More Like this

1. The anti-aromatic dianion and aromatic tetraanion of [18]annulene

   https://doi.org/10.1038/s41557-024-01469-1  

   Stawski, Wojciech; Zhu, Yikun; Rončević, Igor; Wei, Zheng; Petrukhina, Marina A; Anderson, Harry L (June 2024, Nature Chemistry)

   Abstract π-Conjugated macrocycles behave differently from analogous linear chains because their electronic wavefunctions resemble a quantum particle on a ring, leading to aromaticity or anti-aromaticity. [18]Annulene, (CH)₁₈, is the archetypal non-benzenoid aromatic hydrocarbon. Molecules with circuits of 4n + 2 π electrons, such as [18]annulene (n = 4), are aromatic, with enhanced stability and diatropic ring currents (magnetic shielding inside the ring), whereas those with 4nπ electrons, such as the dianion of [18]annulene, are expected to be anti-aromatic and exhibit the opposite behaviour. Here we use¹H NMR spectroscopy to re-evaluate the structure of the [18]annulene dianion. We also show that it can be reduced further to an aromatic tetraanion, which has the same shape as the dianion. The crystal structure of the tetraanion lithium salt confirms its geometry and reveals a metallocene-like sandwich, with five Li⁺cations intercalated between two [18]annulene tetraanions. We also report a heteroleptic sandwich, with [18]annulene and corannulene tetraanion decks. 

   more » « less
2. Recent Advances in Aromatic Antimony Clusters: Recent Advances in Aromatic Antimony Clusters

   https://doi.org/10.1002/cjoc.201800251  

   Li, Lei-Jiao; Ali, Basharat; Chen, Zhongfang; Sun, Zhong-Ming (October 2018, Chinese Journal of Chemistry)
3. Iterative Exponential Growth of Oxygen-Linked Aromatic Polymers Driven by Nucleophilic Aromatic Substitution Reactions

   https://doi.org/10.3389/fchem.2021.620017  

   Jaynes, Tyler J.; Sharafi, Mona; Campbell, Joseph P.; Bocanegra, Jessica; McKay, Kyle T.; Little, Kassondra; Osadchey Brown, Reilly; Gray, Danielle L.; Woods, Toby J.; Li, Jianing; et al (April 2021, Frontiers in Chemistry)

   null (Ed.)

   This work presents the first transition metal-free synthesis of oxygen-linked aromatic polymers by integrating iterative exponential polymer growth (IEG) with nucleophilic aromatic substitution (S N Ar) reactions. Our approach applies methyl sulfones as the leaving groups, which eliminate the need for a transition metal catalyst, while also providing flexibility in functionality and configuration of the building blocks used. As indicated by 1) 1 H- 1 H NOESY NMR spectroscopy, 2) single-crystal X-ray crystallography, and 3) density functional theory (DFT) calculations, the unimolecular polymers obtained are folded by nonclassical hydrogen bonds formed between the oxygens of the electron-rich aromatic rings and the positively polarized C–H bonds of the electron-poor pyrimidine functions. Our results not only introduce a transition metal-free synthetic methodology to access precision polymers but also demonstrate how interactions between relatively small, neutral aromatic units in the polymers can be utilized as new supramolecular interaction pairs to control the folding of precision macromolecules. 

   more » « less
4. How Do Face-to-Face Stacked Aromatic Rings Activate Each Other to Electrophilic Aromatic Substitution?

   https://doi.org/10.1021/acs.orglett.3c01401  

   Kazim, Muhammad; Wang, Muyuan; Vemulapalli, Srini; Nguyen, Phuong Minh; Wang, Yuang; Siegler, Maxime A.; Dudding, Travis; Lectka, Thomas (June 2023, Organic Letters)
5. Electrostatically Driven CO−π Aromatic Interactions

   https://doi.org/10.1021/jacs.9b06363  

   Li, Ping; Vik, Erik C.; Maier, Josef M.; Karki, Ishwor; Strickland, Sharon M.; Umana, Jessica M.; Smith, Mark D.; Pellechia, Perry J.; Shimizu, Ken D. (July 2019, Journal of the American Chemical Society)