Linking Number Analysis of a Pentadecanuclear Metallamacrocycle: A Möbius-Craig System Revealed

An analysis of the pi-electronic topology of a recently reported pentadecanuclear manganese metallacycle in terms of linking number, twist, and writhe confirms its previous assignment as a Möbius system of order six. The total degree of local torsion is reduced by a significant contribution from writhe, thus correcting the previously inferred local torsion at each metal center from 120 degrees to approximately 90 degrees . This latter value suggests a model for the cyclic pi conjugation around the metallacycle, which involves 3d pi-2p pi interactions at the metal center, of a type first suggested by Craig 50 years ago in the context of main group cyclic aromatic systems.