Search

Stigmergy is a generic coordination mechanism widely used by animal societies, in which traces left by individuals in a medium guide and stimulate their subsequent actions. In humans, new forms of stigmergic processes have emerged through the development of online services that extensively use the digital traces left by their users. Here we combine interactive experiments with faithful data-based modeling to investigate how groups of individuals exploit a simple rating system and the resulting traces in an information search task in competitive or non-competitive conditions. We find that stigmergic interactions can help groups to collectively find the cells with the highest values in a table of hidden numbers. We show that individuals can be classified into three behavioral profiles that differ in their degree of cooperation. Moreover, the competitive situation prompts individuals to give deceptive ratings and reinforces the weight of private information versus social information in their decisions.

An anionic mechanism is used to create polymers and copolymers as confined to, or anchored to, high-surface-area porous nanoparticles. Linear polymers with soft and glassy chains, such as polyisoprene and polymethylmethacrylate, were produced by confined anionic polymerization in 3D networks of porous aromatic frameworks. Alternatively, multiple anions were generated on the designed frameworks which bear removal protons at selected positions, and initiate chain propagation, resulting in chains covalently connected to the 3D network. Such growth can continue outside the pores to produce polymer-matrix nanoparticles coated with anchored chains. Sequential reactions were promoted by the living character of this anionic propagation, yielding nanoparticles that were covered by a second polymer anchored by anionic block copolymerization. The intimacy of the matrix and the grown-in polymers was demonstrated by magnetization transfer across the interfaces in 2D 1 H-13 C-HETCOR NMR spectra.

Physical forms of active pharmaceutical ingredients (APIs) play a crucial role in drug discovery since 85% of API molecules exhibit polymorphism and sometimes complicated phase behavior, often resulting in important differences in the respective biochemical and physical properties. Characterization and quantitation of the different forms are becoming more and more essential in the pharmaceutical industry: once these characteristics are known, it is easier to choose the best solid form for development, formulation, manufacturing, and storage. Time domain-nuclear magnetic resonance (TD-NMR) has recently been used to develop a quantitation protocol for solid mixtures, named qSRC, based on the linear combination of T1 saturation recovery curves (SRCs) collected on a bench-top instrument. Despite its potentials and ease of use, a limited number of application cases have been reported in the literature since its development and many aspects remain to be clarified for the technique to be adopted as a robust routinely industrial analytical tool. In the present work, the reliability of the qSRC approach has been studied by focusing on the role played by key experimental variables, including mixture composition, signal-to-noise ratio, and T1 differences. In silico simulations were carried out for a wide range of theoretical cases to predict the expected level of accuracy obtainable for a given sample-parameter acquisition set and to clearly define the range of applicability of the method. Results of the simulation are presented alongside a comparison with three real-case studies of commercially available APIs: piroxicam, naproxen sodium, and benzocaine.

Weak interactions (hydrogen bonds, halogen bonds, CH···π and π-π stacking) can play a significant role in the formation of supramolecular assemblies with desired structural features. In this contribution, we report a systematic investigation on how a halogen bond (XB) can modulate the structural arrangement of silver supramolecular complexes. The complexes are composed of X-phenyl(bispyrazolyl)methane (X = Br, I) and I-alkynophenyl(bispyrazolyl)methane ligands functionalized in meta (L3Br, L3I) and para (L4Br, L4I, L4CCI) positions on a phenyl ring with the purpose of providing different directionalities of the X function with respect to the N,N coordination system. The obtained [Ag(L)2]+ moieties show remarkable geometric similarities, and the L4Br, L4I, and L4CCI ligands exhibit the most conserved types of supramolecular arrangement that are sustained by XB. The increased σ-hole in L4CCI with respect to L4I leads to an occurrence of short (and strong) XB interactions with the anions. [Ag(L4I)2]PF6 and [Ag(L4I)2]CF3SO3 are characterized by the presence of three different phases, and the single-crystal evolution from phase-1 (a honeycomb structure with large 1D cavities) to phase-3 (solventless) occurs by a stepwise decrease in the crystallization solvent content, which promotes an increase in XB interactions in the lattice. The present paper aims to provide useful tools for the selection of appropriate components for the use of coordination compounds to build supramolecular systems based on the halogen bond.

