A Unified Framework for Aromatic Structure and Bonding

Aromaticity is one of the most central and fundamental concepts in chemistry, which interrelates the electronic configuration, structure, bonding, stability. However, it remains a century-old enigma, as the necessary and sufficient conditions for aromaticity and antiaromaticity are not fully understood, and the relationship between stability and aromaticity is still under debate. Here we conclude that magnetic aromaticity and antiaromaticity arise from electronic occupations on simple circularly looping molecular orbitals. By proposing the Magnetic Response Orbital Theory (MROT) through inspection of the asymptotic perturbations of molecular orbitals under infinitesimal magnetic fields, magnetic aromaticity can be directly understood for all categories of single-reference systems once their Magnetic Response Orbitals (MROs) are calculated. We further conclude that there is no causal relationship between magnetic aromaticity and stability. Additionally, by introducing the Aromatic Bonding Theory and Aromatic Octet Rules, we extend the concept of chemical bonds from atom-atom real bonding to cluster-cluster complex bonding. This unprecedentedly simplifies the understanding of p-block hypovalent clusters (especially boranes), enables arrow-pushing practices, and establishes a new paradigm for their rational design.