Stabilization of a high energy molecular conformation by specific intermolecular forces, a novel planar benzylideneaniline system

1997 ◽  
Vol 8 (1) ◽  
pp. 3-11 ◽  
Author(s):  
Oshrit Navon ◽  
Joel Bernstein
Keyword(s):  
Molecular Conformation ◽  
Intermolecular Forces ◽  
High Energy

scholarly journals Geometries and Terahertz Motions Driving Quintet Multiexcitons and Ultimate Triplet-Triplet Dissociations via the Intramolecular Singlet-Fissions

2020 ◽  
Author(s):  
Yasuhiro Kobori ◽  
Masaaki Fuki ◽  
Shunta Nakamura ◽  
Taku Hasobe
Keyword(s):  
Molecular Mechanisms ◽  
Molecular Conformation ◽  
High Energy ◽  
Strongly Correlated ◽  
Spin Conversion ◽  
Paramagnetic Resonance ◽  
Time Resolved ◽  
Strongly Coupled ◽  
Singlet Exciton ◽  
Spin Distributions

Importance of vibronic effects has been highlighted for the singlet-fission (SF) that convert one high-energy singlet exciton into doubled triplet excitons, as strongly correlated multiexcitons. However, molecular mechanisms of spin conversion processes and ultimate de-couplings in the multiexcitons are poorly understood. We have analyzed geometries and exchange couplings of the photoinduced multiexcitons in the pentacene dimers bridged by a phenylene at ortho and meta positions [denoted as <i>o</i>-(Pc)<sub>2</sub> and <i>m</i>-(Pc)<sub>2</sub>] by simulations of the time-resolved electron paramagnetic resonance spectra. We clarified that terahertz molecular conformation dynamics plays a role on the spin conversion from the singlet strongly coupled multiexcitons <sup>1</sup>(TT) to the quintet state <sup>5</sup>(TT). The strongly coupled <sup>5</sup>(TT) multiexcitons are revealed to possess entirely planar conformations stabilized by mutually delocalized spin distributions, while the intramolecular de-coupled spin-correlated triplet pairs generated at 1 microsecond are also stabilized by distorted conformations resulting in two separately localized biradical characters.

scholarly journals Harry Lambert Welsh, 23 March 1910 - 23 July 1984

1994 ◽  
Vol 39 ◽  
pp. 433-450
Keyword(s):  
High Energy Physics ◽  
Molecular Spectroscopy ◽  
Intermolecular Forces ◽  
High Energy ◽  
Alma Mater ◽  
Research Groups ◽  
University Of Toronto ◽  
Physics Department ◽  
The University ◽  
Energy Physics

Harry Lambert Welsh began a long association with the University of Toronto with his enrolment in undergraduate physics in 1926. He brought fame to his Alma Mater with pioneering studies in molecular spectroscopy and intermolecular forces, and he played a major role in the development of the Physics Department with his introduction and establishment of research groups in theoretical, atmospheric, and high-energy physics. Undoubtedly, Harry Welsh’s greatest achievement was the stimulation for scholarly research engendered in 65 Ph.D. students who had the privilege and pleasure to study under his supervision over a period of four decades. These scientists have made, and are continuing to make, important contributions to research in a variety of ways in universities, industry, and government institutions, across Canada and in other countries.

scholarly journals Revisiting the Thermodynamic Stability of Indomethacin Polymorphs with Low-Frequency Vibrational Spectroscopy and Quantum Mechanical Simulations

2018 ◽  
Author(s):  
Michael Ruggiero ◽  
Joshua J. Sutton ◽  
Sara J. Fraser-Miller ◽  
Adam J. Zaczek ◽  
Timothy M. Korter ◽  
...  
Keyword(s):  
Density Functional ◽  
Molecular Conformation ◽  
Low Frequency ◽  
Active Pharmaceutical Ingredient ◽  
Intermolecular Forces ◽  
State Density ◽  
Ab Initio Molecular Dynamics ◽  
Ambient Conditions ◽  
Molecular Dynamics Calculations ◽  
Vibrational Spectroscopies

<pre>The two major polymorphs of the active pharmaceutical ingredient indomethacin were studied using a combination of experimental low-frequency vibrational spectroscopies, theoretical solid-state density functional theory and \textit{ab initio} molecular dynamics calculations. The results enable a complete spectral assignment of the low-frequency IR and Raman spectra, and yield new insight into the energetic and dynamical factors present within the solids to be understood. Ultimately, these results are used to rationalize the thermodynamic properties of the two crystals, which result in a contradiction to the long-held belief that the $\gamma$-form is the more stable polymorph at ambient conditions due to its predominant abundance. Overall, the study highlights the combined role that molecular conformation, bulk packing arrangement, and intermolecular forces have on the ultimate properties of pharmaceutical crystals, and the need for detailed analyses into all of these effects in order to predict the properties of materials. </pre>

scholarly journals Revisiting the Thermodynamic Stability of Indomethacin Polymorphs with Low-Frequency Vibrational Spectroscopy and Quantum Mechanical Simulations

