An Overall Comprehension of Anti‐Aromatic Porphyrinoids Using 3D‐Graphical Chemical Shielding Description

Abstract

A systematic investigation to rank the anti-aromatic porphyrinoids is performed. Based on density functional theory calculations, four rules are summarized to obtain the highest anti-aromatic porphyrinoids: 1) the replacement from meso-C to meso-(─C≡C─), 2) the replacement from pyrrole unit to inner-N to inner-O, 3) the replacement from two opposite meso-C/N atoms to two pyrrole units, and 4) the replacement from one pyrrole ring to a carbonyl benzene ring. It is worth noting that the long chain with alternating single/double bonds is not beneficial or harmful to the anti-aromaticity.

General Design Strategy of Anti‐aromatic Porphyrinoids

“…In contrast, the typical anti‐aromatic skeletons show the opposite distribution that the shielding/deshielding areas locate outside/inside the ring, respectively. Then, we can provide two criteria: [11] …”

“…[11] As an unexpected discovery, we even found that, before that work, some molecules were considered as the anti-aromatic one by their founders, but in fact, they possess both aromatic and antiaromatic properties at the same time, and then we corrected these biases. [11] Now the mathematical and physical tools, including 3D-NICS and IDR, are ready, so today is the right time to reexamine the conjugated molecules once considered as the aromatic/anti-aromatic systems, and strictly sort their aromaticity/anti-aromaticity. Barring accidents, we believe that the sorting work may be an important milestone of the conjugation chemistry: the starting line of strict quantification for the aromatic/anti-aromatic investigation.…”

“…Moreover, with the help of 3D‐NICS calculation, all the details of aromatic/anti‐aromatic properties could be clearly shown for Lu[H(Pc)(Hp)]. In 2020, we applied the 3D‐NICS method to a systematic work including 21 anti‐aromatic porphyrinoid skeletons [11] . More importantly, based on the 3D‐NICS method, we developed the integral of deshielded area in ring (IDR) as a good indicator to rank the anti‐aromatic strength for the first time in that work [11] .…”

“…In 2020, we applied the 3D‐NICS method to a systematic work including 21 anti‐aromatic porphyrinoid skeletons [11] . More importantly, based on the 3D‐NICS method, we developed the integral of deshielded area in ring (IDR) as a good indicator to rank the anti‐aromatic strength for the first time in that work [11] . As an unexpected discovery, we even found that, before that work, some molecules were considered as the anti‐aromatic one by their founders, but in fact, they possess both aromatic and anti‐aromatic properties at the same time, and then we corrected these biases [11] .…”

“…[11] More importantly, based on the 3D-NICS method, we developed the integral of deshielded area in ring (IDR) as a good indicator to rank the anti-aromatic strength for the first time in that work. [11] As an unexpected discovery, we even found that, before that work, some molecules were considered as the anti-aromatic one by their founders, but in fact, they possess both aromatic and antiaromatic properties at the same time, and then we corrected these biases. [11] Now the mathematical and physical tools, including 3D-NICS and IDR, are ready, so today is the right time to reexamine the conjugated molecules once considered as the aromatic/anti-aromatic systems, and strictly sort their aromaticity/anti-aromaticity.…”