The Experts below are selected from a list of 14661 Experts worldwide ranked by ideXlab platform
Davide Bonifazi - One of the best experts on this subject based on the ideXlab platform.
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Programming Recognition Arrays through Double Chalcogen-Bonding Interactions.
Chemistry: A European Journal, 2017Co-Authors: Nicolas Biot, Davide BonifaziAbstract:In this work, we have programmed and synthesized a recognition motif constructed around a Chalcogenazolo-pyridine scaffold (CGP) that, through the formation of frontal double Chalcogen-bonding interactions, associates into dimeric EX-type complexes. The reliability of the double Chalcogen-bonding interaction has been shown at the solid-state by X-ray analysis, depicting the strongest recognition persistence for a Te-congener. The high recognition fidelity, chemical and thermal stability and easy derivatization at the 2-position makes CGP a convenient motif for constructing supramolecular architectures through programmed Chalcogen-bonding interactions.
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supramolecular wiring of benzo 1 3 Chalcogenazoles through programmed Chalcogen bonding interactions
Chemistry: A European Journal, 2016Co-Authors: Adrian Kremer, Andrea Fermi, Nicolas Biot, Johan Wouters, Davide BonifaziAbstract:The high-yielding synthesis of 2-substituted benzo-1,3-tellurazoles and benzo-1,3-selenazoles through a dehydrative cyclization reaction has been reported, giving access to a large variety of benzo-1,3-Chalcogenazoles. Exceptionally, these aromatic heterocycles proved to be very stable and thus very handy to form controlled solid-state organizations in which wire-like polymeric structures are formed through secondary N⋅⋅⋅Y bonding interactions (SBIs) engaging the Chalcogen (Y=Se or Te) and nitrogen atoms. In particular, it has been shown that the recognition properties of the Chalcogen centre at the solid state could be programmed by selectively barring one of its σ-holes through a combination of electronic and steric effects exerted by the substituent at the 2-position. As predicted by the electrostatic potential surfaces calculated by quantum chemical modelling, the pyridyl groups revealed to be the stronger Chalcogen bonding acceptors, and thus the best ligand candidate for programming the molecular organization at the solid state. In contrast, the thiophenyl group is an unsuitable substituent for establishing SBIs in this molecular system as it gives rise to Chalcogen–Chalcogen repulsion. The weaker Chalcogen donor properties of the Se analogues trigger the formation of feeble N⋅⋅⋅Se contacts, which are manifested in similar solid-state polymers featuring longer nitrogen–Chalcogen distances.
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Supramolecular Wiring of Benzo‐1,3‐Chalcogenazoles through Programmed Chalcogen Bonding Interactions
Chemistry: A European Journal, 2016Co-Authors: Adrian Kremer, Andrea Fermi, Nicolas Biot, Johan Wouters, Davide BonifaziAbstract:The high-yielding synthesis of 2-substituted benzo-1,3-tellurazoles and benzo-1,3-selenazoles through a dehydrative cyclization reaction has been reported, giving access to a large variety of benzo-1,3-Chalcogenazoles. Exceptionally, these aromatic heterocycles proved to be very stable and thus very handy to form controlled solid-state organizations in which wire-like polymeric structures are formed through secondary N⋅⋅⋅Y bonding interactions (SBIs) engaging the Chalcogen (Y=Se or Te) and nitrogen atoms. In particular, it has been shown that the recognition properties of the Chalcogen centre at the solid state could be programmed by selectively barring one of its σ-holes through a combination of electronic and steric effects exerted by the substituent at the 2-position. As predicted by the electrostatic potential surfaces calculated by quantum chemical modelling, the pyridyl groups revealed to be the stronger Chalcogen bonding acceptors, and thus the best ligand candidate for programming the molecular organization at the solid state. In contrast, the thiophenyl group is an unsuitable substituent for establishing SBIs in this molecular system as it gives rise to Chalcogen–Chalcogen repulsion. The weaker Chalcogen donor properties of the Se analogues trigger the formation of feeble N⋅⋅⋅Se contacts, which are manifested in similar solid-state polymers featuring longer nitrogen–Chalcogen distances.
