Visualisation of Chemical Shielding Tensors (VIST) to Elucidate Aromaticity and Antiaromaticity

10.26434/chemrxiv.13580885 ◽

2021 ◽

Author(s):

Felix Plasser ◽

Florian Glöcklhofer

Keyword(s):

Materials Science ◽

Quantitative Information ◽

Three Dimensions ◽

Chemical Shielding ◽

Central Concept ◽

Conjugated Systems ◽

Pi Conjugated ◽

Fundamental Understanding ◽

Planar Systems ◽

Shielding Tensors

Aromaticity is a central concept in chemistry, pervading areas from biochemistry to materials science. Recently, chemists also started to exploit intricate phenomena such as the interplay of local and global (anti)aromaticity or aromaticity in non-planar systems and three dimensions. These phenomena pose new challenges in terms of our fundamental understanding and the practical visualisation of aromaticity. To overcome these challenges, a method for the visualisation of chemical shielding tensors (VIST) is developed here that allows for a 3D visualisation with quantitative information about the local variations and anisotropy of the chemical shielding. After exemplifying the method in different planar hydrocarbons, we study two non-planar macrocycles to show the unique benefits of the VIST method for molecules with competing pi-conjugated systems and conclude with a norcorrole dimer showing clear evidence of through-space aromaticity. We believe that the VIST method will be a highly valuable addition to the computational toolbox.

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3D Visualisation of Chemical Shielding Tensors (VIST) to Elucidate Aromaticity and Antiaromaticity

10.26434/chemrxiv.13580885.v1 ◽

2021 ◽

Author(s):

Felix Plasser ◽

Florian Glöcklhofer

Keyword(s):

Materials Science ◽

Molecular Design ◽

Chemical Shifts ◽

Quantitative Information ◽

Three Dimensions ◽

Singlet Ground State ◽

Chemical Shielding ◽

3D Visualisation ◽

Shielding Tensors ◽

Local Aromaticity

Aromaticity is a central concept in chemistry, pervading areas from biochemistry to materials science. Recently, synthetic chemists started to exploit more intricate phenomena such as the interplay of local and global (anti)aromaticity as well as aromaticity in non-planar systems and three dimensions. These phenomena pose new challenges in terms of our fundamental understanding and the practical visualisation of aromaticity, its local variations and anisotropy. To overcome these challenges, a method for the visualisation of chemical shielding tensors (VIST) is developed here. The VIST method is based on nucleus-independent chemical shifts but, in contrast to other methods, allows for a 3D visualisation with quantitative information about the local variations and anisotropy of the chemical shielding. The VIST method is exemplified in benzene to show its main properties, in phenanthrene to highlight various degrees of local aromaticity, and in cyclobuta[l]phenanthrene to illustrate the interplay between local aromaticity and antiaromaticity in its singlet ground state and Baird aromaticity in its triplet excited state.<br>Subsequently, the interplay of local and global aromaticity is investigated in two non-planar macrocycles, paracyclophanetetraene and [8]cycloparaphenylene, exemplifying the unique benefits of the VIST method for studying (anti)aromaticity in molecules with competing $\pi$-conjugated systems aligned in different planes.<br>Finally, a stacked norcorrole dimer is studied, showing clear evidence of through-space aromaticity. In summary, we believe that the VIST method will be a highly valuable addition to the computational toolbox of chemists studying (anti)aromaticity or considering it in their molecular design.

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An Experimental and Theoretical Investigation of the Chemical Shielding Tensors of13Cαof Alanine, Valine, and Leucine Residues in Solid Peptides and in Proteins in Solution

Journal of the American Chemical Society ◽

10.1021/ja0115060 ◽

2001 ◽

Vol 123 (42) ◽

pp. 10362-10369 ◽

Cited By ~ 30

Author(s):

Robert H. Havlin ◽

David D. Laws ◽

Hans-Marcus L. Bitter ◽

Lori K. Sanders ◽

Haihong Sun ◽

...

Keyword(s):

Theoretical Investigation ◽

Chemical Shielding ◽

Shielding Tensors

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Integrated quantitative PIXE analysis and EDX spectroscopy using a laser-driven particle source

Science Advances ◽

10.1126/sciadv.abc8660 ◽

2021 ◽

Vol 7 (3) ◽

pp. eabc8660

Author(s):

F. Mirani ◽

A. Maffini ◽

F. Casamichiela ◽

A. Pazzaglia ◽

A. Formenti ◽

...

Keyword(s):

Experimental Investigation ◽

Materials Science ◽

Quantitative Information ◽

Pixe Analysis ◽

Materials Analysis ◽

Particle Source ◽

X Ray ◽

Analysis Techniques ◽

Sample Structure ◽

Elemental Characterization

Among the existing elemental characterization techniques, particle-induced x-ray emission (PIXE) and energy-dispersive x-ray (EDX) spectroscopy are two of the most widely used in different scientific and technological fields. Here, we present the first quantitative laser-driven PIXE and laser-driven EDX experimental investigation performed at the Centro de Láseres Pulsados in Salamanca. Thanks to their potential for compactness and portability, laser-driven particle sources are very appealing for materials science applications, especially for materials analysis techniques. We demonstrate the possibility to exploit the x-ray signal produced by the co-irradiation with both electrons and protons to identify the elements in the sample. We show that, using the proton beam only, we can successfully obtain quantitative information about the sample structure through laser-driven PIXE analysis. These results pave the way toward the development of a compact and multifunctional apparatus for the elemental analysis of materials based on a laser-driven particle source.

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Visualisation of chemical shielding tensors (VIST) to elucidate aromaticity and antiaromaticity

European Journal of Organic Chemistry ◽

10.1002/ejoc.202100352 ◽

2021 ◽

Author(s):

Felix Plasser ◽

Florian Glöcklhofer

Keyword(s):

Chemical Shielding ◽

Shielding Tensors

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Phosphorus-31 chemical shieldings in a fused cis-1,2,3-benzothiadiphosphole: a dipolar NMR study

Canadian Journal of Chemistry ◽

10.1139/v92-159 ◽

1992 ◽

Vol 70 (4) ◽

pp. 1229-1235 ◽

Cited By ~ 8

Author(s):

Gang Wu ◽

Roderick E. Wasylishen ◽

William P. Power ◽

Graziano Baccolini

Keyword(s):

Line Shape ◽

Magic Angle Spinning ◽

Pair Approximation ◽

Magic Angle ◽

Single Bond ◽

Chemical Shielding ◽

Spin Pair ◽

Nmr Study ◽

Shielding Tensors ◽

Angle Spinning

Phosphorus-31 NMR static powder spectra and high-resolution magic angle spinning spectra have been obtained for a new heterocyclic compound, cis-2,10-dimethyl[1,2,3]benzothiadiphospholo[2,3b][1,2,3]benzothiadiphosphole (1), which contains a P(III)—P(III) single bond. The homonuclear 31P–31P dipolar interaction manifests itself in both the magic angle spinning spectra and the non-spinning line shape. Under the AX spin pair approximation, analysis of the spinning sidebands in the MAS experiment yields a full characterization of the two 31P chemical shielding tensors. This approximation is confirmed by the exact powder line shape simulation for a homonuclear spin pair. Analysis of the dipolar subspectra also yields the absolute sign of 1J(P,P), which is found to be negative. Keywords: phosphorus–phosphorus single bond, chemical shielding tensors, dipolar NMR, MAS, static line shape.

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