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Rakesh Agrawal - One of the best experts on this subject based on the ideXlab platform.
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Role of annealing atmosphere on the crystal structure and composition of tetrahedrite–tennantite alloy nanoparticles
Journal of Materials Chemistry C, 2018Co-Authors: Scott Andrew Mcclary, Robert B. Balow, Rakesh AgrawalAbstract:Tetrahedrite–tennantite (TET–TEN, Cu12Sb4S13–Cu12As4S13) nanoparticle (NP) alloys spanning the entire Sb–As composition range were synthesized using a hot-injection method without any detectable impurities. Thin films of TET–TEN NPs were prepared from colloidal NP inks and heat treated in sulfur vapor, hydrogen sulfide, and nitrogen atmospheres. Under sulfur, the TET–TEN films were oxidized to tetragonal famatinite–luzonite (Cu3As1−xSbxS4). Heat treating under a reducing hydrogen sulfide atmosphere stabilized the mixed TET–TEN alloy compositions, though the endmember compositions partially decomposed via loss of volatile Pnictogen sulfides. Losses of Pnictogen and sulfur atoms were most significant when heat treating under an inert nitrogen atmosphere. Collectively, these results suggest that TET–TEN materials can be reversibly interconverted to famatinite–luzonite by selecting an appropriate annealing atmosphere. Our work serves as the foundation for both the synthesis and production of device-quality TET–TEN and related chalcogenide NP thin films.
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role of annealing atmosphere on the crystal structure and composition of tetrahedrite tennantite alloy nanoparticles
Journal of Materials Chemistry C, 2018Co-Authors: Scott Andrew Mcclary, Robert B. Balow, Rakesh AgrawalAbstract:Tetrahedrite–tennantite (TET–TEN, Cu12Sb4S13–Cu12As4S13) nanoparticle (NP) alloys spanning the entire Sb–As composition range were synthesized using a hot-injection method without any detectable impurities. Thin films of TET–TEN NPs were prepared from colloidal NP inks and heat treated in sulfur vapor, hydrogen sulfide, and nitrogen atmospheres. Under sulfur, the TET–TEN films were oxidized to tetragonal famatinite–luzonite (Cu3As1−xSbxS4). Heat treating under a reducing hydrogen sulfide atmosphere stabilized the mixed TET–TEN alloy compositions, though the endmember compositions partially decomposed via loss of volatile Pnictogen sulfides. Losses of Pnictogen and sulfur atoms were most significant when heat treating under an inert nitrogen atmosphere. Collectively, these results suggest that TET–TEN materials can be reversibly interconverted to famatinite–luzonite by selecting an appropriate annealing atmosphere. Our work serves as the foundation for both the synthesis and production of device-quality TET–TEN and related chalcogenide NP thin films.
Neil Burford - One of the best experts on this subject based on the ideXlab platform.
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tris benzoimidazol amine l complexes of Pnictogen iii and Pnictogen v cations and assessment of the lp 3 lpf2 3 redox couple
Chemical Science, 2018Co-Authors: Ala'aeddeen Swidan, Riccardo Suter, Charles L. B. Macdonald, Neil BurfordAbstract:A series of cationic complexes involving a Pnictogen(III) (Pn = P, As, Sb) centre and the tetradentate ligand tris((1-ethyl-benzoimidazol-2-yl)methyl)amine (BIMEt3) have been synthesized and comprehensively characterized. Oxidation of [P(BIMEt3)]3+ with XeF2 provides access to [PF2(BIMEt3)]3+ representing the first structurally characterized example of a phosphorus(V) centred trication.
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Tris(benzoimidazol)amine (L) complexes of Pnictogen(iii) and Pnictogen(v) cations and assessment of the [LP]3+/[LPF2]3+ redox couple.
Chemical science, 2018Co-Authors: Ala'aeddeen Swidan, Riccardo Suter, Charles L. B. Macdonald, Neil BurfordAbstract:A series of cationic complexes involving a Pnictogen(III) (Pn = P, As, Sb) centre and the tetradentate ligand tris((1-ethyl-benzoimidazol-2-yl)methyl)amine (BIMEt3) have been synthesized and comprehensively characterized. Oxidation of [P(BIMEt3)]3+ with XeF2 provides access to [PF2(BIMEt3)]3+ representing the first structurally characterized example of a phosphorus(V) centred trication.