James W Gauld - One of the best experts on this subject based on the ideXlab platform.
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an assessment of computational methods for calculating accurate structures and energies of bio relevant polysulfur selenium containing compounds
Molecules, 2018Co-Authors: Sahar Nikoo, John J Hayward, Paul Meister, James W GauldAbstract:The heavier Chalcogens sulfur and selenium are important in organic and inorganic chemistry, and the role of such Chalcogens in biological systems has recently gained more attention. Sulfur and, to a lesser extent selenium, are involved in diverse reactions from redox signaling to antioxidant activity and are considered essential nutrients. We investigated the ability of the DFT functionals (B3LYP, B3PW91, ωB97XD, M06-2X, and M08-HX) relative to electron correlation methods MP2 and QCISD to produce reliable and accurate structures as well as thermochemical data for sulfur/selenium-containing systems. Bond lengths, proton affinities (PA), gas phase basicities (GPB), Chalcogen–Chalcogen bond dissociation enthalpies (BDE), and the hydrogen affinities (HA) of thiyl/selenyl radicals were evaluated for a range of small polysulfur/selenium compounds and cysteine per/polysulfide. The S–S bond length was found to be the most sensitive to basis set choice, while the geometry of selenium-containing compounds was less sensitive to basis set. In mixed Chalcogens species of sulfur and selenium, the location of the sulfur atom affects the S–Se bond length as it can hold more negative charge. PA, GPB, BDE, and HA of selenium systems were all lower, indicating more acidity and more stability of radicals. Extending the sulfur chain in cysteine results in a decrease of BDE and HA, but these plateau at a certain point (199 kJ mol−1 and 295 kJ mol−1), and PA and GPB are also decreased relative to the thiol, indicating that the polysulfur species exist as thiolates in a biological system. In general, it was found that ωB97XD/6-311G(2d,p) gave the most reasonable structures and thermochemistry relative to benchmark calculations. However, nuances in performance are observed and discussed.
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An Assessment of Computational Methods for Calculating Accurate Structures and Energies of Bio-Relevant Polysulfur/Selenium-Containing Compounds
Molecules, 2018Co-Authors: Sahar Nikoo, John J Hayward, Paul J. Meister, James W GauldAbstract:The heavier Chalcogens sulfur and selenium are important in organic and inorganic chemistry, and the role of such Chalcogens in biological systems has recently gained more attention. Sulfur and, to a lesser extent selenium, are involved in diverse reactions from redox signaling to antioxidant activity and are considered essential nutrients. We investigated the ability of the DFT functionals (B3LYP, B3PW91, ωB97XD, M06-2X, and M08-HX) relative to electron correlation methods MP2 and QCISD to produce reliable and accurate structures as well as thermochemical data for sulfur/selenium-containing systems. Bond lengths, proton affinities (PA), gas phase basicities (GPB), Chalcogen–Chalcogen bond dissociation enthalpies (BDE), and the hydrogen affinities (HA) of thiyl/selenyl radicals were evaluated for a range of small polysulfur/selenium compounds and cysteine per/polysulfide. The S–S bond length was found to be the most sensitive to basis set choice, while the geometry of selenium-containing compounds was less sensitive to basis set. In mixed Chalcogens species of sulfur and selenium, the location of the sulfur atom affects the S–Se bond length as it can hold more negative charge. PA, GPB, BDE, and HA of selenium systems were all lower, indicating more acidity and more stability of radicals. Extending the sulfur chain in cysteine results in a decrease of BDE and HA, but these plateau at a certain point (199 kJ mol−1 and 295 kJ mol−1), and PA and GPB are also decreased relative to the thiol, indicating that the polysulfur species exist as thiolates in a biological system. In general, it was found that ωB97XD/6-311G(2d,p) gave the most reasonable structures and thermochemistry relative to benchmark calculations. However, nuances in performance are observed and discussed.
