In chemistry

Chemistry

Chemistry is the science of matter, especially its chemical reactions, but also its composition, structure and properties. Chemistry is concerned with atoms and their interactions with other atoms, and particularly with the properties of chemical bonds....

, the term pseudo-oxocarbon anion is used to refer to a negative ion that is conceptually derived from an oxocarbon anion

Oxocarbon anion

In chemistry, an oxocarbon anion is a negative ion consisting solely of carbon and oxygen atoms, and therefore having the general formula CxOyn− for some integers x, y, and n....

 through replacement of one or more of the basic oxygen atoms by chemically similar elements or functional group

Functional group

In organic chemistry, functional groups are specific groups of atoms within molecules that are responsible for the characteristic chemical reactions of those molecules. The same functional group will undergo the same or similar chemical reaction regardless of the size of the molecule it is a part of...

s, such as sulfur

Sulfur

Sulfur or sulphur is the chemical element with atomic number 16. In the periodic table it is represented by the symbol S. It is an abundant, multivalent non-metal. Under normal conditions, sulfur atoms form cyclic octatomic molecules with chemical formula S8. Elemental sulfur is a bright yellow...

 (S), selenium

Selenium

Selenium is a chemical element with atomic number 34, chemical symbol Se, and an atomic mass of 78.96. It is a nonmetal, whose properties are intermediate between those of adjacent chalcogen elements sulfur and tellurium...

 (Se), or dicyanomethylene (=C(CN)₂).

Typical examples are the anions 2-(dicyanomethylene)croconate

2-(Dicyanomethylene)croconate

2-croconate is a divalent anion with chemical formula or 2−. It is one of the pseudo-oxocarbon anions, as it can be described as a derivative of the croconate oxocarbon anion through the replacement of one oxygen atom by a dicyanomethylene group =C2.The anion was syntesized and...

, croconate violet

Croconate violet

Croconate violet or 1,3-biscroconate is a divalent anion with chemical formula or 22−. It is one of the pseudo-oxocarbon anions, as it can be described as a derivative of the croconate oxocarbon anion through the replacement of two oxygen atoms by dicyanomethylene groups =C2...

, and croconate blue

Croconate blue

Croconate blue or 1,2,3-triscroconate is a divalent anion with chemical formula or 32−. It is one of the pseudo-oxocarbon anions, as it can be described as a derivative of the croconate oxocarbon anion through the replacement of three oxygen atoms by dicyanomethylene groups =C2...

, derived from the croconate anion by replacing one, two, or three oxygen atoms by dicyanomethylene groups:

Croconate	2-Dicyanomethylene- croconate	Croconate violet	Croconate blue

These anions retain many of the properties of the parent, including the delocalized bond in the ring and the delocalized charge in the atoms attached to the ring. Similar anions can be obtained from squarate .