# Has the molecular diatomic oxygen trianion been observed or predicted?

Has diatomic oxygen ever been observed with a 3− charge, i.e. $\ce{O_2^{3-}}$? Have any ab intio calculations been done on this ion?

Update:

Just to summarize some of the answers below and add my two cents, it seems that no studies have reported observing this ion experimentally, either in isolation or as part of a condensed phase. Ab initio calculations suggest that $\ce{O_2^{3-}}$ is unstable in isolation, meaning that the loss of an electron is exothermic. However, first-principles calculations have predicted that a molecular oxygen trianion can exist as part of a solid; see Phys. Rev. B 85, 035210 (2012).

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Two things: firstly, when referring to oxidation states, the sign comes before the number, so a thing is in oxidation state +3 or -1, for example. Secondly, an atom has an oxidation state, a molecule has a charge. For charges, the sign comes after, so 2- or 2+. –  Aesin Dec 8 '12 at 15:47
One should notice that the simple existence of such a species is not obvious. Anions always have the possibility to evolve through loss of an electron, which is not the case for positively charged species. Computation of electron affinities is not obvious, as ab initio calculations would "force" the electron to remain bound. Therefore one has to add numerous diffuse orbitals and consider that the presence of the extra electron in diffuse orbitals should be interpreted as a sign of unstability of these species. –  PLD Dec 18 '12 at 12:52
anions form from Gain of electrons and cations form from Loss of electrons. Not the other way around. –  Caters Aug 9 '14 at 21:51
Could you quote the section where they predict the oxygen trianion, please. I was unable to find any such reference, but I am not an expert on polarons and I might have missed it. –  Martin - マーチン Mar 4 at 6:35
They don't use the word "trianion", but I think what they describe on p. 2 is equivalent: "We found that the presence of an excess electron in Li$_2$O$_2$ results in elongation and/or cleavage of one of the O–O bonds...and the excess electron is localized at the cleaved O–O site." –  Max Radin Mar 5 at 8:11

According to "Small Multiply Charged Anions as Building Blocks in Chemistry" Acc. Chem. Res. 1996, 29, 497-502

it is concluded that all isolated diatomic dianions or other multiply charged diatomic anions are not stable to loss of an extra electron or fragmentation in their ground electronic states

So even $\ce{O2^{2-}}$, let alone $\ce{O2^{3-}}$ cannot exist in isolation.

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I don't know of (and a quick search couldn't reveal) any studies on the $\ce O_2^{3-}$ ion. Note that in this ion, oxygen wouldn't have an oxidation state of –3, but –1.5.

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Yes, it is, in $\ce{H3O2}$. This is from an a CCB bond. However, this is highly unlikely.

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Could you perhaps elaborate in your answer on this? –  ManishEarth Dec 17 '12 at 22:00