The Diamagnetic Sucseptibilities and Anisotropies of the Polynuclear Aromatic Compounds

The magnetic susceptibilities of condensed polynuclear aromatic compounds with higher molecular weights (ten hydrocarbons and twelve quinones) have been measured by the Gouy method, and the diamagnetic anisotropies have been approximately evaluated. The diamagnetic anisotropy becomes progressively large as the number of rings increases, when the aromatic condensation takes place in the manner of the closely compact arrangement of rings; while, when it is not the case, it depends strikingly upon the molecular structure. When the diamagnetic anisotropy has a smaller value, notwithstanding the molecule is made of a large number of rings, the localization of the π-electrons or some other excited states must be assumed. Such a case is found, when a molecule is not made of the aromatically conjugated system as a whole but separated into two predominant nuclei, as meso-naphthodianthrene and violanthrone, or when a molecule is made of a long shaped structure as pyranthrene or violanthrene.