1,4-Phenylene-linked cyclotrimer () and cyclotetramer () have been synthesized via Lewis acid-catalyzed self-condensation of appropriate precursors. Structural and Density Functional Theory (DFT) studies reveal the disruption of annulenic conjugation in both and by linking phenylene rings prevented them from global antiaromaticity. The single crystal X-ray structure of reveals all the nitrogens are pointing toward the macrocyclic core with near-planar and square-shaped geometry, thus in sharp contrast to the ring-strained conformation of .
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http://dx.doi.org/10.1021/acs.orglett.1c03903 | DOI Listing |
Comb Chem High Throughput Screen
January 2025
Department of Chemistry, Mashhad Branch, Islamic Azad University, Mashhad, Iran.
Aims: This study aims explore the impact of catechol, dopamine, and L-DOPA on the stability and toxicity of β-amyloid peptides, which play a key role in the neurodegenerative process of Alzheimer's disease, to assess their potential as therapeutic agents.
Background: Alzheimer's disease is marked by the aggregation of β-amyloid peptides, which contribute to neurodegeneration. Exploring how various compounds interact with β-amyloid peptides can offer valuable insights into potential therapeutic strategies.
Nanoscale
January 2023
Institute of Organic Chemistry and Biochemistry, Czech Academy of Sciences, Flemingovo nám. 2, 166 10 Prague 6, Czech Republic.
Fully aromatic helicenes are attractive building blocks for the construction of inherently chiral π-conjugated macrocyclic nanocarbons. These hitherto rare molecular architectures are envisaged to exhibit remarkable (chir)optical properties, self-assembly, charge/spin transport, induced ring current or a fascinating Möbius topology. Here the synthesis of helically chiral macrocycles that combine angular dibenzo[5]helicene units as corners and linear -stilbene-4,4'-diyl linkers as edges is reported.
View Article and Find Full Text PDFOrg Lett
January 2022
Indian Institute of Science Education and Research Thiruvananthapuram, Kerala 695 016, India.
1,4-Phenylene-linked cyclotrimer () and cyclotetramer () have been synthesized via Lewis acid-catalyzed self-condensation of appropriate precursors. Structural and Density Functional Theory (DFT) studies reveal the disruption of annulenic conjugation in both and by linking phenylene rings prevented them from global antiaromaticity. The single crystal X-ray structure of reveals all the nitrogens are pointing toward the macrocyclic core with near-planar and square-shaped geometry, thus in sharp contrast to the ring-strained conformation of .
View Article and Find Full Text PDFJ Am Chem Soc
February 2021
Department of Chemistry, Chemistry Research Laboratory, University of Oxford, Oxford OX1 3TA, U.K.
Enhanced thermodynamic stability is a fundamental characteristic of aromatic molecules, yet most previous studies of aromatic stabilization energy (ASE) have been limited to small rings with up to 18 π-electrons. Here we demonstrate that ASE can be detected experimentally in π-conjugated porphyrin nanorings with Hückel circuits of 76-108 π-electrons. This conclusion is supported by analyzing redox potentials to calculate the energy change for isodesmic reactions that convert an aromatic ring to an antiaromatic ring or vice versa.
View Article and Find Full Text PDFAngew Chem Int Ed Engl
January 2020
Department of Chemistry and Biochemistry, Florida State University, Tallahassee, FL, 32306-4390, USA.
Incorporation of a five-membered ring into a helicene framework disrupts aromatic conjugation and provides a site for selective deprotonation. The deprotonation creates an anionic cyclopentadienyl unit, switches on conjugation, leads to a >200 nm red-shift in the absorbance spectrum and injects a charge into a helical conjugated π-system without injecting a spin. Structural consequences of deprotonation were revealed via analysis of a monoanionic helicene co-crystallized with {K (18-crown-6)(THF)} and {Cs (18-crown-6) }.
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