H. Bernas - One of the best experts on this subject based on the ideXlab platform.
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Synthesis of Lead Chalcogenide Nanocrystals by Sequential Ion Implantation in Silica
Journal of Physical Chemistry B, 2005Co-Authors: R. Espiau De Lamaestre, J. Majimel, F. Jomard, H. BernasAbstract:Lead Chalcogenide (PbS, PbSe, and PbTe) nanocrystals were synthesized by sequential implantation of Pb and one of the Chalcogen species into pure silica. The implantation energy and fluence were chosen so that the implantation profiles practically overlap at a depth $\approx$ 150 nm with a maximum concentration of about 0.3 atom %. Annealing for 1-8 h at 850-900 °C triggers nanocrystal growth, which is monitored by high-resolution (HRTEM) and conventional transmission electron microscopy (TEM), secondary-ion mass spectrometry (SIMS), and Rutherford backscattering spectrometry (RBS). Striking differences are found in the depth distributions and microstructures of the resulting nanocrystals. We show that the differing chemical interactions of Pb and Chalcogens (between each other and with silica) play a crucial role in Chalcogenide nucleation and growth. Using available information on Chalcogen redox states in silicate glass, we propose a nonclassical nucleation and growth mechanism consistent with our experimental results. The complex chemistry involved at the microscopic level is shown to impair control over the nanocrystal size distribution. Finally, PbS nanocrystal-doped silica is shown to emit intense photoluminescence (PL) in the 1.5-2 $\mu$m wavelength range, an effect that we relate to the above nucleation and growth scheme.
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Diffusion properties of Chalcogens (S, Se, Te) into pure silica
Journal of Non-Crystalline Solids, 2005Co-Authors: R. Espiau De Lamaestre, J. Majimel, F. Jomard, H. BernasAbstract:The diffusion properties of Chalcogens (S, Se, Te) implanted into SiO2 were studied via secondary ion mass spectroscopy (SIMS) profiling between room temperature and the glass transition temperature (800–950 °C). Annealing of Te-containing samples leads directly to precipitation of metallic tellurium nanocrystals within the implantation profile. The S and Se concentration profiles were fitted by using a simple diffusion model in order to provide estimates of the diffusion constant and approximate solubility of these fast moving chemical species. A comparison of their differing diffusion behavior with complementary data on these systems suggests that (i) their oxidation states play a crucial role and (ii) the Chalcogen propagation mechanism actually involves complex chemical interactions.
Jonathan M White - One of the best experts on this subject based on the ideXlab platform.
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thermal conversion of a pyridine solvate to a de solvate facilitated by rearrangement of Chalcogen bonds the solvate and non solvate structures of n 2 nitro 4 3 oxobenzo d 1 2 selenazol 2 3h yl phenyl picolinamide
CrystEngComm, 2020Co-Authors: Thomas Fellowes, Martin P Van Koeverden, Jonathan M WhiteAbstract:The pyridine solvate of benzisoselenazolinone 1.pyridine is characterised by planar sheets of the benzisoselenazolinone 1 pierced by channels of pyridine molecules at an angle of 133°, the pyridine molecules are held in place by N⋯Se Chalcogen bonding to the isoselenazolinone moiety. These channels, which extend through the structure to the surface of the crystal, provide a means for escape of pyridine from the lattice when the crystal is heated to ca. 100 °C. Upon loss of the pyridine from these channels the remaining molecules undergo rearrangement to fill the space and in doing so the N⋯Se Chalcogen bond in 1.pyridine is replaced by a CO⋯Se Chalcogen bond to give the non solvate 1(ex.DMF). The geometry of the Chalcogen bond requires that the two benzisoselenazolinone ring systems which are essentially coplanar in 1.pyridine twist by an angle of 138° resulting in the formation of highly corrugated sheets in the non solvate.
Nicolas Biot - One of the best experts on this subject based on the ideXlab platform.
