Organic metals; mono- and 2,5-di-substituted 7,7,8,8-tetracyano-p-quinodimethanes and conductivities of their charge-transfer complexes

Abstract

The syntheses of the electron acceptors methyl-7,7,8,8-tetracyano-p-quinodimethane (MTCNQ)(10), 2,5-dimethyl-7,7,8,8-tetracyano-p-quinodimethane (DMTCNQ)(5a), and 2,5-diethyl-7,7,8,8-tetracyano-p-quinodimethane (DETCNQ)(5b) from commercially available starting materials are described. Purification procedures utilizing multiple recrystallizations from CH₃CN, followed by gradient sublimation, yield high quality materials for the preparation of conducting organic charge-transfer complexes based on these acceptors. Field-ionization mass spectrometry was found to be a convenient means of monitoring the impurity contents during purification. Roomtemperature conductivity data for selected donor–acceptor combinations are reported, together with the electrochemical reduction potentials of the acceptors. The latter indicate that these have slightly poorer electron-accepting properties than unsubstituted TCNQ.