2018 ◽  
Author(s):  
Michael Ruggiero ◽  
Joshua J. Sutton ◽  
Sara J. Fraser-Miller ◽  
Adam J. Zaczek ◽  
Timothy M. Korter ◽  
...  
Keyword(s):  
Density Functional ◽  
Molecular Conformation ◽  
Low Frequency ◽  
Active Pharmaceutical Ingredient ◽  
Intermolecular Forces ◽  
State Density ◽  
Ab Initio Molecular Dynamics ◽  
Ambient Conditions ◽  
Molecular Dynamics Calculations ◽  
Vibrational Spectroscopies

<pre>The two major polymorphs of the active pharmaceutical ingredient indomethacin were studied using a combination of experimental low-frequency vibrational spectroscopies, theoretical solid-state density functional theory and \textit{ab initio} molecular dynamics calculations. The results enable a complete spectral assignment of the low-frequency IR and Raman spectra, and yield new insight into the energetic and dynamical factors present within the solids to be understood. Ultimately, these results are used to rationalize the thermodynamic properties of the two crystals, which result in a contradiction to the long-held belief that the $\gamma$-form is the more stable polymorph at ambient conditions due to its predominant abundance. Overall, the study highlights the combined role that molecular conformation, bulk packing arrangement, and intermolecular forces have on the ultimate properties of pharmaceutical crystals, and the need for detailed analyses into all of these effects in order to predict the properties of materials. </pre>

scholarly journals Geometries and Terahertz Motions Driving Quintet Multiexcitons and Ultimate Triplet-Triplet Dissociations via the Intramolecular Singlet-Fissions

2020 ◽  
Author(s):  
Yasuhiro Kobori ◽  
Masaaki Fuki ◽  
Shunta Nakamura ◽  
Taku Hasobe
Keyword(s):  
Molecular Mechanisms ◽  
Molecular Conformation ◽  
High Energy ◽  
Strongly Correlated ◽  
Spin Conversion ◽  
Paramagnetic Resonance ◽  
Time Resolved ◽  
Strongly Coupled ◽  
Singlet Exciton ◽  
Spin Distributions

Importance of vibronic effects has been highlighted for the singlet-fission (SF) that convert one high-energy singlet exciton into doubled triplet excitons, as strongly correlated multiexcitons. However, molecular mechanisms of spin conversion processes and ultimate de-couplings in the multiexcitons are poorly understood. We have analyzed geometries and exchange couplings of the photoinduced multiexcitons in the pentacene dimers bridged by a phenylene at ortho and meta positions [denoted as <i>o</i>-(Pc)<sub>2</sub> and <i>m</i>-(Pc)<sub>2</sub>] by simulations of the time-resolved electron paramagnetic resonance spectra. We clarified that terahertz molecular conformation dynamics plays a role on the spin conversion from the singlet strongly coupled multiexcitons <sup>1</sup>(TT) to the quintet state <sup>5</sup>(TT). The strongly coupled <sup>5</sup>(TT) multiexcitons are revealed to possess entirely planar conformations stabilized by mutually delocalized spin distributions, while the intramolecular de-coupled spin-correlated triplet pairs generated at 1 microsecond are also stabilized by distorted conformations resulting in two separately localized biradical characters.

scholarly journals Structure and Properties of 1,3-Phenylenediboronic Acid: Combined Experimental and Theoretical Investigations

Crystals ◽  
2019 ◽  
Vol 9 (2) ◽  
pp. 109 ◽  
Author(s):  
Agnieszka Adamczyk-Woźniak ◽  
Michał Cyrański ◽  
Krzysztof Durka ◽  
Jan Gozdalik ◽  
Paulina Klimentowska ◽  
...  
Keyword(s):  
Intermolecular Interaction ◽  
Molecular Conformation ◽  
Phenylboronic Acid ◽  
Topological Analysis ◽  
Intermolecular Forces ◽  
Hydroxyl Groups ◽  
Acidity Constant ◽  
Structure And Properties ◽  
Acid Base Equilibrium ◽  
Nmr Characterization

The structure and properties of 1,3-phenylenediboronic acid are reported. Molecular and crystal structures were determined by single crystal as well as by powder X-ray diffraction methods. Acidity constant, thermal behavior, and NMR characterization of the title compound were also investigated. In addition to the experimental data, calculations of rotational barrier and intermolecular interaction energies were performed. The compound reveals a two-step acid–base equilibrium with different pKa values. TGA and DSC measurements show a typical dehydration reaction with formation of boroxine. In crystals, hydrogen-bonded dimers with syn-anti conformation of hydroxyl groups form large numbers of ribbon motifs. The 2D potential energy surface scan of rotation of two boronic groups with respect to phenyl ring reveals that the rotation barrier is close to 37 kJ⋅mol−1, which is higher than the double value for the rotation of the boronic group in phenylboronic acid. This effect was ascribed to intermolecular interaction with C–H hydrogen atom located between boronic groups. Furthermore, the molecules in the crystal lattice adopt a less stable molecular conformation most likely resulting from intermolecular forces. These were further investigated by periodic DFT calculations supported by an estimation of dimer interaction energy, and also by topological analysis of electron density in the framework of AIM theory.

