The Absorption Colour of Organic Azo Compounds

Abstract

Quantum chemical methods permit one to reveal scope and limitations of composite-molecule models formerly proposed to rationalize the absorption behaviour of azo compounds in the visible region. In order to give a justification of these approaches PPP-type many-electron wave functions have been subjected to “configuration analyses”. The genesis of the colour-determining low-energy excited states has been followed within the framework of the Longuet-Higgins/Murrell method. The position of colour bands of various organic azo compounds are considered to support theoretical conclusions.