7,7,8,8-Tetracyanoquinodimethane

Synthesis Reference(s)

Journal of the American Chemical Society, 84, p. 3370, 1962 DOI: 10.1021/ja00876a028The Journal of Organic Chemistry, 48, p. 1366, 1983 DOI: 10.1021/jo00156a048

General Description

7,7,8,8-Tetracyanoquinodimethane (TCNQ) is a strong organic electron acceptor widely used in optoelectronic applications, such as OLEDs and solar cells, due to its high electron affinity. It forms coordination polymers like Cu(TCNQ), which exhibit tunable electronic properties through reversible iodine absorption, altering conductivity and oxidation states. TCNQ-based materials demonstrate significant potential in developing advanced functional materials for electronic and optical devices.

Applications

7,7,8,8-tetracyanoquinodimethane (TCNQ), with a LUMO at 4.5 eV, is known for the charge-transfer salts formed by its radical anion TCNQ in photovoltaic, light-emitting diodes, and organic field-effect transistor devices. TCNQ and its derivatives have been used as dopants, leading to an increase in hole mobility or to the lowering of injection barriers. One classic example of such is the treatment of tetrathiafulvene (TTF), an electron donor with TCNQ. TFF and TCNQ form an ion pair, the TTF-TCNQ complex. This process of doping leads to the crystallisation of the ion pair into a one-dimensionally stacked polymer. This polymer consists of segregated stacks of cations and anions of the donors and the acceptors, respectively. The complex crystal is an organic semiconductor that exhibits metallic electric conductivity. It also has been shown that TCNQ can effectively modify Cu or Ag surfaces. The formation of Cu-TCNQ and Ag-TCNQ enhances the work function of such electrodes and reduces the hole injection barrier dramatically. Furthermore, it improves electrode/organic layer contact, hence the reduction of contact resistances. Tetracyanoquinodimethane (TCNQ) is also found to act as a p-type doping agent of graphene films due to its powerful electron-accepting capacity.

Definition

ChEBI: A quinodimethane that is p-quinodimethane in which the methylidene hydrogens are replaced by cyano groups.