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Coordination complexes of Pnictogen(V) cations
Coordination Chemistry Reviews, 2016Co-Authors: Paul A. Gray, Neil BurfordAbstract:Abstract The Pnictogen elements can access a wide range of oxidation states and coordination numbers, but are usually associated with molecules that behave as Lewis bases. Some Pnictogen based compounds exhibit Lewis acidic behaviour and the presence of a positive charge augments their electrophilicity. Pnictogen(V)-centred cationic systems have the potential to behave as highly effective Lewis acceptor sites, but are superficially developed. The rare examples of these systems are reviewed herein, including their synthesis, characterisation, structure and bonding. The molecules discussed are categorised by the generic formulae [PnX 4 L] + , [PnX 4 L 2 ] + , [PnX 2 YL] + , [PnY 2 L 2 ] + , [PnX 3 L] 2+ , [PnX 3 L 2 ] 2+ or [PnXYL 2 ] 2+ , where X is a substituent such as halide or alkyl, Y is a divalent substituent such as O, S or NR, and L is a neutral ligand. The compounds represent Pnictogen analogues of transition metal coordination complexes and identify a potentially broad new direction in coordination chemistry.
José Elguero - One of the best experts on this subject based on the ideXlab platform.
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An insight on the aromatic changes in closed shell icosagen, tetrel, and Pnictogen phenalenyl derivatives
Structural Chemistry, 2017Co-Authors: Cristina Trujillo, Goar Sánchez-sanz, Ibon Alkorta, José ElgueroAbstract:A computational study of the aromatic and antiaromatic characteristics of closed shell charged phenalenyl (PLY^+1 and PLY^−1) upon replacement of the central carbon atom by icosagen (B, Al and Ga), tetrel (Si and Ge) and Pnictogen (N, P and As) atoms comprising systems in which the icosagen and Pnictogen derivatives considered are neutral while the tetrel ones are anions or cations, has been carried out at the B3LYP/6–311++G(d,p) computational level. By substitution, two different kinds of structures have been obtained, one planar (N and B) and another one bowl-shaped depending on the size of the central atom. In terms of aromaticity, the substitution of the central C atom causes a loss of the aromatic character in all cases as indicated by nucleus-independent chemical shifts (NICS) profiles and NICS values on the 0.001 au isosurface. Regarding the charge, PLY^+1 presents larger electron delocalisation than PLY^−1, phenomenon associated with aromaticity. Furthermore, the current density maps for those planar systems corroborate NICS findings, showing anticlockwise currents in PLY^+1 (like in benzene) but clockwise in PLY-N^0 and PLY-B^0, indicating aromatic and antiaromatic behaviour, respectively.
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Competition between intramolecular hydrogen and Pnictogen bonds in protonated systems
Theoretical Chemistry Accounts, 2016Co-Authors: Goar Sánchez-sanz, Cristina Trujillo, Ibon Alkorta, José ElgueroAbstract:A theoretical study of the competition between hydrogen (HB) and Pnictogen bonds (ZB) in three different families of compounds, (Z)-1,2-disubstituted ethenes (Eth), 1,2-disubstituted benzenes (Phe) and 1,8-disubstituted naphthalenes (Naph), with a charged group, ZH3+ and a neutral one, Z′H2 (Z, Z′ = N, P, As) as interacting moieties, has been carried out. In those structures with a NH3+ motif, intramolecular hydrogen bond structures are minima while Pnictogen interactions are transition states. The opposite is true for PH3+ and AsH3+ moieties. An analysis of isodesmic energies (Eiso), interaction energies (Eb) and deformation energies (Edef) shows that in Eth derivatives, the most stable compound corresponds to P+–N ZB while in the Phe and Naph ones, the N+–N HB interaction presents the largest negative isodesmic energy. Also, Eth and Phe derivatives show negative Eiso values for all the compounds under study; however, in some cases of Naph derivatives positive isodesmic energies have been found. The Atoms in Molecules (AIM) analysis of the electron density, natural bond orbital (NBO) second-order orbital energies and electron density shift maps (EDS) have been used to better understand these intramolecular interactions.
