Pyrrolo Annelated Tetrathiafulvalenes: The Parent Systems

The synthesis of a number pyrrolo-annelated tetrathiafulvalenes, including the parent bis(pyrrolo[3,4-d])tetrathiafulvalene (7) is decribed. Starting from readily available 4,5-bis(bromomethyl)-1,3-dithiole-2-thione (14) and sodium tosylamide, the parent 7 and the asymmetric monopyrrolo tetrathiafulvalenes 23a,b were prepared in good yields via a nonclassical and simple pyrrole synthesis. Furthermore, a series of asymmetrical N-alkylated monopyrrolo/monodihydropyrrolotetrathiafulvalenes was prepared starting from primary amines and 14. A detailed study of the fundamental redox behavior of this class of heterocycles is reported. NMR spectroscopy, cyclic voltammetry, and PM3 MO calculations revealed that the pyrrolo-annelated tetrathiafulvalenes have highly extended π-surfaces. The X-ray crystallographic analyses of the monopyrrolo tetrathiafulvalenes 22b and 24b, together with preliminary formation of a charge-transfer complex between the parent donor 7 and TCNQ, are also reported.