Directly-linked intramolecular donor–acceptor compounds of ferrocene and tetracyanoanthraquinodimethane

Two new intramolecular donor–acceptor species have been prepared linking ferrocene (Fc) directly to either the 1 (1) or 2 (2) positions of tetracyanoanthraquinodimethane (TCNAQ). Spectroscopic and electrochemical characterisation show significant differences between 1 and 2, revealing the importance of the position of attachment. The Fc part is a poorer donor and the TCNAQ part a poorer acceptor than the respective parent molecules and an intramolecular charge-transfer transition is observed at 604 nm (1) and 634 nm (2). The X-ray structure of 1 shows the TCNAQ component with the typical folded conformation with the ferrocene unit rotated by 38.0° relative to the ring to which it is attached.