Competition Between Sextet Aromaticity and Cyclobutadiene Antiaromaticity within the Same Molecule: Location is Important

Abstract

The interplay between aromaticity and antiaromaticity is maximized in [n]phenylenes. In their smaller isomer sets, some isomers can be aromatic while others can be antiaromatic. The sum of the superimposed constituent circuits contributes to the individual ring aromaticity. Both cyclic conjugated energy (CCEi = efi ) of Bosanac and Gutman and Aihara's topological bond resonance energy (t-BRE) are good measures of relative degree of ring aromatic/antiaromatic character. Topological resonance energy (TRE) is a reliable measure of global molecular aromaticity/antiaromaticity because it is independent of selection of frame-of-reference molecules for calibration.

General Trinajstić Index

“…), which attract the interest of scientists in studying their properties such as resonance energies, topological or circuit resonance energies, currents and aromaticity. [15] Moreover, different variants of the general Trinajstić index can be applied to simplified skeletons (hydrogen-suppressed graphs) of other heteroatomic compounds in which heteroatoms (which are not carbon) are weighted differently [16] or they can be treated as a carbon atom, which is common in quantitative structure-activity-property models. [17] Therefore, the general Trinajstić index could be used in modelling in chemistry as well as other topological indices.…”