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Modulating intramolecular P···N Pnictogen interactions.
Physical chemistry chemical physics : PCCP, 2016Co-Authors: Goar Sánchez-sanz, Cristina Trujillo, Ibon Alkorta, José ElgueroAbstract:A computational study of the intramolecular Pnictogen bond in 8-phosphinonaphthalen-1-amine derivatives (1-NX2, 8-PX2 with X = H, F, Cl, Br, CH3, CN and NC), proton sponge analogues, has been carried out to determine their structural and geometric parameters, interaction energies and electronic properties such as the electron density of the intramolecular interaction. Our results show that substitution of H atoms in the PH2 group by electron withdrawing groups on the Lewis acid moiety strengthens the P⋯N Pnictogen bond, evidenced by the increasing electron density values at the bond critical point and by shorter distances. However, substitutions on the Lewis base moiety (NX2) show weaker P⋯N interactions than when the substitution is done on the Lewis acid counterpart (PX2). Nevertheless, in all cases, Pnictogen bonds are enhanced upon substitution with respect to the parent 1-NH2, 8-PH2 system. Second-order orbital interaction energies, electron density maps, electron delocalization functions and charge transfer corroborate the evolution of the P⋯N strength upon substitution.
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Theoretical study of cyanophosphines: Pnicogen vs. dipole–dipole interactions
Computational and Theoretical Chemistry, 2015Co-Authors: Goar Sánchez-sanz, Cristina Trujillo, Ibon Alkorta, José ElgueroAbstract:Abstract Cyanophosphine derivative dimers, [HXP(CN)] 2 with X = H, F and Cl, have been characterized by means of CCSD(T)/aug′-cc-pVTZ//MP2/aug′-cc-pVTZ computational level calculations. Different interactions have been found upon complexation, such as hydrogen bonds, pnicogen bonds and dipole···dipole interactions. The intermolecular distances range between 2.84 and 3.53 A and the binding energies between −34.7 and −3.6 kJ mol −1 . Compounds with dipole···dipole interactions present shorter contact distances and larger (more negative) binding energies than those with pure P···P pnicogen bonds. Electron density shift maps show larger variations in compounds with dipole···dipole interactions than in those with pure pnicogen ones, in line with the energetic results. However, NBO analysis suggests that the complexes with P···P pnicogen bonds, in special those with XP···PX (X = F, Cl) show E(2) orbital interaction energies much larger than the dipole···dipole ones.
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σ–σ and σ–π pnicogen bonds in complexes H_2XP:PCX, for X = F, Cl, OH, NC, CN, CCH, CH_3, and H
Theoretical Chemistry Accounts, 2014Co-Authors: Janet E. Del Bene, Ibon Alkorta, José ElgueroAbstract:Ab initio MP2/aug’-cc-pVTZ calculations have been carried out on complexes H_2XP_s:P_tCX, for X = F, Cl, OH, NC, CN, CCH, CH_3, and H, in search of complexes stabilized by P···P pnicogen bonds. These intermolecular bonds arise when a pnicogen atom acts as a Lewis acid for complex formation. Three sets of equilibrium structures have been found on the H_2XP_s:P_tCX potential surfaces. Conformation A complexes have P···P σ–σ pnicogen bonds, which involve the σ systems of both P atoms. Conformations B and C are stabilized by σ–π pnicogen bonds, which involve the σ system of H_2XP and the π system of PCX. Binding energies of B and C complexes are similar and are greater than the binding energies of the A conformers. Charge transfer stabilizes A, B, and C conformers. In A complexes, the dominant charge transfer is from the lone pair of PCX to the antibonding σ*P–A orbital of PH_2X, with A the atom of X directly bonded to P. For conformations B and C, the dominant charge transfer is from the P=C π orbital to the σ*P–A orbital of H_2XP. Although the binding energies of these complexes do not correlate with the intermolecular P–P distances, both the charge-transfer energies and the equation-of-motion coupled cluster singles and doubles one-bond ^31P–^31P spin–spin coupling constants do correlate with the P–P distances. The largest coupling constants ^1pJ(P–P) are found for complexes with conformation A, due to the nature of the σ–σ pnicogen bond and the dominance of the Fermi contact term. For a given X, ^1pJ(P–P) values are ordered A > C > B.
