Local aromaticity mapping in the vicinity of planar and nonplanar molecules

Teobald Kupka , Łukasz Gajda , Leszek Stobiński , Łukasz Kołodziej , Adrianna Mnich , Aneta Buczek , Małgorzata A. Broda

Abstract

We report on nucleus‐independent magnetic shielding (NICS) scans over the centers of six‐ and five‐membered rings in selected metal phthalocyanines (MPc) and fullerene C60 for more accurate characterization of local aromaticity in these compounds. Detailed tests were conducted on model aromatic molecules including benzene, pyrrole, indole, isoindole, and carbazole and subsequently applied to H2Pc, ZnPc, Al(OH)Pc, and CuPc. Similar behavior of three selected magnetic probes, Bq, 3 He, and 7 Li+, approaching perpendicularly the ring centers, was observed. For better visualization of shielding zone over the centers of aromatic rings, we introduced a simple mathematical procedure: the first and second derivatives of scan curves with respect to magnetic probe position enabled their additional examination. It allowed an easier localization of curve minimum and discrimination between areas in space varying by the magnetic field magnitude and to illustrate local aromaticity of two different kinds of rings in MPc with better resolution. Our results supported earlier reports on very low aromaticity indexes of pyrrole ring incorporated into MPc and significant aromaticity of the central macrocycle. No direct dependence between harmonic oscillator model of aromaticity and NICS was observed. Instead, a correlation between position of scan curve minimum and its magnitude were observed. In addition, the NICS values and 3 He chemical shifts in the middle of neutral C60 and C606− anion agreed well with the reported experimental NMR values for He@C60 and He@C606−.
Author Teobald Kupka
Teobald Kupka,,
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, Łukasz Gajda
Łukasz Gajda,,
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, Leszek Stobiński (FCPE / GL)
Leszek Stobiński,,
- WUT Grafen Laboratory
, Łukasz Kołodziej
Łukasz Kołodziej,,
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, Adrianna Mnich
Adrianna Mnich,,
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, Aneta Buczek
Aneta Buczek,,
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, Małgorzata A. Broda
Małgorzata A. Broda,,
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Journal seriesMagnetic Resonance in Chemistry, ISSN 0749-1581, (A 20 pkt)
Issue year2019
Vol57
No7
Pages359-372
Publication size in sheets0.65
Keywords in Englisharomaticity, benzene, curve derivatives, metal phthalocyanines, NICS, pyrrole
ASJC Classification2500 General Materials Science; 1600 General Chemistry
DOIDOI:10.1002/mrc.4880
Languageen angielski
File
Kupka T. (i in.) - Local aromaticity mapping....pdf 1.75 MB
Score (nominal)20
ScoreMinisterial score = 20.0, 20-06-2019, ArticleFromJournal
Publication indicators Scopus SNIP (Source Normalised Impact per Paper): 2017 = 0.718; WoS Impact Factor: 2017 = 1.776 (2) - 2017=1.576 (5)
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