Framing the chalcogen-bonding interaction in the supramolecular toolbox for solid-state applications

Out of the supramolecular toolbox, Secondary Bonding Interactions (SBIs) have been a topic of growing interest from the scientific community during the last decades, particularly halogen- and chalcogen-bonding. Those interaction are composed of orbital mixing, electrostatic and dispersion components. Heavier halogen (X) and chalcogen (E) atoms bonded to organic molecules present an anisotropic charge distribution. Specifically, a region of positive potential called a -hole can be found co-linear but opposite to the C-X or C-E bonds. Chalcogen atoms are able to form two covalent bonds and thus, exhibit two -holes. This ability allows them to be inserted in aromatic cycles making the C-E bonds less reactive compared to that of C-X. Those advantages make the chalcogen-bonding an interaction of choice to build new supramolecular architectures. However, the field still lacks a recognition motif showing fidelity and stability (chapter I). In consequence, this work presents the synthesis of a recognition motif bearing Se and Te atoms and showing a strong recognition persistence at the solid -state, namely the CGP array (chapter II). This building block can be easily substituted in 2-positions by various functional groups leading to a strengthening of the interaction or to the introduction of valuable properties. For instance, 1-pyrenyl derivatives have been synthesised showing that organic semi-conductor material can be synthesised relying on EB and − stacking interactions to organise in the solid-state (chapter II). Further functionalisation allowed us to build supramolecular polymers in the form of co-crystal showing an orthogonal behaviour of EB and XB interactions (chapter III). The CGP scaffold could also be functionalised in 5-position leading to the formation of unprecedented multi-type interactions recognition motifs (chapter IV). Exploiting the parallel use of HB and EB, we have synthesised ribbon, wire-like structures and hetero-molecular dimers

Chalcogen-bond driven molecular recognition at work

Out of the supramolecular toolbox, Secondary Bonding Interactions (SBIs) have attracted in the last decades the attention of the chemical community as novel non-covalent interactions of choice for a large number of chemical systems. Amongst all SBIs, halogen-bonding (XBIs) and chalcogen-bonding (EBIs) interactions are certainly the most important. However, the use of EBIs have received marginal consideration if compared to that of XBIs. By sieving the most significant examples, this review focuses on the theoretical and experimental studies carried out with EBIs in functional systems. In a systematic way the reader is guided through the most recent and representative examples in which chemists have rationally designed molecular modules that, through EBIs, trigger the initiation of chemical reactions, molecular recognition events in solutions and at the solid state to produce self-assembled and self-organised functional materials at different length scales. The study and understanding of the fundamental geometrical and physical parameters ruling EBIs is at its infancy, and it still needs to establish those principles to rationally design and program synthons that, undergoing molecular recognition through EBIs, allow the development of new tailored materials for applications in the field of optoelectronic, sensing, catalysis, and drug discovery

Concurring Chalcogen- and halogen-bonding interactions in supramolecular polymers for crystal engineering applications

The engineering of crystalline molecular solids through the simultaneous combination of distinctive non‐covalent interactions is an important field of research as it could allow chemist to prepare materials depicting multiresponsive properties. It is in this contest that, pushed by our will to expand the chemical space of chalcogen‐bonding interactions that, in this work we put forward the concept for which chalcogen‐ and halogen‐bonding interactions can be used simultaneously to engineer multicomponent co‐crystals. Through the rational design of crystallizable molecules, we prepared chalcogenazolo pyridine scaffold (CGP) modules that, bearing either a halogen‐bond acceptor or donor at the 2‐position can interact with suitable complementary molecular modules, undergoing formation of supramolecular polymers at the solid state. The recognition reliability of the CGP moiety to form chalcogen‐bonded dimers allow the formation heteromolecular supramolecular polymers through halogen‐bonding interactions as confirmed by single‐crystal X‐ray diffraction analysis

Substituent-controlled tailoring of chalcogen-bonded supramolecular nanoribbons in the solid state

In this work, we design and synthesize supramolecular 2,5-substituted chalcogenazolo[5,4-β]pyridine (CGP) synthons arranging in supramolecular ribbons at the solid state. A careful choice of the combination of substituents at the 2- and 5-positions on the CGP scaffold is outlined to accomplish supramolecular materials by means of multiple hybrid interactions, comprising both chalcogen and hydrogen bonds. Depending on the steric and electronic properties of the substituents, different solid-state arrangements have been achieved. Among the different moieties on the 5-position, an oxazole unit has been incorporated on the Se- and Te-congeners by Pd-catalyzed cross-coupling reaction and a supramolecular ribbon-like organization was consistently obtained at the solid state

Leveraging fluorescent emission to unitary yield: dimerization of polycyclic aromatic hydrocarbons

