MOLECULAR CURRENTS, HARMONICS, CONJUGATED CIRCUITS AND AROMATICITY
Presented by Prof. Patrick FOWLER
Type: Keynote Lecture
Aromaticity is an elusive chemical concept, with many definitions, but it does have at least one clear manifestation in ‘ring currents’ induced in planar unsaturated molecules by perpendicular magnetic fields. Efficient ab initio calculation of such currents is now a practical possibility. The resulting current-density maps allow us to visualise aromaticity and to develop interpretations and test simpler mathematical models. It turns out that surprisingly simple models give clues about molecular electronic structure and help us identify new classes of aromatics. Most models are counting something (electrons, nodal lines in cylindrical harmonics, conjugated circuits, benzene-like hexagonal rings, …) and all have different insights to offer. This contribution discusses some ways in which combinatorics and graph theory can be applied to the theory of molecular currents in chemistry. The talk includes work done in collaboration with computer scientists (Wendy Myrvold and William Bird, University of Victoria, Canada) and with chemistry research groups in Utrecht (Jenneskens), Groningen (Havenith), Leuven (Ceulemans) and Melbourne (Soncini).