The Experts below are selected from a list of 5241 Experts worldwide ranked by ideXlab platform
J. M. D. Macelroy - One of the best experts on this subject based on the ideXlab platform.
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Towards the design of novel boron- and nitrogen-substituted Ammonia-borane and bifunctional arene ruthenium catalysts for hydrogen storage
Journal of computational chemistry, 2014Co-Authors: Sateesh Bandaru, Niall J. English, Andrew D. Phillips, J. M. D. MacelroyAbstract:Electronic-structure density functional theory calculations have been performed to construct the potential energy surface for H2 release from Ammonia-borane, with a novel bifunctional cationic ruthenium catalyst based on the sterically bulky β-diketiminato ligand (Schreiber et al., ACS Catal. 2012, 2, 2505). The focus is on identifying both a suitable substitution pattern for Ammonia-borane optimized for chemical hydrogen storage and allowing for low-energy dehydrogenation. The interaction of Ammonia-borane, and related substituted Ammonia-Boranes, with a bifunctional η6-arene ruthenium catalyst and associated variants is investigated for dehydrogenation. Interestingly, in a number of cases, hydride-proton transfer from the substituted Ammonia-borane to the catalyst undergoes a barrier-less process in the gas phase, with rapid formation of hydrogenated catalyst in the gas phase. Amongst the catalysts considered, N,N-difluoro Ammonia-borane and N-phenyl Ammonia-borane systems resulted in negative activation energy barriers. However, these types of Ammonia-Boranes are inherently thermodynamically unstable and undergo barrierless decay in the gas phase. Apart from N,N-difluoro Ammonia-borane, the interaction between different types of catalyst and Ammonia borane was modeled in the solvent phase, revealing free-energy barriers slightly higher than those in the gas phase. Amongst the various potential candidate Ru-complexes screened, few are found to differ in terms of efficiency for the dehydrogenation (rate-limiting) step. To model dehydrogenation more accurately, a selection of explicit protic solvent molecules was considered, with the goal of lowering energy barriers for H-H recombination. It was found that primary (1°), 2°, and 3° alcohols are the most suitable to enhance reaction rate. © 2014 Wiley Periodicals, Inc.
Sateesh Bandaru - One of the best experts on this subject based on the ideXlab platform.
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Towards the design of novel boron- and nitrogen-substituted Ammonia-borane and bifunctional arene ruthenium catalysts for hydrogen storage
Journal of computational chemistry, 2014Co-Authors: Sateesh Bandaru, Niall J. English, Andrew D. Phillips, J. M. D. MacelroyAbstract:Electronic-structure density functional theory calculations have been performed to construct the potential energy surface for H2 release from Ammonia-borane, with a novel bifunctional cationic ruthenium catalyst based on the sterically bulky β-diketiminato ligand (Schreiber et al., ACS Catal. 2012, 2, 2505). The focus is on identifying both a suitable substitution pattern for Ammonia-borane optimized for chemical hydrogen storage and allowing for low-energy dehydrogenation. The interaction of Ammonia-borane, and related substituted Ammonia-Boranes, with a bifunctional η6-arene ruthenium catalyst and associated variants is investigated for dehydrogenation. Interestingly, in a number of cases, hydride-proton transfer from the substituted Ammonia-borane to the catalyst undergoes a barrier-less process in the gas phase, with rapid formation of hydrogenated catalyst in the gas phase. Amongst the catalysts considered, N,N-difluoro Ammonia-borane and N-phenyl Ammonia-borane systems resulted in negative activation energy barriers. However, these types of Ammonia-Boranes are inherently thermodynamically unstable and undergo barrierless decay in the gas phase. Apart from N,N-difluoro Ammonia-borane, the interaction between different types of catalyst and Ammonia borane was modeled in the solvent phase, revealing free-energy barriers slightly higher than those in the gas phase. Amongst the various potential candidate Ru-complexes screened, few are found to differ in terms of efficiency for the dehydrogenation (rate-limiting) step. To model dehydrogenation more accurately, a selection of explicit protic solvent molecules was considered, with the goal of lowering energy barriers for H-H recombination. It was found that primary (1°), 2°, and 3° alcohols are the most suitable to enhance reaction rate. © 2014 Wiley Periodicals, Inc.
Keith Fagnou - One of the best experts on this subject based on the ideXlab platform.
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ruthenium catalyzed dehydrogenation of Ammonia Boranes
Journal of the American Chemical Society, 2008Co-Authors: Nicole Blaquiere, Sarah Diallogarcia, Serge I Gorelsky, Daniel A Black, Keith FagnouAbstract:The dehydrogenation of Ammonia borane (AB) and methylAmmonia borane (MeAB) is shown to be catalyzed by several Ru-amido complexes. Up to 1 equiv of H2 (1.0 system wt %) is released from AB by as little as 0.03 mol % Ru within 5 min, and up to 2 equiv of H2 (3.0 system wt %) are released from MeAB with 0.5 mol % Ru in under 10 min at room temperature, the first equivalent emerging within 10 s. Also, a mixture of AB/MeAB yields up to 3.6 system wt % H2 within 1 h with 0.1 mol % Ru. Computational studies were performed to elucidate the mechanism of dehydrogenation of AB. Finally, it was shown that alkylamine-Boranes can serve as a source of H2 in the Ru-catalyzed reduction of ketones and imines.
Sean C. Smith - One of the best experts on this subject based on the ideXlab platform.
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Computational study of methyl derivatives of Ammonia borane for hydrogen storage
Physical chemistry chemical physics : PCCP, 2008Co-Authors: Chenghua Sun, Xiangdong Yao, Sean C. SmithAbstract:The structures and thermodynamic properties of methyl derivatives of Ammonia–borane (BH3NH3, AB) have been studied with the frameworks of density functional theory and second-order Moller–Plesset perturbation theory. It is found that, with respect to pure AB, methyl Ammonia–Boranes show higher complexation energies and lower reaction enthalpies for the release of H2, together with a slight increment of the activation barrier. These results indicate that the methyl substitution can enhance the reversibility of the system and prevent the formation of BH3/NH3, but no enhancement of the release rate of H2 can be expected.
Ajay Chaudhari - One of the best experts on this subject based on the ideXlab platform.
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Mono and di-substituted Ammonia borane: A computational study
Journal of Molecular Liquids, 2015Co-Authors: Mahadevappa Naganathappa, Tahemina Qureshi, Ajay ChaudhariAbstract:Abstract This work reports vibrational spectra and electronic absorption spectra along with the first and second hyperpolarizabilities for Ammonia borane, mono and disubstituted Ammonia Boranes using quantum chemical methods. The substituents used here are Cl, Br and F. A large difference in the vibrational and electronic absorption spectra is observed upon mono and disubstitution. All the electronic transitions for the mono as well as disubstituted Ammonia borane molecules are found to be σ → σ* transitions. Direction of applied field and method dependent hyperpolarizabilities are obtained. The hyperpolarizabilities are found to be higher when the field applied is along Y direction than that applied in X or Z direction. The first hyperpolarizability is found to be enhanced upon mono as well as disubstitution in Ammonia borane. Mono as well as disubstituted Ammonia Boranes are not good materials for second order nonlinear optics.