Darren W. Johnson - One of the best experts on this subject based on the ideXlab platform.
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Coupling Metaloid-Directed Self-Assembly and Dynamic Covalent Systems as a Route to Large Organic Cages and Cyclophanes
2018Co-Authors: Mary S. Collins, Lev N. Zakharov, Ngoc-minh Phan, Darren W. JohnsonAbstract:The synthesis of large cyclic and caged disulfide structures was achieved by Pnictogen-assisted iodine oxidation starting from self-assembled Pnictogen thiolate complexes. The directing behavior of Pnictogen enables rapid and selective syntheses of many discrete disulfide assemblies over competing oligomers/polymers, ranging from structures that are small and strained to those that are large and multifaceted, including 3D cages. Traditional cyclization reactions carried out under kinetic control are generally low-yielding, which often results in the formation of insoluble oligomers and polymers as unwanted side products. The prospect of self-assembling organic structures efficiently under thermodynamic control adds an attractive tool for the synthesis of cyclophanes and other large cage compounds. This method of metaloid-directed self-assembly within a dynamic covalent system allows for the rapid and discriminant self-assembly of disulfide cyclophanes without the consequences sometimes seen in traditional cyclophane syntheses such as poor yields, long reaction times, low ring-closing selectivity, and extensive purifications. The present paper provides an overview of this approach, explores the role of the Pnictogen additive and solvent in this reaction, begins to test the limits of this strategy in complex 3D molecule formation, and extends our strategy to include one-pot syntheses that do not require the use of a Pnictogen additive. This Viewpoint also includes an extended introduction to serve as a minireview highlighting the utility of a self-assembly approach to create organic cage structures. From a practical standpoint, the cyclophanes isolated from this method can serve as precursors in the production of insulating plastics (e.g., through the widely used parylene polymerization process, which uses derivatives of paracyclophane as monomers) or as potential hosts for molecular separations or capture
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Pnictogen-directed synthesis of discrete disulfide macrocycles
Chemical communications (Cambridge England), 2013Co-Authors: Mary S. Collins, Lev N. Zakharov, Matthew E. Carnes, Aaron C. Sather, Orion B. Berryman, Simon J. Teat, Darren W. JohnsonAbstract:Cyclic disulfide macrocycles were rapidly synthesized cleanly and selectively from rigid dithiols via oxidation with iodine when activated by Pnictogen additives (As and Sb). Macrocycles were confirmed by (1)H-NMR spectroscopy and X-ray crystallography. A p-xylyl-based disulfide trimer and tetramer crystallized in hollow, stacked columns stabilized by intermolecular, sulfur···sulfur close contacts.
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Design Considerations for the Group 15 Elements: The Pnictogen···π Interaction As a Complementary Component in Supramolecular Assembly Design
Crystal Growth & Design, 2010Co-Authors: Virginia M. Cangelosi, Melanie A. Pitt, W. Jake Vickaryous, Corinne A. Allen, Lev N. Zakharov, Darren W. JohnsonAbstract:An exhaustive structural survey was analyzed in combination with new structural reports on Pnictogen···π interactions. The Cambridge Structural Database was searched for examples of Pnictogen atoms (As, Sb, and Bi) that lie within the sum of their van der Waals radii with an arene ring. The results were analyzed, and it was concluded that the interaction distance is shorter for the heavier Pnictogens due to the increasingly diffuse nature of the lone pair of electrons on the atom. A weak correlation between the distance and the angle of the interaction was found, implying that the interaction is partially covalent in nature but is primarily a dispersion interaction. These arene···π interactions can be used as driving forces for supramolecular assembly, and the crystal structures of two new arsenic-containing assemblies are presented. The combined analysis of these structures and the structural survey suggest that our supramolecular design strategy can be fine-tuned to take advantage of the Pnictogen···π i...