We report on the synthesis and characterization of novel substituted 1,1′‐biperylene‐2,2′‐diols in which the dihedral angle between the two polycyclic aromatic hydrocarbon (PAH) units is tailored from ca. 60° to ca. 90° in the solid state by introduction of cyclo‐etheric straps or sterically hindered groups such as the triisopropylsilyl (TIPS) group. Depending on the type of substitution, we lock the dihedral angle between the perylenyl moieties enabling fine‐tuning of the molecular optoelectronic properties, with the molecules displaying the smallest angles acting as exceptionally strong emitters with unitary quantum yields

Model-based reconstruction of whole organ growth dynamics reveals invariant patterns in leaf morphogenesis

Plant organ morphogenesis spans several orders of magnitude in time and space. Because of limitations in live-imaging, analysing whole organ growth from initiation to mature stages typically rely on static data sampled from different timepoints and individuals. We introduce a new model-based strategy for dating organs and for reconstructing morphogenetic trajectories over unlimited time windows based on static data. Using this approach, we show that Arabidopsis thaliana leaves are initiated at regular 1-day intervals. Despite contrasted adult morphologies, leaves of different ranks exhibited shared growth dynamics, with linear gradations of growth parameters according to leaf rank. At the sub-organ scale, successive serrations from same or different leaves also followed shared growth dynamics, suggesting that global and local leaf growth patterns are decoupled. Analysing mutants leaves with altered morphology highlighted the decorrelation between adult shapes and morphogenetic trajectories, thus stressing the benefits of our approach in identifying determinants and critical timepoints during organ morphogenesis

Shear-induced pressure changes and seepage phenomena in a deforming porous layer-I

We present a model for flow and seepage in a deforming, shear-dilatant sensitive porous layer that enables estimates of the excess pore fluid pressures and flow rates in both the melt and solid phase to be captured simultaneously as a function of stress rate. Calculations are relevant to crystallizing magma in the solidosity range 0.5–0.8 (50–20 per cent melt), corresponding to a dense region within the solidification front of a crystallizing magma chamber. Composition is expressed only through the viscosity of the fluid phase, making the model generally applicable to a wide range of magma types. A natural scaling emerges that allows results to be presented in non-dimensional form. We show that all length-scales can be expressed as fractions of the layer height H, timescales as fractions of H2(nβ'θ+ 1)/(θk) and pressures as fractions of . Taking as an example the permeability k in the mush of the order of magnitude 1015 m2 Pa1 s1, a layer thickness of tens of metres and a mush strength (θ) in the range 108–1012 Pa, an estimate of the consolidation time for near-incompressible fluids is of the order of 105–109 s. Using mush permeability as a proxy, we show that the greatest maximum excess pore pressures develop consistently in rhyolitic (high-viscosity) magmas at high rates of shear ( , implying that during deformation, the mechanical behaviour of basaltic and rhyolitic magmas will differ. Transport parameters of the granular framework including tortuosity and the ratio of grain size to layer thickness (a/H) will also exert a strong effect on the mechanical behaviour of the layer at a given rate of strain. For dilatant materials under shear, flow of melt into the granular layer is implied. Reduction in excess pore pressure sucks melt into the solidification front at a velocity proportional to the strain rate. For tectonic rates (generally 1014 s1), melt upwelling (or downwelling, if the layer is on the floor of the chamber) is of the order of cm yr1. At higher rates of loading comparable with emplacement of some magmatic intrusions (1010 s1), melt velocities may exceed effects due to instabilities resulting from local changes in density and composition. Such a flow carries particulates with it, and we speculate that these may become trapped in the granular layer depending on their sizes. If on further solidification the segregated grain size distribution of the particulates is frozen in the granular layer, structure formation including layering and grading may result. Finally, as the process settles down to a steady state, the pressure does not continue to decrease. We find no evidence for critical rheological thresholds, and the process is stable until so much shear has been applied that the granular medium fails, but there is no hydraulic failure

Inferring field-scale properties of a fractured aquifer from ground surface deformation during a well test

International audienceFractured aquifers which bear valuable water resources are often difficult to characterize with classical hydrogeological tools due to their intrinsic heterogeneities. Here, we implement ground surface deformation tools (tiltmetry and optical leveling) to monitor groundwater pressure changes induced by a classical hydraulic test at the Ploemeur observatory. By jointly analyzing complementary time constraining data (tilt) and spatially constraining data (vertical displacement), our results strongly suggest that the use of these surface deformation observations allows for estimating storativity and structural properties (dip, root depth, lateral extension) of a large hydraulically active fracture, in good agreement with previous studies. Hence, we demonstrate that ground surface deformation is a useful addition to traditional hydrogeological techniques and opens possibilities for characterizing important large-scale properties of fractured aquifers with short-term well tests as a controlled forcing