The present study focuses on the assembly of organo-cations with organo-anions in water. The anions, characterized by symmetric moieties (carbon-, adamantane-, or calixarene-based) functionalized with directional hydrogen bond (HB) acceptor functions (tetra-sulfonate moieties), are combined with planar guanidinium or terephtalimidamide cations as hydrogen bond donors, the purpose being to integrate water molecules into the lattice. The imbalance between the charge on the two components, and the considerable number of HB donor and acceptor sites, promotes the insertion of water into the structures. In the reported structures, a part of the water molecules serves as a structural linker between the anions and cations, while the remaining molecules cluster into channels and cavities in a loose association with the supramolecular matrix framework.

Physical forms of active pharmaceutical ingredients (APIs) play a crucial role in drug discovery since 85% of API molecules exhibit polymorphism and sometimes complicated phase behavior, often resulting in important differences in the respective biochemical and physical properties. Characterization and quantitation of the different forms are becoming more and more essential in the pharmaceutical industry: once these characteristics are known, it is easier to choose the best solid form for development, formulation, manufacturing, and storage. Time domain-nuclear magnetic resonance (TD-NMR) has recently been used to develop a quantitation protocol for solid mixtures, named qSRC, based on the linear combination of

In the search for flexible molecular crystals endowed with porosity, we achieved the fabrication of expandable crystalline prototypal structures, which allow the absorption of gases, without modifying the crystal architecture. The design brings together highly symmetrical tetrahedral elements to construct swellable porous adamantoid frameworks through co-operation of eight surrounding hydrogen bonds mounted on conformationally flexible groups. The flexibility of the porous crystals manifests itself in response to stimuli of selected gases, which promote reversible conformational changes, inducing breathing in the molecular structure. The backbone of the reticular construction is based on the formation of the carboxylic dimers, which project outwards from the tetrahedral molecular core to consolidate the 3D framework. Contact with proper gases such as CO2, Xe and hexane triggers a 56-70% enlargement of the channel cross-section. The accommodation of CO2 and Xe in the channel chambers was revealed by synchrotron-light X-ray diffraction, combined with molecular dynamics and density functional theory (DFT) theoretical calculations. Rare experimental observations of xenon dynamics, in which Xe diffuses along the channels and experiences different chamber orientations in the crystal, were gathered by analysing 129Xe NMR chemical shift anisotropy profiles, which encode the shape and orientation of each visited cavity along the channel. The jump rate and activation energy experienced was uniquely established by exploring Xe atoms in their diffusional path. Nitrogen showed a low affinity to the matrix and was unable to enlarge the pores, thus it was excluded from the restrictive pores of the empty crystal. Given the properties of molecular crystals, it is possible to outline some advantageous aspects, such as simple design, easy self-assembly, solubility, reversible gas uptake and absence of metal ions, and they can thus be considered for eco-friendly gas capture and separation.

Electrostatic charges patterning along crystalline channels recognize CO2 with high selectivity and promote its fast screwing dynamics through the crystal at one million steps per second, strongly reminiscent of trans-membrane transport in biological channels., Porous molecular materials represent a new front in the endeavor to achieve high-performance sorptive properties and gas transport. Self-assembly of polyfunctional molecules containing multiple charges, namely, tetrahedral tetra-sulfonate anions and bifunctional linear cations, resulted in a permanently porous crystalline material exhibiting tailored sub-nanometer channels with double helices of electrostatic charges that governed the association and transport of CO2 molecules. The charged channels were consolidated by robust hydrogen bonds. Guest recognition by electrostatic interactions remind us of the role played by the dipolar helical channels in regulatory biological membranes. The systematic electrostatic sites provided the perfectly fitting loci of complementary charges in the channels that proved to be extremely selective with respect to N2 (S = 690), a benchmark in the field of porous molecular materials. The unique screwing dynamics of CO2 travelling along the ultramicropores with a step-wise reorientation mechanism was driven by specific host–guest interactions encountered along the helical track. The unusual dynamics with a single-file transport rate of more than 106 steps per second and an energy barrier for the jump to the next site as low as 2.9 kcal mol–1 was revealed unconventionally by complementing in situ13C NMR anisotropic line-shape analysis with DFT modelling of CO2 diffusing in the crystal channels. The peculiar sorption performances and the extraordinary thermal stability up to 450 °C, combined with the ease of preparation and regeneration, highlight the perspective of applying these materials for selective removal of CO2 from other gases.

