J. Indian Chern. Soc., NOTE Vol. 85, October 2008, pp. 1038-1040 Charge transfer complex of p-phenylenediamine and p-chloranil Mukesh Paliwal 0 , M. L. Kalrab and Suresh C. Ameta 0 * 0 Department of Chemistry, bDepartment of Physics, M. L. Sukhadia University, Uqaipur-313 001, Rajasthan, India E-mail : ameta_sc@yahoo.com Manuscript received 14 November 2007, revised 26 May 2008, accepted 16 July 2008 Abstract : The charge transfer (CT) complex of p-phenylenediamine and p-chloranil was prepared in acetonitrile by solution growth, diffusion and microwave methods. The CT complex was characterized by its elemental analysis. IR and 1 H NMR spectral studies. The data obtained indicated the formation of 1 : 1 CT complex between the compounds. The d.c. electrical conductivity of the CT complex showed the semiconductor behaviour of complex at room tempera- ture. Keywords : Charge transfer complex, d.c. electrical conductivity, p-phenylenediamine, p-chloranil. Introduction The Lewis acid-base molecular complexes 1 between organic molecules, or an organic molecule and inorganic molecule, have received considerable attention in con- nection with the studies of the mechanism of electric con- duction by organic compounds. Investigations of one-di- mensional conductors began with the successful growth of single crystal of organic charge transfer complex formed between tetrathiafulvalene as an electron donor and tetracyanoquinodimethane as an electron acceptor (TIF- TCNQ)1·2. Field of conducting organic compounds has provided a promising new generation of functional mate- rials for future technology. Various applications includ- ing thin films application and molecular electronic de- vices3 are currently under active development. Recent advances in novel molecular-scale engineering include switching and memory systems 4 ·5, Schottky and electrolu- minescent diodes 6 • 7 , field effects transistors 8 • 9 , photovol- taic devices and solar cells 10 , rechargeable batteries, non- linear optical devices thennistors and negative-resistance11. Charge transfer complexes ofTCNQ with some drugs12,13 such as ofloxacin, levofloxacin, lomefloxacin, pipemidic acid, ciprofloxacin, norfloxacin, perfloxacin and fleroxa- cin show better antibacterial and biological activities than the parent drugs and this makes them pharmaceutically more important. Some of the charge transfer complexes containing 1038 chloranil (CA) as an acceptor are TTF-CA 14 , TTF-imi- dazole-CA 15 , p-phenylenediamine-CA 1 6, TMPD-CA 17 , aniline-CA 18 , aromatic amines and nitrogen hete-rocycles- CA 19 , N-aryldithiocarbamates-CA 20 , phosphine oxide and tri-n-butyl phosphate-CA 21 etc. It was proposed to prepare CT complex of p-phe- nylenediamine with p-chloranil by different methods like solution growth, diffusion and microwave exPosure method and to study their electrical conducting behaviour at room temperature. Results and discussion The elemental analysis and spectral data suggested that all complexes correspond to 1 : l stoichiometric ra- tios of donor and acceptor, respectively. The general behaviour of d.c. electrical conductivity obeys the relation cr = cr 0 exp (-Eikn, where cr 0 is constant, Ea is the activation energy of conduction pro- cess, Tis the absolute temperature and k is the Boltzmann constant. The room temperature d.c. electrical conduc- tivity of the complex lies in the range 1.96 x to- 10 to 20.50 x w- 6 S cm- 1 and it depends on the method of preparation of charge transfer complex. It indicates that the chemical composition of the complex remains same in all the three methods used, but there are some changes in the crystals of this complex, so that the conductivity is lowest oo- 10 s cm- 1 ) in the crystals prepared by solution growth method but on the other hand, it is 1 oS times