7,7,8,8-Tetracyanoquinodimethane Chemical Properties

Melting point:

287-289 °C (dec.) (lit.)

Boiling point:

332.67°C (rough estimate)

Density 

1.3596 (rough estimate)

refractive index 

1.5000 (estimate)

storage temp. 

Sealed in dry,Room Temperature

form 

Crystalline Powder

color 

Orange-brown to green

Water Solubility 

insoluble

λmax

395nm(CH3CN)(lit.)

BRN 

611604

Stability:

Stable. Incompatible with strong acids, strong bases, strong reducing agents, strong oxidizing agents.

InChI

InChI=1S/C12H4N4/c13-5-11(6-14)9-1-2-10(4-3-9)12(7-15)8-16/h1-4H

InChIKey

PCCVSPMFGIFTHU-UHFFFAOYSA-N

SMILES

C1(=C(C#N)C#N)C=CC(=C(C#N)C#N)C=C1 |c:8,t:0|

CAS DataBase Reference

1518-16-7(CAS DataBase Reference)

NIST Chemistry Reference

Propanedinitrile, 2,2'-(2,5-cyclohexadiene-1,4-diylidene)bis-(1518-16-7)

EPA Substance Registry System

Propanedinitrile, 2,2'-(2,5-cyclohexadiene-1,4-diylidene)bis- (1518-16-7)

Safety Information

Hazard Codes 

Xn,Xi,T

Risk Statements 

22-20/21/22-23/24/25

Safety Statements 

22-24/25-36/37-26-36-45

RIDADR 

3276

WGK Germany 

3

RTECS 

GU4850000

Hazard Note 

Irritant

TSCA 

Yes

HazardClass 

6.1

PackingGroup 

II

HS Code 

29269095

MSDS

• Language:English Provider:7,7,8,8-Tetracyanoquinodimethane
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7,7,8,8-Tetracyanoquinodimethane Usage And Synthesis

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.

Description

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 [1, 2].

Chemical Properties

orange to green crystalline powder

History

The first report on the electrical conductivity in an organic solid appeared in 1954, namely, a perylene—bromine complex with a room-temperature conductivity of 0.1 S cm?1. In 1960, the organic acceptor Tetracyanoquinodimethane (TCNQ; 7,7,8,8-Tetracyanoquinodimethane) was synthesized, as well as a great number of its conducting charge-transfer complexes and radical ion salts. In the 1970s, the organic donor TTF led to the first organic metal TTF-TCNQ. Its room-temperature conductivity (500 S cm?1) increases with a decrease in the temperature to the value of 6000 S cm?1 at 60 K, where a metal-insulator transition occurs[1].

Uses

7,7,8,8-Tetracyanoquinodimethane is an electron-acceptor molecule used to form charge-transfer superconductors. It is an effective catalyst used for the ?-chlorination of carboxylic acids using chlorosulfonic acid; the presence of TCNQ suppresses competing free-radical chlorination.

Definition

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

Synthesis Reference(s)

Journal of the American Chemical Society, 84, p. 3370, 1962 DOI: 10.1021/ja00876a028
The Journal of Organic Chemistry, 48, p. 1366, 1983 DOI: 10.1021/jo00156a048

General Description

7,7,8,8-Tetracyanoquinodimethane (TNCQ) is a strong electron acceptor as it has four cyano groups and π-conjugation bonds that form charge transferring chains and ion radical salts which are mainly used as p-dopants for the fabrication of a variety of semiconductor applications.

References

[1] Tahar Abbaz. “Synthesis and electrochemical proprieties of novel unsymmetrical bis-tetrathiafulvalenes and electrical conductivity of their charge transfer complexes with tetracyanoquinodimethane (TCNQ).” International Journal of Molecular Sciences 13 7 (2012): 7872–7885.

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