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Amabilino D.B.,Campus Universitari | Kellogg R.M.,Syncom BV
Israel Journal of Chemistry | Year: 2011

Chirality can emerge spontaneously from racemizing samples in a remarkably efficient manner. The effect results from the stochastic generation of an excess of one enantiomer in the solid and subsequent amplification of the initial material to the bulk. In this review we shall give examples showing how this effect has proved to be an inspiration for the emergence of chirality from chiral materials, and even for the preparation of pharmaceutically important intermediates. While spontaneous deracemization should produce either enantiomer randomly, the kind of system that demonstrates the phenomenon is very prone to the induction of one handedness with extremely small quantities of chiral inducer, which makes the process exploitable in certain cases. This kind of deracemization is the epitome of the origin, transfer and amplification of chirality. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Riobe F.,Campus Universitari | Schenning A.P.H.J.,TU Eindhoven | Amabilino D.B.,Campus Universitari
Organic and Biomolecular Chemistry | Year: 2012

Induction of chirality in achiral aggregates of an oligo(p- phenylenevinylene) has been used to detect the enantiomeric excess in acids used in the resolution of chiral compounds. The chiral acids which induce helicity in the aggregates are present at only 10% of the concentration of the chromophore, whose chiroptical activity can be detected using circular dichroism spectroscopy. An ee of 10% in mixtures of (+) and (-) acids has been clearly evidenced in a series of samples using only 1.5 μg and concentration of approximately 10 μM of the chiral compound. The composition of both carboxylic and phosphoric acid derivatives can be detected, thanks to their binding to the dimerised core ureidotriazine unit attached at one end of the oligo(p-phenylenevinylene) which induces a preferred twist in the aggregated aromatic rod. This chiral arrangement is reflected in the Cotton effects that the assemblies show. The sign of the induced dichroic signal can be affected by the substituents around a stereogenic centre of otherwise identical configuration, and can lead to ambidextrous assemblies as seen in Cotton effects at different positions for different acids. While this technique can be used to detect enantiomeric excess, screening of the pure enantiomers is wise prior to the use of the method to detect scalemic mixtures. This supramolecular approach to evaluation of chiral content in samples could also be applied to other types of aggregates based on achiral molecules which show sensitivity to molecular chiral inducers. © 2012 The Royal Society of Chemistry.

Puigmarti-Luis J.,Campus Universitari | Saletra W.J.,Campus Universitari | Gonzalez A.,University of Barcelona | Amabilino D.B.,Campus Universitari | Perez-Garcia L.,University of Barcelona
Chemical Communications | Year: 2013

Three different routes to rotor-type systems on a gold surface provide sparse and dense layers of rotors with best control exerted using mixed ordered monolayers that guide the creation of the potential molecular machine components from solution. © 2014 The Royal Society of Chemistry.

Destoop I.,Catholic University of Leuven | Xu H.,Catholic University of Leuven | Oliveras-Gonzalez C.,Campus Universitari | Ghijsens E.,Catholic University of Leuven | And 2 more authors.
Chemical Communications | Year: 2013

Self-assembly of an achiral porphyrin at the interface between a chiral solvent and an atomically flat substrate renders the monolayer chiral, and a non-racemic solvent can even overrule the intrinsic expression of chirality in the self-assembly of chiral molecules. © 2013 The Royal Society of Chemistry.

Corral A.,Campus Universitari | Osso A.,Autonomous University of Barcelona | Llebot J.E.,Autonomous University of Barcelona
Nature Physics | Year: 2010

The influence of climate variability and global warming on the occurrence of tropical cyclones is a controversial issue 1-10. Existing historical databases on the subject are not fully reliable 9,11-13, but a more fundamental hindrance is the lack of basic understanding regarding the intrinsic nature of tropicalcyclone genesis and evolution 14. It is known that tropical cyclones involve more than a passive response to changing external forcing 15, but it is not clear which dynamic behaviour best describes them. Herewe present an approach based on the application of the power dissipation index, which constitutes an estimation of released energy 3, to individual tropical cyclones. A robust law emerges for the statistics of power dissipation index, valid in four different ocean basins and over long time periods. In addition to suggesting a description of the physics of tropical cyclones in terms of critical phenomena 16,17, the scaling law enables us to quantify their response to changing climatic conditions, with an increase in the largest power dissipation index values with sea surface temperature or the presence of El Niño phenomena, depending on the basin under consideration. In this way, we demonstrate that the recent upswing in North Atlantic hurricane activity does not involve tropical cyclones that are quantitatively different from those in other sustained high-activity periods before 1970. © 2010 Macmillan Publishers Limited. All rights reserved.

Danila I.,French National Center for Scientific Research | Pop F.,French National Center for Scientific Research | Escudero C.,Lawrence Berkeley National Laboratory | Feldborg L.N.,Campus Universitari | And 4 more authors.
Chemical Communications | Year: 2012

The formation of helical self-assembled fibres by a C 3 symmetric molecule incorporating three tetrathiafulvalene units is shown to be influenced dramatically by the processing conditions, leading to a variety of different chiral forms, including unprecedented croissants. This journal is © The Royal Society of Chemistry 2012.

