TETRACYANO-4,7-INDANOQUINODIMETHANES - THE FIRST TCNQS WITH AN INDAN NUCLEUS

8,8,9,9-Tetracyano-4,7-indanoquinodimethane and hloro-8,8,9,9-tetracya no-4,7-indanoquinodimethane, the first members of the hitherto unrepor ted family of tetracyanoindanoquinodimethanes, have been synthesized f rom the corresponding 4,7-indandicarboxylic acids by the method of Yam aguchi. The indan-TCNQs are part of a series of polycyclic TCNQs which include 11,11,12,12-tetracyano-9,10-anthraquinodimethane and 9,9,10,1 0-tetracyano-1,4-naphthoquinodimethane, that have been prepared in our laboratory. A disadvantage found with the earlier polycyclic TCNQs wa s the non-coplanarity of their rings and the dicyanomethylene moities: a planar system is essential to efficient electrical conductivity of TCNQs in CT salts. X-ray analysis has shown 8,8,9,9-tetracyano-4,7-ind anoquinodimethane to be more planar compared with tetracyanoanthraquin o dimethanes and tetracyanonaphthoquinodimethanes. The half-wave poten tials of the chlorotetracyanoindanoquinodimethane show it to be a stro nger electron acceptor than several known TCNQs and its cyclic voltamm ogram indicate two single-electron reversible redox processes.