Issue 24, 2023

NO-induced adaptive antiaromaticity in cyclobutadiene

Abstract

Cyclobutadiene (CBD) displays aromaticity in the lowest-lying triplet excited state (T1) according to Baird's 4n electron rule. Hence, antiaromatic CBD in the T1 state has never been reported so far. Here we demonstrate via density functional theory (DFT) calculations that the CBD ring could possess dual antiaromaticity in the lowest singlet state (S0) and T1 states (termed as adaptive antiaromaticity), which is supported by various aromaticity indices including NICS, ACID, ΔBL, ELF and ISE. Furthermore, the spin density localization on the substituent is the key factor for NO-substituted CBD to maintain antiaromaticity in the T1 state. The principal interacting spin orbital (PISO) analysis suggests that the nitrogen atom in the NO substituent tends to form a double bond with the carbon atom in the CBD ring, blocking the delocalization into the CBD ring and resulting in the antiaromaticity in the T1 state. Our findings represent a step forward in aromatic chemistry.

Graphical abstract: NO-induced adaptive antiaromaticity in cyclobutadiene

Supplementary files

Article information

Article type
Research Article
Submitted
16 Sep 2023
Accepted
22 Oct 2023
First published
23 Oct 2023

Org. Chem. Front., 2023,10, 6131-6139

NO-induced adaptive antiaromaticity in cyclobutadiene

Q. Deng, S. Imran, J. Yan and J. Zhu, Org. Chem. Front., 2023, 10, 6131 DOI: 10.1039/D3QO01498C

To request permission to reproduce material from this article, please go to the Copyright Clearance Center request page.

If you are an author contributing to an RSC publication, you do not need to request permission provided correct acknowledgement is given.

If you are the author of this article, you do not need to request permission to reproduce figures and diagrams provided correct acknowledgement is given. If you want to reproduce the whole article in a third-party publication (excluding your thesis/dissertation for which permission is not required) please go to the Copyright Clearance Center request page.

Read more about how to correctly acknowledge RSC content.

Social activity

Spotlight

Advertisements