Caesium sesquioxide

Caesium sesquioxide is a chemical compound with the formula Cs₂O₃ or more accurately Cs₄O₆. It is an oxide of caesium containing oxygen in different oxidation states. It consists of caesium cations Cs⁺, superoxide anions O−2 and peroxide anions O2−2. Caesium in this compound has an oxidation state of +1, while oxygen in superoxide has an oxidation state of −1/2 and oxygen in peroxide has an oxidation state of −1. This compound has a structural formula of (Cs⁺)₄(O−2)₂(O2−2).^[1][2] Compared to the other caesium oxides, this phase is less well studied,^[3] but has been long present in the literature.^[4] It can be created by thermal decomposition of caesium superoxide at 290 °C.^[5]

4 CsO₂ → Cs₄O₆ + O₂

Caesium sesquioxide

Identifiers
3D model (JSmol)	Interactive image
PubChem CID	157422808
InChI InChI=1S/4Cs.2HO2.O2/c;;;;3*1-2/h;;;;2*1H;/q4*+1;;;-2/p-2 Key: CBAPCGFDLAJQPQ-UHFFFAOYSA-L
SMILES [Cs+].[Cs+].[Cs+].[Cs+].[O-][O].[O-][O].[O-][O-]
Properties
Chemical formula	Cs4O6
Molar mass	627.616 g·mol−1
Appearance	black powder[1]
Structure[1]
Crystal structure	Pu2C3 structure type (body-centered cubic)
Space group	I43d (no. 220)
Lattice constant	a = 984.6 pm
Related compounds
Other cations	Rubidium sesquioxide
Related caesium oxides	Caesium suboxides Caesium monoxide Caesium peroxide Caesium superoxide Caesium ozonide
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). Infobox references

The compound is often studied as an example of a Verwey type charge ordering transition at low temperatures.^[6][7][8] There were some theoretical suggestions that Cs₄O₆ would be a ferromagnetic half metal,^[9] but along with the closely related rubidium sesquioxide, experimental results found a magnetically frustrated system.^[1] Below about 200 K, the structure changes to tetragonal symmetry.^[10] Electron paramagnetic resonance and nuclear magnetic resonance measurements show a complicated low temperature magnetic behavior that depends on the orientation of the oxygen dimers and superexchange through the caesium atoms.^[11]