Copper(I) thiocyanate (or cuprous thiocyanate) is a

coordination polymer A coordination polymer is an inorganic or organometallic polymer structure containing metal cation centers linked by ligands. More formally a coordination polymer is a coordination compound with repeating coordination entities extending in 1, 2 ...

with formula CuSCN. It is an air-stable, white solid used as a precursor for the preparation of other thiocyanate salts.

Structure

At least two polymorphs have been characterized by X-ray crystallography. They both feature copper(I) in a characteristic tetrahedral coordination geometry. The sulfur end of the SCN- ligand is triply bridging so that the coordination sphere for copper is CuS3N.Smith, D. L.; Saunders, V. I. "Preparation and Structure Refinement of the 2H Polytype of beta-Copper(I) Thiocyanate" Acta Crystallographica B, 1982, volume 38, 907-909.

Synthesis

Copper(I) thiocyanate forms from the spontaneous decomposition of black copper(II) thiocyanate, releasing thiocyanogen, especially when heated. It is also formed from copper(II) thiocyanate under water, releasing (among others) thiocyanic acid and the highly poisonous

hydrogen cyanide Hydrogen cyanide, sometimes called prussic acid, is a chemical compound with the formula HCN and structure . It is a colorless, extremely poisonous, and flammable liquid that boils slightly above room temperature, at . HCN is produced on a ...

. It is conveniently prepared from relatively dilute solutions of copper(II) in water, such as copper(II) sulphate. To a copper(II) solution

sulphurous acid Sulfurous acid (also sulfuric(IV) acid, sulphurous acid (UK), sulphuric(IV) acid (UK)) is the chemical compound with the formula . There is no evidence that sulfurous acid exists in solution, but the molecule has been detected in the gas phase. ...

is added and then a soluble thiocyanate is added (preferably slowly, while stirring). Copper(I) thiocyanate is precipitated as a white powder. Alternatively, a

thiosulfate Thiosulfate ( IUPAC-recommended spelling; sometimes thiosulphate in British English) is an oxyanion of sulfur with the chemical formula . Thiosulfate also refers to the compounds containing this anion, which are the salts of thiosulfuric acid, e ...

solution may be used as a reducing agent.

Double salts

Copper(I) thiocyanate forms one double salt with the group 1 elements, CsCu(SCN)₂. The double salt only forms from concentrated solutions of CsSCN, into which CuSCN dissolves. From less concentrated solutions, solid CuSCN separates reflecting its low solubility. When brought together with

potassium Potassium is the chemical element with the symbol K (from Neo-Latin '' kalium'') and atomic number19. Potassium is a silvery-white metal that is soft enough to be cut with a knife with little force. Potassium metal reacts rapidly with atmos ...

sodium Sodium is a chemical element with the symbol Na (from Latin ''natrium'') and atomic number 11. It is a soft, silvery-white, highly reactive metal. Sodium is an alkali metal, being in group 1 of the periodic table. Its only stable ...

barium thiocyanate Barium thiocyanate is a colorless water-soluble salt that is very hygroscopic. It is highly toxic to ingestion and irritates the skin. It is also soluble in most alcohols and insoluble in simple alkanes. Uses Barium thiocyanate is used in dyeing ...

, and brought to crystallisation by concentrating the solution, mixed salts will crystallise out. These are not considered true double salts. As with CsCu (SNC)₂, copper(I) thiocyanate separates out when these mixed salts are redissolved or their solutions diluted.

Uses

Copper(I) thiocyanate is a hole conductor, a

semiconductor A semiconductor is a material which has an electrical conductivity value falling between that of a conductor, such as copper, and an insulator, such as glass. Its resistivity falls as its temperature rises; metals behave in the opposite way ...

with a

wide WIDE or Wide may refer to: *Wide (cricket) *Wide and narrow data, terms used to describe two different presentations for tabular data *WIDE Project, Widely Integrated Distributed Environment *Wide-angle Infinity Display Equipment *WIDE-LP, a radio ...

band gap In solid-state physics, a band gap, also called an energy gap, is an energy range in a solid where no electronic states can exist. In graphs of the electronic band structure of solids, the band gap generally refers to the energy difference ( ...

(3.6 eV, therefore transparent to visible and near infrared light). It is used in

photovoltaics Photovoltaics (PV) is the conversion of light into electricity using semiconducting materials that exhibit the photovoltaic effect, a phenomenon studied in physics, photochemistry, and electrochemistry. The photovoltaic effect is commercially ...

in some third-generation cells as a hole transfer layer. It acts as a

P-type semiconductor An extrinsic semiconductor is one that has been '' doped''; during manufacture of the semiconductor crystal a trace element or chemical called a doping agent has been incorporated chemically into the crystal, for the purpose of giving it differen ...

and as a solid-state electrolyte. It is often used in

dye-sensitized solar cell A dye-sensitized solar cell (DSSC, DSC, DYSC or Grätzel cell) is a low-cost solar cell belonging to the group of thin film solar cells. It is based on a semiconductor formed between a photo-sensitized anode and an electrolyte, a '' photoelec ...

s. Its hole conductivity is however relatively poor (0.01 S·m⁻¹). This can be improved by various treatments, e.g. exposure to gaseous

chlorine Chlorine is a chemical element with the symbol Cl and atomic number 17. The second-lightest of the halogens, it appears between fluorine and bromine in the periodic table and its properties are mostly intermediate between them. Chlorine i ...

or doping with (SCN)₂. CuSCN with

NiO are two wrathful and muscular guardians of the Buddha standing today at the entrance of many Buddhist temples in East Asian Buddhism in the form of frightening wrestler-like statues. They are dharmapala manifestations of the bodhisattva Vajrap ...

act synergically as a smoke suppressant additive in polyvinyl chloride (PVC). CuSCN precipitated on carbon support can be used for conversion of aryl halides to aryl thiocyanates. Copper thiocyanate is used in some

anti-fouling paint Anti-fouling paint is a specialized category of coatings applied as the outer (outboard) layer to the hull of a ship or boat, to slow the growth of and facilitate detachment of subaquatic organisms that attach to the hull and can affect a vess ...

s.V.F. Vetere et al, "Solubility and Toxic Effect of the Cuprous Thiocyanate Antifouling Pigment on Barnacle Larvae", Journal of Coatings Technology, 69:39 (March 1997)
/ref> Advantages compared to

cuprous oxide Copper(I) oxide or cuprous oxide is the inorganic compound with the formula Cu2O. It is one of the principal oxides of copper, the other being or copper(II) oxide or cupric oxide (CuO). This red-coloured solid is a component of some antifouling p ...

include that the compound is white and a more efficient

biocide A biocide is defined in the European legislation as a chemical substance or microorganism intended to destroy, deter, render harmless, or exert a controlling effect on any harmful organism. The US Environmental Protection Agency (EPA) uses a sli ...

References

{{DEFAULTSORT:Copper(I) thiocyanate Copper(I) compounds Thiocyanates Semiconductor materials Coordination polymers