Tetracyano-4,7-indanoquinodimethanes: The first TCNQs with an indan nucleus

Article abstract of DOI:10.1055/s-1997-1316

8,8,9,9-Tetracyano-4,7-indanoquinodimethane 5-chloro-8,8,9,9-tetracyano-4,7-indanoquinodimethane, the first members of the hitherto unreported family of tetracyanoindanoquinodimethanes, have been synthesized from the corresponding 4,7-indandicarboxylic acids by the method of Yamaguchi. The indan-TCNQs are part of a series of polycyclic TCNQs which include 11,11,12,12-tetracyano-9,10-anthraquinodimethane and 9,9,10,10-tetracyano-1,4-naphthoquinodimethane, that have been prepared in our laboratory. A disadvantage found with the earlier polycyclic TCNQs was 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-indanoquinodimethane to be more planar compared with tetracyanoanthraquinodimethanes and tetracyanonaphthoquinodimethanes. The half-wave potentials of the chlorotetracyanoindanoquinodimethane show it to be a stronger electron acceptor than several known TCNQs and its cyclic voltammogram indicate two single-electron reversible redox processes.