cis- and trans-Conformations for peroxynitrite anions

The biochemically important anion, peroxynitrite, is commonly thought to ha ve a cis-conformation which is stable. This is thought to have a cyclic str ucture, which blocks the formation of the trans-conformation. Furthermore, it is often suggested that the latter structure isomerises to the far more stable nitrate ion. Here I suggest that the cis-structure has comparable st ability to the trans-structure, and they are in rapid equilibrium at room t emperature. This is supported by the very large linewidths for certain vibr ational bands at room temperature, which become narrow, well-separated band s at 4 K. Lifetimes are about 10(-12) s for each isomer. (C) 2000 Elsevier Science Inc. All rights reserved.