# Can polyatomic ions (CO₃, PO₄, SO₄, NO₃) be considered conjugated systems?

From my perspective these resonance structures allow these specific polyatomic ions to act as donor-acceptor molecules. Many donor-acceptor molecules also tend to be conjugated systems because they have chains of alternating conjugated π orbitals.

So does this imply that these ions (due to their resonance structures) can act as though they had a conjugated system or am I making too big of an assumption?

Curious on others perspectives/if I'm totally of my rocker.

• I think you're a bit off ;) To my understanding, the IUPAC Gold Book restricts the term conjugation to organic chemistry. I'm highly biased and too much an organic chemist to disagree :D – Klaus-Dieter Warzecha Jan 28 '14 at 20:42
• @Klaus Warzecha: If the OP substituted "delocalized" in place of "conjugated", would that make for a better statement? – ron Jan 28 '14 at 22:40
• I appreciate the thoughts guys! I think what I'm hunting for is what lies in the stricter definitions of what makes something conjugated vs what makes something resonant. Though in both cases I would consider the electrons delocalized as @ron mentioned. Thanks guys! – Sean Jan 29 '14 at 23:01

Consider nitrate. Inorganikers would say $\ce{N^{5+}}$, $\ce{^{-}O-N(=O)2}$, with five bonds to the nitrogen. The negative charge 1,3-shifts around all three oxygens. Organikers would see it as $\ce{N^{3+}}$, $\ce{[^{-}O{}-]_2N^{+}=O}%edit$, with four bonds to the nitrogen. 1,3 shifts, etc. Is nitrate ever a bidentate ligand? YES! But it is just another resonance structure.