The material is a flexible polymer film that can be handled and exhibits gel behavior and membrane performance. The film features a chemically anchored salicylaldehyde benzoylhydrazone derivative as an aluminum ion fluorescence sensor. A novel procedure for measuring Al(III) at the ppb level using a single solution drop in 20 min was developed. In this procedure, a drop was allowed to enter the hydrophilic material for 15 min before a 5 min drying period. The process forced the Al(III) to interact with the sensory motifs within the membrane before measuring the fluorescence of the system. The limit of detection of Al(III) was 22 ppm. Furthermore, a water-soluble sensory polymer containing the same sensory motifs was developed with a limit of detection of Al(III) of 1.5 ppb, which was significantly lower than the Environmental Protection Agency recommendations for drinking water.

Aromatic polyamides and acrylic polymers as solid sensory materials and smart coated fibres for high acidity colorimetric sensing

Reusable colorimetric acid responsive coated fibres and manageable films or membranes have been successfully designed and prepared herein. The design of the materials rely on the preparation of condensation and addition monomers both having the azobenzene group, which is used as a dye moiety and as a weak basic motif, and a N,N-dimethylamino moiety. The N,N-dimethylamino moiety is also used as a weak, albeit stronger, basic group as well as an electron donor or electron withdrawal group, depending on its protonation state. For the sake of applicability, the coated fibres were cotton commodity fabrics, and high-tech aromatic polyamide yarns and fabrics. The high-performance aromatic polyamides and the versatile acrylic structures, along with the pendant weak basic groups, with pKas in water ranging from 1.78 to −0.5 and in air from −1.5 to −3.9, provide the materials with a colorimetric sensing capability over a wide acidity sensing window. This sensing window ranges from 1 × 10−2 to 3 M for perchloric acid in water and from 4 × 10−7 to 9 × 10−2 atm for vapour pressure of hydrogen chloride in air. The colour change of the sensory materials from yellow/blank to red or purple, which occurs upon contact with acidic media, was easily identified using the naked eye. Washing these materials with pure water recovered their original colour and permitted their reuse.

Methacrylate copolymers with pendant piperazinedione-sensing motifs as fluorescent chemosensory materials for the detection of Cr(VI) in aqueous media

A fluorogenic sensory film, or dense membrane, capable of detecting Cr(VI), Fe(III), and Hg(II) in water was prepared. The film was prepared by a bulk radical polymerization of different comonomers, one of which contained a piperazinedione motif as sensory fluorophore. The film exhibited gel-like behavior and was highly tractable, even after being swollen in water. The sensing conditions were chosen to overcome interference from iron and mercury cations, giving rise to a material with a detection limit of 1 ppb for Cr(VI).

Polymer chemosensors as solid films and coated fibres for extreme acidity colorimetric sensing

We have designed and successfully prepared polymer membranes as manageable films for colorimetric sensor materials for the visual detection of the acidity of water in the low pH range, below 4, and beyond the pH scale, up to a concentration of 11.6 M of perchloric acid. For this purpose, two monomers with weakly basic groups were synthesised, with these monomers containing up to four protonisable groups in the aforementioned acidic regions. The pKa values were calculated for the membranes in water, which exhibited gel behaviour, and ranged between 2.7 and −6.5. Accordingly, visual colour changes qualitatively indicated the acidity of water containing perchloric acid, and the quantification was performed inexpensively by UV/Vis spectroscopy. Titration with other acids is foreseen for practical applications. Moreover, polymer coatings of conventional cotton and high-tech p-aramid fibres, using the designed sensor monomers, yielded smart fabrics, which responded colorimetrically to the acidity of the water media. Furthermore, both membranes and smart fibres exhibited colour changes in air under acidic atmospheres, demonstrating the future development of fully sensory apparels and smart tags with envisaged health and safety applications. In addition, the sensor materials are reusable, because the protonation under acidic conditions is reverted by washing with water, and are highly stable under acidic conditions for long periods of time.

Photophysical and electrochemical characterization of PdII cyclometallated complexes with 2-acetylpyridine-phenylhydrazone

Abstract The absorption spectra, emission spectra, emission lifetimes and photochemical and electrochemical behaviour of six monomeric cyclometallated complexes [Pd(CNN)X] 0,+ (where CNN is the C-deprotonated form of 2-acetylpyridine-phenylhydrazone and X is I − , Cl − , 4-Mepy, PPh 3 , P(OPh) 3 , P(OMe) 3 ) and two dimeric cyclometallated complexes [(CNN)Pd(XX)Pd(NNC)] 2+ (where XX is 4,4′-bipyridine (4,4′-bpy) or bis(diphenylphosphino)methane (dppm)) were studied. The relatively intense absorption band exhibited by the complexes at 450 nm and the luminescence emission observed at 298 and 77 K were assigned to intraligand (IL) transitions with remarkable charge transfer character (ILCT).

Acid-base behavior of some orthopalladated complexes

The acid dissociation constants of some orthopalladated complexes have been determined in 10% v/v DMSO/water mixed solvent. The positive charge is located on the Pd(II) atom; in basic medium the H atom on the ligand is partially released, which convert these complexes into zwitterions. The ionization constants of the two overlapping equilibria of the HA-dppm-AH complex were evaluated by application of the separation method.

A phosphino-substituted isoindole obtained by cyclization of a thiourea derivative

A phosphorous functionalized isoindole derivative has been formed in the cyclization reaction of 3-chloro-p-tolylmethylene-1,1-diethylthiourea with lithium diphenylphosphide. The reaction involves thiourea desulfuration and C-S to P-S sulfur transfer.