Visualizing electron delocalization in contorted polycyclic aromatic hydrocarbons

Abstract

Electron delocalization in contorted polycyclic aromatic hydrocarbon (PAH) molecules was examined through 3D isotropic magnetic shielding (IMS) contour maps built around the molecules using pseudo-van der Waals surfaces. The resulting...

BenzAI: A Program to Design Benzenoids with Defined Properties Using Constraint Programming

“…These molecules were obtained by a trimerization of helicenes (formally a [2 + 2 + 2] reaction; see Figure 11). 39 The trimerization leads to the formation of a new C 6 cycle, which is referred to as the central cycle in the following discussion. Such molecules could exhibit magnetic properties if their π-extensions would stabilize unpaired electrons.…”

“…Recently, a large set of PAHs and their local aromaticity was computed . Some software is also available to study aromaticity in general, such as the Aroma package, which scans nucleus-independent chemical shift (NICS) values on a grid above a molecular plane. − The newly developed ims3d.py suite does the same kind of work in a general fashion, which allows for the study of aromaticity in distorted molecules, for which the determination of a plane is ambiguous . In this context, BenzAI aims at being an easy to use software that is flexible and expandable.…”

“…17−19 The newly developed ims3d.py suite does the same kind of work in a general fashion, which allows for the study of aromaticity in distorted molecules, for which the determination of a plane is ambiguous. 20 aims at being an easy to use software that is flexible and expandable. It handles fragment combination for the generation of benzenoids, which is not covered by the software previously cited, and deals with the electronic structure analysis based on graph theory.…”

Synthesis, Photophysical Properties, and Aromaticity of Pyrazine-Fused Tetrazapentalenes

“…Apart from the standard single-point approach, richer pictures of NICS in molecules can be obtained by mapping NICS or the corresponding magnetic shielding σ (the negative of NICS), using two-dimensional (2D) , and three-dimensional (3D) grids. , Mapping isotropic magnetic shielding [σ iso = −NICS iso = (σ xx + σ yy + σ zz )/3] in a plane located at 1 Å from the molecular plane provided the 2D σ iso maps of PyTeAP-H and its individual cyclic constituents (Figure , left). The results for the corresponding anisotropic σ zz (=–NICS zz ) maps are detailed in the Supporting Information (Figure S4 section VI).…”

Multidimensional Isotropic Magnetic Shielding Contour Maps for the Visualization of Aromaticity in ortho-Arynes and Their Reactions

“…The 2D IMS contour maps were generated in a plane located 1 Å above the mean plane defined by the C atoms of the considered aromatic system, 7 while 3D IMS contour maps were generated on a surface made of 1 Å radius spheres around all atoms, Template for SYNTHESIS Thieme including some artificially introduced dummy atoms at specific locations. 8 Interpretation of the 2D and 3D IMS contour maps is intuitive: color becomes darker with an increase of the absolute value of IMS with blue indicating an aromatic character (positive IMS), and red indicating an antiaromatic character (negative IMS). Dark blue rings indicate plain aromaticity as in benzene (see example in Figure 1a).…”