Molecular motions in amorphous ibuprofen as studied by broadband dielectric spectroscopy

The molecular mobility of amorphous ibuprofen has been investigated by broadband dielectric relaxation spectroscopy (DRS) covering a temperature range of more than 200 K. Four different relaxation processes, labeled as alpha, beta, gamma, and D, were detected and characterized, and a complete relaxation map was given for the first time. The gamma-process has activation energy E a = 31 kJ.mol (-1), typical for local mobility. The weak beta-relaxation, observed in the glassy state as well as in the supercooled state was identified as the genuine Johari-Goldstein process. The temperature dependence of the relaxation time of the alpha-process (dynamic glass transition) does not obey a single VFTH law. Instead two VFTH regimes are observed separated by a crossover temperature, T B = 265 K. From the low temperature VFTH regime, a T g (diel) (tau =100 s) = 226 K was estimated, and a fragility or steepness index m = 93, was calculated showing that ibuprofen is a fragile glass former. The D-process has a Debye-like relaxation function but the temperature dependence of relaxation time also follows the VFTH behavior, with a Vogel temperature and a pre-exponential factor which seem to indicate that its dynamics is governed by the alpha-process. It has similar features as the Debye-type process observed in a variety of associating liquids, related to hydrogen bonding dynamics. The strong tendency of ibuprofen to form hydrogen bonded aggregates such as dimers and trimers either cyclic or linear which seems to control in particular the molecular mobility of ibuprofen was confirmed by IR spectroscopy, electrospray ionization mass spectrometry, and MD simulations.     

Octadecylsilane-modified silicas in the adsorption of toluene

A series of octadecylsilane-modified silicas were prepared by sol-gel and grafting methods. Carbon contents and octadecyl chain conformations were shown to depend on the preparative route. Grafting engenders a low carbon content and a liquid-like chain conformation, while the sol-gel method affords a much higher carbon content and a crystalline conformation. The relationships between the toluene adsorption of the hybrid silicas and their chain conformations, their carbon contents and their textural characteristics are discussed. These sorbents, when used in combination with ultraviolet diffuse reflectance spectroscopy (UV DRS), can be employed as a rapid screening method for detection of aromatic compounds in water and air environmental matrices. Figure Octadecylsilane-modified silicas in the adsorption of toluene     

Evaluation of Antifungal Activity and Potential Application as Fluorescent Probes of Indolenine and Benzo[e]Indole-Based Squarylium Dyes

The antifungal performance and the possible use as fluorescent probes of a series of squarylium dyes derived from indolenine and benzo[e]indole previously synthesized was evaluated. Some photophysical properties were performed in ethanol and phosphate buffer, and the type of aggregates form in phosphate buffer was analyzed. Using the 1,3-diphenylisobenzofuran assay, a qualitative assessment of the capacity of dyes to produce singlet oxygen after irradiation was performed. Regarding the antifungal activity, this was studied through a broth microdilution assay using Saccharomyces cerevisiae PYCC 4072 as a biological model. The effect of irradiation of the dyes, with an appropriate light emitting diode system, on the antifungal activity was also evaluated, and it was verified that some of the dyes improve their activity after irradiation. Using fluorescence microscopy techniques, the colocalization of dyes in S. cerevisae cells was investigated and it was possible to verify that some of the squarylium dyes with a barbituric moiety in the four-membered central ring stained and accumulated preferentially in the mitochondrial web and perinuclear membrane of the cells. The possible use as a fluorescent probe for the detection of HSA was also evaluated for one of the dyes of the series, demonstrating a linear variation in the fluorescence intensity accompanied by the increase in the protein concentration.     

Disentangling Excimer Emission from Chiral Induction in Nanoscale Helical Silica Scaffolds Bearing Achiral Chromophores

The synthesis and characterization of diketopyrrolopyrroles and perylenemonoimidodiesters linked to a substituted benzoic acid in the ortho, meta, and para positions, are reported. Grafting of these dyes on the surface of chiral silica nanohelices is used to probe how the morphology of the platform at the mesoscopic level affects the induction of chiroptical properties onto achiral molecular chromophores. The grafted structures are weakly (diketopyrrolopyrroles) or strongly (perylenemonoimidodiesters) emissive, exhibiting both locally-excited state emission and a broad, structureless emission assigned to excimers. The dissymmetry factors obtained using circular dichroism highlight optimized supramolecular organization between the chromophores for enhancing the chiroptical properties of the system. In the ortho- derivatives, poor organization due to steric hindrance is reflected in a low density of chromophores on walls of the silica-nanostructures (<0.1 vs. >0.3 and up to 0.6 molecules/nm² for the ortho and meta or para derivatives, respectively) and lower g_abs values than in the other derivatives (g_abs<2×10⁻⁵ vs 6×10⁻⁵ for the ortho and para derivatives, respectively). The para derivatives presented a better organization and increased values of g_abs. All grafted chromophores evidence varying degrees of excimer emission which was not found to directly correlate to their grafting density.     