Porous molecular materials represent a new front in the endeavor to achieve high-performance sorptive properties and gas transport. Self-assembly of polyfunctional molecules containing multiple charges, namely, tetrahedral tetra-sulfonate anions and bifunctional linear cations, resulted in a permanently porous crystalline material exhibiting tailored sub-nanometer channels with double helices of electrostatic charges that governed the association and transport of CO2 molecules. The charged channels were consolidated by robust hydrogen bonds. Guest recognition by electrostatic interactions remind us of the role played by the dipolar helical channels in regulatory biological membranes. The systematic electrostatic sites provided the perfectly fitting loci of complementary charges in the channels that proved to be extremely selective with respect to N2 (S = 690), a benchmark in the field of porous molecular materials. The unique screwing dynamics of CO2 travelling along the ultramicropores with a step-wise reorientation mechanism was driven by specific host–guest interactions encountered along the helical track. The unusual dynamics with a single-file transport rate of more than 106 steps per second and an energy barrier for the jump to the next site as low as 2.9 kcal mol−1 was revealed unconventionally by complementing in situ13C NMR anisotropic line-shape analysis with DFT modelling of CO2 diffusing in the crystal channels. The peculiar sorption performances and the extraordinary thermal stability up to 450 °C, combined with the ease of preparation and regeneration, highlight the perspective of applying these materials for selective removal of CO2 from other gases.

Essential oils (EOs) have deserved much attention in the past decades for their antimicrobial activity, since many of them have demonstrated efficacy against food-borne pathogenic and spoilage microorganisms. Moreover, they have potential application in animal nutrition as multifunctional feed supplements, avoiding or diminishing the use of antibiotics in livestock. However, low solubility and bioavailability as well as volatility and marked aromatic note are important limitations in food and feed applications. In this study we present the synthesis, characterization and evaluation of the antibacterial activity of new thymol, carvacrol and menthol derivatives. The new compounds have been designed to overcome the limitations of the precursors, such as poor water solubility and volatility, still maintaining a good antimicrobial profile. We evaluated the activity of the synthetized compounds against pathogens causing important foodborne diseases, i . e . Clostridium perfringens , Salmonella typhimurium , Salmonella enteritidis and Escherichia coli . The low MICs and MBCs values for some of the studied compounds, combined with water solubility and negligible cytotoxicity towards HT-29 human cells, confirmed the potential use for EOs derivatives in the food industry.

