Synthesis, photophysical properties, and laser behavior of 3-amino and 3-acetamido BODIPY dyes

The asymmetrically substituted BODIPY dyes 9a and 9b have been synthesized through a key redox step involving the alpha-nitroso derivative of the starting pyrrol. Both dyes emit fluorescence with quantum yields of ca. 0.7, but only 8b behaves as a good laser dye, with an efficiency of 48% in ethanol solution.     

Effects of ethylene glycol addition on the aggregation and micellar growth of gemini surfactants

Micellization of three didodecyl dicationic dibromide gemini surfactants with different methylene spacer lengths, 12-s-12,2Br- where s = 3-5 methylene groups, has been investigated in water-ethylene glycol, EG, mixtures with weight percentages of EG up to 50%. Subsequently, effects of the addition of the organic solvent on the micellar growth of these surfactants and on the surfactant concentration range where sphere-to-rod transitions occur were studied by means of steady-state and time-resolved fluorescence quenching and spectroscopic measurements. Results show that an increase in the weight percentage of ethylene glycol added to aqueous 12-s-12,2Br- (s = 3-5) micellar solutions causes the sphere-to-rod transition to occur at higher surfactant concentrations than in pure water. The diminution in the average aggregation number, N(agg), when wt % EG increases, provoked by the decrease in the interfacial Gibbs energy contribution to DeltaG degrees M, is the main factor responsible for this observation. The decrease in N(agg) is accompanied by a decrease in the ionic interactions and the extra packing contribution to the deformation of the surfactants tails, making formation of cylindrical micelles less favorable. Besides, an increase in the solvent content and polarity of the interfacial region does not favor formation of direct ion pairs, decreasing the tendency of micelles to grow.     

Surface properties of mixed monolayers of sulfobetaines and ionic surfactants

To study the influence of the head group in the properties of the mixed monolayers adsorbed at the air-water interface, the surface tension and surface potential of binary mixtures of surfactant have been determined as a function of the surfactant composition. Experiments were carried out with anionic-zwitterionic sodium dodecyl sulfate and dodecyl dimethyl ammoniopropane sulfonate (SDS/DDPS), and cationic-zwitterionic dodecyl trimethylammonium bromide and dodecyl dimethyl ammoniopropane sulfonate (DTAB/DDPS), and dodecyl trimethylammonium bromide and tetradecyl dimethyl ammoniopropane sulfonate (DTAB/TDPS). It was shown that mixed monolayers of cationic-zwitterionic surfactant exhibit small negative deviations of ideal behavior, whereas for SDS/DDPS monolayers show strong negative deviation from the ideality. Deviations of ideal behavior are interpreted by regular solution theory. The surface potential values agree very well with the concentration of the ionic component at the interface. The dynamic surface tension values show that the adsorption kinetics on the interface is a diffusion-controlled process. In monolayers with significant deviation of the ideal behavior, anionic-zwitterionic, there is some evidence of intermolecular attractions after diffusion of both surfactants at the interface.     

Mechanism of the base-assisted displacement of chloride by alcohol in sulfinyl derivatives

A computational study with density functional theory (DFT) is carried out on the reaction between methyl sulfinyl chloride (MSC) and methanol in the presence of trimethylamine, a process which is a general model for two different methods used in practice for the obtention of chiral sulfoxides through dynamic kinetic resolution. Two mechanistic options are considered: in one of them, chloride is initially displaced by the base (ion pair mechanism), whereas in the other, chloride stays bound to sulfur until its final displacement by methoxy (neutral mechanism). In both cases, the approach of the alcohol to sulfur is coupled with a hydrogen transfer from methanol to the oxo group of MSC in a single concerted transition state. The presence of a trimethylamine molecule facilitates substantially the reaction by reducing the nucleophilic substitution barrier by more than 10 kcal/mol through the formation of a N-H bond with the hydrogen atom being transferred. The neutral mechanism presents a free energy barrier lower than the ion pair alternative and is thus preferred.     