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Programming Recognition Arrays through Double Chalcogen-Bonding Interactions.
Chemistry: A European Journal, 2017Co-Authors: Nicolas Biot, Davide BonifaziAbstract:In this work, we have programmed and synthesized a recognition motif constructed around a Chalcogenazolo-pyridine scaffold (CGP) that, through the formation of frontal double Chalcogen-bonding interactions, associates into dimeric EX-type complexes. The reliability of the double Chalcogen-bonding interaction has been shown at the solid-state by X-ray analysis, depicting the strongest recognition persistence for a Te-congener. The high recognition fidelity, chemical and thermal stability and easy derivatization at the 2-position makes CGP a convenient motif for constructing supramolecular architectures through programmed Chalcogen-bonding interactions.
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supramolecular wiring of benzo 1 3 Chalcogenazoles through programmed Chalcogen bonding interactions
Chemistry: A European Journal, 2016Co-Authors: Adrian Kremer, Andrea Fermi, Nicolas Biot, Johan Wouters, Davide BonifaziAbstract:The high-yielding synthesis of 2-substituted benzo-1,3-tellurazoles and benzo-1,3-selenazoles through a dehydrative cyclization reaction has been reported, giving access to a large variety of benzo-1,3-Chalcogenazoles. Exceptionally, these aromatic heterocycles proved to be very stable and thus very handy to form controlled solid-state organizations in which wire-like polymeric structures are formed through secondary N⋅⋅⋅Y bonding interactions (SBIs) engaging the Chalcogen (Y=Se or Te) and nitrogen atoms. In particular, it has been shown that the recognition properties of the Chalcogen centre at the solid state could be programmed by selectively barring one of its σ-holes through a combination of electronic and steric effects exerted by the substituent at the 2-position. As predicted by the electrostatic potential surfaces calculated by quantum chemical modelling, the pyridyl groups revealed to be the stronger Chalcogen bonding acceptors, and thus the best ligand candidate for programming the molecular organization at the solid state. In contrast, the thiophenyl group is an unsuitable substituent for establishing SBIs in this molecular system as it gives rise to Chalcogen–Chalcogen repulsion. The weaker Chalcogen donor properties of the Se analogues trigger the formation of feeble N⋅⋅⋅Se contacts, which are manifested in similar solid-state polymers featuring longer nitrogen–Chalcogen distances.
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Supramolecular Wiring of Benzo‐1,3‐Chalcogenazoles through Programmed Chalcogen Bonding Interactions
Chemistry: A European Journal, 2016Co-Authors: Adrian Kremer, Andrea Fermi, Nicolas Biot, Johan Wouters, Davide BonifaziAbstract:The high-yielding synthesis of 2-substituted benzo-1,3-tellurazoles and benzo-1,3-selenazoles through a dehydrative cyclization reaction has been reported, giving access to a large variety of benzo-1,3-Chalcogenazoles. Exceptionally, these aromatic heterocycles proved to be very stable and thus very handy to form controlled solid-state organizations in which wire-like polymeric structures are formed through secondary N⋅⋅⋅Y bonding interactions (SBIs) engaging the Chalcogen (Y=Se or Te) and nitrogen atoms. In particular, it has been shown that the recognition properties of the Chalcogen centre at the solid state could be programmed by selectively barring one of its σ-holes through a combination of electronic and steric effects exerted by the substituent at the 2-position. As predicted by the electrostatic potential surfaces calculated by quantum chemical modelling, the pyridyl groups revealed to be the stronger Chalcogen bonding acceptors, and thus the best ligand candidate for programming the molecular organization at the solid state. In contrast, the thiophenyl group is an unsuitable substituent for establishing SBIs in this molecular system as it gives rise to Chalcogen–Chalcogen repulsion. The weaker Chalcogen donor properties of the Se analogues trigger the formation of feeble N⋅⋅⋅Se contacts, which are manifested in similar solid-state polymers featuring longer nitrogen–Chalcogen distances.
