Electronic Aromaticity Index for Large Rings

TL;DR

This paper introduces AV1245, a new electronic aromaticity index for large rings that is size-extensive, computationally efficient, and applicable to diverse molecular structures, improving the assessment of aromaticity in large conjugated systems.

Contribution

The paper presents AV1245, a novel aromaticity index based on 4-center MCI values, with a new algorithm for large rings, enabling accurate and efficient aromaticity evaluation without reference dependence.

Findings

AV1245 effectively measures aromaticity in large rings.

The new algorithm allows linear scaling with ring size.

AV1245 is versatile across different atom types and geometries.

Abstract

We introduce a new electronic aromaticity index, AV1245, consisting in the average of the 4-center MCI values along the ring that keep a positional relationship of 1,2,4,5. AV1245 measures the extent of transferability of the delocalized electrons between bonds 1-2 and 4-5, which is expected to be large in conjugated circuits and, therefore, in aromatic molecules. A new algorithm for the calculation of MCI for large rings is also introduced and used to produce the data for the calibration of the new aromaticity index. AV1245 does not rely on reference values, does not suffer from large numerical precision errors, and it does not present any limitation on the nature of atoms, the molecular geometry or the level of calculation. It is a size-extensive measure with a small computational cost that grows linearly with the number of ring members. Therefore, it is specially suitable to study the aromaticity of large molecular rings as those occurring in belt-shaped M\"obius structures or porphyrins.