Influence of rotational barrier of single-molecule electric revolving door on energies, aromaticity and quadrupole moment

Farhadi, Saeed; Gholipour, Alireza; Neyband, Razieh Sadat; Gholipour, Mehrsa

doi:10.1080/00268976.2015.1137371

Cited by 1 publication

(2 citation statements)

References 27 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…4 − 11 However, recently, problems with the evaluation of aromaticity in non-planar and/or non-rigid molecules have been raised. 12 − 14 It seems that the more novel and the more useful a molecule is, the less planar and the more flexible the rings need to be analyzed for their aromaticity. 15 − 20 Interestingly, one of the issues which, although signalized, 21 has not been systematically studied is the variation of the aromaticity indices with the substituent conformation.…”

Section: Introductionmentioning

confidence: 99%

“…Regardless of the aromaticity aspect, the majority of studies have been focused on planar ring systems uninvolved in conformational equilibria. − However, recently, problems with the evaluation of aromaticity in non-planar and/or non-rigid molecules have been raised. − It seems that the more novel and the more useful a molecule is, the less planar and the more flexible the rings need to be analyzed for their aromaticity. − Interestingly, one of the issues which, although signalized, has not been systematically studied is the variation of the aromaticity indices with the substituent conformation. This is because even for relatively simple molecules like biogenic amino acids, several hundreds of conformers have to be taken into account .…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

On Aromaticity of the Aromatic α-Amino Acids and Tuning of the NICS Indices to Find the Aromaticity Order

2022

View full text Add to dashboard Cite

The NICS aromaticity indices of the rings in flexible phenylalanine (Phe), tryptophan (Trp), tyrosine (Tyr), and histidine (His) chiral molecules were analyzed. These molecules have several dozens of conformers, and their rings are slightly non-planar. Therefore, the population-averaged NICS pav index was defined, and the NICS scans had to be performed with respect to planes found by the least-squares routine. A rule differentiating an obverse and a reverse ring face in aromatic amino acids was formulated. The NICS scan minima corresponding to the obverse and reverse face were unequal, which prompted us to use the term ring face aromaticity/ring face tropicity. It appeared that for Phe, Trp, Tyr, and His, the reverse face has always had higher ring face aromaticity/ring face tropicity than the obverse one. Despite the NICS modifications, uncertainty about the amino acid aromaticity order remained. This motivated us to use the integral INICS index newly proposed by Stanger as well. Then, the following sequence was obtained: Trp(phenyl) > Phe > Trp(pyrrole) > His > Tyr. The juxtaposition of the INICS indices of amino acids with that of some model rings revealed a fair transferability of the values. Finally, analysis of the substituent effect on INICS demonstrated that the aromaticity of Tyr is the lowest due to the strength of the OH group π-electron-donating effect able to perturb enough the ring charge distribution and its magnetic aromaticity. The NICS calculations were executed using the ARONICS program written within the project.

show abstract