Monitoring of chicken meat freshness by means of a colorimetric sensor array

A new optoelectronic nose to monitor chicken meat ageing has been developed. It is based on 16 pigments prepared by the incorporation of different dyes (pH indicators, Lewis acids, hydrogen-bonding derivatives, selective probes and natural dyes) into inorganic materials (UVM-7, silica and alumina). The colour changes of the sensor array were characteristic of chicken ageing in a modified packaging atmosphere (30% CO(2)-70% N(2)). The chromogenic array data were processed with qualitative (PCA) and quantitative (PLS) tools. The PCA statistical analysis showed a high degree of dispersion, with nine dimensions required to explain 95% of variance. Despite this high dimensionality, a tridimensional representation of the three principal components was able to differentiate ageing with 2-day intervals. Moreover, the PLS statistical analysis allows the creation of a model to correlate the chromogenic data with chicken meat ageing. The model offers a PLS prediction model for ageing with values of 0.9937, 0.0389 and 0.994 for the slope, the intercept and the regression coefficient, respectively, and is in agreement with the perfect fit between the predicted and measured values observed. The results suggest the feasibility of this system to help develop optoelectronic noses that monitor food freshness.     

Copper(I) complexes with bipyridyl and phosphine ligands: a systematic study

Phosphorescent copper(I) complexes carrying 2,2'-bipyridyl derivatives and phosphine ligands have been prepared and fully characterised. The role of the bipyridyl as well as the phosphine ligands in defining the optical, as well as the chemical properties of the complexes, are discussed. The light emission of these complexes is investigated as a function of the molecular geometry: rigid complexes with restricted freedom to rearrange in the excited state are found to show a quantum yield of phosphorescence one order of magnitude higher than those complexes with no steric constraint. The complexes have been extruded in a polymer matrix as a proof of principle of their processability.     

An Approach to Minimize Tumour Proliferation by Reducing the Formation of Components for Cell Membrane

Isoprenoids are natural compounds essential for a great number of cellular functions. One of them is farnesol (FOH), which can reduce cell proliferation, but its low solubility in aqueous solvents limits its possible clinical use as a pharmacological tool. One alternative is the use of cyclodextrins (CDs) which house hydrophobic molecules forming inclusion complexes. To assess FOH potential application in anticancer treatments, Sulfobutylated β-cyclodextrin Sodium Salt (SBE-β-CD) was selected, due to it has high solubility, approbation by the FDA, and numerous studies that ensure its safety to be administered parenterally or orally without nephrotoxicity associated. The therapeutic action of farnesol and complex were studied in different carcinoma cells, compared with a normal cell line. Farnesol showed selectivity, affecting the viability of colon and liver cancer cells more than in breast cancer cells and fibroblasts. All cells suffered apoptosis after being treated with 150 μM of free FOH, but the complex reduced their cell viability between 50 and 75%. Similar results were obtained for both types of isomers, and the addition of phosphatidylcholine reverses this effect. Finally, cell cycle analysis corroborates the action of FOH as inducer of a G0/G1 phase; when the cells were treated using the complex form, this viability was reduced, reaching 50% in the case of colon and liver, 60% in fibroblasts, and only 75% in breast cancer.     

Different Coordinative (N,N) and (N,O) Bidentate Behaviour of N‐2‐Pyridyl‐Sulfonamides. Electrochemical Synthesis and Characterization of Cadmium(II) Complexes

Electrochemical oxidation of cadmium in an acetonitrile solution of N‐2‐pyridyl‐sulfonamides (HL) afforded cadmium coordination compounds of composition [CdL₂]. Heteroleptic complexes of composition [CdL₂L′] (L′ = 2, 2′‐bipyridine or 1, 10‐phenanthroline) were obtained when the coligand L′ was added to the electrolytic phase. The crystal structures of several compounds have been determined by X‐ray diffraction. In all cases the cadmium atom is hexacoordinated, but the coordinative behaviour of the N‐2‐pyridyl‐sulfonamide ligand depends on the location of the substituents in the pyridyl ring. When the substituent is in position 3, the ligands act as N, O‐donors. In all other cases, the ligands act as N, N′‐bidentate systems.     

Investigation of 3D Contour Map and Intermolecular Interaction of Dopamine with β-Cyclodextrin and 2-Hydroxypropyl-β-cyclodextrin

The interactions of the neurotransmitter dopamine (DA) with β-cyclodextrin and 2-hydroxypropyl-β-cyclodextrin (HP-β-CD) was characterized using UV–visible, 2D fluorescence, 3D fluorescence, FT–IR, PXRD and SEM techniques. PM3, PM7 and DFT methods were used to optimize the structures of the inclusion complexes in the gas phase. The absorbance and fluorescence intensities of DA increased in the presence of CDs in aqueous solution. The binding energy, HOMO–LUMO energy gap and Mulliken atomic charges were computed for the inclusion complexes. NBO analysis revealed a greater number of intermolecular hydrogen bonds in DA:HP-β-CD. Experimental and theoretical results suggested that the DA molecule is deeply embedded in the cavities of both CDs.