The sensitivity of 129Xe NMR to the size and shape of the cavities makes, both thermally-polarized and hyper-polarized techniques, invaluable for the characterization of porous materials, such as MOFs and molecular crystals [1-2]. In this presentation, the chemical shift anisotropy (CSA) pattern mirrors not only shape and symmetry of the explored rooms, but also the dynamics of xenon jumping from one site to the next. This study belongs to a program for generating ultra-fast molecular rotors and understanding dynamics in porous crystals [3-4]. Tetra-carboxylic molecules could be obtained in the permanently porous form for the stability imparted by 8 hydrogen bonds: the material was explored by xenon and the anisotropic 129Xe signal resonates in the 220-320 ppm range, indicating a tight fit of the gas atom in the adsorption sites [5]. The intriguing line-shape evolution (see figure) denotes a temperature dependent exchange dynamics (observed at 10 bar loading pressure) and was interpreted as the effect of thermally activated Xe jumps to adjacent vacant sites along the channels. Each site is marked by the relative orientations. Indeed, the explored cavities show elliptical cross-sections (e = 0.75), alternatively rotated by 90° about the channel axis, as CSA profile below 240 K depicts. At higher temperatures, xenon atoms dynamically explore the two orientations and, when the exchange rates exceed the frequency span of the tensor principal components, Xe perceives an averaged interaction. This interpretation allowed us to simulate the anisotropy and assign at each pattern a specific jump-rate and to measure, by an Arrhenius plot, the energy barrier for an individual jump of 1.8 kcal/mol. Ab initio calculations and molecular dynamics confirm the high mobility of xenon atoms inside the structure and evaluate a consistent energy barrier. The experimental single-jump frequency and energy were the basis to establish xenon diffusion rate in the narrow channels. Source of founding PRIN 2017-20 -NAZ-104, Cariplo Foundation 2017-19 BALANCE and INSTM-Lombardy 2017-18. References: [1] Porous Materials Explored by Hyperpolarized Xenon NMR; P. Sozzani, S. Bracco, A. Comotti in Hyperpolarized Xenon-129 Magnetic Resonance T. Meersman and E. Brunner (Eds.), 2015, 164. [2] A. Comotti, S. Bracco, P. Sozzani, S. Horike, R. Matsuda, S. Kitagawa JACS, 2008, 130,13664. [3] Review: Molecular rotors build in porous materials; S. Bracco, A. Comotti, P. Sozzani, Acc. Chem. Res., 2016, 49, 1701. [4] S. Bracco, F. Castiglioni, A. Comotti, S. Galli, M. Negroni, A. Maspero, P. Sozzani, Chem. Eur. J., 2017, 23, 11210. [5] I. Bassanetti, S. Bracco, A. Comotti, M. Negroni, C. Bezuidenhout, S. Canossa, P. P. Mazzeo, L. Marchio’, P. Sozzani J Mater. Chem A (in press).

A series of porous organic polymers were synthetized through extensive cross-linking of aromatic monomers containing multiple reactive sites. The inefficient packing of monomeric units determined the formation of highly porous frameworks with surface areas up to 4800 m2/g and broad pore size distributions. Besides, the formation of strong covalent bonds accounted for high chemical and thermal stability. In depth solid state NMR analysis allowed us to check the purity of samples and to determine the connectivity and the microstructure of porous frameworks. Due to their possible application in Adsorbed Natural Gas technology (ANG) methane uptake was measured up to 180 bar at room temperature. The methane uptake at high pressure was related to the surface area and the total pore volume obtained by nitrogen adsorption isotherms at 77K. For example, triptycene-based material (TRIP) with surface area as high as 1600 m2/g could adsorb more than 400 cm3/g of methane at 180 bar. We also evaluated the volumetric methane uptake (cm3 of adsorbate per cm3 of adsorbent) at high pressure which is a critical parameter in methane transportation by ships. Moreover, the volumetric uptake allowed us to compare the results directly with compressed natural gas technology (CNG). At 180 bar the methane adsorption of TRIP sample reached a considerable value of 220 cm3/cm3. Furthermore, we could evaluate the gain in methane storage due to the presence of the porous material by comparing the total volumetric uptake of CH4 in presence of TRIP with pure compressed methane: a gain above 100% could be achieved up to 65 bar (Figure1). The isosteric heat of adsorption, as measured by the Clausius-Clapeyron equation, provided an insight into the strength of interactions between the methane molecules and the pore walls. At low coverage it ranged from 19 to 21 KJ/mol and it was among the highest value reported in literature. Such high values were attributed to multiple CH-π interactions between the methane molecules and the electron-rich aromatic rings. Lastly, we investigated carbon dioxide uptake up to 10 bar. All samples showed high CO2 uptake, isosteric heat of adsorption up to 30 KJ/mol and an excellent CO2/N2 selectivity ranging from 20 to 25 at room temperature (estimated by the Ideal Adsorbed Solution Theory IAST). These adsorption properties combined with the high chemical and thermal resistance and low hydrophilicity made porous organic polymers attractive for post-combustion treatment of industrial emissions. [1] Bracco, S.; Piga, D.; Bassanetti, I.; Perego J.; Comotti A.; Sozzani P. J. Mater. Chem. A 2017, 5, 10328-10337.

