New ' ‘Te-TTF’ dimers, aryl-substituted TCNQ and quinone derivatives: Synthesis, electrochemistry and molecular structure

Our efforts in the field of ’organic metals’ have been focused mainly on the preparation and structural determination of D-A-D (D= donor, A= acceptor) and A-D-A molecular units in which donors and acceptors are chemically attached via bridging atoms. The strategy that directs the synthetic work aims to gain some control over architectural aspects, which are vital pre-conditions for electrical conductivity in organic materials. Thus, constructing such molecular units pre-determines the D-A molar ratio as well as the maximum degree of charge transfer. Moreover, it might also lead to the desired crystallographic arrangement, characterized by segregated stacks of both donors and acceptors, with significant overlap between adjacent units in the stack. Following this approach we have synthesized two types of molecules: one contains two donors linked to one acceptor via a -CH2- or S bridges, and the other, two acceptors linked to one donor via -CH2- bridges. Representative examples of both types show promising structural properties and partial charge transfer in their ground state. The importance of introducing heavy atoms in charge-transfer complexes has been recognized.Consequently, extensive work has been carried out on the synthesis of various TTF derivatives, in which Se and Te atoms substitute sulfur or hydrogen atoms in the TTF framework. Recently we have synthesized new compounds in which two TTF molecules are bridged via tellurium atoms: TTF-Te-TTF and TTF-Te-Te-TTF. Their synthesis, electrochemical properties and molecular structural features are presented.