Triptycene scaffolds: Synthesis and properties of triptycene-derived Schiff base compounds for the selective and sensitive detection of CN− and Cu2+

A series of triptycene-derived Schiff bases were synthesized by condensation between amino triptycenes with an appropriate aldehyde and were isolated in good to excellent (85–90%) yields. Amongst these, a triptycene-hydroxybenzaldehyde Schiff base compound proved to be a selective sensor for cyanide. It exhibited a “turn-on” fluorescence response at 490 nm to CN^? facilitated by the nucleophilic addition of CN^? to the aldehyde group, accompanied by a visible color change from orange to yellow. Likewise, a triptycene salicylaldehyde adduct was shown to be highly sensitive towards the detection of the CN^? ion with a detection limit of 0.9 μM. On the other hand a triptycene-BODIPY Schiff base compound could be used for the detection of Cu²⁺ ions over other competing, biologically relevant metal ions in acetonitrile. Photophysical studies revealed a 1:1 binding model for the triptycene-BODIPY compound.     

An organocatalytic approach to the core of eunicellin

A stereocontrolled synthesis of the core of eunicellin is described featuring a Claisen rearrangement and a diastereoselective organocatalytic Diels-Alder reaction as the key steps.     

The quorum-sensing molecule <Emphasis Type="Italic">N</Emphasis>-3-oxododecanoyl homoserine lactone (3OC12-HSL) enhances the host defence by activating human polymorphonuclear neutrophils (PMN)

The P. aeruginosa quorum-sensing molecule N-3-oxododecanoyl homoserine lactone (3OC12-HSL) interacts not only with bacteria, but also with mammalian cells, among others with those of the immune defence system. We focussed on the possible interaction of 3OC12-HSL with human polymorphonuclear neutrophils (PMN), because these cells are the first to enter an infected site. We found that 3OC12-HSL attracts PMN, and up-regulates expression of receptors known to be involved in host defence, including the adhesion proteins CD11b/CD18 and the immunoglobulin receptors CD16 and CD64. Furthermore, the uptake of bacteria (phagocytosis), which is crucial for an efficient defence against infection, was enhanced. Thus, recognising and responding to 3OC12-HSL not only attracts the PMN to the site of a developing biofilm, but also reinforces their defence mechanisms, and hence could be a means to control the infection in an early stage and to prevent biofilm formation.     

Laser cooling in an optical shaker

We propose a novel generic approach to laser cooling based on the nonresonant interactions of atoms and molecules with optical standing waves experiencing sudden phase jumps. The technique, termed "optical shaking," combines the elements of stochastic cooling and Sisyphus cooling. An optical signal that measures the instantaneous force applied by the standing wave on the ensemble of particles is used as feedback to determine the phase jumps. This guarantees a drift towards lower energies and higher phase-space density without the loss of particles typical of evaporative cooling.     

Homo- and Hetero-dinuclear Arene-Linked Osmium(II) and Ruthenium(II) Organometallics: Probing the Impact of Metal Variation on Reactivity and Biological Activity

Dinuclear metallodrugs offer much potential in the development of novel anticancer chemotherapeutics as a result of the distinct interactions possible with bio-macromolecular targets and the unique biological activity that can result. Herein, we describe the development of isostructural homo-dinuclear Os^II–Os^II and hetero-dinuclear Os^II–Ru^II organometallic complexes formed from linking the arene ligands of [M(η⁶-arene)(C₂O₄)(PTA)] units (M=Os/Ru; PTA=1,3,5-triaza-7-phosphaadamantane). Using these complexes together with the known Ru^II–Ru^II analogue, a chromatin-modifying agent, we probed the impact of varying the metal ions on the structure, reactivity and biological activity of these complexes. The complexes were structurally characterised by X-ray diffraction experiments, their stability and reactivity were examined by using ¹H and ³¹P NMR spectroscopy, and their biological activity was assessed, alongside that of mononuclear analogues, through MTT assays and cell-cycle analysis (HT-29 cell line). The results revealed high antiproliferative activity in each case, with cell-cycle profiles of the dinuclear complexes found to be similar to that for untreated cells, and similar but distinct profiles for the mononuclear complexes. These results indicate these complexes impact on cell viability predominantly through a non-DNA-damaging mechanism of action. The new Os^II–Os^II and Os^II–Ru^II complexes reported here are further examples of a family of compounds operating via mechanisms of action atypical of the majority of metallodrugs, and which have potential as tools in chromatin research.     

Conductance distribution in two-dimensional localized systems with and without magnetic fields

We have obtained the universal conductance distribution of two-dimensional disordered systems in the strongly localized limit. This distribution is directly related to the Tracy-Widom distribution, which has recently appeared in many different problems. We first map a forward scattering paths model into a problem of directed random polymers previously solved. We show numerically that the same distribution also applies to other forward scattering paths models and to the Anderson model. We show that most of the electric current follows a preferential percolation-type path. The particular form of the distribution depends on the type of leads used to measure the conductance. The application of a moderate magnetic field changes the average conductance and the size of fluctuations, but not the distribution when properly scaled. Although the presence of magnetic field changes the universality class, we show that the conductance distribution in the strongly localized limit is the same for both classes.     

Genotoxic halofuranones in water: isomerization and acidity of mucohalic acids

Among the genotoxic halofuranones formed by chlorination in water are mucochloric acid (MCA, 3,4‐dichloro‐5‐hydroxyfuran‐2(5H)‐one) and mucobromic acid (MBA, 3,4‐dibromo‐5‐hydroxyfuran‐2(5H)‐one). These acids are direct genotoxins and potential carcinogens, with the capacity to alkylate the DNA bases. In recent years, they have also attracted attention in the synthesis of furanone derivatives. Mucohalic acids (MXA) exist in solution as an equilibrium between three species; a cyclic lactone‐lactol , an open‐chain aldehyde‐acid , and the dissociated form of the latter . The distribution of the three species in the equilibrium has synthetic, toxicological, and environmental implications owing to their different functionalization. The case of the neutral open‐chain form is of special interest, since it is expected to be highly reactive. We have experimentally determined the apparent dissociation constant of the cyclic species . Their values suggest that at neutral pH MXA are mostly present as the dissociated carboxylate‐aldehyde. The dissociation constant of the open‐chain neutral species and the cyclization equilibrium constant were determined in water and organic solvents, using density functional theory and ab initio methods. The results suggest that the undissociated aldehyde is a minor species at any given pH. The structure of MXA in solution and the influence of the level of theory on the calculated geometry are discussed. Copyright © 2011 John Wiley & Sons, Ltd.     

Dimensional dependence of the energy transfer in MBE grown MnS layers

MBE grown MnS layers with different thicknesses have been studied by time resolved photoluminescence spectroscopy. The temporal evolution of the internal Mn²⁺ (3d⁵) luminescence is measured over 3 orders of magnitude in intensity. The decay curves obtained reveal a surprising but distinct dependence on the layer thickness with longer lifetime than thinner layers. The observed non-exponential behavior of those time transients can be well described by an energy diffusion model within the 3d states of the manganese subsystem and a subsequent dipole–dipole energy transfer to radiationless centers.