Crystal structure of 3-[(3,4-dinitro-1H-pyrazol-1-yl)-NNO-azoxy]-4-nitro-1,2,5-oxadiazole

2021 ◽  
pp. 1-5
Author(s):  
A. O. Dmitrienko ◽  
A. A. Konnov ◽  
M. S. Klenov
Keyword(s):  
Crystal Structure ◽  
Diffraction Data ◽  
Density Functional ◽  
Molecular Conformation ◽  
High Energy ◽  
High Energy Density ◽  
Functional Theory ◽  
Step Density ◽  
High Energy Density Material ◽  
Intramolecular Hydrogen

The crystal structure of a novel high-energy density material 3-[(3,4-dinitro-1H-pyrazol-1-yl)-NNO-azoxy]-4-nitro-1,2,5-oxadiazole C5HN9O8 was determined and refined using laboratory powder diffraction data. The diffraction data and database analysis were insufficient to distinguish two candidate structures from the solution step. Density functional theory with periodic boundary conditions optimizations were used to choose the correct one. 3-[(3,4-Dinitro1H-pyrazol-1-yl)-NNO-azoxy]-4-nitro-1,2,5-oxadiazole crystallizes in space group Pbca with a = 8.3104(2) Å, b = 14.2198(5) Å, c = 19.4264(7) Å, V = 2295.66(14) Å3. The molecular conformation contains a weak intramolecular hydrogen bond C–H⋯O–N, and the structure is dominated by weak O⋯π and O⋯O contacts.

Crystal structure of 3,3′-(E)-diazene-1,2-diylbis{4-[(3,4-dinitro-1H-pyrazol-1-yl)-NNO-azoxy]-1,2,5-oxadiazole}

2021 ◽  
pp. 1-6
Author(s):  
A. O. Dmitrienko ◽  
A. A. Konnov ◽  
M. S. Klenov
Keyword(s):  
Crystal Structure ◽  
Hydrogen Bond ◽  
Energy Density ◽  
Molecular Conformation ◽  
High Energy ◽  
High Energy Density ◽  
Powder Diffraction Data ◽  
Asymmetric Unit ◽  
High Energy Density Material ◽  
Intramolecular Hydrogen

The crystal structure of a novel high-energy density material 3,3′-(E)diazene-1,2-diylbis{4-[(3,4-dinitro-1H-pyrazol-1-yl)-NNO-azoxy]-1,2,5-oxadiazole} (C10H2N18O12) was determined and refined using laboratory powder diffraction data. The title compound crystallizes in space group P21/c with a = 9.5089(3) Å, b = 11.6331(4) Å, c = 10.6270(3) Å, β = 116.2370(12), V = 1054.43(6) Å3. The asymmetric unit contains half of the molecule. The molecular conformation contains a weak intramolecular hydrogen bond C–H⋯O–N, both nitro groups are disordered, and the structure is dominated by weak O⋯π and O⋯O contacts.

The E-ring: interactions with plasma and implications for its evolution

1984 ◽  
Vol 75 ◽  
pp. 599-602
Author(s):  
T.V. Johnson ◽  
G.E. Morfill ◽  
E. Grun
Keyword(s):  
Time Scale ◽  
Particle Density ◽  
High Energy ◽  
Particle Removal ◽  
Density Region ◽  
Drag Forces ◽  
Orbit Evolution ◽  
History Of ◽  
Ring Particle ◽  
Ring Material

A number of lines of evidence suggest that the particles making up the E-ring are small, on the order of a few microns or less in size (Terrile and Tokunaga, 1980, BAAS; Pang et al., 1982 Saturn meeting; Tucson, AZ). This suggests that a variety of electromagnetic and plasma affects may be important in considering the history of such particles. We have shown (Morfill et al., 1982, J. Geophys. Res., in press) that plasma drags forces from the corotating plasma will rapidly evolve E-ring particle orbits to increasing distance from Saturn until a point is reached where radiation drag forces acting to decrease orbital radius balance this outward acceleration. This occurs at approximately Rhea's orbit, although the exact value is subject to many uncertainties. The time scale for plasma drag to move particles from Enceladus' orbit to the outer E-ring is ~104yr. A variety of effects also act to remove particles, primarily sputtering by both high energy charged particles (Cheng et al., 1982, J. Geophys. Res., in press) and corotating plasma (Morfill et al., 1982). The time scale for sputtering away one micron particles is also short, 102 - 10 yrs. Thus the detailed particle density profile in the E-ring is set by a competition between orbit evolution and particle removal. The high density region near Enceladus' orbit may result from the sputtering yeild of corotating ions being less than unity at this radius (e.g. Eviatar et al., 1982, Saturn meeting). In any case, an active source of E-ring material is required if the feature is not very ephemeral - Enceladus itself, with its geologically recent surface, appears still to be the best candidate for the ultimate source of E-ring material.

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