On the variation of the belt and chiral screw and spring conformations of substituted regioregular HT undecathiophenes

Dobrowolski, Jan Cz.; Jamróz, Michał H.

doi:10.1039/c7ra12777d

Cited by 5 publications

(7 citation statements)

References 41 publications

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“…The average twisted angle (SÀ CÀ CÀ S) between thiophene monomers remains around the 155°r eported previously. [63] Van der Waals forces, particularly π-π and H-interactions, are the main factors that govern this complex orientation. The conformation where the oligomer is extended and interacting with the steroidal skeleton (5oligomer B) was slightly more stable.…”

Section: Resultsmentioning

confidence: 99%

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Hybrid Steroid‐[60]Fullerene as n‐Type Material for Organic Photovoltaics

Lemos,

Perez‐Badell,

Ortiz

et al. 2023

Eur J Org Chem

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Fullerene derivatives have been used as electron acceptor and transport materials in organic photovoltaics as well as in perovskite solar cells. Among them, [6,6]‐phenyl‐C61‐butyric acid methyl ester (PC61BM) has been one of the most widely used, in combination with poly‐3‐hexylthiophene (P3HT) as an electron donor semiconducting polymer, for the fabrication of organic bulk heterojunction solar cells (BHJ‐OSC). In this work, a steroid‐fullerene hybrid was synthesized through the Bingel–Hirsch reaction to compare its properties with PC61BM as the reference structure. Different spectroscopic techniques were employed to characterize the new fullerene derivative, namely 1D and 2D nuclear magnetic resonance (NMR), Fourier Transform Infrared Spectroscopy (FTIR), and high‐resolution mass spectrometry (HRMS). In addition, thermogravimetric analysis (TGA), and cyclic voltammetry were also performed. The characterization was completed by transmission electron microscopy (TEM), which explore the hybrid‘s morphology, where the presence of the steroid moiety increases the solubility of the fullerene material. DFT/PBE−D3(BJ)/6‐311G(d,p) calculations for both the steroid‐fullerene hybrid and PC61BM allowed to obtain geometry optimizations and electronic structure data. A comparative study to analyze the nature of the electronic properties of the synthesized steroid‐[60]fullerene hybrid and PC61BM with an oligomer of ten thiophene units, used in the active layer of organic solar cells, was carried out. Electron density maps using the [CIS|CNDOL/21] approach illustrate the photoexcitation of the donor followed by an electron‐charge transfer to the acceptor fullerene.

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Section: Resultsmentioning

confidence: 99%

“…The complexes' excited states energies and charge displacements were modeled by CNDOL approximation together with configuration interaction of single excitations (CIS). [36,63]…”

Section: Methodsmentioning

confidence: 99%

Hybrid Steroid‐[60]Fullerene as n‐Type Material for Organic Photovoltaics

Lemos,

Perez‐Badell,

Ortiz

et al. 2023

Eur J Org Chem

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“…For alkenes and polythiophenes, the index increases and converges to values above 0.6, while for polypyrrole, it reaches ca. 0.8. , This can suggest the increase of π-electron delocalization with an increase in the number of units. , The HOMA indices were also used to study linear and branched alkanes, and for n -alkanes, a good correlation with the boiling points was found. On the other hand, for n -alkane constitutional isomers, the HOMA index tends to increase with the boiling points from the most branched to the most extended isomer …”

Section: Introductionmentioning

confidence: 99%

“…0.8. 13,15 This can suggest the increase of π-electron delocalization with an increase in the number of units. 13,16 The HOMA indices were also used to study linear and branched alkanes, and for n-alkanes, a good correlation with the boiling points was found.…”

Section: Introductionmentioning

confidence: 99%

HOMA Index Establishes Similarity to a Reference Molecule

Dobrowolski,

Ostrowski

2023

J. Chem. Inf. Model.

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The article shows that the definition of the HOMA index of geometrical aromaticity satisfies the axioms of a similarity function between the examined and benzene ring. Consequently, for purely mathematical reasons, the index works exceptionally well as an index of aromaticity: it expresses a geometric similarity to the archetypal aromatic benzene. Thus, if the molecule is geometrically similar to benzene, then it is also chemically similar, and therefore, it is aromatic. However, the similarity property legitimizes using the HOMA-like indices to express similarity to molecules other than benzene, whether cyclic or linear and existing or hypothetical. The paper demonstrates an example of HOMA-similarity to cyclohexane, which expresses a (relaxed)-saturicity property not accompanied by strong structural strains or steric hindrances. Further, it is also shown that the HOMA index can evaluate the properties of whole molecules, such as 25 unbranched catacondensed isomers of hexacene. The index exhibits a significant quadratic correlation with the total energy differences of planar isomers from which the nonplanar ones deviate. Moreover, the HOMA index of hexacene isomers significantly correlates with the Kekulé count connected to the resonance energy in the Hückel approximation. As a result, the study shows that the HOMA index can be used not only for aromaticity analyses but also as a general chemical descriptor applicable to rings, chains, composed molecular moieties, or even whole molecules.

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“…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%

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

2022

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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.

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On the variation of the belt and chiral screw and spring conformations of substituted regioregular HT undecathiophenes

Abstract: The stability and characteristics of shape and π-electron delocalization of a belt- and two chiral screw- and spring-conformers of HT regioregular substituted undecathiophenes was calculated.

Cited by 5 publications

References 41 publications

Hybrid Steroid‐[60]Fullerene as n‐Type Material for Organic Photovoltaics

Hybrid Steroid‐[60]Fullerene as n‐Type Material for Organic Photovoltaics

HOMA Index Establishes Similarity to a Reference Molecule

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

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