The magnetically induced current density of the [12]infinitene dianion

Abstract

The magnetically induced current-density susceptibility (MICD) of the [12]infinitene dianion and the induced magnetic field around it have been calculated at the density functional theory level. Separation of the MICD...

Understanding Aromaticity in [5]Helicene-Bridged Cyclophanes: A Comprehensive Study

“…However, for helical structures, interpretations of aromaticity based on magnetic shielding functions differ from the insights gained through current− density computations. [13][14][15]27 Namely, B z ind displays a deshielding cone, which is typical for antiaromatic systems, whereas the NICS calculations predict an aromatic character, which is evident through the formation of shielding cones at all 6-MRs. The differences originate due to the helical structure, in which the induced current density flows along the perimeter of the helicenes.…”

“…The NICS function has been commonly used to discuss aromaticity in three-dimensional systems because, unlike B z ind , it is a quantity that does not depend on the orientation of the external magnetic field. However, for helical structures, interpretations of aromaticity based on magnetic shielding functions differ from the insights gained through current–density computations. − , Namely, B z ind displays a deshielding cone, which is typical for antiaromatic systems, whereas the NICS calculations predict an aromatic character, which is evident through the formation of shielding cones at all 6-MRs. The differences originate due to the helical structure, in which the induced current density flows along the perimeter of the helicenes. , It is these changes in the direction of the current–density flux in conjunction with the orientation of the rings with respect to the external field that causes the in-plane x - and y -components of B ind to become important. , Therefore, NICS(0) and B z ind (0) calculations provide a different aromatic nature for each ring of the studied molecules.…”

“…The differences originate due to the helical structure, in which the induced current density flows along the perimeter of the helicenes. , It is these changes in the direction of the current–density flux in conjunction with the orientation of the rings with respect to the external field that causes the in-plane x - and y -components of B ind to become important. , Therefore, NICS(0) and B z ind (0) calculations provide a different aromatic nature for each ring of the studied molecules. When two stacked aromatic molecules such as the benzene dimer are considered, the overlap of their shielding cones is constructive and results in a more pronounced shielding. ,,, In the case of helical molecules, the overlap leads to a wrong interpretation. − Our experience is that when different features are predicted by the NICS and B z ind functions, it is often due to complex current–density pathways. − Furthermore, the pseudo-π model, which is designed to mimic the magnetic response of the π electrons, yields a similar behavior for the NICS and B z ind functions implying that characterizing the aromaticity of I based on magnetic shielding calculations is challenging.…”

“…The aromaticity of three-dimensional systems, especially in helicenes, has proven to be challenging and controversial, particularly when using magnetic response analyses. , Helical structures consist of stacked rings, which can complicate the interpretation of magnetic shielding calculations. − It has been found that local nucleus-independent chemical shift , (NICS) calculations assign different degrees of aromaticity to the individual rings of helicenes, , which originates from the overlap of the shielding cones of the stacked rings. A more precise comprehension of the π delocalization has been obtained by performing an orbital analysis of the magnetic response. , NICS(0) values are substantially affected by contributions parallel to the plane due to the orientation of the rings with respect to the external magnetic field .…”

Carbon Nanobelts: Brief History and Perspective

“…X-ray crystal structure analysis has shown that the combined lamellar and herringbone-like packing structure introduced three-dimensional electronic interactions caused by the infinity shape. Since this report, fascinating properties of infinitene have been predicted. − Wu and Isobe et al synthesized a twisted CNB in 2021 and a fused [5]helicene dimer in 2023 , as a related molecule of infinitene. In addition to aromatic hydrocarbon-based CNBs, heteroatom-embedded CNBs have also been reported. − In 2019, Tanaka et al synthesized the first oxygen-embedded CNB by rhodium-catalyzed alkyne cyclotrimerization .…”