Our approach is to design porosity in combination with switchable dynamics and flexibility in porous materials for gaining control over gas capture and selectivity. This approach was made possible by fabricating rotor-on-axel molecular struts and tetrahedral building blocks. Ultra-fast molecular rotors as fast as 1011 Hz were engineered in porous crystalline frameworks (molecular crystals, MOFs and mesoporous organosilicas) containing rod-like linkers as amphidynamic elements. The porous frameworks promise access to the control of rotary motion by chemical and physical stimuli. If a gas or a vapor is diffused to the cavities, such as CO 2, iodine and hydrocarbon vapors, rotor dynamics is hampered. In turn, on/off switching produces modulated physical responses. When C-F dipoles were mounted on the rotors, they induced fast oscillating dipoles that interact with an applied electric field. Direct evidence of hostguest interactions at the molecular level were established by 2D solid-state NMR. We achieved the fabrication of swellable porous adamantoid frameworks by the use of highly symmetrical tetrahedral elements and the co-operation of 8 surrounding hydrogen bonds mounted on conformationally flexible groups. The flexibility of the porous crystals manifests itself in response to stimuli of selected gases: CO2, Xe and hexane triggers the enlargement of channel cross-section. The accomodation of CO2 and Xe in the channel chambers was revealed by synchrotron-light XRD, combined with modelling. Xenon dynamics was gathered by 129Xe NMR chemical shift anisotropy profiles, which encode the shape and orientation of each visited cavity. Jump rate and activation energy experienced by exploring Xe atoms were uniquely established. Covalent connection of tetrahedral nodes results in expandable frameworks, especially if 3 instead of all 4 branches are cross-linked: the forth branch can be dedicated to bearing a functional group to catch the gas molecules (CO 2 is retained by –NH2 group by an energy as high as 54 kJ/mol). Moreover, photo-responsive molecular crystals were fabricated by tetrahedral azobenzene tetramers that form porous molecular crystals in their trans configuration. The efficient trans-to-cis photoisomerization converts the crystals into a non-porous phase but crystallinity and porosity are restored upon reverse isomerization promoted by heat. We demonstrated that the photo-isomerization enables reversible on/off switching of optical properties as well as CO2 capture from the gas phase. We thank Cariplo Foundation, Lombardy Region/INSTM Consortium and PRIN 2016. References 1. Acc.Chem.Res.2016,49,1701; 2. Chem.Eur.J. 2017,23,11210; 3. J.Am.Chem.Soc.2014,136,618; 4. Angew.Chem.Int.Ed. 2014,53,1043. 5. Chem.Comm.2017,53,7776; 6. J.Mater.Chem.A2018,6,14231; 7. Chem.Comm. DOI:10.1039/C8CC03951H; 8. NatureChem. 2015,7,634.

Two novel pillared Zn(II)-based Metal–Organic Frameworks were de novo synthesized exploiting N,N′-(1,1′-biphenyl)-4,4′-diylbis-4-pyridinecarboxamide (bpba) and its fluorinated analogous N,N′-(perfluoro-1,1′-biphenyl-4,4′-diyl)diisonicotinamide (F-bpba) as suitable pillar linkers and 2,6-naphthalene dicarboxylic acid as carboxylic ligand. The resulting heteroleptic MOFs, namely, PUM210, [Zn4(bpba)1.5·(ndc)4·(H2O)]n and PUM210F, [Zn3(F-bpba)1·(ndc)3·(DMF)]n, feature an uncommon truncation of the Zn(II) paddle-wheel nodes along the pillaring direction. PUM210 and PUM210F exhibit a polycatenated architecture, resulting in microporous channels decorated by amide moieties. The activated forms show a permanent porosity and a selective adsorption of CO2 over N2. Moreover, the partially transmetalated Cu-PUM210 and Cu-PUM210F were obtained by convenient transmetalation protocol and their adsorption propriety toward CO2 were subsequently investigated.

