Synthesis and characterisation of charge transfer complexes of new electron acceptors

Abstract

New electron acceptors, possessing various skeletal frameworks have been prepared and characterised. Complexation with a range of metal and organic cations reveal the suitability of the electron acceptors in the field of conducting charge-transfer complexes. Unsuccessful attempts to synthesise sterically demanding TCNQ derivatives, directly from the corresponding p-benzoquinone in the presence of titanium tetrachloride, provided a convenient route to a range of mono (dicyanomethylated)alkyl-p-benzoquinones, which were converted into N,7,7-tricyanoquinomethaneimine derivatives. Semi conducting charge-transfer salts of these new acceptors are described. Reduction of 2-dicyanomethylene-1,3-indandione (DCID) with cationic iodides, initiated a fascinating rearrangement to afford crystalline salts of the isomeric 2,3-dicyano-1,4-naphthoquinone (DCNQ), as confirmed by X-ray analysis.1,3-Metadinitrobenzene and 1,3,5-trinitrobenzene both form neutral, insulating, diamagnetic complexes with tetrathiafulvalene. The crystal structure of each complex is characterised by mixed stacks of alternate donor and acceptor molecules. The study of tetrachloro-DCID and l,3-bis(dicyanomethylene)indane further establishes that a wide range of electron acceptors belong in the development of organic metals.