José V. Cuevas

Turn‐On Fluorogenic Probes for the Selective and Quantitative Detection of the Cyanide Anion from Natural Sources

We report new indene derivatives that are good fluorogenic probes for the cyanide anion, one of which is a highly selective and sensitive fluorogenic probe for the fluorescent detection--as well as reliable quantification--of the cyanide anion in water or buffer, with a 10(3)-fold increase of fluorescence and low detection limit. It is therefore useful for the quantification of natural cyanide from aqueous extracts of green almond seeds, thus proving that the system is suitable for fast detection and quantification of cyanide from natural sources.

A Selective Chromogenic Probe for Mercury(II) and Cyanide in Aqueous Buffered Solution from a Cycloaddition Reaction of an Ynamine to Polycyclic Dithiolethiones

The synthesis of some new polysulfur-nitrogen heterocycles by cycloaddition of an ynamine to bisdithiolothiazine ketothiones or dithiones is described and the interconversion between regioisomers is studied by DFT calculations, showing that the double bond isomerizes at room temperature. This series is a new selective and sensitive chromogenic probe for the naked-eye detection of mercury(II) cation and cyanide anion in buffered (HEPES 0.05 M, pH 7.14) water/acetonitrile 1:1 mixture, with sub-micromolar sensitivity, and constitutes the first example of a new class of colorimetric chemical probes for Hg(2+) and CN(-).

Intramolecular CN bond formation in the reductive elimination of ortho-palladated arylhydrazones of acetophenone

Abstract Carbonylation in dichloromethane at room temperature of the dimeric ortho-palladated complex [Pd{C6H4C(CH3)NNHC6H5}(μ-Cl)]2 yields in a first step the monocarbonyl [Pd{C6H4C(CH3)NNHC6H5}Cl(CO)] which very slowly (days) undergoes in solution reductive elimination of palladium to give high yield of the isoindolinone derivative, 2-anilino-3-methylene-isoindolin-1-one. Addition of the stoichiometric amount of NaOMe to the monocarbonyl complex [Pd{C6H4C(CH3)NNHC6H5}Cl(CO)] in solution leads instantaneously to reductive elimination and affords the indazole derivative, 3-methyl-1-phenyl-indazole, in high yield. Carbonylation of the related complex [Pd{C6H4C(CH3)NNHC6H4-p-NO2}(μ-Cl)]2 yields in solution the monocarbonyl [Pd{C6H4C(CH3)NNHC6H4-p-NO2}Cl(CO)] which in minutes affords high yield of the isoindolinone derivative, 2-(4-nitroanilino)-3-methylene-isoindolin-1-one. Such different behaviour sheds light on the mechanistic grounds that govern the intramolecular CN bond formation and the cyclization of ortho-palladated acetophenonearylhydrazones, and shows that the acidity of the NH bond controls the rate of the reactions. The requirement of the formation of a palladium–nitrogen amido bond cis to a palladium–carbon bond is supported for these results. We suggest that a tautomeric equilibrium of the hydrazonato ligand accounts for the two alternate pathways.

Synthesis and Structure of an Asymmetric Binuclear Phenylhydrazonato Anionic Complex of Palladium Containing a Pd−C(aryl) Bondcis to a Pd−N(amido) Bond

The synthesis and structure of a unique asymmetric folded binuclear anionic complex of palladium containing two different hydrazonato ligands and showing a Pd−N(amido) bond cis to a Pd−C(aryl) bond is described.

Solvent-Free Off-On Detection of the Improvised Explosive Triacetone Triperoxide (TATP) with Fluorogenic Materials

A fluorogenic perylenediimide-functionalized polyacrylate capable of generating color and fluorescence changes in the presence of triacetone triperoxide TATP), an improvised explosive used in terrorist attacks, under solvent-free, solid-state conditions has been developed. The material works by accumulating volatile TATP until it reaches a threshold; therefore, triggering colorimetric and fluorescent responses.

Synthesis of pyrrolidine-fused 1,3-dithiolane oligomers by the cycloaddition of polycyclic dithiolethiones to maleimides and evaluation as mercury(II) indicators.

