Kinetics & Mechanism of Solid State Reaction between o-Phenylenediamine & p-Benzoquinone

Abstract

<em>o</em>-Phenylenediamine (oPDA) reacts with <em>p</em>-benzoquinone (BO) in the solid state forming the complex oPDA₂^.BQ₁, which is dark brown in colour. ESR spectrum of the complex confirms the presence of free radical in oPDA₂^.BQ₁. Spectroscopic studies (IR, UV) indicate that charge transfer interaction stabilised by H-bonding is involved in the formation of the complex. During the course of solid state reaction, BQ molecules diffuse in oPDA through surface migration and the reaction goes to completion by the penetration of BO molecules into the crystal lattice of oPDA. Electrical conductivity measurement of solid oPDA₂^.BQ₁, below 575 K shows that the complex behaves as a semiconductor, with a energy band gap of 3.00 eV.