Haq S.,University of Liverpool | Hanke F.,University of Liverpool | Dyer M.S.,University of Liverpool | Persson M.,University of Liverpool | And 4 more authors.
Journal of the American Chemical Society | Year: 2011

The direct coupling of complex, functional organic molecules at a surface is one of the outstanding challenges in the road map to future molecular devices. Equally demanding is to meet this challenge without recourse to additional functionalization of the molecular building blocks and via clean surface reactions that leave no surface contamination. Here, we demonstrate the directional coupling of unfunctionalized porphyrin molecules- large aromatic multifunctional building blocks- on a single crystal copper surface, which generates highly oriented one-dimensional organometallic macromolecular nanostructures (wires) in a reaction which generates gaseous hydrogen as the only byproduct. In situ scanning tunneling microscopy and temperature programmed desorption, supported by theoretical modeling, reveal that the process is driven by C-H bond scission and the incorporation of copper atoms in between the organic components to form a very stable organocopper oligomer comprising organometallic edge-to-edge porphyrin-Cu-porphyrin connections on the surface that are unprecedented in solution chemistry. The hydrogen generated during the reaction leaves the surface and, therefore, produces no surface contamination. A remarkable feature of the wires is their stability at high temperatures (up to 670 K) and their preference for 1D growth along a prescribed crystallographic direction of the surface. The on-surface formation of directional organometallic wires that link highly functional porphyrin cores via direct C-Cu-C bonds in a single-step synthesis is a new development in surface-based molecular systems and provides a versatile approach to create functional organic nanostructures at surfaces. © 2011 American Chemical Society.

Haq S.,University of Liverpool | Hanke F.,University of Liverpool | Sharp J.,University of Liverpool | Persson M.,University of Liverpool | And 3 more authors.
ACS Nano | Year: 2014

The heterocoupling of organic building blocks to give complex multicomponent macromolecules directly at a surface holds the key to creating advanced molecular devices. While "on-surface" synthesis with prefunctionalized molecules has recently led to specific one-and two-component products, a central challenge is to discover universal connection strategies that are applicable to a wide range of molecules. Here, we show that direct activation of C-H bonds intrinsic to π-functional molecules is a highly generic route for connecting different building blocks on a copper surface. Scanning tunneling microscopy (STM) reveals that covalent π functional macromolecular heterostructures, displaying diverse compositions, structures and topologies, are created with ease from seven distinct building blocks (including porphyrins, pentacene and perylene). By exploiting differences in C-H bond reactivity in the deposition and heating protocols we also demonstrate controlled synthesis of specific products, such as block copolymers. Further, the symmetry and geometry of the molecules and the surface also play a critical role in determining the outcome of the covalent bond forming reactions. Our "pick-mix-and-link" strategy opens up the capability to generate libraries of multivariate macromolecules directly at a surface, which in conjunction with nanoscale probing techniques could accelerate the discovery of functional interfaces. © 2014 American Chemical Society.

Amabilino D.B.,Campus Universitari | Puigmarti-Luis J.,Campus Universitari
Soft Matter | Year: 2010

The preparation of supramolecular nanowires capable of conducting electricity can be achieved via the gel state. These wires, which range in width from a few to several tens of nanometres, are connected in a network - characteristic of organogels - which can provide bulk conducting materials thanks to close contacts between the fibres. They are easy to process and do not rely on the crystalline state for their properties, and importantly do not depend on the surface to which they are applied. The gel state can also be used as a route for the preparation of nanocomposite materials, whose structure can be controlled by modifying the compatibility between the components. In addition, they contain nanowires which, provided their location could be controlled, may prove of utility in nanoscale devices. © 2010 The Royal Society of Chemistry.

Rodrigues M.,University of Barcelona | Calpena A.C.,University of Barcelona | Amabilino D.B.,Campus Universitari | Garduno-Ramirez M.L.,Autonomous University of the State of Morelos | Perez-Garcia L.,University of Barcelona
Journal of Materials Chemistry B | Year: 2014

A novel physical gel was obtained using a gemini imidazolium-based amphiphilic molecule dissolved in ethanol-water mixtures. The structure of the gel is comprised of intertwining nanofibres with widths of approximately 80 nm. The ethanol/water ratio has an important influence on the gelation process: the gelator is sparingly soluble in water and soluble in ethanol. The gelator is capable of incorporating anionic drugs in its fibrillar network easily; sodium ibuprofenate, indomethacin and the sodium salt of methotrexate were used as model drugs that were incorporated into the quickly forming gels. The characterization of these composite xerogels was made by different microscopy techniques as well as X-ray powder diffraction. The ability of the amphiphile to form a gel is largely maintained in the presence of the different model drugs and the overall morphology of the gels (that present a fibre like structure in all cases with intertwined ribbons) is very similar. Furthermore the in vitro release of the drugs from the gel and the in vivo anti-inflammatory efficacy was studied. The overall results show better release profiles and anti-inflammatory efficacy for indomethacin, and prove the promise of this molecular gel in controlled drug release, in the present case dermatological application. © 2014 the Partner Organisations.

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