Electronic spectra of five (Bis(X‐phenyl)‐Ethane diimine] compounds I‐V, have been investigated in various organic solvents and aqueous buffer solutions of varying pH's. The observed visible band is assigned to intramolecular CT transition. Furthermore, it is deduced that structure of the o‐hydroxy derivative is not entirely planar. The acid dissociation constant values of the hydroxy derivatives have been determined and are discussed. Copyright © 1990 The Chemical Society Located in Taipei & Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim, Germany