Benzenoid hydrocarbons having eigenvalues of ±√2

Abstract

The structural origin of eigenvalues ±√2 is discussed. Particular attention is given to the questions of how to recognise their occurrence without evaluating the complete eigenspectrum, and on how to construct and count such benzenoid species. The method is generally applicable and is illustrated with a detailed study of catacon-densed and some other fused and polymeric benzenoids. A collection of subspectral structures together with some homologous series are tabulated.