Iron oxychloride is the inorganic compound

Inorganic compound

Inorganic compounds have traditionally been considered to be of inanimate, non-biological origin. In contrast, organic compounds have an explicit biological origin. However, over the past century, the classification of inorganic vs organic compounds has become less important to scientists,...

 with the formula FeOCl. This purple solid adopts a layered structure, akin to that of cadmium chloride. The material slowly hydrolyses in moist air. The solid intercalates

Intercalation (chemistry)

In chemistry, intercalation is the reversible inclusion of a molecule between two other molecules . Examples include DNA intercalation and graphite intercalation compounds.- DNA intercalation :...

 electron-donors such as tetrathiafulvalene

Tetrathiafulvalene

Tetrathiafulvalene is a organosulfur compound with the formula 2. Studies on this heterocyclic compound contributed to the development of molecular electronics. TTF is related to the hydrocarbon fulvalene, 2, by replacement of four CH groups with sulfur atoms...

 and even pyridine

Pyridine

Pyridine is a basic heterocyclic organic compound with the chemical formula C5H5N. It is structurally related to benzene, with one C-H group replaced by a nitrogen atom...

 to give mixed valence charge-transfer salts. Intercalation is accompanied by a marked increase in electrical conductivity and a color change to black.

FeOCl is prepared by heating iron(III) oxide

Iron(III) oxide

Iron oxide or ferric oxide is the inorganic compound with the formula Fe2O3. It is one of the three main oxides of iron, the other two being iron oxide , which is rare, and iron oxide , which also occurs naturally as the mineral magnetite. As the mineral known as hematite, Fe2O3 is the main...

 with ferric chloride at 370 °C over the course of several days:

Fe₂O₃ + FeCl₃ → 3 FeOCl