Confining the Sol-Gel Reaction at the Water/Oil Interface: Creating Compartmentalized Enzymatic Nano-Organelles for Artificial Cells

Living organisms compartmentalize their catalytic reactions in membranes for increased efficiency and selectivity. To mimic the organelles of eukaryotic cells, we develop a mild approach for in situ encapsulating enzymes in aqueous-core silica nanocapsules. In order to confine the sol-gel reaction at the water/oil interface of miniemulsion, we introduce an aminosilane to the silica precursors, which serves as both catalyst and an amphiphilic anchor that electrostatically assembles with negatively charged hydrolyzed alkoxysilanes at the interface. The semi-permeable shell protects enzymes from proteolytic attack, and allows the transport of reactants and products. The enzyme-carrying nanocapsules, as synthetic nano-organelles, are able to perform cascade reactions when enveloped in a polymer vesicle, mimicking the hierarchically compartmentalized reactions in eukaryotic cells. This in situ encapsulation approach provides a versatile platform for the delivery of biomacromolecules.     

Multiway chemometric decomposition of EEM of fluorescence of CdTe quantum dots obtained as function of pH

The effect of the pH (from 3 to 10) on the excitation emission matrices (EEMs) of fluorescence of CdTe quantum dots (QDs), capped with mercaptopropionic acid (MPA), were analyzed by multiway decomposition methods of parallel factor analysis (PARAFAC), a variant of the parallel factor analysis method (PARAFAC2) and multivariate curve resolution alternating least squares (MCR-ALS). Three different sized CdTe QDs with emission maximum at 555 nm (QDa), 594 nm (QDb) and 628 nm (QDc) were selected for analysis. The three-way data structures composed of sets of EEMs obtained as function of the pH (EEMs, pH) do not have a trilinear structure. A marked deviation to the trilinearity is observed in the emission wavelength order—the emission spectra suffers wavelength shift as the pH is varied. The pH-induced variation of the fluorescence properties of QDs is described with only one-component PARAFAC2 or MCR-ALS models—other components are necessary to model scattering and/or other background signals in (EEMs, pH) data structures. Bigger sized QDs are more suitable tools for analytical methodologies because they show higher Stokes shifts (resulting in simpler models) and higher pH range sensitivity. The pH dependence of the maximum wavelength of the emission spectra is particularly suitable for the development of QDs/EEMs wavelength-encoded pH sensor bioimaging or biological label methodologies when coupled to multiway chemometric decomposition.     

Lignans from the Bark of Magnolia kobus

The Et₂O‐soluble fraction from the bark of Magnolia kobus led to the isolation of two new lignans, (+)‐(7α,7′α,8α,8′α)‐3′,4,4′,5,5′‐pentamethoxy‐7,9′: 7′,9‐diepoxylignan‐3‐ol ( 1 ) and (+)‐(7α,7′α,8α,8′α)‐4,5‐dimethoxy‐3′,4′‐(methylenedioxy)‐7,9′: 7′,9‐diepoxylignan‐3‐ol ( 2 ), along with five known lignans 3 – 7 . Their structures were established on the basis of various spectroscopic analyses including 1D‐ (¹H, ¹³C, and DEPT) and 2D‐NMR (COSY, NOESY, HMQC, and HMBC) and by comparison of their spectral data with those of related compounds.     

Insertion of a spin crossover Fe(III) complex into an oxalate-based layered material: coexistence of spin canting and spin crossover in a hybrid magnet

The syntheses, structures, and magnetic properties of the compounds of formula [Fe (III)(sal 2trien)] 2[Mn (II) 2(ox) 3].4H 2O.C 3H 7NO ( 1) and [In (III)(sal 2trien)] 2[Mn (II) 2(ox) 3].3H 2O.CH 3OH (2) are reported. The structure presents a homometallic 2D honeycomb anionic layer formed by Mn (II) ions linked through oxalate ligands and a cationic double layer of [Fe(sal 2trien)] (+) or [In(sal 2trien)] (+) complexes intercalated between the 2D oxalate network. The magnetic properties and M?ssbauer spectroscopy of 1 indicate the coexistence of a magnetic ordering of the Mn(II) oxalate network that behaves as a weak ferromagnet and a gradual spin crossover of the intercalated [Fe(sal 2trien)] (+) complexes.     

Vapour pressure data of ε-caprolactone, δ-hexalactone,and γ-caprolactone

This work reports new vapour pressure data of ε-caprolactone, δ-hexalactone, and γ-caprolactone. Vapour pressure measurements were carried out over the temperature range of (283 to 343) K using the static method with a differential pressure transducer. Degassing was performed inside the equilibrium cell by freezing and thawing the samples under moderate vacuum (about 50 kPa). For ε-caprolactone and δ-hexalactone vapour pressure values varied in the range of (0.045 to 0.769) kPa and (0.005 to 0.354) kPa, respectively, while for γ-caprolactone a maximum value of 1.367 kPa was found. Experimental vapour pressure data were correlated by the Antoine equation with a good agreement between experiment and model.