In this study, we show how the combination of metal ions, counter-anions and opportunely functionalized and preorganized ligands gives rise to two distinct supramolecular isomers, coordination polymeric chains and hexameric macrocycles. The hexamers then aggregate to form a cubic structure exhibiting permanent microporosity. The supramolecular assemblies are formed with Ag(+), thioether functionalized bis(pirazolyl)methane ligands and CF3SO3(-)/PF6(-) as the counter-anions. Five different ligands were prepared by modifying the peripheral thioether moiety with naphthyl, methoxy, m-Me, p-Me and F groups (L(SNf), L(SPhOMe), L(SPhm-Me), L(SPhp-Me), and L(SPhF)). Helicoidal coordination polymeric chains are formed with CF3SO3(-) (general formula [Ag(L)]n(CF3SO3)n), whereas macrocyclic hexamers are formed with PF6(-) (general formula [Ag(L)]6(PF6)6). The macrocycles self-assemble into ordered capsules with the shape of a tetrahedron, and the overall framework is sustained by Ag(+)···(PF6(-))···Ag(+) contacts. The capsules generate a highly symmetric structural arrangement, which is characterized by permanent microporosity arising from two distinct types of microporous chambers in the structure. The gas absorption isotherms show that the materials can selectively adsorb CO2 and N2O over CH4 and N2. The modulation of the microporosity of the materials is achieved by the different thioether functionalization of the ligands L(SNf), L(SPhOMe), L(SPhm-Me), and L(SPhF). The diffusion and localization of the gas molecules within the cavities were investigated by 2D (1)H-(13)C solid state NMR on samples loaded with enriched (13)CO2, showing that both types of cavities are accessible to guest molecules from the gas phase.

This work examines the crystal structures of 15 Ag(I) complexes with thioether functionalized bis(pyrazolyl)methane derivatives to rationalize the influence of the ligand on the formation of (a) coordination polymers (CPs), (b) oligonuclear (hexameric and dinuclear) complexes, and (c) mononuclear complexes. It was previously reported how this ligand class could generate microporous architectures with permanent porosity. Some ligand modifications could induce a cavity size modulation while preserving the same overall architecture. The bis(pyrazolyl)methane scaffold can be easily functionalized with various structural fragments; hence the structural outcomes were studied in this work using various ligand modifications and Ag(I) salts. In particular, six new ligand classes were prepared with the following features: (1) The steric hindrance on the pyrazole rings L3,3′Me, L5,5′Me, L5,3′Me, LCF3, and LBr was modified. (2) The steric hindrance was reduced on the peripheral thioether group: LSMe. (3) Finally, the...

The following AgI bis(pyrazolyl)methane complexes with BF4–/NO3– as counteranions were synthesized and characterized: [Ag(LpzH)]2(NO3)2 (1), [Ag(LpzMe)]2(NO3)2 (2), [Ag(LpzH)]n(BF4)n (3), and [Ag(LpzMe)]n(BF4)n (4) [LpzH = bis(pyrazolyl)methane; LpzMe = bis(3,5-dimethylpyrazolyl)methane]. These complexes were prepared to identify optimum precursors for the thermolytic deposition of metallic silver. The crystal structures of 1 and 2 show that the complexes are dinuclear and that the NO3– anions interact with the metals. In contrast, 3 is polymeric and the BF4– does not interact with the metal. When crystallizing 1–4 in non-anhydrous solvents, the presence of adventitious water further reacts with 3 and 4 (but not with 1 and 2) to yield dinuclear complexes [Ag(LpzH)(H2O)2]2(BF4)2 (3a) and [Ag(LpzMe)(H2O)2]2(BF4)2 (4a). All of the dinuclear species 1, 2, 3a and 4a exhibit an argentophilic interaction with Ag···Ag distances in the range 3.18–2.99 A. Thermogravimetric analysis (TGA) shows that 1 and 2 have lower decomposition temperatures (231 and 255 °C, respectively) than 3 and 4 (298 and 331 °C, respectively). 2 was further investigated as a precursor for metallic silver deposition by spin-coating solutions (10–3 M, THF/DMSO, 4:1), followed by annealing at 310 °C on 52100 steel substrates. According to energy-dispersive X-ray spectroscopy (EDS) and scanning electron microscopy (SEM) the metal deposition proceeds primarily via an island growth (Volmer–Weber) mechanism.