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design considerations for the group 15 elements the Pnictogen π interaction as a complementary component in supramolecular assembly design
Crystal Growth & Design, 2010Co-Authors: Virginia M. Cangelosi, Melanie A. Pitt, Corinne A. Allen, Lev N. Zakharov, Jake W Vickaryous, Darren W. JohnsonAbstract:An exhaustive structural survey was analyzed in combination with new structural reports on Pnictogen···π interactions. The Cambridge Structural Database was searched for examples of Pnictogen atoms (As, Sb, and Bi) that lie within the sum of their van der Waals radii with an arene ring. The results were analyzed, and it was concluded that the interaction distance is shorter for the heavier Pnictogens due to the increasingly diffuse nature of the lone pair of electrons on the atom. A weak correlation between the distance and the angle of the interaction was found, implying that the interaction is partially covalent in nature but is primarily a dispersion interaction. These arene···π interactions can be used as driving forces for supramolecular assembly, and the crystal structures of two new arsenic-containing assemblies are presented. The combined analysis of these structures and the structural survey suggest that our supramolecular design strategy can be fine-tuned to take advantage of the Pnictogen···π i...
Scott Andrew Mcclary - One of the best experts on this subject based on the ideXlab platform.
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Role of annealing atmosphere on the crystal structure and composition of tetrahedrite–tennantite alloy nanoparticles
Journal of Materials Chemistry C, 2018Co-Authors: Scott Andrew Mcclary, Robert B. Balow, Rakesh AgrawalAbstract:Tetrahedrite–tennantite (TET–TEN, Cu12Sb4S13–Cu12As4S13) nanoparticle (NP) alloys spanning the entire Sb–As composition range were synthesized using a hot-injection method without any detectable impurities. Thin films of TET–TEN NPs were prepared from colloidal NP inks and heat treated in sulfur vapor, hydrogen sulfide, and nitrogen atmospheres. Under sulfur, the TET–TEN films were oxidized to tetragonal famatinite–luzonite (Cu3As1−xSbxS4). Heat treating under a reducing hydrogen sulfide atmosphere stabilized the mixed TET–TEN alloy compositions, though the endmember compositions partially decomposed via loss of volatile Pnictogen sulfides. Losses of Pnictogen and sulfur atoms were most significant when heat treating under an inert nitrogen atmosphere. Collectively, these results suggest that TET–TEN materials can be reversibly interconverted to famatinite–luzonite by selecting an appropriate annealing atmosphere. Our work serves as the foundation for both the synthesis and production of device-quality TET–TEN and related chalcogenide NP thin films.
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role of annealing atmosphere on the crystal structure and composition of tetrahedrite tennantite alloy nanoparticles
Journal of Materials Chemistry C, 2018Co-Authors: Scott Andrew Mcclary, Robert B. Balow, Rakesh AgrawalAbstract:Tetrahedrite–tennantite (TET–TEN, Cu12Sb4S13–Cu12As4S13) nanoparticle (NP) alloys spanning the entire Sb–As composition range were synthesized using a hot-injection method without any detectable impurities. Thin films of TET–TEN NPs were prepared from colloidal NP inks and heat treated in sulfur vapor, hydrogen sulfide, and nitrogen atmospheres. Under sulfur, the TET–TEN films were oxidized to tetragonal famatinite–luzonite (Cu3As1−xSbxS4). Heat treating under a reducing hydrogen sulfide atmosphere stabilized the mixed TET–TEN alloy compositions, though the endmember compositions partially decomposed via loss of volatile Pnictogen sulfides. Losses of Pnictogen and sulfur atoms were most significant when heat treating under an inert nitrogen atmosphere. Collectively, these results suggest that TET–TEN materials can be reversibly interconverted to famatinite–luzonite by selecting an appropriate annealing atmosphere. Our work serves as the foundation for both the synthesis and production of device-quality TET–TEN and related chalcogenide NP thin films.