The scandium triflate-catalyzed cycloaddition reaction of polycyclic 1,2-dithiolethiones to maleimides is described. The reaction constitutes an easy approach to linear as well as branched oligomeric cis-fused dihydro[1,3]dithiolo[4,5-c]pyrrole-4,6-dione rings interconnected by 3,5-diylidenethiomorpholine-2,6-dithione or ylidene-6-thioxo[1,2]dithiolo[3,4-b][1,4]thiazin-3-one groups. The presence of highly colored, highly polarized push-pull α,β-unsaturated thione groups in their structures make these compounds sensitive to the presence of mercury(II) cation in organic or mixed organic/aqueous solvents.

Dalton communications. Synthesis, structural characterisation and electrochemistry of the tetranuclear compound [{Pd2(µ-RNNNR)2}2(µ-Cl)4](R = C6H4Me-p): a precursor to triazenido-bridged palladium(II) complexes

The tetranuclear complexes [{Pd2(µ-RNNNR)2}2(µ-X)4](R = C6H4Me-p, X = Cl or I), in which two triazenido-bridged dipalladium units are linked by halide bridges to give an S4N4-like Pd4Cl4 core, are novel precursors to redox-active triazenido-bridged derivatives.

Surface Functionalized Silica Nanoparticles for the Off-On Fluorogenic Detection of an Improvised Explosive, TATP, in a Vapour Flow

We report the development of new fluorogenic silica nanomaterials that were able to generate fluorescence in the presence of vapours of triacetone triperoxide, TATP, an improvised explosive used in terrorist attacks. The materials worked in a vapour flow of TATP, giving a permanent and strongly fluorescent response.

Revealing the diastereomeric nature of pincer terdentate nitrogen ligands 2,6-bis(arylaminomethyl)pyridine through coordination to palladium

Palladium complexes of formula [PdLCl]X (X = Cl 1, BF42) containing the pincer terdentate ligands L [L = 2,6-(ArNHCH2)2C5H3N (Ar = 4-MeC6H41a and 2a, 4-MeOC6H41b and 2b); L = 2,6-(4-MeC6H4NMeCH2)2C5H3N 1c and 2c] have been synthesised as cis–trans diastereomeric mixtures. The chiral nature of both amine arms of the pincer ligands accounts for the mixtures of isomers. All the complexes show dynamic behavior assigned to conversion between diastereomers. A ΔG‡273 of 68.9 kJ mol−1 for 2a and a ΔG‡273 of 65.8 kJ mol−1 for 2c were found through complete DNMR line-shape analysis of the –CH2– signals in the 1H spectra. The cis–trans conversion requires the inversion of the pyramidal nitrogen of one of the coordinated amine arms. Two putative pathways have been proposed for such inversion: a) dissociation of one of the amine nitrogen atoms followed by inversion of the nitrogen atom and reformation of the nitrogen–palladium bond and b) deprotonation of one of the N–H bond leading to an amido intermediate which can reprotonate on the other side. Experimental evidence is given for both mechanisms. The structural characterization of 1a is described.

Strong Influence of the Ancillary Ligand over the Photodynamic Anticancer Properties of Neutral Biscyclometalated Ir(III) Complexes Bearing 2-Benzoazole-Phenolates

In this paper, the synthesis, comprehensive characterization and biological and photocatalytic properties of two series of neutral IrIII biscyclometalated complexes of general formula [Ir(C^N)2 (N^O)], where the N^O ligands are 2-(benzimidazolyl)phenolate-N,O (L1, series a) and 2-(benzothiazolyl)phenolate-N,O (L2, series b), and the C^N ligands are 2-(phenyl)pyridinate or its derivatives, are described,. Complexes of types a and b exhibit dissimilar photophysical and biological properties. In vitro cytotoxicity tests conclusively prove that derivatives of series a are harmless in the dark against SW480 cancer cells (colon adenocarcinoma), but express enhanced cytotoxicity versus the same cells after stimulation with UV or blue light. In contrast, complexes of type b show a very high cytotoxic activity in the dark, but low photosensitizing ability. Thus, the ancillary N^O ligand is the main factor in terms of cytotoxic activity both in the dark and upon irradiation. However, the C^N ligands play a key role regarding cellular uptake. In particular, the complex of formula [Ir(dfppy)2 (L1)] (dfppy=2-(4,6-difluorophenyl)pyridinate) [3 a] has been identified as both an efficient photosensitizer for 1 O2 generation and a potential agent for photodynamic therapy. These capabilities are probably related to a combination of its notable cellular internalization, remarkable photostability, high photoluminescence quantum yield, and long triplet excited-state lifetime. Both types of complexes exhibit notable catalytic activity in the photooxidation of thioanisole and S-containing aminoacids with full selectivity.